WO2006119764A1 - Determination of the position of an object - Google Patents

Determination of the position of an object Download PDF

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Publication number
WO2006119764A1
WO2006119764A1 PCT/DK2005/000323 DK2005000323W WO2006119764A1 WO 2006119764 A1 WO2006119764 A1 WO 2006119764A1 DK 2005000323 W DK2005000323 W DK 2005000323W WO 2006119764 A1 WO2006119764 A1 WO 2006119764A1
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WO
WIPO (PCT)
Prior art keywords
station
tracking station
tracking
determining
ultrasound
Prior art date
Application number
PCT/DK2005/000323
Other languages
French (fr)
Inventor
Claus Blaabjerg
Finn Kryger Nielsen
Original Assignee
Brüel & Kjær Sound & Vibration Measurement A/S
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
Application filed by Brüel & Kjær Sound & Vibration Measurement A/S filed Critical Brüel & Kjær Sound & Vibration Measurement A/S
Priority to PCT/DK2005/000323 priority Critical patent/WO2006119764A1/en
Publication of WO2006119764A1 publication Critical patent/WO2006119764A1/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
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/18—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using ultrasonic, sonic, or infrasonic waves
    • G01S5/186—Determination of attitude

Definitions

  • the invention relates to professional and scientific measurement of sound and vibration, where the position of the measuring transducer or array of measuring transducers must be accurately known. Such uses include identification and localisation of sound sources
  • Noise can seriously jeopardize not only comfort but also the health of humans. It is therefore important to reduce noise, and for effectively reducing noise it is important to identify noise sources and their individual contribution to the noise level at locations where people are present.
  • Mechanical structures such as body and wall panels can vibrate and emit noise, and large structures can have "hot spots” that emit more noise than "cold spots”. Not all hot spots may be serious contributors to the noise level resulting at a "listening position", and, vice versa, cold spots may contribute more seriously than ex- pected. Such phenomena can e.g. be due to conditions in the transmission path from the source to the listening position.
  • EP 0 015 852 discloses a three-dimensional array of microphones for measuring the total or directional acoustic power emitted by a sound source. Such an array is suitable for use with the method of the present invention.
  • US 2002/0035456 discloses a method for predicting the sound pressure at a point resulting from waves generated by or scattered from a body.
  • the method uses acoustic transfer vectors and the reciprocity principle.
  • a purely numerical reciprocal determination of acoustic transfer vectors is disclosed through simulation of a monopole point source in the listening position, numerical determination of the response at the body surface, and hence elements in the acoustic transfer vector.
  • DE 2 704 511 discloses a system for determining the positions of sites on a vehicle body.
  • the system has a plurality of ultrasound transmitters in fixed positions external to the vehicle body, and an ultrasound receiving microphone is placed at the site on the vehicle body, whose coordinates are to be determined.
  • US 4 811 250 shows a system for the same purpose where an ultrasound transmitter is placed at the site on the vehicle body, whose coordinates are to be determined, and a plurality of ultrasound receiving microphones is placed in fixed positions external to the vehicle body.
  • WO 2004/034083 discloses a system and a method for acoustic measurement e.g. in a car cabin.
  • a plurality of ultrasound transmitters is arranged in predetermined positions on the microphone array.
  • a base station with a plurality of ultrasound receivers (microphones) is arranged in a predetermined position.
  • the base station receives sequentially emitted ultrasound signals from the ultrasound transmitters, which forms the basis for determining the position and orientation of the microphone array is determined by receiving.
  • This method requires unobstructed Iine-of-sight ultrasound transmis- sion, and the use of base stations at several locations is therefore disclosed.
  • the InterSense, Inc. Motion Tracking System IS-900 disclosed on the Web site www.isense.com is a 6 degree of freedom motion tracking system based on a hybrid technology of inertia and ultrasonic tracking.
  • the position and orientation of the tracking stations are determined by the output of the accel- erometers and gyros.
  • Drift correction is accomplished by fusing the output of the inertia! sensors with range measurements obtained from the ultrasonic components.
  • the position and orientation of only the tracking station itself are determined.
  • the problem to be solved by the invention is to provide a system and a method of determining the position of an object such as a measuring microphone, a particle velocity transducer, an accelerometer or other vibration transducer, or an array of such transducers using ultrasound communication for the determination, but which is not limited to unobstructed Iine-of-sight ultrasound communication.
  • the invention solves this problem by providing a system for determining the position of an object such as an array of measuring transducers relative to a fixed station of the system, where the system comprises a tracking station, means for determining the position of the tracking station including means for ultrasound communication between the tracking station and the fixed station, and means for determining the position of the object when the tracking station is in a predetermined spatial relationship with the object, where the sys- tern further comprises inertia-based sensors for detecting changes in the position of the tracking station.
  • the system thus uses a combination of the ultrasound communication the inertia-based system, whereby it is possible to determine the coordinates of the object even in more or less "hidden" positions with partially or totally obstructed ultrasound communication.
  • the tracking station When used e.g. in a car cabin the tracking station will typically be detachably connected to an array of measuring microphones, whose position is to be determined, and the fixed station is mounted in a predetermined position, e.g. under the ceiling. In any position with unobstructed line-of-sight ultrasound transmission between the tracking station and the fixed station can be established, this can be used for accurately determining the position and possibly the orientation of the tracking station, i.e. 6 degrees of freedom, and the tracking station with the microphone array connected thereto can be moved around in the car cabin to make measurements in different positions.
  • the system of the invention does not need fully unobstructed ultrasound communication and among the multiple ultrasound transmission paths some may be obstructed, and the system will still be able to compensate for DC drift in the determination of position.
  • the tracking station should therefore be in a position with at least partial line-of-sight ultrasound communication between the tracking station and the fixed station, where the ultrasound communication is used to correct possible errors that may have accu- mulated.
  • Such a system can be used for determining the position and orientation, i.e. in all 6 degrees of freedom, of an object such as an array of measuring microphones, whether or not direct line-of-sight communication between the tracking station and the fixed station exists.
  • the position includes three spatial coordinates such as X, Y and Z, and the orientation includes the angular position about each of these axes, also referred to as pitch, yaw and roll.
  • Figure 1 is a plan view of a portion of a three-dimensional array of microphones that can be used with the invention
  • Figure 2 is an edge view of the three-dimensional array of microphones in figure 1 ,
  • FIG. 3 illustrates a tracking station used with the invention
  • Figure 4 illustrates the tracking station of figure 3 connected to the microphone array of figures 1 and 2 in a measurement set-up for measuring in e.g. a car cabin,
  • Figure 5 illustrates the tracking station of figure 3 connected to a rod with pointed end
  • Figure 6 illustrates the tracking station of figure 3 connected to a rod with a member shaped to fit to an object, whose position and orientation is to be determined.
  • a three-dimensional array 10 of a plurality of microphones M is shown as an illustrative example of the invention.
  • the term "microphone” is here used as the generally accepted term for a transducer that generates an (electrical) output signal in response to pressure variations in the fluid (air, water etc.) that surrounds the transducer.
  • the array comprises two identical, parallel layers of microphones M spaced a vertical distance d v apart. In each layer the microphones are distributed in two sets of parallel rows forming a square grid with the rows spaced horizontal distances d hX and d hy , respectively, apart.
  • the vertical dis- tance d v and the horizontal distances dhx and dhy are identical, whereby the microphones are uniformly distributed and form a cubic lattice.
  • a non-periodic or non-uniform, such as pseudo-random, distribution of the microphones can also be used.
  • the microphones have well-defined, preferably identical, electro-acoustical properties.
  • the array of microphones preferably has a multi- pole plug (not shown) for connecting the microphones to measuring equipment. Each layer of the array can have e.g. 6x6 or 8x8 or any other suitable arrangement of microphones.
  • the vertical and horizontal spacing determine the upper frequency limit at which the array can be used.
  • the two layers are separate layers that are assembled and can be disassembled and used independent of each other.
  • the two layers are here planar layers mounted back-to-back, but a fixed three- dimensional array may also be used.
  • FIG 3 a tracking station 20 with a gripping end 21 shaped as a handle to be gripped by an operator of the tracking station.
  • An extension 22 has a free end 23 with means (not shown) for detachably connecting the tracking station as explained below in connection with figures 4, 5 and 6.
  • Microphones, such as M1 and M2 are provided on the tracking station for receiving ultrasound signals in communication with ultrasound transmitters on one or more fixed stations.
  • a system 24 with three inertia-based sensors such as DC-accelerometers or other sensors for detecting changes in the position of the tracking station is provided in the tracking station.
  • the system 24 further comprises gyros or other sensors that are sensitive to angular movements.
  • a common technical working principle of the DC-accelerometers and the gyros is that all are inertia based.
  • the ultrasound microphones M1 and M2 and the inertia-based sensors provide output signals to a (not shown) system for determining, as explained below, the position and orientation of the tracking station.
  • the microphone array 10 detachably connected to the tracking station 20 so that the tracking station is in a predetermined and known spatial relationship with the microphone array, i.e. with a well-known geometry.
  • the thus combined microphone array 10 and tracking station 20 are placed within an enclosure 30 such as a car cabin, where a seat 31 is shown.
  • an enclosure 30 such as a car cabin, where a seat 31 is shown.
  • ultrasound transmitters T1 and T2 arranged in well-known positions within the enclosure 30, where they are the essential parts of a fixed station.
  • the above-described arrangement is operated as follows. With the mi- crophone array 10 it is desirable to measure sound in one or more well- known positions of the microphone array.
  • the position and orientation of the combined microphone array 10 and tracking station 20 are determined using the inertia-based sensors.
  • Ultrasound communication between the microphones M1 and M2 on the tracking station and the transmitters T1 and T2 on the fixed station is used to compensate for accumulated errors in the inertia- based determination of position and orientation.
  • ultrasound signals are emitted from the transmitters T1 and T2 and received by the microphones M1 and M2.
  • the transmitters can be activated sequentially or to emit individually encoded signals, and the receivers may likewise be activated sequentially.
  • the (not shown) system keeps track of the position in three dimensions of each of the receivers on the tracking station. Due to the known geometrical relationship between the tracking station and the microphone array it is possible to calculate the position and orientation of the microphone array relative to the fixed station.
  • the ultrasound-based measurement requires unobstructed line-of-sight ultrasound communication between at least some of the transmitters on the fixed station and the microphones on the tracking station, and in all such positions the position and orientation of the microphone array is determined using such ultrasound transmission.
  • the position of the microphone array is determined as follows. First, the track- ing station with the microphone array attached is moved to the measuring position, and during this movement the output signals from the inertia-based transducers are used to track the movement in all six degrees of freedom independent of the ultrasound-based measurements. During this movement the position can be determined using ultrasound communication as described above.
  • the microphone array 10 can be used to perform sound measurements even in "hidden" positions with obstructed ultrasound communication between some pairs of transmitters and receivers.
  • the system will preferably constantly use the ultrasound-based method or other methods such as magnetic fields in combination with the inertia-based method.
  • the system will primarily rely on the inertia-based method and use ultrasound communication or magnetic field communication to compensate for drift in the results from the inertia-based method.
  • the number of ultrasound transmitters and their spatial arrangement within the enclosure and the number of ultrasound receivers and their spatial arrangement on the tracking station depend on the actual task, and the skilled person will know how to do this.
  • FIG 5 is shown the tracking station 20 with a rod 11 having a pointed end 12.
  • the pointed end 12 is in a well-known spatial position, i.e. at a well- known distance and in a well-known direction, relative to the tracking station. This is used for determining the three-dimensional coordinates of a point of interest, when the pointed end is brought to touch the point of interest.
  • the point of interest can be a point on a structure to be measured, or it can be a point on a vibration transducer such as an accelerometer or other transducer, e.g. in the form of small grooves at well-defined position for receiving the pointed end 12 of the rod 11.
  • a transducer can be provided with three such points of interest with a proper spacing, whereby the position and orientation of the transducer can be determined.
  • a transducer 40 such as an accelerometer, whose position and orientation is to be determined.
  • the tracking station 20 has a rod 13 attached with a cup 14 at its end.
  • the cup 14 has a shape that fits over the transducer 40, so that the tracking station will be in a well-defined position relative to transducer, and when the cup is fitted over the transducer the position and orientation of the transducer can be determined using the above- described method of the invention.
  • the transducer 40 may have a cavity in which the free end of the rod 13 fits.
  • ultrasound transmitters as being part of the fixed station, and ultrasound receivers being part of the tracking station.
  • ultrasound transmitters and ultrasound receivers may be fully or partly interchanged to fully or partly reverse the transmission direction of the ultrasound communication.
  • Many transducers are reciprocal transducers that may function both as a transmitter and as a receiver, and when using reciprocal transducers the ultrasound transmission can be in either direction or a combination of both directions.

Abstract

A system for determining the position of an object (10, 40) such as an array (10) of measuring microphones (M) relative to a fixed station of the system, where the system comprises a tracking station (20), means for determining the position of the tracking station (20) including means (T1, T2, M1, M2) for ultrasound communication between the tracking station (20) and the fixed station, and means for determining the position of the object when the tracking station (20) is in a predetermined spatial relationship with the object. The system further comprises inertia-based sensors (24) for detecting changes in the position of the tracking station (20). The system uses the inertia-based system for relative measurements and the ultrasound communication for absolute measurements, whereby it is possible to determine the coordinates of the object even in “hidden” positions with obstructed ultrasound communication.

Description

DETERMINATION OF THE POSITION OF AN OBJECT
Field of the invention
The invention relates to professional and scientific measurement of sound and vibration, where the position of the measuring transducer or array of measuring transducers must be accurately known. Such uses include identification and localisation of sound sources
Background of the invention Protection of the environment and human beings has become increasingly important. Buildings, vehicles such as cars, buses and aircraft, household appliances and industrial machinery have noise producing components such as engines, motors, gears, transmissions etc. In order to protect individuals from such noise, the noise generating components and the transmission path of the noise to a human being have been investigated with the purpose of reducing the generated noise at the source and of reducing the noise transmitted from the source to human beings.
Testing of acoustic properties of noise generating and noise transmitting me- dia such as mechanical structures and air or other fluids is an important part of the process of noise reduction. In complex structures with several noise sources, such as mentioned above, it can be complicated to identify noise sources and transmission paths and their contributions to the perceived noise.
When designing e.g. vehicles such as cars, buses and aircraft the comfort of the passengers, the driver and crewmembers is of importance. Noise can seriously jeopardize not only comfort but also the health of humans. It is therefore important to reduce noise, and for effectively reducing noise it is important to identify noise sources and their individual contribution to the noise level at locations where people are present. Mechanical structures such as body and wall panels can vibrate and emit noise, and large structures can have "hot spots" that emit more noise than "cold spots". Not all hot spots may be serious contributors to the noise level resulting at a "listening position", and, vice versa, cold spots may contribute more seriously than ex- pected. Such phenomena can e.g. be due to conditions in the transmission path from the source to the listening position.
EP 0 015 852 discloses a three-dimensional array of microphones for measuring the total or directional acoustic power emitted by a sound source. Such an array is suitable for use with the method of the present invention.
US 2002/0035456 discloses a method for predicting the sound pressure at a point resulting from waves generated by or scattered from a body. The method uses acoustic transfer vectors and the reciprocity principle. A purely numerical reciprocal determination of acoustic transfer vectors is disclosed through simulation of a monopole point source in the listening position, numerical determination of the response at the body surface, and hence elements in the acoustic transfer vector.
DE 2 704 511 discloses a system for determining the positions of sites on a vehicle body. The system has a plurality of ultrasound transmitters in fixed positions external to the vehicle body, and an ultrasound receiving microphone is placed at the site on the vehicle body, whose coordinates are to be determined.
US 4 811 250 shows a system for the same purpose where an ultrasound transmitter is placed at the site on the vehicle body, whose coordinates are to be determined, and a plurality of ultrasound receiving microphones is placed in fixed positions external to the vehicle body. WO 2004/034083 discloses a system and a method for acoustic measurement e.g. in a car cabin. For accurate determination of the position and orientation of a microphone array, a plurality of ultrasound transmitters is arranged in predetermined positions on the microphone array. A base station with a plurality of ultrasound receivers (microphones) is arranged in a predetermined position. The base station receives sequentially emitted ultrasound signals from the ultrasound transmitters, which forms the basis for determining the position and orientation of the microphone array is determined by receiving. This method requires unobstructed Iine-of-sight ultrasound transmis- sion, and the use of base stations at several locations is therefore disclosed.
The InterSense, Inc. Motion Tracking System IS-900 disclosed on the Web site www.isense.com is a 6 degree of freedom motion tracking system based on a hybrid technology of inertia and ultrasonic tracking. The position and orientation of the tracking stations are determined by the output of the accel- erometers and gyros. Drift correction is accomplished by fusing the output of the inertia! sensors with range measurements obtained from the ultrasonic components. In the IS-900 system the position and orientation of only the tracking station itself are determined.
The problem to be solved by the invention is to provide a system and a method of determining the position of an object such as a measuring microphone, a particle velocity transducer, an accelerometer or other vibration transducer, or an array of such transducers using ultrasound communication for the determination, but which is not limited to unobstructed Iine-of-sight ultrasound communication.
Summary of the invention
The invention solves this problem by providing a system for determining the position of an object such as an array of measuring transducers relative to a fixed station of the system, where the system comprises a tracking station, means for determining the position of the tracking station including means for ultrasound communication between the tracking station and the fixed station, and means for determining the position of the object when the tracking station is in a predetermined spatial relationship with the object, where the sys- tern further comprises inertia-based sensors for detecting changes in the position of the tracking station. The system thus uses a combination of the ultrasound communication the inertia-based system, whereby it is possible to determine the coordinates of the object even in more or less "hidden" positions with partially or totally obstructed ultrasound communication.
When used e.g. in a car cabin the tracking station will typically be detachably connected to an array of measuring microphones, whose position is to be determined, and the fixed station is mounted in a predetermined position, e.g. under the ceiling. In any position with unobstructed line-of-sight ultrasound transmission between the tracking station and the fixed station can be established, this can be used for accurately determining the position and possibly the orientation of the tracking station, i.e. 6 degrees of freedom, and the tracking station with the microphone array connected thereto can be moved around in the car cabin to make measurements in different positions. The system of the invention does not need fully unobstructed ultrasound communication and among the multiple ultrasound transmission paths some may be obstructed, and the system will still be able to compensate for DC drift in the determination of position.
An alternative to ultrasound communication for determining the position, other touch-free methods can be use, such as magnetic fields with a known spatial variation.
Signals from DC accelerometers are double integrated in order to obtain the position, and even small errors are thereby accumulated in the calculation of position, and such DC signals therefore tend to drift with time. Consequently, the system needs to compensate for such errors. The tracking station should therefore be in a position with at least partial line-of-sight ultrasound communication between the tracking station and the fixed station, where the ultrasound communication is used to correct possible errors that may have accu- mulated.
Such a system can be used for determining the position and orientation, i.e. in all 6 degrees of freedom, of an object such as an array of measuring microphones, whether or not direct line-of-sight communication between the tracking station and the fixed station exists. The position includes three spatial coordinates such as X, Y and Z, and the orientation includes the angular position about each of these axes, also referred to as pitch, yaw and roll.
Brief description of the drawings Figure 1 is a plan view of a portion of a three-dimensional array of microphones that can be used with the invention,
Figure 2 is an edge view of the three-dimensional array of microphones in figure 1 ,
Figure 3 illustrates a tracking station used with the invention,
Figure 4 illustrates the tracking station of figure 3 connected to the microphone array of figures 1 and 2 in a measurement set-up for measuring in e.g. a car cabin,
Figure 5 illustrates the tracking station of figure 3 connected to a rod with pointed end, and Figure 6 illustrates the tracking station of figure 3 connected to a rod with a member shaped to fit to an object, whose position and orientation is to be determined.
Detailed description of the invention
In figures 1 and 2 a three-dimensional array 10 of a plurality of microphones M is shown as an illustrative example of the invention. The term "microphone" is here used as the generally accepted term for a transducer that generates an (electrical) output signal in response to pressure variations in the fluid (air, water etc.) that surrounds the transducer. The array comprises two identical, parallel layers of microphones M spaced a vertical distance dv apart. In each layer the microphones are distributed in two sets of parallel rows forming a square grid with the rows spaced horizontal distances dhX and dhy, respectively, apart. In the preferred embodiment shown, the vertical dis- tance dv and the horizontal distances dhx and dhy are identical, whereby the microphones are uniformly distributed and form a cubic lattice. A non-periodic or non-uniform, such as pseudo-random, distribution of the microphones can also be used. The microphones have well-defined, preferably identical, electro-acoustical properties. The array of microphones preferably has a multi- pole plug (not shown) for connecting the microphones to measuring equipment. Each layer of the array can have e.g. 6x6 or 8x8 or any other suitable arrangement of microphones. The vertical and horizontal spacing determine the upper frequency limit at which the array can be used.
As indicated in figure 2, the two layers are separate layers that are assembled and can be disassembled and used independent of each other. The two layers are here planar layers mounted back-to-back, but a fixed three- dimensional array may also be used.
In figure 3 is shown a tracking station 20 with a gripping end 21 shaped as a handle to be gripped by an operator of the tracking station. An extension 22 has a free end 23 with means (not shown) for detachably connecting the tracking station as explained below in connection with figures 4, 5 and 6. Microphones, such as M1 and M2, are provided on the tracking station for receiving ultrasound signals in communication with ultrasound transmitters on one or more fixed stations. A system 24 with three inertia-based sensors such as DC-accelerometers or other sensors for detecting changes in the position of the tracking station is provided in the tracking station. The system 24 further comprises gyros or other sensors that are sensitive to angular movements. A common technical working principle of the DC-accelerometers and the gyros is that all are inertia based. The ultrasound microphones M1 and M2 and the inertia-based sensors provide output signals to a (not shown) system for determining, as explained below, the position and orientation of the tracking station.
In figure 4 is shown the microphone array 10 detachably connected to the tracking station 20 so that the tracking station is in a predetermined and known spatial relationship with the microphone array, i.e. with a well-known geometry. As shown, the thus combined microphone array 10 and tracking station 20 are placed within an enclosure 30 such as a car cabin, where a seat 31 is shown. Within the car cabin are also shown ultrasound transmitters T1 and T2 arranged in well-known positions within the enclosure 30, where they are the essential parts of a fixed station.
In use the above-described arrangement is operated as follows. With the mi- crophone array 10 it is desirable to measure sound in one or more well- known positions of the microphone array. The position and orientation of the combined microphone array 10 and tracking station 20 are determined using the inertia-based sensors. Ultrasound communication between the microphones M1 and M2 on the tracking station and the transmitters T1 and T2 on the fixed station is used to compensate for accumulated errors in the inertia- based determination of position and orientation. To achieve this ultrasound signals are emitted from the transmitters T1 and T2 and received by the microphones M1 and M2. The transmitters can be activated sequentially or to emit individually encoded signals, and the receivers may likewise be activated sequentially. Based on the transmission times from each of the trans- mitters to each of the receivers the (not shown) system keeps track of the position in three dimensions of each of the receivers on the tracking station. Due to the known geometrical relationship between the tracking station and the microphone array it is possible to calculate the position and orientation of the microphone array relative to the fixed station.
The ultrasound-based measurement requires unobstructed line-of-sight ultrasound communication between at least some of the transmitters on the fixed station and the microphones on the tracking station, and in all such positions the position and orientation of the microphone array is determined using such ultrasound transmission.
In positions where the ultrasound communication between some pairs of transmitters and receivers is obstructed, e.g. by the seat 31 in the car cabin, the position of the microphone array is determined as follows. First, the track- ing station with the microphone array attached is moved to the measuring position, and during this movement the output signals from the inertia-based transducers are used to track the movement in all six degrees of freedom independent of the ultrasound-based measurements. During this movement the position can be determined using ultrasound communication as described above. Hereby the microphone array 10 can be used to perform sound measurements even in "hidden" positions with obstructed ultrasound communication between some pairs of transmitters and receivers.
Depending on the drift characteristics of the inertia-based system for position determination it will be necessary for the tracking to be in positions with un- obstructed ultrasound communication in order to compensate for possible accumulated errors in the position determination.
The system will preferably constantly use the ultrasound-based method or other methods such as magnetic fields in combination with the inertia-based method. The system will primarily rely on the inertia-based method and use ultrasound communication or magnetic field communication to compensate for drift in the results from the inertia-based method.
The number of ultrasound transmitters and their spatial arrangement within the enclosure and the number of ultrasound receivers and their spatial arrangement on the tracking station depend on the actual task, and the skilled person will know how to do this.
In figure 5 is shown the tracking station 20 with a rod 11 having a pointed end 12. The pointed end 12 is in a well-known spatial position, i.e. at a well- known distance and in a well-known direction, relative to the tracking station. This is used for determining the three-dimensional coordinates of a point of interest, when the pointed end is brought to touch the point of interest.
The point of interest can be a point on a structure to be measured, or it can be a point on a vibration transducer such as an accelerometer or other transducer, e.g. in the form of small grooves at well-defined position for receiving the pointed end 12 of the rod 11. A transducer can be provided with three such points of interest with a proper spacing, whereby the position and orientation of the transducer can be determined.
In figure 6 is shown a transducer 40 such as an accelerometer, whose position and orientation is to be determined. The tracking station 20 has a rod 13 attached with a cup 14 at its end. The cup 14 has a shape that fits over the transducer 40, so that the tracking station will be in a well-defined position relative to transducer, and when the cup is fitted over the transducer the position and orientation of the transducer can be determined using the above- described method of the invention. Alternatively the transducer 40 may have a cavity in which the free end of the rod 13 fits.
The system and the method of the invention are described with ultrasound transmitters as being part of the fixed station, and ultrasound receivers being part of the tracking station. The skilled person will know that the ultrasound transmitters and ultrasound receivers may be fully or partly interchanged to fully or partly reverse the transmission direction of the ultrasound communication. Many transducers are reciprocal transducers that may function both as a transmitter and as a receiver, and when using reciprocal transducers the ultrasound transmission can be in either direction or a combination of both directions.

Claims

Claims:
1. A system for determining the position of an object (10, 40) relative to a fixed station of the system, the system comprising • a tracking station (20),
• means for determining the position of the tracking station (20) including means (T1 , T2, M1 , M2) for ultrasound communication between the tracking station (20) and the fixed station, and
• means for determining the position of the object (10, 40) when the track- ing station (20) is in a predetermined spatial relationship with the object
, (10, 40), c h a r a c t e r i z e d in that the system further comprises inertia- based sensors (24) for detecting changes in the position of the tracking station (20).
2. A system according to claim 1 wherein the inertia-based sensors (24) comprise at least one DC-accelerometer for detecting linear motion of the tracking station (20).
3. A system according to claim 1 or 2 wherein the inertia-based sensors (24) comprise at least one gyro for detecting angular motion of the tracking station (20).
4. A system according to any one of claims 1-3 comprising means for multi- path ultrasound communication between the tracking station (20) and the fixed station.
5. A system according to any one of claims 1-4 wherein the tracking station (20) has means (11 , 12, 13, 14, 23) for being detachably connected to the object (10, 40).
6. A system according to any one of claims 1-5 wherein the tracking station (20) comprises a member (14) shaped to fit to the object (40) in a detachable shape-fitting engagement with the tracking station (20) in a predetermined position and a predetermined orientation relative to the object (40).
7. A system according to any one of claims 1-6 wherein the object (10) comprises a microphone (M).
8. A system according to any one of claims 1-7 wherein the object (10) com- prises an array of a plurality of microphones (M).
9. A system according to any one of claims 1-6 wherein the tracking station (20) comprises a member (11 ) with a pointed end (12) for being brought into contact with the object.
10. A method for determining the position of an object (10, 40) relative to a fixed station, the method comprising
• providing a tracking station (20),
• bringing the tracking station (20) in a predetermined spatial relationship with the object (10, 40),
• determining, using ultrasound communication between the tracking station (20) and the fixed station, the position of the tracking station (20) relative to the fixed station,
• determining the position of the object (10, 40) in the predetermined spatial relationship with the tracking station (20),
• determining, using inertia-based sensors (24), changes in the position of the tracking station (20).
11. A method according to claim 10 further comprising • correcting, using ultrasound communication between the tracking station (20) and the fixed station, drift in the inertia-based sensors (24).
PCT/DK2005/000323 2005-05-13 2005-05-13 Determination of the position of an object WO2006119764A1 (en)

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Applications Claiming Priority (1)

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DE4327937A1 (en) * 1993-08-19 1995-02-23 Volkswagen Ag Device for determining the geometrical position (orientation) of object points
US6409687B1 (en) * 1998-04-17 2002-06-25 Massachusetts Institute Of Technology Motion tracking system
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WO2004034083A2 (en) * 2002-10-08 2004-04-22 01Db - Metravib Installation and method for acoustic measurement with marker microphone in space

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108387871A (en) * 2018-01-30 2018-08-10 吉林大学 A kind of ultrasonic three-dimensional positioning system and localization method for realizing that six degree of freedom measures

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