WO2001057553A1

WO2001057553A1 - Laser distance meter for use in an anti-collision systems

Info

Publication number: WO2001057553A1
Application number: PCT/EP2000/006145
Authority: WO
Inventors: Joachim Tiedecke; Egbert Ronald Ivo Casimir Visscher
Original assignee: Idm Gmbh Infrarot Sensoren
Priority date: 2000-01-31
Filing date: 2000-07-01
Publication date: 2001-08-09
Also published as: AU5822800A; DE10004010A1; EP1315982A1

Abstract

The invention relates to a sensor configuration for devices (1) that can be displaced substantially in a linear manner along a trajectory (2). Said sensor configuration comprises at least one first distance meter (6) that measures the distance in the sense of the trajectory (2) and that determines the distance to a neighboring object (3) on the basis of the propagation time of an impulse sent along the measuring beam (7). A second distance meter (8) determines the position of the device (1) relative to the marks (4) provided along the trajectory.

Description

Laser rangefinder for anti-collision applications

The present invention relates to a sensor arrangement with the features of the preamble of claim 1 and a method for operation along a track device.

Generic sensor arrangements are known, for example, as distance sensors for cranes from the prior art. Distance sensors are used to determine the distance of the crane from the end point of a crane runway or the distance of the crane from a second crane traveling on the same crane runway in overhead cranes or trolleys and to influence the motor control of the crane in such a way that the travel speed of the crane falls below a minimum distance Crane lowered or the crane is finally stopped completely. The known sensor arrangements work Usually with a light beam in the infrared range, the transit time of which is measured to a reflector attached to the opposite object, which gives the distance directly.

Other known sensors detect a ruler made of markings along the track, in which either the markings are paid off and the sensor calculates the position from a starting position in this way, or a so-called gray code is applied, in which the sensor also without the reference an anchor point can determine within a certain accuracy where the sensor is currently.

With the transit time sensors, especially with long crane runways outdoors, there is occasionally the problem that the visibility can be impaired. With the cranes, some of which are several hundred meters long, for example in fog, the signal is completely lost and the associated safety function fails. D It also applies when using infrared light, where the range is approximately twice the optical range. Such conditions occur relatively frequently, particularly in port areas.

Incremental sensors are not subject to any restrictions due to limited visibility in fog, but in the simple version, in which only markings from a measuring tape are paid, they require a referencing run at the start of the respective measurement, in which the end stop is detected. This occurs, for example, in the event of a power failure. The coding of crane runways using the gray code method is complex and correspondingly expensive, since the coding must enable a clear position determination over the entire length of the crane runway.

It is therefore an object of the present invention to provide an apparatus and a method in which technically relatively simple sensor means enable high accuracy, no homing run is required at the start of a measurement or power failure, and the use of simple markings along the crane track is sufficient.

This object is achieved by a sensor arrangement with the features of claim 1. Because, in addition to the range finder for the absolute distance to an adjacent object, a second range finder is provided on the basis of the travel time, which detects a position of the device relative to markings arranged on the track, at the start of a measurement via the travel time sensor, this can initially be done with the inherent accuracy Sensor position can be determined. The exact position with an accuracy in the range of a few millimeters can then be detected via the incremental sensor. If the visibility conditions deteriorate during operation, the incremental sensor can continuously track and determine the position by counting up or down the path markings, even if the transit time sensor is interrupted. The incremental sensor can work in a particularly simple manner with individual markings along the path and does not require any coding, since the initial information is transmitted by the runtime sensor. The second sensor is preferably an incremental sensor, which has a position-resolving detector means and optics for projecting the markings onto the detector means. With these features, relatively inexpensive sensors can be implemented, which nevertheless achieve an accuracy in the range of 1 mm. Updating the location when the transit time sensor is interrupted is particularly easy if the markings are arranged at regular intervals, for example m intervals of one meter each. Furthermore, the markings can be assigned to specific objects along the track and, if necessary, be arranged at irregular distances if the absolute value from the end point is not the value to be determined, but a relative position to the marked object is to be approached. Such a requirement exists, for example, for elevators that have to move to a defined position with respect to a floor level of a building.

It can further be provided that the first and / or the second range finder is provided to transmit data with the measuring beam. In the case of two cranes that use a common crane runway, the information about the position, speed and relative distance of the cranes can be present in each of the two cranes. If one sensor system fails, the other sensor system can determine the complete movement data of both cranes and keep them redundant.

In a specific embodiment, it can be provided that a common evaluation means is provided for the first and the second range finder. This evaluation means can then determine the position from both signals with great reliability and accuracy calculate. It can further be provided that the first range finder or a third range finder measures the distance to an object that is also movable along the runway, for example a second overhead crane, and the position of the movable object is transmitted to the first range finder or to the evaluation means. In this case, there is information about the distance to a fixed reference point as well as information about the distance to the next relatively movable object. It can further be provided that the evaluation means is set up to compare those of the first and the second rangefinder and possibly the third rangefinder and the absolute position, speed and / or acceleration of the device on the track and possibly the distance to an adjacent one to calculate moving object. In this embodiment, the complete movement variables of the movable device are determined, and knowing the applicable constants, the maximum dynamics of the system can be fully exploited in any state.

In a method according to the invention for operating a device which can be moved along a track and having at least one sensor arrangement of the type described above, the following is provided:

a) determining the absolute position of the device on the track on the basis of the first range finder with a measurement error of less than half the distance between two adjacent markings; and b) determine the relative position of the device to the closest marking with a smaller measurement error than in step a).

With this method, a clear identification of the closest marker is possible on the basis of the first range finder. The exact position relative to this marking can be determined with the second range finder. The position of a device along a track is thus clearly defined. In this case, steps a) and b) are preferably carried out synchronously, which avoids following errors which would lead to differences in the measurement result if the steps were carried out sequentially without compensation.

If it is further provided that the absolute position of the device is determined from the combination of the results of steps a) and b) and a known position of the markings, then the absolute value of the distance between the device and a fixed reference point, for example the end the crane runway or an elevator shaft, can be clearly determined with high accuracy. If, in addition, the determination of the complete movement data (location, speed, acceleration) of the device is provided, the full speed and acceleration or braking potential can be exhausted when the device is moved.

If it is further provided to transmit the movement data and / or the distance to an adjacent, essentially similar device to the adjacent device, the movement data of the neighboring device in a calculation of the possible movements in terms of speed, acceleration and braking. In this way, even if the two devices move towards each other, the full speed potential available can be used.

In addition, it can be provided to control a drive of the device in such a way that a collision with the ends of the raceway and / or the adjacent similar device is excluded. The automatic or semi-automatic operation of devices equipped in this way is thus possible.

An advantageous application of the sensors and methods described so far results in particular for overhead traveling cranes, elevators and forklifts for high-bay warehouses.

Exemplary embodiments of the present invention are described below with reference to the drawing.

Show it:

Figure 1: A single overhead crane with two

Rangefinders on a transit time or incremental basis;

Figure 2: two overhead cranes with the invention

Sensor arrangement on a common track; such as

Figure 3: a crane system with a total of three

Overhead cranes on a common crane runway. 1 shows a overhead crane 1 m from a top view. The overhead crane 1 can be moved linearly along a crane runway 2. An optical reflector 3 is arranged at an end of the track 2. Next to the side of the crane runway 2 there is a scale of markings 4 arranged in an aquidistant manner.

The crane itself carries a first range finder 6, which determines the distance to the reflector 3 by emitting a pulsed measuring beam 7 along a measuring section. Furthermore, a second range finder 8 is provided, which determines the position relative to the closest marking 4 by emitting a continuous measuring beam 9. Furthermore, the first range finder 6 and the second range finder 8 are connected via connection lines 10 to a common control 11, which in turn also contains the motor control (not shown) of the overhead crane 1.

In operation, the distance of the crane 1 from the reflector 3 is determined via the first range finder 6 by emitting the measuring beam 7 and its transit time to the reflector 3 and back. This distance is determined with an accuracy that is better than half the distance between the two markings 4. The second range finder 8 sends the, for example, continuous measuring beam 9 to the markings, which in turn are formed by line-shaped retroreflectors. The next marker 4 reflects the light of the measuring beam 9 and is imaged via optics, for example on a CCD line, the resolution of which with 256 pixels enables an accuracy of 1 mm if the markers are at a distance of one meter from one another. The controller 11 Now determines in the vicinity of which mark 4 the crane is located, while the information given by the second range finder 8 gives the exact position of the crane 1 with respect to the individual mark 4. Both information are evaluated together with the knowledge of the distance of the individual markings from the end of the track 2 and thus result in the exact, millimeter-precise position of the overhead crane 1 on the track 2. These measurements are continuously continued, so that even when the measuring beam 7 is interrupted Position can be determined continuously based on the counting of the individual markings 4.

2 shows an arrangement of two bridge cranes 1 and 1 ^λ is shown, wherein like elements bear like designations as in FIG. 1 The corresponding components assigned to the second overhead traveling crane 1 are each identified by a line. In addition to the illustration according to FIG. 1, the crane 1 carries a third range finder 13, which emits a measuring pulse to a reflector 15 along a measuring beam 14. The reflector 15 is fixedly arranged on the second overhead crane 1. In a corresponding manner, a third range finder 13 ^{λ of} the second overhead crane 1 ^{Λ is} aligned with the first overhead crane 1 and sends a signal along the measuring section 14 to the reflector 15 ^λ , which in turn is arranged on the first overhead crane 1. The second overhead crane 1 determines its position thereby to by a measuring beam 7 directed ^λ relative to the reflector 3 opposite end of the track 2 to a fixed reflector 3 ^λ and the duration of a pulse is measured. In this device, each of the cranes 1, 1 ^Λ can first determine its absolute position relative to the reflector 3 or 3 ^Λ with the first range finder 6, 6 ^Λ as described in connection with FIG. 1. The relative position to a marking 4 is determined by a range finder 8, 8 ', which works incrementally. For each control 11, 11 'm this clearly results in the exact position of the traveling crane 1, 1 ^Λ on the running track 2 without having to carry out a homing run.

The relative distance of the traveling cranes 1, 1 to one another is determined by the respective third range finder 13, 13 ^λ with reference to the opposite reflector 15, 15 ^Λ , so that here too, knowledge of the movement data of the cranes 1, 1 provides complete information about in the frame permissible movements are present in the safety area and the crane controller 11, 11 ^x can automatically move the crane 1, l ^λ when required and in particular can brake it. Since all measuring data present on the cranes 1, 1 are transmitted from the range finder 13, 13 ^Λ to a data receiver 16, 16 ^integrierten integrated in the reflector 15, 15 ^λ via the measuring beams 14, 14 ^λ , in particular if one of the sensors 6, 6 fails, 8, 8 ^Λ or 13, 13 'still provide all information about the movement of both cranes from the system that has remained intact. The information determined from three sensors is sufficient to completely solve the complete equations of motion. In this respect there is full redundancy of the sensor system.

In FIG. 3, a further system with a total of three overhead cranes on a runway 2 is provided. With these three cranes are provided essentially the same elements as in Figure 2. The third crane is marked with its associated components with two lines.

The two outer cranes 1, l ^λ> point in the figure 2 each have a first distance meter 6, ^6, for determining the distance to an opposing, fixed reflector 3, 3 and an incremental sensor with a second range finder 8, ^{8, Λ} on. The mean crane 1 ^λ has next to the incremental sensor 8 comprises a first distance meter 13 and a second ^Λ ^Λ rangefinder 23, which, more specifically, measures the relative distance to the respective opposite crane 1, l ^λΛ to the reflector 15 25th

In this system, each of the two outer traveling cranes can determine its absolute position on the running track 2 with an accuracy of a few millimeters, as described in connection with FIG. Only the middle crane can determine with the range finders 13 ^λ , 23 ^Λ only the distance relative to the neighboring cranes 1, 1 ^, and determine the position of the measuring beam 9 ^Λ with respect to a marking 4. To calculate an absolute position on the runway 2, the respective current position of at least one neighboring crane 1, 1 must be transmitted.

In this system, too, the movement data relevant to each crane are determined several times, namely once by the crane itself (or by its control 11, 11 ^λ , 11 ^Λ ) and on the other hand by the neighboring crane, which, in addition to its own movement data, the distance destined for the neighboring crane. A data transfer from one Crane to next consequently ensures that the neighboring crane also receives a complete set of movement data which remains available even if one or more sensors fail.

The design of the sensors and the described methods ensure that the crane control is ensured in such a way that the positions can be reliably determined even when visibility is impaired. The movement data required for safe control of the crane on the one hand and for maximum utilization of the possible speeds and accelerations of the cranes on the other hand, which ultimately lead to the solution of the movement equations, are available in full and multiple redundancy. In this respect, the crane control can work semi-automatically or fully automatically even under adverse conditions and with protection against malfunctions. Impairment of performance through unnecessary interventions in crane travel is avoided.

An embodiment corresponding to the example depicted in FIG. 1 can also be provided, for example, for lifts in which a range finder determines the absolute height of the car in relation to the floor of the elevator shaft. A second incremental sensor measures the relative orientation of the elevator car with respect to a marking assigned to the respective floor. So the elevator can move to a floor at high speed and brake before reaching the floor marking to stop at that floor. If the floor marking then comes into view of the incremental sensor, i.e. the second range finder, the position can be resolved with millimeter accuracy and the elevator with it great accuracy and great speed can be stopped exactly at the desired position. The floor height of the building can be variable with this sensor system for lifts. The exact distance between the markings does not matter. For example, the mark as a reflective strip can already be applied by the elevator manufacturer to the respective door frame without it being important for exact positioning. In particular, the elevator can also continue to be operated in an emergency operation program if one of the two sensors fails. If the first rangefinder, which determines the absolute distance to the floor of the elevator shaft, fails, the elevator can continue to be operated without compromising comfort by paying up or down the markings as the elevator drives past, thus continuously tracking the position of the elevator. Only the elevator travel will be carried out at a lower speed than the maximum possible, so that the elevator cabs can be braked in time for reaching the intended stopping point. If the second rangefinder, ie the incremental sensor, fails, the positioning of the elevator with respect to the respective floor level is impaired, so that a step can arise in the elevator exit. This does not affect the safety of elevator operation.

Claims

P a te nt to talk

1. Sensor arrangement for devices (1) which can be moved essentially linearly along a path (2), with at least one first distance meter (6) measuring in the direction of the path (2), which measures the distance to an adjacent object (3) on the basis of the transit time of a pulse emitted along a measuring beam (7), since you are characterized by the fact that a second range finder (8) is provided which detects a position of the device (1) relative to the markings (4) arranged on the track (2) ) certainly.

2. Sensor arrangement according to claim 1, since you r c h ge k e nn z e i ch n e t that the second sensor (8) is an incremental sensor, which has a spatially resolving detector means and an optical system for projecting the markings (4) onto the detector means.

3. Sensor arrangement according to one of the preceding claims, since you r ch ge k enn z e i c hn e t that the markings (4) are arranged at regular intervals.

4. Sensor arrangement according to one of the preceding claims 1 to 3, since you r ch ge ke nn zei ch n t that the markings (4) are assigned to certain objects along the track (2) and may be arranged at irregular intervals.

5. Sensor arrangement according to one of the preceding claims, since you r ch ge k e n n z e i chn e t that the first and / or the second range finder (6,8) is set up to transmit data with the measuring beam (7).

6. Sensor arrangement according to one of the preceding claims, that a common evaluation means (11) is provided for the first and the second range finder (6, 8).

7. Sensor arrangement according to one of the preceding claims, characterized in that the first range finder (6) or a third range finder (13) measures the distance to a likewise along the track (2) movable object (1 ^Λ ) and the position of the movable object ( l) is transmitted to the first range finder (6) or to the evaluation means (11).

8. Sensor arrangement according to one of the preceding claims, characterized in that the evaluation means (11) is set up to compare the values determined by the first and the second range finder (6, 8) and possibly the third range finder (13) and the absolute Position, speed and / or acceleration of the device (1) on the track (2) and, if necessary, calculate the distance to an adjacent moving object (l ^λ ).

9. Method of operating along a running track

(2) movable device (1) with at least one sensor arrangement (6, 8) according to one of the preceding claims, with the following steps:

a. Determining the absolute position of the device (1) on the track (2) on the basis of the first range finder (6) with a measurement error of less than half the distance between two adjacent markings (4);

b. Determining the relative position of the device (1) to the closest marking with a smaller measurement error than in step a).

10. The method according to claim 9, since you have to ensure that steps a) and b) are carried out simultaneously.

11. The method according to any one of the preceding claims, since you r ch ge k n e z e i chn e t that the following step is provided:

c. Determining the absolute position of the device (1) from the combination of the results of steps a) and b) and a known position of the markings (4).

12. The method according to any one of the preceding claims, characterized in that the following step is provided: d. Determine the complete movement data

(Location, speed, acceleration) of the device (1).

13. The method of claim 12, d a d u r c h g e k e n n z e i c h n e t that the following step is provided:

e. Transmission of the movement data and / or the distance to an adjacent essentially similar device (l ^Λ , l ^Λ ) to the adjacent device.

14. The method according to any one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the following step is provided:

f. Control of a drive of the device (1) in such a way that a collision with ends of the track and / or the adjacent similar device (l ^λ , l ^{, Λ} ) is excluded.

15. The method according to any one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the following step is provided:

G. Control of a drive of the device (1) in such a way that a certain position along the track is approached with high accuracy, the accuracy being better than 1 cm, in particular being at or below 1 mm.

16. Sensor arrangement or method according to one of the preceding claims, since you r ch characterized in that the device is an elevator, an overhead crane or a stacker of a high-bay warehouse.