WO1999010803A1 - Method and apparatus for perimeter sensing for vehicles - Google Patents

Method and apparatus for perimeter sensing for vehicles Download PDF

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Publication number
WO1999010803A1
WO1999010803A1 PCT/US1998/017533 US9817533W WO9910803A1 WO 1999010803 A1 WO1999010803 A1 WO 1999010803A1 US 9817533 W US9817533 W US 9817533W WO 9910803 A1 WO9910803 A1 WO 9910803A1
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WO
WIPO (PCT)
Prior art keywords
time
pulses
vehicle
flight
determining
Prior art date
Application number
PCT/US1998/017533
Other languages
French (fr)
Inventor
Robert L. Scully
Original Assignee
Scully Robert L
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US08/918,826 external-priority patent/US6012008A/en
Application filed by Scully Robert L filed Critical Scully Robert L
Publication of WO1999010803A1 publication Critical patent/WO1999010803A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
    • G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/06—Systems determining position data of a target
    • G01S13/46—Indirect determination of position data
    • G01S13/48—Indirect determination of position data using multiple beams at emission or reception
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
    • B60R21/01—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents
    • B60R21/013—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents including means for detecting collisions, impending collisions or roll-over
    • B60R21/0134—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents including means for detecting collisions, impending collisions or roll-over responsive to imminent contact with an obstacle, e.g. using radar systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
    • G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G01S2013/9315—Monitoring blind spots
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
    • G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G01S2013/93185—Controlling the brakes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
    • G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G01S2013/9323—Alternative operation using light waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
    • G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G01S2013/9327—Sensor installation details
    • G01S2013/93271—Sensor installation details in the front of the vehicles
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
    • G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G01S2013/9327—Sensor installation details
    • G01S2013/93272—Sensor installation details in the back of the vehicles
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
    • G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G01S2013/9327—Sensor installation details
    • G01S2013/93274—Sensor installation details on the side of the vehicles

Definitions

  • This relates to a method and apparatus for sensing around vehicles. It is particularly useful for predicting a collision, for initiating reactions in response to such a prediction and for sensing the presence of overtaking vehicles.
  • Automobile airbag safety systems rely on sensors to provide indication during a crash that the crash is of sufficient severity to warrant the deployment of an airbag. These sensors are reactive in the sense that they can only measure the response of the car during the actual physical crash. The sensor system however, must provide adequate warning to permit airbag deployment.
  • a general rule of performance is the "5 inch - 30 millisecond" rule: as a general norm, an airbag must be fully deployed after a travel of 5 inches in the front seat of the passenger compartment, where the travel is defined as the integration of the velocity change during the accident at the location of the passenger compartment. Since it takes approximately 30 milliseconds to deploy a passenger side airbag fully, the sensor system must provide an indication 30 milliseconds before the front seat has traveled 5 inches during the crash. In assessing this requirement it is helpful to recall that a vehicle traveling at 60 miles per hour is traveling at 88 feet per second or 0.88 feet per 10 milliseconds.
  • the sensor system must be capable of separating "must-fire” crashes from “no-fire” crashes, since not all crashes are severe enough to warrant the deployment of an airbag.
  • a velocity of 14 mph separates crashes requiring an airbag from those that do not require an airbag.
  • SUBSTITUTE SHEET (RULE 25) Sensors that are employed include mechanical, electromechanical and electronic devices.
  • a mechanical sensor might involve the movement of a mass against a restraint arm. If the movement is sufficient, a spring loaded firing pin is released, puncturing a primer that initiates the airbag firing.
  • an electromechanical sensor such as the ball-in-tube sensor, an electrical contact is closed if a magnetically restrained ball breaks free and closes the contacts of an external circuit.
  • Both mechanical and electromechanical sensors are located near the point of initial contact, i.e. the front of the vehicle for frontal crashes. More than one sensor is usually required. In the mechanical and electromechanical sensor systems, the separation of "must- fire" crashes from “no-fire” crashes is accomplished with bias and damping parameters built into the sensor design, since these sensors are basically switches.
  • Electronic sensors rely on micromachined silicon capacitive or piezoresistive accelerometers. These sensors are typically located on a structural component close to the front of the passenger compartment, and measure the acceleration along the longitudinal axis of the car. The output of the electronic sensor is a voltage proportional to the acceleration along the axis of the vehicle.
  • a microcontroller continually monitors the electronic sensor output and by means of a suitable algorithm determines if a crash is occurring and if it is severe enough to warrant airbag deployment.
  • the electronic sensor can be configured as a single unit. Because of the advantages of this arrangement, the present industry trend is towards a single electronic sensor located on a structural component near the front of the passenger compartment.
  • Another source of collisions is a vehicle that is backing up.
  • a common cause of such accidents is simply that the driver was not able to see all areas behind the vehicl while he was backing up.
  • Still another source of collisions is sideswipes between two vehicles moving alongside one another.
  • Multilane highways afford the opportunity for passing on both sides of a vehicle, and aggressive drivers commonly weave their way through traffic, changing lanes many times in the process. All this places demands on the driver to be aware of the surroundings and to be alert to changes which can happen quickly. It is also well known that side mounted mirrors have "blind spots" where overtaking vehicles may go undetected.
  • an advance warning of a crash would be of value in alerting the driver to the possibility of imminent collision and/or in preparing vehicle safety systems for an impact.
  • a knowledge of where the contact will occur and the potential severity based on relative velocity would permit algorithms monitoring accelerometer based sensors to come to a decision at an earlier time during the actual crash.
  • a predictive collision sensing system would provide this additional warning.
  • a predictive collision sensing system could provide advance warning of a high velocity impact in a limited area, which is characteristic of a pole crash, as well as an all clear signal across the front of a vehicle supporting a rough road determination by the safety system diagnostic unit.
  • a predictive collision sensing system could also provide significant value for a vehicle side impact system, where response time requirements for reactive sensors are severe.
  • a predictive collision sensing system could provide an early alert to safety restraint and "smart" airbag systems currently under development.
  • the method and apparatus of the present invention projects a sensing envelope outwards from the surface of the vehicle and detects objects, either stationary or mobile, that intrude into this volume.
  • This sensing envelope is kept as close to the surface of the vehicle as is possible, e.g. on the order of two to six feet and preferably about four feet, to eliminate the requirements of processing extraneous signals and to eliminate the generation of false indications.
  • the invention is implemented in a system comprising a control unit and multiple transmitting and sensing units that working together (1) locate approaching obstacles, (2) by time-of-flight analysis calculate the time-to-impact, and (3) provide indication of an imminent collision. This indication can then, for example, be used to actuate the airbags in a conventional airbag system.
  • the system is implemented using pulsed infrared laser transmitters; photodiode receiver circuits including amplification and signal conditioning; a digital clock for elapsed time measurement; and one or more digital signal processors or microprocessors for system control and algorithm realization.
  • sensing distances in the preferred embodiment to approximately four feet has additional advantages that include increased probability of receiving reflected signals, even under adverse weather conditions. It also permits operation of the pulsed infrared laser within power limits that will meet eye safety requirements under all conceivable conditions.
  • the invention may also be practiced in a system which could provide information to the driver prior to a lane change, on vehicles in the "blind spot" of the mirror system, to provide an additional measure of safety. Furthermore, if this system could be incorporated into or added onto the existing structure of the side mounted mirror and provide visual indication to the driver when the side mirror is viewed, then the device would require no additional driver actions beyond what is normally performed in a lane change.
  • the method and apparatus of the present invention detects the presence of objects within a sensing volume that encompasses the "blind spot" of the side mirrors provided on all vehicles.
  • the "blind spot" of the side mirror system is a property of the vehicle body design, the mirror position and the viewing position of the vehicle operator.
  • the sensing volume is defined as the volume covered by one or more sensing beams, each of which detects the presence of obstacles along its line of sight.
  • the number of beams, directional orientation and beam width are arranged to provide indication of any obstacle above a minimum size corresponding to a motor vehicle or motorcycle, that may be present in the sensing volume, which itself covers the vehicle's "blind spot".
  • the invention is implemented in a system comprising a control unit and multiple transmitting and sensing units that working together (1) locate objects along the lines-of- sight of the respective sensing elements, (2) by time-of-flight analysis calculate the distance to the sensed object, and (3) provide indication of objects within a predefined sensing envelope.
  • the system is implemented using pulsed infrared laser transmitters, photodiode receiver circuits including amplification and signal conditioning, a digital clock for elapsed time measurement, one or more digital signal processors or microprocessors for system control and algorithm realization, and a display module for indication of sensing volume status.
  • the invention relies on the principle of the time-of-flight measurement of short infrared pulses to determine the distance, on a suitable algorithm to filter the result through a range gate corresponding to a selected range along the line of sight, and on multiple sensing beam to provide full target area coverage.
  • system provides visual display at the location of the vehicle side mounted mirror permitting simultaneous viewing of the mirror image of the roadway and the indicator display of the present invention.
  • the invention may also be used to sense nearby objects behind a vehicle while the vehicle is backing up.
  • Fig.l is a block diagram illustrating a preferred embodiment of the invention.
  • Fig.2 is a flowchart depicting the processing of information within the system
  • Fig 3 is a plot depicting time-to-impact as a function of closing velocity with isochrones for specific tim ⁇ s-to-impact;
  • Fig. 4 is a plot depicting time-to-impact vs. distance for given closing velocities;
  • Fig. 5. is a schematic depicting the invention mounted on the front of a vehicle;
  • Fig. 6 is a schematic depicting the invention mounted on the side of the vehicle.
  • Fig. 7 is a functional block diagram of the preferred embodiment of the invention.
  • Fig. 8 is a flow chart illustrating the processing of information within the system
  • Fig. 9 is a schematic depicting the area of coverage of a multiple rangefinder system.
  • Fig. 10 is a schematic outline of the invention as appended to the side mirror structure.
  • the system of the present invention comprises a main control unit 100 and at least one, and preferably several, rangefinder units 200.
  • Each rangefinder unit comprises a pulse transmitter 10, a pulse receiver 20, a signal conditioner 30, a threshold discriminator 40, a clock 50, a counter 60 and an averager 70.
  • Control unit 100 sets the firing sequence of the individual units, stores data from the rangefinder units, provides analysis of individual unit response and overall system response, and provides alarm signals for external safety systems.
  • control unit 100 is a conventional microprocessor, microcontroller, or a digital signal processor.
  • Each individual rangefinder unit 200 measures the distance to objects in its sensing direction through the measurement of the time-of-flight of a short infrared pulse.
  • Each transmitter 10 projects a narrow beam infrared pulse and each receiver unit 20 detects reflected return pulses and provides initial amplification.
  • each transmitter operates at a pulse repetition rate of 10 MHz so that one pulse is emitted every 100 nanoseconds.
  • Return pulses are amplified and gain adjusted in signal conditioner 30, in order to provide a uniform return signal for further analysis.
  • a threshold/discriminator 40 may optionally be employed for further return signal control.
  • a digital clock 50 and a counter 60 are used to determine the time interval between the initiation of the transmitted pulse and the return of the reflected pulse.
  • a signal from transmitter 10 causes counter 60 to begin counting clock pulses when an infrared pulse is emitted by the transmitter; and a signal from receiver 20 causes counter 60 to stop counting when the reflected infrared pulse is received by receiver 20.
  • the count is then provided to data averager 70.
  • Data averager 70 stores a rolling record of a predetermined number (e.g. ten) of the most recent time records that occur within a predetermined time window. Upon receipt of a new reading, the least recent value is dropped from the record.
  • the time-of-flight is determined for pulses that are returned within a time window of approximately 8 nanoseconds from the initiation of the transmitted pulse.
  • the response is set to an arbitrarily high value by the averager 70, effectively indicating no collision when interpreted by system algorithms. Since the speed of light is approximately 1 foot per nanosecond, this effectively limits the unit of the preferred embodiment to a sensing distance of four feet.
  • the return signal time window, the number of time records that are averaged, and the pulse repetition rate can be adjusted as needed for final system configuration. While it is difficult to anticipate all the system configurations in which my invention may ultimately prove useful.
  • the invention would be practiced with a sensing distance in excess often feet which corresponds to a time window of approximately 20 nanoseconds.
  • the sensing distance should be in the range of about two to six feet and preferably about four feet.
  • the transmitter unit 10 is an infrared laser diode that produces a fast rise time pulse. Pulse width is of the order of one nanosecond or smaller. A beam width of approximately 10 degrees is formed. At a distance of four feet from the transmitter the beam width is about 8 inches.
  • the receiver 20 is a photodiode or avalanche photodiode, and the signal conditioner 30 produces a uniform response to reflected pulses that are received by the receiver.
  • the time reading constitutes the basic measured parameter that is used in system algorithms.
  • the time measured by each rangefinder unit is read, stored and utilized by the control unit 100 on a periodic basis. Illustratively, for a seven unit system, successive rangefinder units are polled at a 10 microsecond interval, requiring 70 microseconds for system update.
  • control unit 100 triggers the pulse transmitter 10 of each rangefinder unit so that each transmitter operates at a pulse repetition rate of 10 7 pulses per second.
  • control unit 100 polls averager 70 of each rangefinder unit to read its time data. This data is then stored at step 240 in memory at the control unit.
  • Time (interval between measurements) / [ (t N- ⁇ /t N ) - 1] where I is the most recent time measurement by the rangefinder.
  • Fig. 3 illustrates the concept of time-to-impact as a function of distance, for various closing velocities.
  • Fig. 3 indicates that at 60 mph, a decision must be made and the warning issued when 1.75 feet remain between the colliding objects, and at 14 mph a decision must be made and the warning issued by 0.41 feet.
  • Fig. 4 When viewed as a function of range, as shown in Fig. 4, at a distance of 4 feet from impact, 45 milliseconds are available to reach a decision and issue a warning at velocities of 60 mph and 195 milliseconds are available at closing velocities of 14 mph.
  • a decision that impact is about to occur can be made in about 10 to 20 milliseconds using a conventional microprocessor.
  • velocity is also calculated at step 250 and this resulting value is used at step 260 to adjust the time interval at which the rangefinder units are polled.
  • the polling interval is adjusted so that the rangefmders are polled more frequently at higher velocities.
  • the system advantageously has multiple warning or response levels. These levels are a function of time-to-impact. Accordingly, upon computing time-to- impact at step 250, the system then tests at step 270 if that time requires a specific warning or response and issues the warning or response if it does. Such warning might include various levels or types of audible alarms or flashing lights on the instrument panel. Different responses might include these warnings or activation of the braking system.
  • the system evaluates input from all the rangefmders to determine if a significant condition exists based on the time-to-impact, extent of the response of all units, and the sequence in which the individual units developed warning signals. If it determines that a serious collision is imminent, the system produces an output at step 290 that can be used to initiate deployment of the airbag system.
  • the output is provided about 10 to 40 milliseconds before collision occurs.
  • a system of seven rangefmders under the control of a single control module is mounted on the front of the host vehicle.
  • Sensor units are spaced approximately 8 inches apart along a contour line across the front of the vehicle at the approximate level of the head lamps. The beams project from the front of the vehicle forming a sensing barrier. Objects are detected within the volume out to about 4 feet from the sensor units. Target distance data from within this volume is collected by the transmission and reception of infrared pulses by transmitters 10 and receivers 20 and is analyzed by the system to determine if a collision will occur and to provide warning if required.
  • a similar system might be mounted on the rear of the host vehicle.
  • a typical system algorithm for use with the forwardly armed rangefmders might provide levels of warning corresponding to a projected collision when 5 of the 7 units indicate velocity of impact above 14 mph; for 3 contiguous units indicating velocity of impact above 25 mph; and for a single unit indicating velocity of impact above 40 mph.
  • the location of the impacted area along the front of the vehicle can be factored into algorithms for interpreting accelerometer data, permitting an earlier decision from these units.
  • a system of four transmitter/receiver units is mounted on the side panel of the front doors of the host vehicle.
  • the beams project out from the side of the vehicle forming a sensing barrier.
  • Objects are detected in the volume that extends out to 4 feet from the side of the vehicle. Again, target data from within this volume is collected and analyzed to determine if a collision will occur and to provide warning of a collision approximately 10 to 40 milliseconds before it occurs.
  • a typical system algorithm would provide levels of warning corresponding to at least 3 units indicating velocity of impact at or above 14 mph; or 2 units indicating velocity of impact above 25 mph.
  • the system determines time-of-flight and time-to-impact and assesses the situation on those determinations.
  • time-of-flight information can be stored as a time measurement or converted to a distance measurement by using the speed of pulses emitted by transmitter 10.
  • the running measurement that is stored by data averager 70 can be a running total or a running average. In either case the data is a measure of the location of the object that reflected the pulses.
  • time-to-impact seems preferable to use to determine the need for an alarm or activation of an airbag
  • distance and velocity information is also available and conceivably might be more readily used in some algorithms.
  • the data that is available for use by the system constitutes a measure of time-to-impact.
  • Other variations in the invention may be achieved by shifting more of the calculation and/or signal shaping effort from the rangefinder unit to the control unit.
  • the function of the data averager might readily be transferred to the processor.
  • Other variations will be apparent to those skilled in the art.
  • the system of the present invention comprises a main control unit 500 and at least one, and preferably several, rangefinder units 600.
  • Each rangefinder unit comprises a pulse transmitter, 410, a pulse receiver 420, a signal conditioner 430, a clock 440, a counter 450, an averager 460 and a range gate discriminator 470.
  • Control unit 500 sets the firing sequence of the individual units, stores data from the rangefinder units, provides system analysis and provides output for display of status in the display unit 700.
  • control unit 500 is a conventional microprocessor, microcontroller, or a digital signal processor.
  • Each individual rangefinder unit 600 measures the distance to objects in its sensing direction through the measurement of the time-of-flight of a short infrared pulse.
  • Each transmitter 410 projects a narrow beam infrared pulse and each receiver unit 420 detects reflected return pulses and provides initial amplification.
  • each transmitter operates at a pulse repetition rate of 60 kHz, so that a single pulse is emitted every 16.7 ⁇ seconds.
  • Return signals are amplified and gain adjusted in signal conditioner 430, in order to provide a uniform return signal for further analysis.
  • a digital clock 440 and a counter 450 are used to determine the time interval between the initiation of the transmitted pulse and the return of the reflected pulse.
  • a signal from transmitter 410 causes counter 450 to begin counting clock pulses when an infrared pulse is emitted by the transmitter; and a signal from receiver 420 through signal conditioner 430 causes counter 450 to stop counting when the reflected pulse is received by receiver 420.
  • the count is then provided to the data averager 460.
  • the data averager 460 collects and stores the average of a predetermined number of successive readings (e.g. ten).
  • the average reading is provided to the range gate 470, which tests the reading to determine if it falls within the preset sensing limits. If the output for any single one of the rangefinder units 600 represents a return signal from a distance which falls within the range gate window for that rangefinder, then the control unit 500 provides an indication in display unit 700 that an obstacle is within the sensing volume.
  • each transmitter unit 410 is an infrared laser diode that produces a fast rise time pulse. Pulse width is of the order of one nanosecond or smaller. A beam width of approximately 10 degrees is formed.
  • the receiver 420 is a photodiode or avalanche photodiode, and the signal conditioner 430 provides a uniform response to reflected pulses that are received by the receiver.
  • Display unit 700 has visual displays preferably utilizing light emitting diodes (LEDs) which indicate power on. no obstacle present in the sensing volume or obstacle present in the sensing volume. These conditions respectively are indicated by energized LEDs of yellow, green and red color, permitting instantaneous reading of sensing volume status.
  • the LEDs can be continuously lit or blinking.
  • the time reading of the transit time of the reflected pulse constitutes the basic measured parameter of the system.
  • the time measurement of each rangefinder is used as a measure of the distance to the obstacle that reflects the transmitted pulse.
  • control unit 500 triggers the pulse transmitter 410 of each rangefinder unit so that each transmitter operates at a pulse repetition rate of 6.0 x 10 4 pulses per second, for a predetermined number of pulses (e.g. ten).
  • a predetermined number of pulses e.g. ten.
  • an average time-of-flight is determined by the system averager 460.
  • the range gate discriminator 470 is applied to the time-of-flight determination to ascertain whether the measurement falls within the limits of the sensing volume for the path of that rangefinder unit.
  • the main control unit reads the range gate discriminator and provides an update in step 840 to the display unit 700.
  • the main control unit 500 repeats the process for the next rangefinder unit 600, and continuously provides update to the display unit 700. Since the system will provide an indication of an obstacle within the sensing volume, the response of the individual rangefinder units are independently considered by the main control unit and it is only necessary for a single unit to register an obstacle within its range gate for the main control unit to provide an indication of an obstacle present.
  • Fig. 9 illustrates the concept of the sensing volume that is covered with the system of this invention.
  • the rangefinder unit 600 and the display unit 700 are mounted in an enclosure 900 that fits beneath the side mirror and can be incorporated into the mirror structure.
  • the control unit 500 can also be mounted within the enclosure. A schematic outline drawing of enclosure 900 is shown in Fig. 10.
  • Fig. 3 What is depicted in Fig. 3 is a four beam system, each beam being shown with an approximate 8 degree width.
  • the lined area 850 corresponds to the sensing volume and the range gate for each individual beam is defined as the closest distance, D mm , and the farthest distance, D max , from the rangefinder 600, along the beam direction, that falls within the lined area. Since distance from the rangefinder unit is given by one-half the pulse transit time multiplied by the speed of light, D mm can be converted to a T min , according to the equation:
  • each beam has a unique range gate corresponding to its transverse of the sensing volume.
  • the range gate will be different for each rangefinder. For those that look sideways from the vehicle a minimum range distance of 3 feet is suitable. Maximum range for a sideways looking rangefinder is adjustable to suit driver preference and is typically about the width of one traffic lane. For those that look backwards it preferably will vary with the driver and driving conditions. However it should be sufficient to have a maximum range of 100 feet. Since the speed of light is approximately 1 foot per nanosecond, these distances correspond to a time range of 6 ns to 200 ns.
  • Fig. 9 shows the system as employed on the driver's side of the vehicle, it is readily apparent that a similar system can be deployed on the passenger side of the vehicle, as is also included within this invention.
  • a four beam system can be updated in less than one millisecond.
  • the system is essentially updated instantaneously.
  • Fig. 9 shows a four beam system it is readily apparent that the same system could be employed with a different number of beams, e.g. six beams instead of four.
  • the number of beams to be employed depends on the beam width and desired area of coverage, and many variations are apparent. Due to the size of the obstacles being detected it is not necessary to have 100 percent area coverage, and the precise percent of coverage is a design parameter of the system.
  • time-of-flight determines the time-of-flight and assesses the situation on that determination.
  • time-of- flight information can be stored as a time measurement or converted to a distance measurement by using the speed of the pulses emitted by the transmitter 410, i.e. the speed of light.
  • the measurement that is stored in the data averager 460 can be a running total or a running average. In either case the data is a measure of the location of the object that reflected the pulses.
  • the 60kHz frequency of the rangefinder can also be varied over a wide range of frequencies and the same result achieved.
  • rangefmders 600 are pulsed sequentially. As is also apparent, these rangefinder units can be operated continuously and sampled as required.
  • the invention may also be practiced in detecting possible collisions when backing up.
  • the circuitry can be the same as that of Fig. 1, and the pulse transmitters located so that they project a narrow beam infrared pulse to the rear of the vehicle.
  • the sensing range can be in the range of two to six feet and preferably four feet.
  • an adjustable sensing range For Example, in parking, it would be very useful to know how much distance there was between the front and/or rear bumpers of the driver's vehicle and those immediately before or after it. This information can be provided by a ranging system such as shown in Fig. 7 or by providing a device for adjusting the sensing distance with a calibrated scale that indicates the relationships between the sensing distance and the position of the device.

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Abstract

Method and apparatus relating to a system for sensing crash for a vehicle. The system is mounted on the vehicle and determines the time-to-impact for approaching obstacles that are within a limited distance for the host vehicle. The system comprises a main control unit (100) and at least, and preferably several, rangefinder units (200). Each rangefinder unit comprises a pulse transmitter (10), a pulse receiver (20), a signal conditioner (30), a threshold discriminator (40), a clock (50), a counter (60) and an averager (70). Each rangefinder (200) measures the distance to objects in its sensing direction through the measurement of the time-of-flight of a short infrared pulse. Each transmitter (10) projects a narrow beam infrared and each receiver unit (20) detects or receives reflected return pulses and provides initial amplification. A time-to-impact is determined based on the time-of-flight and it is determined whether a crash will occur based on the time-to-impact information.

Description

METHOD AND APPARATUS FOR PERIMETER SENSING FOR VEHICLES
Field of Invention
This relates to a method and apparatus for sensing around vehicles. It is particularly useful for predicting a collision, for initiating reactions in response to such a prediction and for sensing the presence of overtaking vehicles.
Background of the Invention
Present day automobiles rely on sensors to perform functions within many systems, including active safety systems which deploy airbags in the event of an accident. In addition there are passive systems such as side mirrors that provide critical information while operating an automobile. Limitations on both of these systems are presented herein.
Automobile airbag safety systems rely on sensors to provide indication during a crash that the crash is of sufficient severity to warrant the deployment of an airbag. These sensors are reactive in the sense that they can only measure the response of the car during the actual physical crash. The sensor system however, must provide adequate warning to permit airbag deployment. A general rule of performance is the "5 inch - 30 millisecond" rule: as a general norm, an airbag must be fully deployed after a travel of 5 inches in the front seat of the passenger compartment, where the travel is defined as the integration of the velocity change during the accident at the location of the passenger compartment. Since it takes approximately 30 milliseconds to deploy a passenger side airbag fully, the sensor system must provide an indication 30 milliseconds before the front seat has traveled 5 inches during the crash. In assessing this requirement it is helpful to recall that a vehicle traveling at 60 miles per hour is traveling at 88 feet per second or 0.88 feet per 10 milliseconds.
In addition to providing this advance indication, the sensor system must be capable of separating "must-fire" crashes from "no-fire" crashes, since not all crashes are severe enough to warrant the deployment of an airbag. Typically for a frontal crash, a velocity of 14 mph separates crashes requiring an airbag from those that do not require an airbag.
SUBSTITUTE SHEET (RULE 25) Sensors that are employed include mechanical, electromechanical and electronic devices. A mechanical sensor might involve the movement of a mass against a restraint arm. If the movement is sufficient, a spring loaded firing pin is released, puncturing a primer that initiates the airbag firing. In an electromechanical sensor, such as the ball-in-tube sensor, an electrical contact is closed if a magnetically restrained ball breaks free and closes the contacts of an external circuit. Both mechanical and electromechanical sensors are located near the point of initial contact, i.e. the front of the vehicle for frontal crashes. More than one sensor is usually required. In the mechanical and electromechanical sensor systems, the separation of "must- fire" crashes from "no-fire" crashes is accomplished with bias and damping parameters built into the sensor design, since these sensors are basically switches.
Electronic sensors rely on micromachined silicon capacitive or piezoresistive accelerometers. These sensors are typically located on a structural component close to the front of the passenger compartment, and measure the acceleration along the longitudinal axis of the car. The output of the electronic sensor is a voltage proportional to the acceleration along the axis of the vehicle. A microcontroller continually monitors the electronic sensor output and by means of a suitable algorithm determines if a crash is occurring and if it is severe enough to warrant airbag deployment.
Whereas mechanical and electromechanical systems typically require several sensors, some of which are located close to the front of the vehicle, and a system diagnostic unit, the electronic sensor can be configured as a single unit. Because of the advantages of this arrangement, the present industry trend is towards a single electronic sensor located on a structural component near the front of the passenger compartment.
The response of any sensing system is both vehicle specific and crash specific. While some vehicles and some crashes are relatively easy for the sensing system to diagnose, others are not. Two types of condition present particular difficulty: pole crashes and rough road conditions. In the case of pole crashes, it has been found that a pole can effectively slice through the front of the vehicle a considerable distance, using up valuable time, until the signature of a severe crash is recognized. In the latter case, rough roads can provide false indications of a crash. For side impact crashes, the situation is more severe since the extent of the vehicle between the impacting object and the vehicle interior is much less than frontal crashes, providing less time for interpretation of data and for an airbag deployment decision.
In addition to these considerations, potentially adverse consequences of full airbag deployment when passengers are out of position, are leading to the development of "smart" airbag systems that deploy on the basis of occupant size and position. Pretensioning of seat belt restraints and integration of seat belt systems with "smart" airbag systems is also under development.
Another source of collisions is a vehicle that is backing up. A common cause of such accidents is simply that the driver was not able to see all areas behind the vehicl while he was backing up.
Still another source of collisions is sideswipes between two vehicles moving alongside one another.
Present day vehicular traffic in many areas can often be characterized as high density and high speed. Multilane highways afford the opportunity for passing on both sides of a vehicle, and aggressive drivers commonly weave their way through traffic, changing lanes many times in the process. All this places demands on the driver to be aware of the surroundings and to be alert to changes which can happen quickly. It is also well known that side mounted mirrors have "blind spots" where overtaking vehicles may go undetected.
Summary of the Invention
With these considerations in mind, an advance warning of a crash would be of value in alerting the driver to the possibility of imminent collision and/or in preparing vehicle safety systems for an impact. A knowledge of where the contact will occur and the potential severity based on relative velocity would permit algorithms monitoring accelerometer based sensors to come to a decision at an earlier time during the actual crash. A predictive collision sensing system would provide this additional warning. Further, a predictive collision sensing system could provide advance warning of a high velocity impact in a limited area, which is characteristic of a pole crash, as well as an all clear signal across the front of a vehicle supporting a rough road determination by the safety system diagnostic unit. A predictive collision sensing system could also provide significant value for a vehicle side impact system, where response time requirements for reactive sensors are severe. A predictive collision sensing system could provide an early alert to safety restraint and "smart" airbag systems currently under development.
The method and apparatus of the present invention projects a sensing envelope outwards from the surface of the vehicle and detects objects, either stationary or mobile, that intrude into this volume. This sensing envelope is kept as close to the surface of the vehicle as is possible, e.g. on the order of two to six feet and preferably about four feet, to eliminate the requirements of processing extraneous signals and to eliminate the generation of false indications.
Preferably, the invention is implemented in a system comprising a control unit and multiple transmitting and sensing units that working together (1) locate approaching obstacles, (2) by time-of-flight analysis calculate the time-to-impact, and (3) provide indication of an imminent collision. This indication can then, for example, be used to actuate the airbags in a conventional airbag system.
Advantageously, the system is implemented using pulsed infrared laser transmitters; photodiode receiver circuits including amplification and signal conditioning; a digital clock for elapsed time measurement; and one or more digital signal processors or microprocessors for system control and algorithm realization.
In the case of airbag deployment systems limiting the sensing distance to close distances, e.g. four feet, removes the necessity for target tracking that is a characteristic of present collision avoidance systems. The technique and system described herein recognizes that the closer the decision is made to the surface of the vehicle, the more reliable the indication. With a decision being made at a distance of approximately two feet, the probability of a contact not occurring for velocities that would require an airbag is virtually zero, since the deceleration necessary to prevent a collision is beyond the capabilities of the vehicle operator. For example, at a distance of 2 feet from an obstacle and with a vehicle moving at 14 miles per hour, the lowest velocity of impact requiring a frontal airbag, the braking required to prevent collision is larger than 3 g's. Even though a decision is not made until this close approach has been realized, the warning of 10 to 40 milliseconds that is provided by the system of the present invention is still of value to occupant safety systems.
The limitation of sensing distances in the preferred embodiment to approximately four feet has additional advantages that include increased probability of receiving reflected signals, even under adverse weather conditions. It also permits operation of the pulsed infrared laser within power limits that will meet eye safety requirements under all conceivable conditions.
The invention may also be practiced in a system which could provide information to the driver prior to a lane change, on vehicles in the "blind spot" of the mirror system, to provide an additional measure of safety. Furthermore, if this system could be incorporated into or added onto the existing structure of the side mounted mirror and provide visual indication to the driver when the side mirror is viewed, then the device would require no additional driver actions beyond what is normally performed in a lane change.
In this application, the method and apparatus of the present invention detects the presence of objects within a sensing volume that encompasses the "blind spot" of the side mirrors provided on all vehicles. The "blind spot" of the side mirror system is a property of the vehicle body design, the mirror position and the viewing position of the vehicle operator. The sensing volume is defined as the volume covered by one or more sensing beams, each of which detects the presence of obstacles along its line of sight. The number of beams, directional orientation and beam width are arranged to provide indication of any obstacle above a minimum size corresponding to a motor vehicle or motorcycle, that may be present in the sensing volume, which itself covers the vehicle's "blind spot".
Preferably, the invention is implemented in a system comprising a control unit and multiple transmitting and sensing units that working together (1) locate objects along the lines-of- sight of the respective sensing elements, (2) by time-of-flight analysis calculate the distance to the sensed object, and (3) provide indication of objects within a predefined sensing envelope. Advantageously, the system is implemented using pulsed infrared laser transmitters, photodiode receiver circuits including amplification and signal conditioning, a digital clock for elapsed time measurement, one or more digital signal processors or microprocessors for system control and algorithm realization, and a display module for indication of sensing volume status.
The invention relies on the principle of the time-of-flight measurement of short infrared pulses to determine the distance, on a suitable algorithm to filter the result through a range gate corresponding to a selected range along the line of sight, and on multiple sensing beam to provide full target area coverage.
Additionally the system provides visual display at the location of the vehicle side mounted mirror permitting simultaneous viewing of the mirror image of the roadway and the indicator display of the present invention.
In similar fashion, the invention may also be used to sense nearby objects behind a vehicle while the vehicle is backing up.
Brief Description of Drawings.
These and other objects, features and advantages of the invention will be more readily apparent from the following detailed descriptions of the invention in which:
Fig.l is a block diagram illustrating a preferred embodiment of the invention;
Fig.2 is a flowchart depicting the processing of information within the system;
Fig 3 is a plot depicting time-to-impact as a function of closing velocity with isochrones for specific timεs-to-impact;
Fig. 4 is a plot depicting time-to-impact vs. distance for given closing velocities; Fig. 5. is a schematic depicting the invention mounted on the front of a vehicle; and
Fig. 6 is a schematic depicting the invention mounted on the side of the vehicle.
Fig. 7 is a functional block diagram of the preferred embodiment of the invention;
Fig. 8 is a flow chart illustrating the processing of information within the system;
Fig. 9 is a schematic depicting the area of coverage of a multiple rangefinder system; and
Fig. 10 is a schematic outline of the invention as appended to the side mirror structure.
Detailed Description of the Preferred Embodiments
For convenience, the application of the invention in the context of a collision detection and airbag deployment system will be described first. The modification necessary to use the system for detecting overtaking vehicles will then be described. Finally, the use of inventions in detecting imminent collisions while backing up will be described.
As shown in Fig. 1, the system of the present invention comprises a main control unit 100 and at least one, and preferably several, rangefinder units 200. Each rangefinder unit comprises a pulse transmitter 10, a pulse receiver 20, a signal conditioner 30, a threshold discriminator 40, a clock 50, a counter 60 and an averager 70.
Control unit 100 sets the firing sequence of the individual units, stores data from the rangefinder units, provides analysis of individual unit response and overall system response, and provides alarm signals for external safety systems. Illustratively, control unit 100 is a conventional microprocessor, microcontroller, or a digital signal processor.
Each individual rangefinder unit 200 measures the distance to objects in its sensing direction through the measurement of the time-of-flight of a short infrared pulse. Each transmitter 10 projects a narrow beam infrared pulse and each receiver unit 20 detects reflected return pulses and provides initial amplification. Illustratively, each transmitter operates at a pulse repetition rate of 10 MHz so that one pulse is emitted every 100 nanoseconds. Return pulses are amplified and gain adjusted in signal conditioner 30, in order to provide a uniform return signal for further analysis. A threshold/discriminator 40 may optionally be employed for further return signal control. A digital clock 50 and a counter 60 are used to determine the time interval between the initiation of the transmitted pulse and the return of the reflected pulse. In particular, a signal from transmitter 10 causes counter 60 to begin counting clock pulses when an infrared pulse is emitted by the transmitter; and a signal from receiver 20 causes counter 60 to stop counting when the reflected infrared pulse is received by receiver 20. The count is then provided to data averager 70. Data averager 70 stores a rolling record of a predetermined number (e.g. ten) of the most recent time records that occur within a predetermined time window. Upon receipt of a new reading, the least recent value is dropped from the record.
In the preferred embodiment of the invention the time-of-flight is determined for pulses that are returned within a time window of approximately 8 nanoseconds from the initiation of the transmitted pulse. For return signals of greater time delays, the response is set to an arbitrarily high value by the averager 70, effectively indicating no collision when interpreted by system algorithms. Since the speed of light is approximately 1 foot per nanosecond, this effectively limits the unit of the preferred embodiment to a sensing distance of four feet. Advantageously, the return signal time window, the number of time records that are averaged, and the pulse repetition rate can be adjusted as needed for final system configuration. While it is difficult to anticipate all the system configurations in which my invention may ultimately prove useful. I do not at this time anticipate that in the context of an automobile the invention would be practiced with a sensing distance in excess often feet which corresponds to a time window of approximately 20 nanoseconds. Advantageously, the sensing distance should be in the range of about two to six feet and preferably about four feet.
Advantageously, the transmitter unit 10 is an infrared laser diode that produces a fast rise time pulse. Pulse width is of the order of one nanosecond or smaller. A beam width of approximately 10 degrees is formed. At a distance of four feet from the transmitter the beam width is about 8 inches. Advantageously, the receiver 20 is a photodiode or avalanche photodiode, and the signal conditioner 30 produces a uniform response to reflected pulses that are received by the receiver. The time reading constitutes the basic measured parameter that is used in system algorithms. The time measured by each rangefinder unit is read, stored and utilized by the control unit 100 on a periodic basis. Illustratively, for a seven unit system, successive rangefinder units are polled at a 10 microsecond interval, requiring 70 microseconds for system update.
A flowchart depicting the operation of the system is set forth in Fig. 2. At step 220, control unit 100 triggers the pulse transmitter 10 of each rangefinder unit so that each transmitter operates at a pulse repetition rate of 107 pulses per second. At step 230, control unit 100 polls averager 70 of each rangefinder unit to read its time data. This data is then stored at step 240 in memory at the control unit.
Next at step 250, the control unit determines the time to impact. Time-to-impact is given by Time = ( Distance ) / ( Velocity) where Distance is equal to one-half the most recent time measurement by the rangefinder multiplied by the speed of light and Velocity is determined by dividing the difference between the two most recent measurements of Distance by the time interval between these measurements. Combining these terms, we have
Time = [ (1/2) c tN ] / { [ 1/2 c (tχ.ι - tN) ] / (interval between measurements) }
Time = (interval between measurements) / [ (tN-ι/tN) - 1] where I is the most recent time measurement by the rangefinder.
Fig. 3 illustrates the concept of time-to-impact as a function of distance, for various closing velocities. In order to provide a 20 millisecond warning before impact, Fig. 3 indicates that at 60 mph, a decision must be made and the warning issued when 1.75 feet remain between the colliding objects, and at 14 mph a decision must be made and the warning issued by 0.41 feet. When viewed as a function of range, as shown in Fig. 4, at a distance of 4 feet from impact, 45 milliseconds are available to reach a decision and issue a warning at velocities of 60 mph and 195 milliseconds are available at closing velocities of 14 mph. Illustratively, a decision that impact is about to occur can be made in about 10 to 20 milliseconds using a conventional microprocessor.
Advantageously, velocity is also calculated at step 250 and this resulting value is used at step 260 to adjust the time interval at which the rangefinder units are polled. In particular, the polling interval is adjusted so that the rangefmders are polled more frequently at higher velocities.
In addition, as indicated at step 270, the system advantageously has multiple warning or response levels. These levels are a function of time-to-impact. Accordingly, upon computing time-to- impact at step 250, the system then tests at step 270 if that time requires a specific warning or response and issues the warning or response if it does. Such warning might include various levels or types of audible alarms or flashing lights on the instrument panel. Different responses might include these warnings or activation of the braking system.
Next, at step 280 the system evaluates input from all the rangefmders to determine if a significant condition exists based on the time-to-impact, extent of the response of all units, and the sequence in which the individual units developed warning signals. If it determines that a serious collision is imminent, the system produces an output at step 290 that can be used to initiate deployment of the airbag system. Advantageously, the output is provided about 10 to 40 milliseconds before collision occurs.
As illustrated in Fig. 5, a system of seven rangefmders under the control of a single control module is mounted on the front of the host vehicle. Sensor units are spaced approximately 8 inches apart along a contour line across the front of the vehicle at the approximate level of the head lamps. The beams project from the front of the vehicle forming a sensing barrier. Objects are detected within the volume out to about 4 feet from the sensor units. Target distance data from within this volume is collected by the transmission and reception of infrared pulses by transmitters 10 and receivers 20 and is analyzed by the system to determine if a collision will occur and to provide warning if required. A similar system might be mounted on the rear of the host vehicle. A typical system algorithm for use with the forwardly armed rangefmders might provide levels of warning corresponding to a projected collision when 5 of the 7 units indicate velocity of impact above 14 mph; for 3 contiguous units indicating velocity of impact above 25 mph; and for a single unit indicating velocity of impact above 40 mph. In addition the location of the impacted area along the front of the vehicle can be factored into algorithms for interpreting accelerometer data, permitting an earlier decision from these units.
In Fig. 6, a system of four transmitter/receiver units is mounted on the side panel of the front doors of the host vehicle. The beams project out from the side of the vehicle forming a sensing barrier. Objects are detected in the volume that extends out to 4 feet from the side of the vehicle. Again, target data from within this volume is collected and analyzed to determine if a collision will occur and to provide warning of a collision approximately 10 to 40 milliseconds before it occurs.
In the embodiment of Fig. 6 a typical system algorithm would provide levels of warning corresponding to at least 3 units indicating velocity of impact at or above 14 mph; or 2 units indicating velocity of impact above 25 mph.
In the preferred embodiment, the system determines time-of-flight and time-to-impact and assesses the situation on those determinations. As will be apparent, the relationship between distance, velocity and time makes it possible to use distance and velocity determinations to achieve the same result and such usage will be recognized as the equivalent of the use of time-of- flight and time-to-impact. For example, time-of-flight information can be stored as a time measurement or converted to a distance measurement by using the speed of pulses emitted by transmitter 10. And the running measurement that is stored by data averager 70 can be a running total or a running average. In either case the data is a measure of the location of the object that reflected the pulses. Similarly, while time-to-impact seems preferable to use to determine the need for an alarm or activation of an airbag, distance and velocity information is also available and conceivably might be more readily used in some algorithms. In all these cases, however, the data that is available for use by the system constitutes a measure of time-to-impact. Other variations in the invention may be achieved by shifting more of the calculation and/or signal shaping effort from the rangefinder unit to the control unit. For example, the function of the data averager might readily be transferred to the processor. Other variations will be apparent to those skilled in the art.
Similar apparatus may also be used to detect overtaking cars. As shown in Fig. 7, the system of the present invention comprises a main control unit 500 and at least one, and preferably several, rangefinder units 600. Each rangefinder unit comprises a pulse transmitter, 410, a pulse receiver 420, a signal conditioner 430, a clock 440, a counter 450, an averager 460 and a range gate discriminator 470.
Control unit 500 sets the firing sequence of the individual units, stores data from the rangefinder units, provides system analysis and provides output for display of status in the display unit 700. Illustratively, control unit 500 is a conventional microprocessor, microcontroller, or a digital signal processor.
Each individual rangefinder unit 600 measures the distance to objects in its sensing direction through the measurement of the time-of-flight of a short infrared pulse. Each transmitter 410 projects a narrow beam infrared pulse and each receiver unit 420 detects reflected return pulses and provides initial amplification. Illustratively, each transmitter operates at a pulse repetition rate of 60 kHz, so that a single pulse is emitted every 16.7 μseconds. Return signals are amplified and gain adjusted in signal conditioner 430, in order to provide a uniform return signal for further analysis. A digital clock 440 and a counter 450 are used to determine the time interval between the initiation of the transmitted pulse and the return of the reflected pulse. In particular, a signal from transmitter 410 causes counter 450 to begin counting clock pulses when an infrared pulse is emitted by the transmitter; and a signal from receiver 420 through signal conditioner 430 causes counter 450 to stop counting when the reflected pulse is received by receiver 420. The count is then provided to the data averager 460. The data averager 460 collects and stores the average of a predetermined number of successive readings (e.g. ten). The average reading is provided to the range gate 470, which tests the reading to determine if it falls within the preset sensing limits. If the output for any single one of the rangefinder units 600 represents a return signal from a distance which falls within the range gate window for that rangefinder, then the control unit 500 provides an indication in display unit 700 that an obstacle is within the sensing volume.
Advantageously, each transmitter unit 410 is an infrared laser diode that produces a fast rise time pulse. Pulse width is of the order of one nanosecond or smaller. A beam width of approximately 10 degrees is formed. Advantageously, the receiver 420 is a photodiode or avalanche photodiode, and the signal conditioner 430 provides a uniform response to reflected pulses that are received by the receiver.
Display unit 700 has visual displays preferably utilizing light emitting diodes (LEDs) which indicate power on. no obstacle present in the sensing volume or obstacle present in the sensing volume. These conditions respectively are indicated by energized LEDs of yellow, green and red color, permitting instantaneous reading of sensing volume status. The LEDs can be continuously lit or blinking.
The time reading of the transit time of the reflected pulse constitutes the basic measured parameter of the system. The time measurement of each rangefinder is used as a measure of the distance to the obstacle that reflects the transmitted pulse.
A flowchart depicting the operation of the system is set forth in Fig. 8. At step 800, control unit 500 triggers the pulse transmitter 410 of each rangefinder unit so that each transmitter operates at a pulse repetition rate of 6.0 x 104 pulses per second, for a predetermined number of pulses (e.g. ten). At step 810. an average time-of-flight is determined by the system averager 460. At step 820, the range gate discriminator 470 is applied to the time-of-flight determination to ascertain whether the measurement falls within the limits of the sensing volume for the path of that rangefinder unit. At step 830 the main control unit reads the range gate discriminator and provides an update in step 840 to the display unit 700. The main control unit 500 repeats the process for the next rangefinder unit 600, and continuously provides update to the display unit 700. Since the system will provide an indication of an obstacle within the sensing volume, the response of the individual rangefinder units are independently considered by the main control unit and it is only necessary for a single unit to register an obstacle within its range gate for the main control unit to provide an indication of an obstacle present. Fig. 9 illustrates the concept of the sensing volume that is covered with the system of this invention. In the preferred embodiment, the rangefinder unit 600 and the display unit 700 are mounted in an enclosure 900 that fits beneath the side mirror and can be incorporated into the mirror structure. The control unit 500 can also be mounted within the enclosure. A schematic outline drawing of enclosure 900 is shown in Fig. 10.
What is depicted in Fig. 3 is a four beam system, each beam being shown with an approximate 8 degree width. The lined area 850 corresponds to the sensing volume and the range gate for each individual beam is defined as the closest distance, Dmm, and the farthest distance, Dmax, from the rangefinder 600, along the beam direction, that falls within the lined area. Since distance from the rangefinder unit is given by one-half the pulse transit time multiplied by the speed of light, Dmm can be converted to a Tmin, according to the equation:
I mm — _£ X J mln )/ C where c is the speed of light and Dmιn is the desired minimum range, and Tm,n is the corresponding minimum transit time.
A similar equation can be written for the maximum transit time interval.
As can be seen from Fig. 9, each beam has a unique range gate corresponding to its transverse of the sensing volume. The range gate will be different for each rangefinder. For those that look sideways from the vehicle a minimum range distance of 3 feet is suitable. Maximum range for a sideways looking rangefinder is adjustable to suit driver preference and is typically about the width of one traffic lane. For those that look backwards it preferably will vary with the driver and driving conditions. However it should be sufficient to have a maximum range of 100 feet. Since the speed of light is approximately 1 foot per nanosecond, these distances correspond to a time range of 6 ns to 200 ns.
Although Fig. 9 shows the system as employed on the driver's side of the vehicle, it is readily apparent that a similar system can be deployed on the passenger side of the vehicle, as is also included within this invention. With each beam operated at 60 kHz, and using as an example ten successive pulses to define an averaged reading, it can be seen that a four beam system can be updated in less than one millisecond. An overtaking vehicle, closing at a relative speed of 40 miles per hour as an example, reduces the distance at a rate of less than one inch per millisecond. The system is essentially updated instantaneously.
While Fig. 9 shows a four beam system it is readily apparent that the same system could be employed with a different number of beams, e.g. six beams instead of four. The number of beams to be employed depends on the beam width and desired area of coverage, and many variations are apparent. Due to the size of the obstacles being detected it is not necessary to have 100 percent area coverage, and the precise percent of coverage is a design parameter of the system.
In the preferred embodiment, the system determines the time-of-flight and assesses the situation on that determination. As will be apparent, the relationship between time and distance and velocity makes it possible to use distance determinations to achieve the same result and such usage will be recognized as the equivalent of the use of time-of-flight. For example, time-of- flight information can be stored as a time measurement or converted to a distance measurement by using the speed of the pulses emitted by the transmitter 410, i.e. the speed of light. And the measurement that is stored in the data averager 460 can be a running total or a running average. In either case the data is a measure of the location of the object that reflected the pulses.
As is also apparent, the 60kHz frequency of the rangefinder can also be varied over a wide range of frequencies and the same result achieved.
As described the rangefmders 600 are pulsed sequentially. As is also apparent, these rangefinder units can be operated continuously and sampled as required.
Other variations in the invention may be achieved by shifting more of the calculation and/or signal processing effort from the rangefinder 600 to the control unit 500. For example, the function of the data averager 460 and range gate discriminator 470 might readily be transferred to the control unit 500. Furthermore the operation of the system and the optics of the receiver units 420 may permit use of a single receiver unit 420 by multiple transmitter units 410. It is also possible to locate the rangefinder units 200 within the tail light assembly with the display unit 700 located at the side mirror position. Other variations will be apparent to those skilled in the art.
The invention may also be practiced in detecting possible collisions when backing up. In this case, the circuitry can be the same as that of Fig. 1, and the pulse transmitters located so that they project a narrow beam infrared pulse to the rear of the vehicle. Again, the sensing range can be in the range of two to six feet and preferably four feet.
It may also be possible to provide for an adjustable sensing range. For Example, in parking, it would be very useful to know how much distance there was between the front and/or rear bumpers of the driver's vehicle and those immediately before or after it. This information can be provided by a ranging system such as shown in Fig. 7 or by providing a device for adjusting the sensing distance with a calibrated scale that indicates the relationships between the sensing distance and the position of the device.
As will be apparent to those skilled in the art, my invention may be practiced in numerous variations of the specific embodiment disclosed herein. The operating parameters given are only illustrative and are intended to be conservative. Other parameters can be used.

Claims

What is Claimed is
1. A predictive crash sensing system comprising: a rangefinder comprising: a transmitter of pulses of electromagnetic radiation; a receiver that receives radiation pulses transmitted from the transmitter and reflected by an object; and a timing device for determining a time-of-flight of pulses transmitted by said transmitter and received by said receiver where the time-of-flight is less than approximately 20 nanoseconds; means for determining a time-to-impact from the time-of-flight of two pulses and the time between such pulses; and means for determining if a crash will occur from the time-to-impact information.
2. The system of claim 1 further comprising means for activating an airbag deployment system in response to a determination made from the time-to-impact information.
3. The system of claim 1 further comprising means for activating a braking system in response to a determination made from the time-to-impact information.
4. The system of claim 1 further comprising a data averager that maintains a running average of time-of-flight information.
5. The system of claim 1 further comprising a plurality of rangefmders wherein the means for determining if a crash will occur considers information from each rangefinder in making its determination.
6. The system of claiml further comprising a plurality of rangefmders wherein the means for determining if a crash will occur considers information from at least two rangefmders in making its determination.
7. The system of claim 1 wherein the time-of-flight is less than approximately 8 nanoseconds.
8. The system of claim 1 wherein the transmitter is an infrared transmitter.
9. A method for predicting a crash comprising the steps of: transmitting from a moving vehicle pulses of electromagnetic radiation; receiving said pulses at the moving vehicle after they are reflected from an object; determining a time-of-flight for the received pulses where the time-of-flight is less than approximately 20 nanoseconds; determining a time-to-impact from the time-to-flight of two pulses and the time between such pulses; and determining if a crash will occur from the time-to-impact information.
10. The method of claim 9 further comprising the step of activating an airbag deployment system in response to a determination made from time-to-impact information.
11. The method of claim 9 further comprising the step of activating a braking system in response to a determination made from time-to-impact information.
12. The method of claim 9 wherein the time-of-flight is less than approximately 8 nanoseconds.
13. A method for predicting a crash comprising the steps of: transmitting from a moving vehicle pulses of electromagnetic radiation, receiving said pulses at the moving vehicle after they are reflected from an object, determining a measure of the distance to the object where the distance to the object is less then approximately ten feet ( three meters), determining a measure of time-to-impact from at least two measures of the distance and time between such measurements of distance and, determining if a crash will occur from the measure of time-to-impact.
14. The method of claim 13 further comprising the step of activating an airbag deployment system in response to a determination made from the measure of time-to-impact.
15. The method of claim 13 further comprising the step of activating a braking system in response to a determination made from the measure of time-to-impact.
16. A system for detecting an external obstacle within a specific volume on a side of a vehicle comprising: a rangefinder comprising: a transmitter of pulses of electromagnetic radiation; a receiver that receives radiation pulses transmitted from the transmitter and reflected by said obstacle; and a timing device for determining a time-of-flight of pulses transmitted by said transmitter and received by said receiver where the time-of-flight is less than approximately 200 nanoseconds; means for determining if the distance to said obstacle falls within a preset range between a lower distance bound and an upper distance bound; and a display for displaying the results of the determination to the operator of the vehicle.
17. The system of claim 16 further comprising a data averager that maintains a running average of time-of-flight information.
18. The system of claim 16 further comprising a plurality of rangefinders wherein the means for determining if an object is within the sensing volume considers information from each rangefinder in making its determination.
19. The system of claim 16 wherein the transmitter is an infrared transmitter.
20. A method for detecting an external object within a specific volume on a side of a vehicle comprising the steps of: transmitting from the vehicle pulses of electromagnetic radiation; receiving said pulses at the vehicle after they are reflected from said object; determining a time-of-flight for the received pulses where the time-of-flight is less than approximately 200 nanoseconds; determining if an external object is present within a predefined volume by consideration of time-of-flight information; and displaying to an operator of the vehicle an indication whether an external object is present within the predefined volume.
21. A method for detecting an external object within a specific volume on a side of a vehicle comprising the steps of: transmitting from the vehicle pulses of electromagnetic radiation; receiving said pulses at the vehicle after they are reflected from said object; determining a measure of distance to said object where the distance to the object is less than approximately 100 feet; and determining if an external object is present within a predefined volume by consideration of the distance information; and displaying to an operator of the vehicle an indication whether an external object is present within the predefined volume.
PCT/US1998/017533 1997-08-26 1998-08-25 Method and apparatus for perimeter sensing for vehicles WO1999010803A1 (en)

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US08/918,826 US6012008A (en) 1997-08-26 1997-08-26 Method and apparatus for predicting a crash and reacting thereto
US08/918,826 1997-08-26
US96463997A 1997-11-05 1997-11-05
US08/964,639 1997-11-05

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