SE545367C2 - Method and system for position determination - Google Patents
Method and system for position determinationInfo
- Publication number
- SE545367C2 SE545367C2 SE2151495A SE2151495A SE545367C2 SE 545367 C2 SE545367 C2 SE 545367C2 SE 2151495 A SE2151495 A SE 2151495A SE 2151495 A SE2151495 A SE 2151495A SE 545367 C2 SE545367 C2 SE 545367C2
- Authority
- SE
- Sweden
- Prior art keywords
- internal clock
- relation
- positioning time
- ofthe
- time
- Prior art date
Links
Classifications
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- 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
- G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
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- 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
- G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
- G01S5/0257—Hybrid positioning
- G01S5/0263—Hybrid positioning by combining or switching between positions derived from two or more separate positioning systems
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- 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
- G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
- G01S5/14—Determining absolute distances from a plurality of spaced points of known location
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- 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
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/4808—Evaluating distance, position or velocity data
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- 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
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
Abstract
A method in a positioning system for determining the position of a movable device (3) comprises the steps of- repeatedly transmitting, from a first device (Dl), first messages (8) comprising at least first transmit times obtained from a first internal clock (4),- determining a mathematical model of the state of the first internal clock (4) in relation to the state of a second internal clock (6),- receiving, at the first and a second device (D1, D2), an identification message (11) from the movable device (3) and obtaining corresponding first and second positioning times (Tpos1, Tpos2),- determining the position of the movable device (3) in relation to the first device (Dl) and the second device (D2) based on the first positioning time (Tpos1), the second positioning time (Tpos2), and the mathematical model.
Description
l\/IETHOD AND SYSTEl\/l FOR POSITION DETERl\/IINATION TECHNICAL FIELD The present invention relates to a method and a system for determining the position of a movable device.
BACKGROUND ART ln the information age we expect to be able to easily locate anything anywhere. GPS solves this and has given humanity a vast number of advantages, too many to list here. GPS has one weakness, namely that GPS does not work in environments where radio waves are obstructed. For ease of reading we will primarily consider underground mines as an example environment, as it has many ofthe adversities commonly found in positioning. GPS builds on one measurement technique, time difference of arrival (henceforth denoted as TDoA). Short about TDoA, with TDoA one can locate the source of a radio signal (henceforth denoted as a tag) by listening to the radio signal and knowing the difference in time of when it arrives at known locations (henceforth denoted as anchors). This is how lost people are found via their phone signal. This positioning requires that all anchors share a common time reference. Synchronizing clocks is a difficult problem without the use of atomic clocks, the problem grows in complexity with the number of clocks you want to synchronize. Current precision without atomic clocks are within a kilometer.
US 2014/0364142 describes TDOA based positioning with calculation of correction factors for compensating the clock offsets of unsynchronized network stations. The method and arrangement described in US 2014/0364142 allows for a correct location estimation of a user device without having synchronized clocks. The method and arrangement relies on the estimation ofthe respective offsets of a first clock and a second clock relative to a third clock as a function of time. Receiving a signal from a device to be localized at the first device and the second device and determining the respective reception times of the signal and estimating the position ofthe device to be localized using the respective reception times and the respective offsets of the first clock and the second clock as a function of time. ln order to be able to 2 determine the respective offsets at the reception time of the signal from the device to be localized, the respective offsets are measured during a time period bracketing the reception time. A polynomial is fitted to the pairs of offsets during the time period and the value of the offsets at the reception time is obtained from the fitted polynomial.
The method described in US 2014/0364142 has the drawback that measurements of the respective offsets must be performed before as well as after the time of reception ofthe signal from the device to be localized.
SUMMARY OF THE INVENTION An object of the present invention is to provide a method for determining the position and a positioning system, for determining the position of a movable device in relation to a first device and a second device, which method and system alleviates at least one ofthe problems with the methods and systems for positioning according to the prior art.
Another object of the present invention is to provide a method for positioning and a positioning system, for determining the position of a movable device in relation to a first device and a second device, which method and system is suitable for use in mining tunnels.
At least one of the above objects is achieved with a method for determining the position and a positioning system according to the independent claims. Further advantages are provided with the features of the dependent claims.
According to a first aspect a method is provided for determining the position of a movable device in relation to at least a first device and a second device. The first device and the second device are arranged at a known distance from each other corresponding to a propagation delay for a signal between the first device and the second device. The first device comprises a first internal clock and the second device comprises a second internal clock. The method comprises the steps of repeatedly transmitting, from the first device, first messages comprising the state of the first internal clock, which state comprise at least the time obtained from the first internal clock. The method further comprises the steps of receiving the first messages at the second device and obtaining corresponding first times of reception from thesecond internal clock, and determining a mathematical model ofthe state of the first internal clock in relation to the state of the second internal clock based on the first transmit times, the first times of reception and the propagation delay, wherein the state ofthe first internal clock at least comprises the time of the first internal clock in relation to the time ofthe second internal clock. The method further comprises the steps of receiving, at the first device, an identification message with an identification code from the movable device and obtaining a corresponding first positioning time from the first internal clock, wherein the identification code is unique for the movable device, receiving, at the second device, the identification message with the identification code from the movable device and obtaining a corresponding second positioning time from the second internal clock, and determining the position of the movable device in relation to the first device and the second device based on the known distance, the first positioning time, the second positioning time, and the mathematical model of the first internal clock in relation to the second internal clock.
With a method according to the first aspect an alternative is provided to present methods for position determination. The method provides the possibility of synchronisation over an unlimited area. The method relies on the fact that the positions of the first device and the second device are known.
The identification code is at least unique for the movable device. The method for determining the position relies on the measurement of the times of the reception of the identification message at the different devices. To be able to track the position ofthe movable device over time the movable device has to transmit identification messages with an identification code, repeatedly. To be able to distinguish between identification messages sent at different times the identification codes may be unique also between different identification messages sent from the same movable device.
The known distance may be determined in many different ways, either automatically by the devices or by input of the distance by an operator of the system.
The determination of the mathematical model of the state ofthe first internal clock in relation to the state of the second internal clock may be made in the second device. Also, the first device may correspondingly determine a mathematical model of the state ofthe second internal clock in relation to the state of the first internal clock. 4 Alternatively, the determination of the mathematical model of the state ofthe first internal clock in relation to the state of the second internal clock may be made in a server which is in communication with the first and second devices. lt is to be understood that the method may comprise more than two devices. The method may be used for a system with any number of devices. The position of the movable device may be determined using the times of reception of the identification message from at least a pair of devices.
The determination of the position of the movable device in relation to the first device and the second device may be performed in the second device or in a server which is in communication with the devices.
A server is to be understood as a device comprising means for computing and means for communication with the devices.
The state of the internal clocks may also include skew and/or temperature and/or the age of a clock crystal in the internal clocks and/or any other observable effect that can be mapped to an effect directly or indirectly to time.
The mathematical model may be a statistical model. This is favourable in that the model then may be updated according to the first messages comprising the state of the first internal clock.
The statistical model may be updated at the reception of each one of the first messages at the second device. This is favourable in that the statistical model then predicts the state of the first internal clock as accurately as possible.
The statistical model of the first internal clock in relation to the second internal clock is corrected, using a state estimator, based on the received first transmit times. The use of a state estimator is an efficient method for correcting a statistical model. The state estimator may be a Kalman filter. A Kalman filter is an optimal state estimator.
The method may comprise the steps of transmitting from the first device to the second device the first positioning time, determining, in the second device, an adjusted first positioning time based on the first positioning time and the mathematical model ofthe state of the first internal clock in relation to the second internal clock, and to transmit the adjusted firstpositioning time and the second positioning time to the server, wherein the server is configured to perform the determination ofthe position of the movable device in relation to the first device and the second device. This is an robust way of performing the method in which the first device and preferably all devices determine mathematical models of the state of the internal clock in the neighbouring device/devices. ln case any of the device in the system stops working it is only necessary to restart that device while the other devices are unaffected. Also, by distributing the statistical models to all devices is also possible for each device to identify by itself any outliers in the received transmit times.
According to a second aspect a positioning system is provided, which comprises at least a first device and a second device, for determining the position of a movable device in relation to the first device and the second device, and wherein the first device comprises a first internal clock and a first transceiver, and the second device comprises a second internal clock and a second transceiver. The first device and the second device are configured to be arranged at a known distance from each other corresponding to a propagation delay for a signal between the first device and the second device. The system is configured to repeatedly transmit, from the first device, first messages comprising first transmit times obtained from the first internal clock, receive the first messages at the second device and obtaining corresponding first times of reception from the second internal clock, and determine a mathematical model of the state of the first internal clock in relation to the second internal clock based on the first transmit times, the first times of reception and the propagation delay. The state ofthe first internal clock at least comprises the time of the first internal clock in relation to the second internal clock. The system is also configured to receive, at the first device, an identification message with an identification code from the movable device and obtaining a corresponding first positioning time from the first internal clock, wherein the identification code is unique for the movable device, and to receive, at the second device, the identification message with the identification code from the movable device and obtaining a corresponding second positioning time from the second internal clock. The system is also configured to determine the position of the movable device in relation to the first device and the second device based on the known distance, the first positioning time, the second positioning time, and the mathematical model of the first internal clock in relation to the second internal clock. 6 With a system according to the second aspect an alternative is provided to present systems for position determination. The system provides the possibility of synchronisation over an unlimited area. The function of the system re|ies on the fact that the positions of the first device and the second device are known.
The known distance may be determined in many different ways, either automatically by the devices or by input of the distance into the devices by an operator of the system.
The identification code is at least unique for the movable device. The method for determining the position re|ies on the measurement ofthe times ofthe reception of the identification message at the different devices. To be able to track the position ofthe movable device over time the movable device has to transmit identification messages with an identification code, repeatedly. To be able to distinguish between identification messages sent at different times the identification codes may be unique also between different identification messages sent from the same movable device.
The determination of the mathematical model of the state ofthe first internal clock in relation to the state of the second internal clock may be made in the second device. Also, the first device may correspondingly determine a mathematical model ofthe state ofthe second internal clock in relation to the state of the first internal clock.
Alternatively, the determination of the mathematical model ofthe state ofthe first internal clock in relation to the state of the second internal clock may be made in a server which is in communication with the first and second devices. lt is to be understood that the method may comprise more than two devices. The method may be used for a system with any number of devices. The position of the movable device may be determined using the times of reception of the identification message from at least a pair of devices.
The determination of the position of the movable device in relation to the first device and the second device may be performed in the second device or in a server which is in communication with the devices and which is a part ofthe system.
A server is to be understood as a device comprising means for computing and means for communication with the devices.The state of the internal clocks may also include skew and/or temperature.
The mathematical model may be a statistical model. This is favourable in that the model then may be updated according to the first messages comprising the state of the first internal clock.
The statistical model may be updated at the reception of each ofthe first messages at the second device. This is favourable in that the statistical model then predicts the state of the first internal clock as accurately as possible.
The positioning system may comprise a server, wherein the first device is configured to transmit the first positioning time to the second device. The second device may be configured to determine an adjusted first positioning time based on the first positioning time and the mathematical model of the state of the first internal clock in relation to the second internal clock, and to transmit the adjusted first positioning time and the second positioning time to the server. The server may be configured to perform the determination of the position ofthe movable device in relation to the first device and the second device. This is an efficient way of performing the method in which the first device and preferably all devices determine mathematical models of the state ofthe internal clock in the neighbouring device/devices.
The positioning system may be configured such that the determination of a statistical model of the state of the first internal clock in relation to the second internal clock is performed in the second device. Correspondingly, it is preferable if all devices in the system determines a statistical model of the state of the internal clock of their neighbouring devices. By arranging the system in this way the computing is distributed among all devices which provides a more robust system. ln case any of the device in the system stops working it is only necessary to restart that device while the other devices are unaffected. Also, by distributing the statistical models to all devices is also possible for each device to identify by itself any outliers in the received transmit times.
Alternatively, the second device may be configured to transmit to the server the first transmit time and the first time of reception, and wherein the server is configured to obtain the propagation delay and to determine the mathematical model of the state of the first internal clock in relation to the second internal clock. Such a system is not as robust as all mathematical models are determined in the server. 8 The positioning system may be configured to correct the model of the state of the first internal clock in relation to the second internal clock using a state estimator. The use of a state estimator is an efficient method for correcting a statistical model.
The state estimator may be a Kalman filter. A Kalman filter is an optimal state estimator.
The positioning system may also be configured to determine the accuracy of the first positioning time and the second positioning time and to determine the accuracy ofthe position ofthe movable device using the accuracy ofthe first positioning time and the second positioning time. ln the following embodiments of the invention will be described with reference to the appended drawings on which: BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows schematically a positioning system according to an embodiment of the present invention, comprising a first device and a second device.
Figure 2 illustrates the determination of the position of a movable device in relation to a first device and a second device according to Figure Figure 3 shows schematically a positioning system according to another embodiment of the present invention, comprising a plurality of devices.
Figure 4 is a flow diagram illustrating the method according to an embodiment of the present invention.
DETAILED DESCRIPTION ln the following description of embodiments ofthe invention the same reference numerals will be used for similar features in different figures. The drawings are not drawn to scale.
Figure 1 shows schematically a positioning system 100 according to an embodiment of the present invention, comprising a first device D1 and a second device D2. The positioning system100 is configured for determining the position of a movable device 3 in relation to the first device D1 and the second device D2. In the embodiment of Figure 1 the third device is a radio transmitter which is carried by a human. It is of course possible to arranged the movable device 3 on any movable object of interest. The movable device 3 repeatedly transmits an identification message 11 with an identification code ID, which is unique for the movable device 3. The different identification messages 11 sent at different times may comprise the same unique identification code ID, but may alternatively comprise different unique identification codes, such that a specific message may be identified. |fthe different identification messages 11 sent at different times comprise the same unique identification code ID, the identification messages 11 should be sent at sufficiently long intervals to avoid mixing up of the different identification messages at the receiving first device D1 and second device D The first device comprises a first internal clock 4 and a first transceiver 5, the second device comprises a second internal clock 6 and a second transceiver 7. Preferably, the first transceiver 5 and the second transceiver 7 transmits using the so called Ultra Wide Band, UWB, which allows for time measurements with a precision of down to 10"" seconds. The first device D1 and the second device D2 are arranged at known positions at a known distance from each other corresponding to a propagation delay Tdel for a signal between the first device and the second device. The propagation delay is determined during initiation of the positioning system 100. In the embodiment of Figure 1 the first device comprises a first control unit 9 and the second device comprises a second control unit 10. The first control unit 9 is in communication with the first transceiver 5 and the first internal clock 4 and controls the tranmission and reception of messages to/from the first device 1. The second control unit 10 is in communication with the second transceiver 7 and the second internal clock 6 and controls the transmission and reception of messages to/from the second device The positioning system 100 is configured to repeatedly transmit from the first device D1 first messages 8, which is illustrated as the letter 8 in Figure 1. The first messages 8 are sent repeatedly, preferably with fixed time intervals At. The first messages 8 comprises information on the state of the first internal clock 4. In the present embodiment the state of the first internal clock 4 comprises first transmit times Ttr1 obtained from the first internal clock. The first messages 8 are received at the second device D2. The second device 2 obtains corresponding first times of reception Trc1 from the second internal clock The second control unit 10 is also configured to determine a mathematical model ofthe state ofthe first internal clock 4 in relation to the state ofthe second internal clock 6 based on the first transmit times Ttr1, the first times of reception Trc1 and the propagation delay Tdel. ln the embodiment of Figure 1 the state of the first internal clock 4 comprises the time of the first internal clock 4 in relation to the time ofthe second internal clock 6. Preferably, the first control unit determines a corresponding mathematical model of the time ofthe second internal clock 6 in relation to the time of the first internal clock ln the following a detailed example for the state space model will be described to further illustrate the system according to the description.
The following example of a linear state space model may be used, which is assumed to be corrupted with Gaussian noise. :ur å? ššiä W ln our case u = 0, as there is no input to the system, a clock is seen as only dependent on itself. 1 w/f av» > f f. íflflflflMvfl/»fl/fl, w/z where x is the estimated time. Equation 1 is a continuous time model and converting it to discrete time with a time period of At is as follows. The At is the time between two consecutive first messages 8 from the first device . vs; \ ,. š? / m, . 'lr y-v/h- ~ > ,...f 1,» ïfffffffffflffffffffffff, f» « w 11 The statistical model is updated at the reception of each ofthe first messages at the second device. Between updates ofthe statistical model based on the reception of the first messages, the statistical model is corrected using a state estimator such, preferably a Kalman filter.
Process noise is derived using an integrated continuous time Gaussian over At to give an impulse covariance Q: and observation noise is a scalar R that we use to tune the filter. The Kalman filter is updated according to theory.
The determination of the position ofthe movable device will now be described. The first device D1 receives the identification message 11 with the identification code ID and obtains a corresponding first positioning time Tpos1 from the first internal clock 4. The second device D2 receives the identification message with the identification code ID and obtains a corresponding second positioning time Tpos2 from the second internal clock 6. The first device transmits a positioning message 12 with the first positioning time Tpos1. The second device 2 receives the positioning message with the first positioning time Tpos1 and determines the position ofthe movable device 3 in relation to the first device D1 and the second device 2 based on the first positioning time Tpos1, the second positioning time Tpos2, and the mathematical model ofthe time ofthe first internal clock 4 in relation to the time ofthe second internal clock Figure 2 illustrates the determination ofthe position ofthe movable device 3 in a tunnel in relation to a first device D1 and a second device D2 according to Figure 1. The second device D2 determines the time of reception of the identification message as the second positioning time Tpos2 and the second device D2 receives the corresponding first positioning time Tpos1 from the first device D1. The second device D2 moves the first positioning time Tpos1 to the time frame of the second clock 6 using the statistical model of the first clock 4, resulting in an adjusted first positioning time Tpos1'. The difference between Tpos1' and Tpos2 corresponds to the difference between the distance S1 from the movable object 3 to the first device D12 and the distance S2 from the movable object 3 to the second device D2. Correspondingly, the propagation delay Tde| corresponds to the distance S0 between the first device D1 and the second device D2. Also, the relation S1+S2=S0 may be used to determine the position of the movable object 3 in relation to the second device D As mentioned above the first device may be configured to determine a corresponding statistical model and be arranged to determine a position of the movable device 3 in a corresponding way.
Figure 3 shows schematically a positioning system 100 according to another embodiment of the present invention, comprising a plurality of devices D1-D6. The positioning system 100 in Figure 2 comprises a server 13 wherein the plurality of devices D1-D6 are each configured as has been described for the first and second device in relation to Figure 1. Each one of the devices D1-D6 repeatedly transmits messages, preferably with fixed time intervals At. The first messages comprise information on the state of the first internal clock 4. ln the present embodiment the state of the first internal clock 4 comprises transmit times Ttr1-Ttr6 obtained from the corresponding internal clocks. Depending on the arrangement ofthe different devices D1-D6 each device receives messages from one or more neighbouring devices. ln the present embodiment lines indicate the reception of messages from neighbouring devices. Thus, the first device D1 receives messages with transmit times from the second device D2 and the third device D3 and creates a model D1modD2 of the time ofthe internal clock in the second device D2 and a model D2mod3 of the time ofthe internal clock in the third device D The second device D2 receives messages with transmit times from the second device D2 and the third device D3 and creates a model D2modD1 of the time ofthe internal clock in the first device D1 and a model D2modD3 of the time ofthe internal clock in the third device D The third device D3 receives messages with transmit times from the first device D1, the second device D2 and the fourth device D4 and creates a model D3modD1 of the time ofthe internal clock in the first device D1, a model D3modD2 of the time ofthe internal clock in the second device D2 and a model D3modD4 of the time ofthe internal clock in the fourth device D 13 The fourth device D4 receives messages with transmit times from the third device D3 and the fifth device D5 and creates a model D4modD3 of the time ofthe internal clock in the third device D3 and a model D4modD5 of the time ofthe internal clock in the fifth device D The fifth device D5 receives messages with transmit times from the fourth device D4 and the sixth device D6 and creates a model D5modD4 of the time ofthe internal clock in the fourth device D4 and a model D5modD6 of the time ofthe internal clock in the sixth device D The sixth device D6 receives messages with transmit times from the fifth device D5 and possibly further devices and creates a model D6modD5 of the time ofthe internal clock in the fifth device D5 and models of the time of the internal clock in possible further devices.
Each device ofthe first to the sixth device D1-D6 which receives the identification message 11 with the identification code ID registers a corresponding positioning time Tpos1-Tpos6 retreived from their respective internal clock 4. In the embodiment of Figure 3 the movable device is positioned between the first device D1 and the second device D2 and the first device D1, the second device D2 and the third device D3 receives the identification message 11 with the identification code ID from the movable device 3. The first device D1 determines the time of reception of the identification message 11 as the first positioning time Tpos1 and the first device D2 receives the corresponding second positioning time Tpos2 from the second device D2 and the corresponding third positioning time Tpos3 from the third device. The first device D1 moves the second positioning time Tpos2 to the time frame of the first device D1 using the model D1modD2 of the time ofthe internal clock in the second device D2, resulting in an adjusted second positioning time Tpos2'. Correspondingly, the first device D1 moves the third positioning time Tpos3 to the time frame of the first device D2 using the model D1modD3 of the time ofthe internal clock in the second device D3, resulting in an adjusted third positioning time Tpos3'. The first device transmits to the server 13 the ID together with the first positioning time Tpos1, the adjusted second positioning time Tpos2', and the adjusted third positioning time Tpos3'. The server has knowledge of the mutual positions of the first device D1, the second device D2 and the third device D3. The server is configured to determine the position of the movable device in relation to the first device D1, the second device D2 and the third device D3, based on the mutual positions of the first device D1, the 14 second device D2 and the third device D3, and the first positioning time Tpos1, the adjusted second positioning time Tpos2', and the adjusted third positioning time Tpos3'.
The second device D2 and the third device D3 may be configured in the same way as the first device and will correspondingly transmit to the server 13 the ID together with positioning times. Thus, the server 13 will in this example be able to determine the position of the movable device 3 based on information from the first device D1, and/or the second device D2, and/or the third device D As mentioned above the movable device may transmit identification messages 11 repeatedly, wherein the identification code ID is unique, not only for the movable device but for unique for every message. For example, the identification code ID may consist of two parts, a first part being a device ID and the second part being a sequence number defining the sequence number of an identification code ID.
The server may then group the received information based on device ID and sequence number to group information relating to the same identification message from the same movable device.
Figure 4 is a flow diagram illustrating the method for determining the position of the movable device 3. In a first step 101 messages, comprising the state ofthe first internal clock (Figure 1), are repeatedly sent from the first device D1. The first states comprise at least first transmit times Ttr1 obtained from the first internal clock. In a second step 102 the first messages are received at the second device D2 and corresponding first times of reception are obtained from the second internal clock. In a third step 103 a mathematical model of the state ofthe first internal clock in relation to the state of the second internal clock is determined based on the first transmit times Ttr1, the first times of reception Trc1 and the propagation delay Tdel, wherein the state of the first internal clock 4 at least comprises the time of the first internal clock in relation to the time ofthe second internal clock. In a fourth step 104 an identification message with an identification code from the movable device is received, at the first device D1, and a corresponding first positioning time is obtained from the first internal clock, wherein the identification code is unique for the movable device. In a fifth step 105 the identification message with the identification code from the movable device is received at the second device, and a corresponding second positioning time is obtaining from the second internal clock. ln a sixth step 106 the position of the movable device 3 in relation to the first device and the second device is determined based on the first positioning time, the second positioning time, the known distance S0 and the mathematical model of the first internal clock 4 in relation to the second internal clock The third step 103 of determining a mathematical model of the state ofthe first internal clock in relation to the state of the second internal clock may be performed in the second device but may alternatively be performed in the server.
The sixth step 106 may be achieved in many different ways. As described above in relation to Figure 1 the first positioning time may be sent to the second device which then determines an adjusted first positioning time using the mathematical model of the first internal clock in relation to the second internal clock. The second device may then determine the position or transmit the adjusted first positioning time and the second positioning time to a server which determines the position.
The positioning system 100 may also be configured to determine the accuracy of the first positioning time Tpos1 and the second positioning time Tpos2 and to determine the accuracy of the position of the movable device 3 using the accuracy of first positioning time Tpos1 and the second positioning time Tpos2. The accuracy of the first positioning time Tpos1 and the second positioning time Tpos2 may be determined in many different ways. According to a first example the accuracy ofthe first positioning time Tpos1 may be determined from the fluctuations of the first transmit times Ttr1. Alternatively, the first internal clock 4 may send its factory accuracy in the first messages 8. The factory accuracy has been determine in advance. Alternatively, if a Kalman filter is used the accuracy may be determined using the Kalman filter.
The described embodiments may be amended in many ways without departing from the scope ofthe invention which is limited only by the appended claims.
Claims (14)
1. A method En a positioning system for determining the position of a movable device (3) in relation to at least a first device (1) and a second device (2), wherein the first device (1) and the second device (2) are arranged at a known distance (S0) from each other corresponding to a propagation delay (Tdel) for a signal between the first device (D1) and the second device (D2), wherein the first device (D1) comprises a first internal clock (4) and the second device (D2) comprises a second internal clock (6), wherein the method comprises the steps of - repeatedly transmitting, from the first device (D1), first messages (8) comprising the state of the first internal clock (4), which states comprise at least first transmit times obtained from the first internal clock (4), - receiving the first messages (8) at the second device (D2) and obtaining corresponding first times of reception from the second internal clock (6), - determining a mathematical model of the state of the first internal clock (4) in relation to the state of the second internal clock (6) based on the first transmit times, the first times of reception and the propagation delay (Tdel), wherein the state ofthe first internal clock (4) at least comprises the time of the first internal clock (4) in relation to the time of the second internal clock (6), - receiving, at the first device (D1), an identification message (11) with an identification code (ID) from the movable device (3) and obtaining a corresponding first positioning time (Tpos1) from the first internal clock (4), wherein the identification code (ID) is unique for the movable device (3), - receiving, at the second device (D2), the identification message (11) with the identification code (ID) from the movable device (3) and obtaining a corresponding second positioning time (Tpos2) from the second internal clock (6), - determining the position of the movable device (3) in relation to the first device (D1) and the second device (D2) based on the known distance (S0), the first positioning time (Tpos1), the second positioning time (Tpos2), and the mathematical model of the first internal clock (4) in relation to the second internal clock (6).
2. The method according to claim 1, wherein the mathematical model is a statistical model. 17
3. The method according to claim 2, wherein the statistical model is updated at the reception of each one of the first messages (8) at the second device (D2).
4. The method according to claim 3, wherein the statistical model of the first internal clock (4) in relation to the second internal clock (6) is corrected, using a state estimator, based on the received first transmit times.
5. The method according to claim 4, wherein the state estimator is a Kalman filter.
6. The method according to claim 1, 2 or 3, comprising the steps of - transmitting from the first device (D1) to the second device (D2) the first positioning time, -determining, in the second device, an adjusted first positioning time based on the first positioning time and the mathematical model of the state ofthe first internal clock in relation to the second internal clock, and - to transmit the adjusted first positioning time and the second positioning time to a server (13), wherein the server (13) is configured to perform the determination ofthe position of the movable device in relation to the first device (D1) and the second device (D2).
7. A positioning system (100), comprising at least a first device (D1) and a second device (D2) at a known distance (S0) from each other, for determining the position of a movable device (3) in relation to the first device (D1) and the second device (D2), wherein the first device (D1) comprises a first internal clock (4) and a first transceiver (5), wherein the second device comprises a second internal clock (6) and a second transceiver (7), wherein the first device (D1) and the second device (D2) are configured to be arranged at a known distance (S0) from each other corresponding to a propagation delay (Tdel) for a signal between the first device (D1) and the second device (D2), wherein the system (100) is configured to - repeatedly transmit, from the first device (D1), first messages (8) comprising first transmit times (Ttr1) obtained from the first internal clock (4), - receive the first messages (8) at the second device (D2) and obtaining corresponding first times of reception (Ttr1) from the second internal clock, - determine a mathematical model of the state of the first internal clock (4) in relation to the second internal clock (6) based on the first transmit times (Ttr1), the first times of reception (Trc1) and the propagation delay (Tdel), wherein the state ofthe first internal clock (4) at least comprises the time of the first internal clock (4) in relation to the second internal clock (6),- receive, at the first device (4), an identification message (11) with an identification code (ID) from the movable device (3) and obtaining a corresponding first positioning time (Tposl) from the first internal clock (4), wherein the identification code (ID) is unique for the movable device (3), - receive, at the second device (D2), the identification message (11) with the identification code (ID) from the movable device (3) and obtaining a corresponding second positioning time (Tpos2) from the second internal clock (6), and - determine the position of the movable device (3) in relation to the first device (D1) and the second device (D2) based on the known distance (S0), the first positioning time (Tposl), the second positioning time (Tpos2), and the mathematical model ofthe first internal clock in relation to the second internal clock. __.. ._ _. .___m__\_._\. ._ “x-km.. »_ .JN-kw --.~ t. t .. _ ,\\. .-.. ..._.~....l\§ nä.. ...\\\f^~\:2. v :à .» ._ . 'cæäftëï u _ h-.åï-*tlh . _. t .. .I . -f/ 'I f 1 r f »w .» 'I I f <7 1 » 1 » å; 1 all, n vf, 4 å; 1. o *r i? W- The positioning system (100) according to claim Läge-å; comprising a server (13), wherein the first device (D1) is configured to transmit the first positioning time (Tposl) to the second device (D2), wherein the second device (D2) is configured to determine an adjusted first positioning time (Tpos1') based on the first positioning time (Tposl) and the mathematical model ofthe state of the first internal clock (4) in relation to the second internal clock (6), and to transmit the adjusted first positioning time (Tpos1') and the second positioning time (Tpos2) to tigga server (13), and wherein the server (13) is configured to perform the determination ofthe position ofthe movable device (3) in relation to the first device (D1) and the second device (D2). ._ u. ~ 'ti w» ._..- ~ _ ut .> .-:-- 4-2.-~-i _. .-.~§.- I ~ UEPÉ* “m3 'csâêëïï Qèw. k-'xfsšššia:ïiiï NES) ;>~\<š:ê;>~t::..<š: ïšïšš-Luàë is 19 11. The positioning system (100) according to claims Så or 103-313, wherein the determination of aíhgwstatistical model of the state of the first internal clock (4) in relation to the second internal clock (6) is performed in the second device (D2). 12. The positioning system (100) according to any one of claims 7-11, wherein the system (100) is configured to correct the model ofthe state of the first internal clock (4) in relation to the second internal clock (6) using a state estimator. 13. The positioning system according to claim 12, wherein the state estimator is a Kalman filter. 14. The positioning system (100) according to any one of claims 7-13, wherein the system is also configured to determine the accuracy ofthe first positioning time (Tpos1) and the second positioning time (Tpos2) and to determine the accuracy of the position of the movable device (3) using the accuracy ofthe first positioning time (Tpos1) and the second positioning time (Tpos2).
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20140364142A1 (en) * | 2009-12-10 | 2014-12-11 | Rockstar Consortium Us Lp | Tdoa based positioning with calculation of correction factors for compensating the clock offsets of unsynchronized network stations |
| WO2015041687A1 (en) * | 2013-09-20 | 2015-03-26 | Caterpillar Inc. | Positioning system using radio frequency signals |
| US20150097412A1 (en) * | 2013-10-09 | 2015-04-09 | Caterpillar Inc. | Determing an activity of a mobile machine |
| WO2017063018A1 (en) * | 2015-10-16 | 2017-04-20 | Caterpillar Underground Mining Pty Ltd | A mobile machine and a system for determining a mobile machine's position |
| EP3690471A1 (en) * | 2019-02-04 | 2020-08-05 | HERE Global B.V. | Determining a plurality of installation positions of a plurality of radio devices |
-
2021
- 2021-12-07 SE SE2151495A patent/SE545367C2/en unknown
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20140364142A1 (en) * | 2009-12-10 | 2014-12-11 | Rockstar Consortium Us Lp | Tdoa based positioning with calculation of correction factors for compensating the clock offsets of unsynchronized network stations |
| WO2015041687A1 (en) * | 2013-09-20 | 2015-03-26 | Caterpillar Inc. | Positioning system using radio frequency signals |
| US20150097412A1 (en) * | 2013-10-09 | 2015-04-09 | Caterpillar Inc. | Determing an activity of a mobile machine |
| WO2017063018A1 (en) * | 2015-10-16 | 2017-04-20 | Caterpillar Underground Mining Pty Ltd | A mobile machine and a system for determining a mobile machine's position |
| EP3690471A1 (en) * | 2019-02-04 | 2020-08-05 | HERE Global B.V. | Determining a plurality of installation positions of a plurality of radio devices |
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