WO2009112935A1

WO2009112935A1 - Positioning device for moving body

Info

Publication number: WO2009112935A1
Application number: PCT/IB2009/000501
Authority: WO
Inventors: Norimasa Kobori; Naoto Hasegawa; Kazunori Kagawa; Masayuki Kurimoto
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2008-03-13
Filing date: 2009-03-12
Publication date: 2009-09-17
Also published as: JP2009222438A

Abstract

A positioning device includes a positioning unit (12) that determines a position etc. of a moving body at a reference time, a state detection sensor (14) that detects a state of the moving body, a transmission path (16) that transmits a detection result in a clock period, and a synchronization unit (11). The synchronization unit includes a first synchronization unit that specifies a detection result that has to be synchronized, an estimation unit that estimates the reference time, a time difference calculation unit that calculates a time difference between a detection time when the detection result has been detected and the reference time, and a second synchronization unit that calculates a position of the moving body at the detection time by using the calculated time difference and positioning determination results at the reference time, and associates a calculation result of the moving body position and the specified detection result.

Description

POSITIONING DEVICE FOR MOVING BODY

BACKGROUND OF THE INVENTION

1. Field of the Invention [0001] This invention relates to a positioning device for a moving body that includes means for synchronizing a positioning result with a detection result of another sensor.

2. Description of the Related Art

[0002] A conventional navigation device is available in which an internal system time is set based on time required for positioning computation with a Global Positioning System (GPS) receiver, and a detection result from a sensor that detects a moving body state is synchronized with a positioning computation result obtained with the GPS receiver by using the system time that has been set (see, for example, Japanese Patent Application Publication No. 2001-324560 (JP-A-2001-324560)).

[0003] However, the sensor detection result is transmitted via a bus such as a Controller Area Network (CAN) in a predetermined clock period. Therefore, a problem associated with a configuration in which synchronization is performed by taking into account only the result obtained by positioning computation in a GPS receiver, as in JP-A-2001-324560, is that a time error that is equal to or less than the clock period cannot be eliminated. Furthermore, another problem associated with JP-A-2001-324560 is that a delay caused by a transfer of positioning result after positioning computations in the GPS receiver is not taken into account and synchronization accuracy is insufficient.

SUMMARY OF THE INVENTION

[0004] Accordingly, the invention provides a positioning device for a moving body that can synchronize a positioning result and a detection result of another sensor with good accuracy.

[0005] The first aspect of the invention relates to a positioning device for a moving body, including: positioning means for determining a position and a speed of a moving body at a reference time on the basis of a reception result of a radio wave from a satellite; a state detection sensor that detects a state of the moving body; a transmission path that transmits a detection result of the state detection sensor in a predetermined clock period; and synchronization means for synchronizing a detection result of the state detection sensor and a positioning determination result of the positioning means. The synchronization means includes: first synchronization means for specifying a detection result that has to be synchronized, from among a plurality of detection results of the state detection sensor that have been received via the transmission path over a plurality of consecutive clock periods; estimation means for estimating the reference time; time difference calculation means for calculating a time difference between a detection time at which the detection result specified by the first synchronization means has been detected and a reference time estimated by the estimation means; and second synchronization means for calculating by interpolation a position of the moving body at the detection time by using a time difference calculated by the time difference calculation means and positioning determination results of the position and speed of the moving body at the ^' reference time, and associating a calculation result of the moving body position and a detection result specified by the first synchronization means.

[0006] In the positioning device for a moving body according to the above-describes aspect, the first synchronization means may specify, by using an estimation result of the estimation means, a detection result in a clock period corresponding to the reference time, a detection result in a clock period immediately after the clock period corresponding to the reference time, or a detection result at a detection time that is the closest to the reference time, as the detection result that has to be synchronized.

[0007] The second synchronization means may calculate a movement amount of the moving body within a time difference calculated by the time difference calculation means on the basis of the positioning determination result of a speed of the moving body at the reference time and calculate a position of the moving body at the detection time on the basis of the calculated movement amount and positioning determination result of a position of the moving body at the reference time.

[0008] The positioning determination result of a speed of the moving body may be derived using an observation result of a Doppler frequency of an electromagnetic wave from a satellite.

[0009] The estimation means may estimate the reference time by taking into account a positioning computation time required for positioning computations of the positioning means and a transmission time required when a positioning result from the positioning means is transmitted to the synchronization means.

[0010] The positioning means may be realized by a GPS receiver, the synchronization means may be realized by a computer connected via a second transmission path to the GPS receiver, and the transmission time may be a transmission time in the second transmission path.

[0011] The time difference calculation means may estimate a detection time at which a detection result specified by the first synchronization means has been detected, on the basis of a time of reception of a detection result in a clock period of a predetermined number, from among detection results of the state detection sensor received via the transmission path over a plurality of consecutive clock periods, and on a basis of a difference in frequency between the clock period of the predetermined number and a clock period of a detection result specified by the first synchronization means.

[0012] The second aspect of the invention relates to a positioning device for a moving body, including: positioning means for determining a position and a speed of a moving body at a reference time on the basis of a reception result of a radio wave from a satellite; a state detection sensor that detects a state of the moving body; a transmission path that transmits a detection result of the state detection sensor in a predetermined clock period; and synchronization means for specifying a detection result that has to be synchronized, from among a plurality of detection results of the state detection sensor received via the transmission path over a plurality of consecutive clock periods, and associates the specified detection result with the positioning determination result of the position or speed of the moving body at the reference time. The synchronization means includes: estimation means for estimating the reference time by taking into account a positioning computation time required for positioning computations of the positioning means and a transmission time required when a positioning determination result from the positioning means is transmitted to the synchronization means; and specifies a detection result in a clock period corresponding or close to a reference time estimated by the estimation means, as a detection result that has to be synchronized. [0013] The positioning means may be realized by a GPS receiver, the synchronization means may be realized by a computer connected via a second transmission path to the GPS receiver, and the transmission time may be a transmission time in the second transmission path.

[0014] The third aspect of the invention relates to a positioning device for a moving body, including: positioning means for determining a position and a speed of a moving body at a reference time on the basis of a reception result of a radio wave from a satellite; a state detection sensor that detects a state of the moving body; a transmission path that transmits a detection result of the state detection sensor in a predetermined clock period; and synchronization means for specifying a detection result that has to be synchronized, from among a plurality of detection results of the state detection sensor received via the transmission path over a plurality of consecutive clock periods, and associates the specified detection result with the positioning determination result of the position of the moving body at the reference time. A state of the moving body detected by the state detection sensor includes a speed of the moving body and also a state other than a speed of the moving body; and the synchronization means retrieves a detection result that is the closest to a positioning determination result of a speed of the moving body at the reference time, from among a plurality of detection results of a speed of the moving body transmitted from the state detection sensor over a plurality of consecutive clock periods; and specifies a detection result in a clock period relating to the closest detection result, as a detection result that has to be synchronized.

[0015] The positioning means may be realized by a GPS receiver, the synchronization means may be realized by a computer connected to the GPS receiver, and a PPS signal representing the reference time may not be transmitted from the GPS receiver to the computer. [0016] The positioning means may be realized by a GPS receiver, the synchronization means may be realized by a computer connected to the GPS receiver, and the synchronization means may function when a PPS signal is not supplied from the GPS receiver to the computer. [0017J A state of the moving body detected by the state detection sensor may include at least one from among a speed, an acceleration, an angular speed, and a steering angle of the moving body.

[0018] The moving body may be a vehicle.

[0019] The fourth aspect of the invention relates to a computer that realizes the synchronization means in the positioning device for a moving body.

[0020] The invention makes it possible to obtain a positioning device for a moving body that can synchronize a positioning result and a detection result of another sensor with good accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The foregoing and further features and advantages of the invention will become apparent from the following description of example embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements, and wherein: FIG 1 is a system configuration diagram illustrating the entire configuration of GPS employing the positioning device 1 for a moving body according to the invention;

FIG 2 shows a principal configuration of one embodiment of the positioning device 1 for a moving body;

FIG. 3 illustrates conventional technology as a reference example; FIGS. 4A, 4B, and 4C are explanatory drawings illustrating the synchronization processing in Embodiment 1;

FIG 5 is a flowchart illustrating an example of synchronization processing executed by the microcomputer 11 in Embodiment 1;

FIG 6 is an explanatory drawing illustrating synchronization processing in Embodiment 2;

FIG 7 is a flowchart illustrating an example of synchronization processing executed by the microcomputer 11 in Embodiment 2;

FIG. 8 is a flowchart illustrating an example of synchronization processing executed by the microcomputer 11 in Embodiment 3; and

FIGS. 9Aand 9B illustrate an INS positioning example.

DETAILED DESCRIPTION OF EMBODIMENTS

[0022] An embodiment of the invention will be described below with reference to the appended drawings.

[0023] FIG 1 is a system configuration diagram illustrating the entire configuration of a GPS employing a positioning device 1 for a moving body of an embodiment of the invention. As shown in FIG 1, the GPS is configured by GPS satellites 10 rotating around the earth and a vehicle 90 that is positioned on the earth and can move on the earth. The vehicle 90 is merely an example of a moving body. Other examples of the moving body include a motorcycle, a railroad train, a ship, an airplane, a forklift, a robot, and an information terminal such as a cellular phone that moves following the movement of a person.

[0024] The GPS satellite 10 constantly transmits a navigation message (satellite signal) toward the earth. The navigation message includes satellite orbit information relating to the corresponding GPS satellite 10 (Ephemeris or Almanac), correction value of a watch, and a correction factor of ionosphere. The navigation message is diffused by a C/A code, placed on a Ll wave (frequency: 1575.42 MHz), and constantly transmitted toward the earth. The Ll wave is a composite wave of a Sin wave modulated by the C/A code and a Cos wave modulated by a P code (Precision Code); this composite wave is orthogonally modulated. The C/A code and P code are pseudonoise codes and code strings in which -1 and 1 are arranged periodically and irregularly.

[0025] Presently a total of 24 GPS satellites 10 rotate about the earth at an altitude of about 20,000 km and are uniformly arranged by four GPS satellites 10 on six orbits inclined by 55 degrees each. Therefore, in any location on the earth at least five GPS satellites 10 can be observed at all times, provided that the sky is clear. [0026] The vehicle 90 carries a positioning device 1 for a moving body. [0027] FIG 2 shows a principal configuration of an embodiment of the positioning device 1 for a moving body.

[0028] As shown in FIG 2, the positioning device 1 for a moving body includes a microcomputer 11, a GPS receiver 12 connected to the microcomputer 11 via a transmission path 18, and a vehicle sensor 14 connected to the microcomputer 11 via a transmission path 16. The microcomputer 11 is an in-system Electronic Control Unit (ECU) that uses both the positioning results of the GPS receiver 12 and the detection results of the vehicle sensor 14.

[0029] The GPS receiver 12 converts an electromagnetic wave received from the GPS satellite 10 via a GPS antenna into an intermediate frequency, then performs C/A code synchronization by using the C/A code generated in the GPS receiver and extracts a navigation message. Furthermore, the GPS receiver 12 also determines the position and speed of the vehicle 90 on the basis of the electromagnetic wave received from the GPS satellite 10. Any positioning method such as independent positioning or interference positioning may be used. The vehicle speed may be determined by using a Doppler frequency of a carrier wave. [0030] The positioning results of the GPS receiver 12 (also will be referred to hereinbelow as "GPS positioning results") are sent to the microcomputer 11 via the transmission path 18 at a predetermined clock period ΔT1. The predetermined clock period ΔT1 is, for example, a comparatively long period of 1 sec and may be equal to a period of PPS signal. The clock period ΔT1 is not required to be identical to an oscillation period of an oscillator (clock) and can include an integral multiple period thereof.

[0031] The vehicle sensor 14 may be any sensor that detects the vehicle state, such as a vehicle speed sensor (vehicle wheel speed sensor), an acceleration speed sensor, a gyroscope (yaw rate sensor), a steering angle sensor, a pressure sensor, a temperature sensor, a load sensor, and a geomagnetic sensor.

[0032] The detection result of the vehicle sensor 14 is transmitted to the transmission path 16 at a predetermined clock period ΔT2 (a different clock period may be used for each sensor). The clock period ΔT2 depends on the application of sensor output and the like, but is typically sufficiently smaller than the clock period ΔT1 for transmission of positioning result. The clock period ΔT2 is not required to be identical to the oscillation frequency of the oscillator (clock) and can include an integral multiple period thereof. The transmission path 16 may be any path, for example, a CAN, a Body Electronics Area Network (BEAN) (one of bidirectional multiplexing communication networks), and a Local Interconnect Network (LIN).

[0033] Because both the positioning result of the GPS receiver 12 and the detection result of the vehicle sensor 14 serve as information obtained by detecting the vehicle state, the state of the vehicle can be detected from various perspectives with good accuracy by combining these results. However, by contrast with the detection result of the vehicle sensor 14, the positioning result of the GPS receiver 12 requires processing with a high computation load. Therefore, the positioning result of the GPS receiver 12 is delayed in time due to the time required for computation processing in the GPS receiver 12. For this reason, within the framework of the related technology, a synchronization error caused by the delay of positioning results of the GPS receiver 12 in time is prevented, as shown in FIG 3, by extracting a PPS signal from the GPS receiver, inputting the signal into a synchronization circuit, and performing synchronization of positioning results of the GPS receiver and detection results of the vehicle sensor on the basis of the PPS signal.

[0034] However, a problem associated with such related technology is that a terminal and a transmission path are necessary to extracts the PPS signal from the GPS receiver and the utility is low. Thus, for example, navigation devices can be used and replaced, as wished by the user, by products manufactured by a large number of different manufacturers. Therefore, it would be valuable to ensure versatility that enables synchronization even for navigation devices provided with a GPS receiver in which the PPS signal is difficult or impossible to extract.

[0035] Accordingly, as will be described hereinbelow in greater detail, the positioning device 1 for a moving body is provided with configuration such that the positioning result of the GPS receiver 12 and the detection result of the vehicle sensor 14 can be adequately synchronized even in a navigation device provided with a GPS receiver 12 in which the PPS signal is difficult or impossible to extract.

[0036] FIG 4 is an explanatory drawing illustrating synchronization processing in Embodiment 1. FIG. 4 A shows a time sequence of the principal processing in the GPS receiver 12, FIG. 4B shows a time series of data (data stream) transmitted from the vehicle sensor 14, and FIG 4C shows a time series of principal processing in the microcomputer 11.

[0037] In the example shown in FIG 4, as shown in FIG 4A₁ the GPS receiver 12 executes positioning computation synchronously with the PPS signal and transmits the GPS positioning results (GPS data A) obtained in such computations to the microcomputer 11 via the transmission path 18. In this case, a time required for positioning computation is tl and a time required to transfer the data A is t2. The GPS data A obtained in this case are data that are synchronized with the timing of the PPS signal.

[0038] Further, as shown in FIG 4B, data from the vehicle sensor 14 are transmitted via the transmission path 16 to the microcomputer 11 at a predetermined clock period ΔT2 (in this example, ΔT2 = a) such as mentioned hereinabove. In this example, data from the vehicle sensor 14 are stored in a predetermined memory of the microcomputer 11 for every 10-period data (dataO to data9). As described hereinabove, the data of each period (data*) may include detection data (detection data, for example, speed, acceleration, and steering angle) of a plurality of vehicle sensors 14. In this case, it is assumed that these data are synchronized. The symbol "*" used in "data*" etc. means any of 0 to 9.

[0039] Further, as shown in FIG. 4C, each time dataO is inputted, the microcomputer 11 stores the timing Ti thereof (that is, input timing of data 0) in a predetermined memory and also stores the 10-period data (dataO to data9) including and preceding data 9 that are immediately precede data O. Each time the GPS positioning results (GPS data A) are inputted, the microcomputer 11 stores the timing Tg thereof (that is, input timing of GPS data A) and also stores the data A in the predetermined memory. Where the microcomputer 11 stores the GPS data A in the predetermined memory, the microcomputer executes the synchronization processing shown in FIG 5.

[0040] FIG 5 is a flowchart showing an example of synchronization processing executed by the microcomputer 11 in Embodiment 1.

[0041] In step 100, a transfer time t2 (see FIG 4) of the GPS data A is calculated. The transfer time t2 is derived from preliminary tests or the like and may be stored in advance as known information in a memory that can be accessed by the microcomputer 11.

[0042] In step 102, a positioning computation time tl (see FIG 4) is estimated. Similarly to the transfer time t2, the positioning computation time tl is derived from preliminary tests or the like and may be stored in advance as known information in a memory that can be accessed by the microcomputer 11.

[0043] In step 104, a PPS signal generation time Tp is estimated. More specifically, the PPS signal generation time Tp = Tg - tl - 12 is calculated using the input time Tg of the aforementioned GPS data A. [0044] In step 106, detection time TiO to Ti9 is allocated to 10-period data (dataO to data9) by using the input time Ti of data 0 and the period ΔT2 (= a) of the vehicle sensor 14. More specifically, a detection time Ti9 = Ti - a is allocated to data9, a detection time Ti8 = Ti - 2 x a is allocated to data8. Similarly, a detection period TiO = Ti - 10 x a is allocated to dataO. • The detection time TiO to Ti9 corresponds to time at which dataO to data9 are detected. In this case, the delay of processing time and transmission time in the vehicle sensor 14 is very small and ignored. However, the detection time TiO to Ti9 may be derived by subtracting these processing time and/or transmission time.

[0045] In step 108, the PPS signal generation time Tp estimated in the step 104 and the detection time TiO to Tϊ9 allocated in the step 106 are compared, data* relating to a clock period corresponding to the PPS signal generation time Tp, from among the detection time TiO to Ti9, is specified, and the specified data* are associated with the GPS data A that are presently inputted (synchronized). In the example shown in FIG 4, the PPS signal generation time Tp corresponds to the Ti7 to Ti8 clock period. Therefore, data7 relating to the to the Ti7 to Ti8 clock period are associated with the presently inputted GPS data A. Alternatively, data* relating to the detection time Ti* that is the closest to the PPS signal generation time Tp may be are associated with the presently inputted GPS data A. In this case, in the example shown in FIG 4, the PPS signal generation time Tp is closer to the detection time Ti8 than to the detection time TΪ7. Therefore, dataδ relating to the detection time Ti8 that is the closest to the PPS signal generation time Tp are associated with the presently inputted GPS data A. In yet another alternative example, data* of the clock period immediately following the clock period corresponding to the PPS signal generation time Tp may be are associated with the presently inputted GPS data A. In this case, in the example shown in FIG. 4, dataδ of the clock period immediately following the clock period corresponding to the PPS signal generation time Tp are associated with the presently inputted GPS data A.

[0046] The GPS data A that were thus synchronized and the data* of the vehicle sensor 14 can be used in a variety of different systems. For example, the synchronized GPS data A and data* of the vehicle sensor 14 may be used in a positioning system based on inertial navigation, in various information output systems or vehicle travel control systems using position information of GPS data A, or in map matching.

[0047] Thus, with Embodiment 1, the positioning results of the GPS receiver 12 and detection results of the vehicle sensor 14 can be synchronized by using software even in a navigation device provided with the GPS receiver 12 in which the PPS signals are difficult or impossible to extract. Furthermore, with Embodiment 1, the PPS signal generation time Tp is estimated by taking into account not only the positioning computation time tl, but also the transfer time t2 of GPS data A. Therefore, the estimation accuracy is high, thereby making it possible to reduce effectively the synchronization error. [0048] Embodiment 2 differs from the above-described Embodiment 1 only in the details of synchronization processing executed by the microcomputer 11. Therefore, only a feature specific to Embodiment 2 will be described below, and other features may be similar to those of the above-described Embodiment 1. [0049] FlG 6 is an explanatory drawing of synchronization processing performed in

Embodiment 2. Here, the synchronization processing in Embodiment 2 will be explained with reference to the contents shown in FIG 4. In the above-described Embodiment 1, the data* with the predetermined clock period are associated, as described hereinabove, with the GPS data A. For example, in the example shown in FIG 4, when data7 relating to a clock period corresponding to the PPS signal generation time Tp are associated with the GPS data A, a synchronization error remain that is equal to time difference (= a - β) between the PPS signal generation time Tp and the detection time Tϊ7.

[0050] Accordingly, in Embodiment 2, in order to eliminate the synchronization error equal to or less than the clock period, the microcomputer 11 calculates the time difference ΔTp between the PPS signal generation time Tp and detection time Ti* relating to data* that have to be synchronized, corrects the GPS positioning result (GPS data A) by extrapolation and interpolation by the time difference ΔTp, and then associates the result with the data* that have to be synchronized. In Embodiment 2, an example is shown in which the positioning results of the position of vehicle 90, from among the GPS positioning results, are associated (synchronized) with the detection results of the vehicle sensor 14.

[0051] Here, a case will be considered by way of example in which data8 relating to detection time Ti8 that is the closest to the PPS signal generation time Tp are associated with the GPS data A. In this case, as shown in FIG 6, the time difference ΔTp between the PPS signal generation time Tp and the detection time TΪ8 relating to data 8 that have to be synchronized becomes ΔTp = Ti8 - Tp (= β). Therefore, by extrapolating and interpolating the GPS positioning results (GPS data A) by the time difference ΔTp (= β), the microcomputer 11 calculates the GPS positioning results after the time ΔTp has elapsed since the PPS signal generation time Tp and associates the calculated GPS positioning result with dataδ. The extrapolation- interpolation is implemented by calculating the movement amount of the vehicle 90 within the time difference ΔTp on the basis of speed information of the vehicle 90 and integrating this movement amount with the positioning result of the position of the vehicle 90 relating to the PPS signal generation time Tp. For example, a positioning result of a speed of the vehicle 90 relating to the PPS signal generation time Tp (for example, a speed calculated using the Doppler frequency observation results) is used as the speed information of the vehicle 90.

[0052] Any positioning method may be used for determining a speed of the vehicle 90 by using the Doppler frequency observation results. For example, the following method may be used. A Doppler frequency Δf_k(i) (= fr - fu) in a period (i) corresponding to the PPS signal generation time Tp is measured based on a frequency fr of a replica carrier and a carrier wave frequency fπ (1575.42 MHz) that is already known. Then, a speed vector v = (v_x(i), V_y(i), v_z(i)) of the vehicle 90 in the period (i) corresponding to the PPS signal generation time Tp is determined using the Doppler frequency Δf_k(i). This determination may be performed using a least square method, for example, on the basis of a relational expression shown below. Black circle symbols provided above the letters represent dots (derivative with respect to time). For example, a Doppler range dp_k is a p_k dot (derivative of a pseudo-distance P_k with respect to time). [Formula 1]

[0053] An I dot and a T dot represent a variation amount of an ionosphere error and a variation amount of a troposphere error. However, they are very small and, therefore, handled herein as white noise ε. Furthermore, a b dot is a differential value of a clock error. A VfI_k portion of (Vk - v)-l_k is an inner product of a unit vector l_k(i) and a satellite movement speed vector V^i). The satellite movement speed vector V_k(i) is calculated based on satellite trajectory information of the above-described navigation message, and the unit vector l_k(i) may be calculated in the following manner by using a position (X_u(i), Y_u(i), Zu(i)) of the vehicle 90 positioned in the period (i) and a satellite position (X_k(i), Y_kO), Z_k(i)) ^of the GPS satellite 10_k calculated in the period (i). [Formula 2]

h = HX_ki-X_uUY_ki~Yj,Z^- 2J)

where

[0054] Furthermore, the Doppler range dp_t(i) is calculated, for example, by dp_t(i) = λ-Δf_k(i) by using a wavelength λ (already known) of the carrier wave and a Doppler frequency Δfk(i) relating to the GPS satellite 10_k obtained in the period (i). In this case, extrapolation and interpolation are realized by multiplying the obtained speed vector v = (vχ(0_> Vy(i), V₂(I)) by the time difference ΔTp and adding up the displacement vector obtained by such multiplication to the position (X_u(i), Y_u(i), Z₁₁O)) of the vehicle 90 positioned in the period (i). Thus, the position (X_u(i), Y_u(i)_> ZuO)) of the vehicle 90 after correction is (X_u'(i), Y_u'(i), Z₁₁ ¹O)) = ΔTp-(v_x(i), v/i), V₂O)) + (X_u0), YoO), Z₁₁(I)). [0055] FIG 7 shows a flowchart illustrating an example of synchronization processing executed by the microcomputer 11 in Embodiment 2.

[0056] In step 200, the transfer time t2 (see FIG 4) of the GPS data A is calculated. The transfer time t2 is derived from preliminary tests or the like and may be stored in advance as known information in a memory that can be accessed by the microcomputer 11.

[0057] In step 202, the positioning computation time tl (see FIG 4) is estimated. Similarly to the transfer time t2, the positioning computation time tl is derived from preliminary tests or the like and may be stored in advance as known information in a memory that can be accessed by the microcomputer 11.

[0058] In step 204, a PPS signal generation time Tp is estimated. More specifically, the PPS signal generation time Tp = Tg - tl - 12 is calculated using the input time Tg of the aforementioned GPS data A. [0059] In step 206, detection time TiO to Ti9 is allocated to 10-period data (dataO to data9) by using the input time Ti of dataO and the period ΔT2 (= a) of the vehicle sensor 14. More specifically, a detection time TΪ9 = Ti - a is allocated to data 9, a detection time Ti8 = Ti - 2 x a is allocated to data8. Similarly, a detection period TiO = Ti - 10 x a is allocated to dataO. The detection time TiO to Ti9 corresponds to a time at which dataO to data9 are detected. In this case, the delay of processing time and transmission time in the vehicle sensor 14 is very small and ignored. However, the detection time TiO to Ti9 may be derived by subtracting these processing time and/or transmission time.

[0060] In step 208, the PPS signal generation time Tp estimated in the step 204 and the detection time TiO to Ti9 allocated in the step 206 are compared, and data* relating to a clock period corresponding to the PPS signal generation time Tp, from among the detection time TiO to Ti9, are specified as data* that have to be associated (have to be synchronized) with the presently inputted GPS data A. In the example shown in FIG 4, data7 relating to the clock period corresponding to the PPS signal generation time Tp are specified. Alternatively, data* relating to the detection time Ti* that is the closest to the PPS signal generation time Tp may be specified. In this case, in the example shown in FIG. 4, dataδ relating to the detection time Ti8 that is the closest to the PPS signal generation time Tp are specified. In yet another alternative example, data* of the clock period immediately following the clock period corresponding to the PPS signal generation time Tp may be specified. In this case, in the example shown in FIG. 4, data8 of the clock period immediately following the clock period corresponding to the PPS signal generation time Tp are specified. In Embodiment 2, extrapolation and interpolation are performed in the following step 214 as described hereinabove. Therefore, data* of the clock period immediately following the clock period corresponding to the PPS signal generation time Tp may be specified. The explanation will be continued below under an assumption that data* of the clock period immediately following the clock period corresponding to the PPS signal generation time Tp are specified.

[0061] In step 210, the time difference ΔTp (= Ti* - Tp) between the PPS signal generation time Tp and the detection time Ti* relating to the data* specified in step 208 is calculated.

[0062] In step 212, the positioning result of the position of the vehicle 90 relating to the PPS signal generation time Tp is extrapolated and interpolated based on the time difference ΔTp calculated in step 210. The above-described method may be used as the extrapolation and interpolation method.

[0063] In step 214, the positioning result of the position of the vehicle 90 that has been corrected by extrapolation and interpolation is associated (synchronized) with data* specified in step 208. The GPS data A and data* of the vehicle sensor 14 that have thus been synchronized can be used in a variety of different systems. For example, the synchronized GPS data A and data * of the vehicle sensor 14 may be used in a positioning system based on inertial navigation, in various information output systems or vehicle travel control systems using position information of GPS data A, or in map matching. [0064] Thus, with Embodiment 2, the positioning results of the GPS receiver 12 and the detection results of the vehicle sensor 14 can be synchronized by using software even in a navigation device provided with the GPS receiver 12 in which the PPS signals are difficult or impossible to extract. Furthermore, with Embodiment 2, as described hereinabove, the positioning result of the position of the vehicle 90 is corrected by interpolation using the time difference ΔTp equal to or less than the clock period and then synchronized with the detection result of the vehicle sensor 14. Therefore, the synchronization error equal to or less than the clock period can be eliminated. Furthermore, with Embodiment 2, the PPS signal generation time Tp is estimated by taking into account not only the positioning computation time tl, but also the transfer time t2 of GPS data A. Therefore, the estimation accuracy is high, thereby making it possible to reduce effectively the synchronization error.

[0065] Embodiment 3 differs from the above-described Embodiment 1 only in the details of synchronization processing executed by the microcomputer 11. Therefore, only features specific to Embodiment 3 will be described below, and other features may be similar to those of the above-described Embodiment 1.

[0066] FIG 8 is a flowchart illustrating an example of synchronization processing executed by the microcomputer 11 in Embodiment 3.

[0067] In step 300, speed information (positioning results of the speed of the vehicle 90) is extracted from the GPS data A.

[0068] In step 302, the extracted speed information of the GPS data A is compared with 10-period data (dataO to data9) of the vehicle sensor 14. In this case, speed information (for example, speed information from the vehicle speed sensor) in data* of the vehicle sensor 14 is compared with the speed information of the GPS data A. For this purpose, data* of the vehicle sensor 14 may directly include the speed information such as speed information from the vehicle speed sensor, or may include data such as acceleration information from which speed information can be derived, instead of the speed information from the vehicle speed sensor. Furthermore, data* of the vehicle sensor 14 include information (for example, acceleration information or steering angle information) other than the speed information from the vehicle speed sensor. This is because when data* of the vehicle sensor 14 contain only the speed information, the meaning of synchronization in Embodiment 3 is essentially lost.

[0069] In step 304, data* of the vehicle sensor 14 including speed information that is the closest to the speed information of the GPS data A are specified from among the 10-period data (dataO to data9) of the vehicle sensor 14 on the basis of comparison results obtained in step 302, and the specified data* are associated (synchronized) with the presently inputted GPS data A. In the example shown in FIG 4, when the speed information relating to dataδ relating to the detection time Ti8 is the closest to the speed information of the GPS data A, data8 relating to the detection time Tϊ8 are associated with the presently inputted GPS data A. Thus, in this case, the detection time Ti8 is estimated as the PPS signal generation time Tp, and dataδ relating to the detection time Ti8 are associated with the presently inputted GPS data A.

[0070] The GPS data A and data* of the vehicle sensor 14 that have thus been synchronized can be used in a variety of different systems. For example, the synchronized GPS data A and data* of the vehicle sensor 14 may be used in a positioning system based on inertial navigation, in various information output systems or vehicle travel control systems using position information of GPS data A, or in map matching.

[0071] Thus, with Embodiment 3, the positioning results of the GPS receiver 12 and the detection results of the vehicle sensor 14 can be synchronized by using software even in a navigation device provided with the GPS receiver 12 in which the PPS signals are difficult or impossible to extract. Furthermore, with Embodiment 3, as described hereinabove, the PPS signal generation time Tp can be estimated with good accuracy and the positioning results of the GPS receiver 12 and the detection results of the vehicle sensor 14 can be synchronized even in the case in which the positioning computation time tl or the transfer time t2 of the GPS data A is difficult or impossible to derive. [0072] FIG 9A shows a positioning result obtained with an inertial navigation method employing INS in the case in which the positioning results of the GPS receiver 12 and the detection results of the vehicle sensor 14 have not been synchronized. FIG 9B shows the positioning results obtained when the positioning results of the GPS receiver 12 and the detection results of the vehicle sensor 14 have been synchronized by the above-described embodiment. The positioning result is a result after a Karman filter, but it is clear that in the case in which synchronization has been performed, a smooth trajectory is plotted. [0073] Embodiments of the invention are described above, but the invention is not limited to the embodiments and the above-described embodiments can be changed and modified in a variety of ways, without departing from the scope of the invention.

[0074] For example, in the above-described embodiments, the PPS signal generation time Tp is estimated as a reference time by taking into account that the PPS signal generation time Tp is normally used synchronously in GPS positioning, but another time may be also set and estimated as the reference time. For example, a reception time of the GPS electromagnetic wave to be used for positioning or a transmission time (electromagnetic wave generation time of the GPS satellite 10) of the GPS electromagnetic wave to be used for positioning may be equivalently set and estimated as the reference time.

[0075] Furthermore, in Embodiment 2, extrapolation and interpolation are executed by using speed information obtained by positioning from a Doppler frequency of an electromagnetic wave from the satellite, but speed information obtained by positioning performed by another method may be also used. For example, speed information may be derived and the extrapolation and interpolation may be executed using the speed information by deriving a differential vector of a position (X_u(i), YuO). Zu(O) ⁰^ the vehicle 90 positioned in the period (i) corresponding to the PPS signal generation time Tp and a position (X«(i -1), Y_u(i -1), Z_u(i -I)) of the vehicle 90 positioned in the preceding period (i -1) and dividing this differential vector by a period time.

[0076] Furthermore, in the above-described Embodiment 2, the PPS signal generation time Tp is estimated by taking into account not only the positioning computation time tl, but also the transfer time t2 of the GPS data A, but the PPS signal generation time Tp may be also estimated by taking into account only one of them (for example, the positioning computation time tl).

[0077] In the above-described embodiments, the microcomputer 11 may execute the above-described synchronization processing only when no PPS signal is inputted from the GPS receiver. Thus, when a PPS signal is inputted from the GPS receiver, the microcomputer 11 may perform synchronization based on the PPS signal in the same manner as in the conventional configuration.

[0078] Furthermore, in the above-described embodiments, the detection results of the vehicle sensor 14 are stored in the units of 10-period data (dataO to data9), but this number (10) of periods is merely an example, and the detection result may be stored in data units of any number of periods. For example, data may be stored for each period. In this case, the processing of step 106 shown by way of example in FIG. 5 is unnecessary.

[0079] In the above-described embodiments, an example of applying the invention to GPS is described, but the invention can be also applied to satellite systems other that GPS, for example, to other Global Navigation Satellite System (GNSS) such as Galileo.

Claims

CLAIMS 1. A positioning device for a moving body, characterized by comprising: positioning means for determining a position and a speed of a moving body at a reference time on the basis of a reception result of a radio wave from a satellite; a state detection sensor that detects a state of the moving body; a transmission path that transmits a detection result of the state detection sensor in a predetermined clock period; and synchronization means for synchronizing a detection result of the state detection sensor and a positioning determination result of the positioning means, wherein the synchronization means comprises: first synchronization means for specifying a detection result that has to be synchronized, from among a plurality of detection results of the state detection sensor that have been received via the transmission path over a plurality of consecutive clock periods; estimation means for estimating the reference time; time difference calculation means for calculating a time difference between a detection time at which the detection result specified by the first synchronization means has been detected and a reference time estimated by the estimation means; and second synchronization means for calculating by interpolation a position of the moving body at the detection time by using a time difference calculated by the time difference calculation means and positioning determination results of the position and speed of the moving body at the reference time, and associating a calculation result of the moving body position and a detection result specified by the first synchronization means.

2. The positioning device for a moving body according to claim 1, wherein the first synchronization means specifies, by using an estimation result of the estimation means, a detection result in a clock period corresponding to the reference time, a detection result in a clock period immediately after the clock period corresponding to the reference time, or a detection result at a detection time that is the closest to the reference time, as the detection result that has to be synchronized.

3. The positioning device for a moving body according to claim 1, wherein the second synchronization means calculates a movement amount of the moving body within a time difference calculated by the time difference calculation means on the basis of the positioning determination result of a speed of the moving body at the reference time and calculates a position of the moving body at the detection time on the basis of the calculated movement amount and positioning determination result of a position of the moving body at the reference time.

4. The positioning device for a moving body according to claim 1, wherein the positioning determination result of a speed of the moving body is derived using an observation result of a Doppler frequency of a radio wave from a satellite.

5. The positioning device for a moving body according to claim 1, wherein the estimation means estimates the reference time by taking into account a positioning computation time required for positioning computations of the positioning means and a transmission time required when a positioning result from the positioning means is transmitted to the synchronization means.

6. The positioning device for a moving body according to claim 5, wherein the positioning means is realized by a GPS receiver, the synchronization means is realized by a computer connected via a second transmission path to the GPS receiver, and the transmission time is a transmission time in the second transmission path.

7. The positioning device for a moving body according to claim 1, wherein the time difference calculation means estimates a detection time at which a detection result specified by the first synchronization means has been detected, on the basis of a time of reception of a detection result in a clock period of a predetermined number, from among detection results of the state detection sensor received via the transmission path over a plurality of consecutive clock periods, and on a basis of a difference in frequency between the clock period of the predetermined number and a clock period of a detection result specified by the first synchronization means.

8. A positioning device for a moving body, characterized by comprising: positioning means for determining a position and a speed of a moving body at a reference time on the basis of a reception result of a radio wave from a satellite; a state detection sensor that detects a state of the moving body; a transmission path that transmits a detection result of the state detection sensor in a predetermined clock period; and synchronization means for specifying a detection result that has to be synchronized, from among a plurality of detection results of the state detection sensor received via the transmission path over a plurality of consecutive clock periods, and associates the specified detection result with the positioning determination result of the position or speed of the moving body at the reference time, wherein the synchronization means comprises estimation means for estimating the reference time by taking into account a positioning computation time required for positioning computations of the positioning means and a transmission time required when a positioning determination result from the positioning means is transmitted to the synchronization means, and specifies a detection result in a clock period corresponding or close to a reference time estimated by the estimation means, as a detection result that has to be synchronized.

9. The positioning device for a moving body according to claim 8, wherein the positioning means is realized by a GPS receiver, the synchronization means is realized by a computer connected via a second transmission path to the GPS receiver, and the transmission time is a transmission time in the second transmission path.

10. A positioning device for a moving body, characterized by comprising: positioning means for determining a position and a speed of a moving body at a reference time on the basis of a reception result of a radio wave from a satellite; a state detection sensor that detects a state of the moving body; a transmission path that transmits a detection result of the state detection sensor in a predetermined clock period; and synchronization means for specifying a detection result that has to be synchronized, from among a plurality of detection results of the state detection sensor received via the transmission path over a plurality of consecutive clock periods, and associates the specified detection result with the positioning determination result of the position of the moving body at the reference time, wherein a state of the moving body detected by the state detection sensor includes a speed of the moving body and also a state other than a speed of the moving body; and the synchronization means retrieves a detection result that is the closest to a positioning determination result of a speed of the moving body at the reference time, from among a plurality of detection results of a speed of the moving body transmitted from the state detection sensor over a plurality of consecutive clock periods, and specifies a detection result in a clock period relating to the closest detection result, as a detection result that has to be synchronized.

11. The positioning device for a moving body according to any one of claims 1 to 10, wherein the positioning means is realized by a GPS receiver, the synchronization means is realized by a computer connected to the GPS receiver, and a PPS signal representing the reference time is not transmitted from the GPS receiver to the computer.

12. The positioning device for a moving body according to any one of claims 1 to 10, wherein the positioning means is realized by a GPS receiver, the synchronization means is realized by a computer connected to the GPS receiver, and the synchronization means functions when a PPS signal is not supplied from the GPS receiver to the computer.

13. The positioning device for a moving body according to any one of claims 1 to 9, wherein a state of the moving body detected by the state detection sensor includes at least one from among a speed, an acceleration, an angular speed, and a steering angle of the moving body.

14. The positioning device for a moving body according to any one of claims 1 to 13, wherein the moving body is a vehicle.

15. A computer that realizes the synchronization means in the positioning device for a moving body according to any one of claims 1 to 14.

16. A positioning device for a moving body, characterized by comprising: a positioning unit that determines a position and a speed of a moving body at a reference time on the basis of a reception result of a radio wave from a satellite; a state detection sensor that detects a state of the moving body; a transmission path that transmits a detection result of the state detection sensor in a predetermined clock period; and a synchronization unit that synchronizes a detection result of the state detection sensor and a positioning detection result of the positioning unit, wherein the synchronization unit comprises: a first synchronization unit that specifies a detection result that has to be synchronized, from among a plurality of detection results of the state detection sensor that have been received via the transmission path over a plurality of consecutive clock periods; an estimation unit that estimates the reference time; a time difference calculation unit that calculates a time difference between a detection time at which the detection result specified by the first synchronization unit has been detected and a reference time estimated by the estimation unit; and a second synchronization unit that calculates by interpolation a position of the moving body at the detection time by using a time difference calculated by the time difference calculation unit and positioning determination results of the position and speed of the moving body at the reference time, and associates a calculation result of the moving body position and a detection result specified by the first synchronization unit.

17. A positioning device for a moving body, characterized by comprising: a positioning unit that determines a position and a speed of a moving body at a reference time on the basis of a reception result of a radio wave from a satellite; a state detection sensor that detects a state of the moving body; a transmission path that transmits a detection result of the state detection sensor in a predetermined clock period; and a synchronization unit that specifies a detection result that has to be synchronized, from among a plurality of detection results of the state detection sensor received via the transmission path over a plurality of consecutive clock periods, and associates the specified detection result with the positioning determination result of the position or speed of the moving body at the reference time, wherein the synchronization unit comprises an estimation unit that estimates the reference time by taking into account a positioning computation time required for positioning computations of the positioning unit and a transmission time required when a positioning result from the positioning unit is transmitted to the synchronization unit, and specifies a detection result in a clock period corresponding or close to a reference time estimated by the estimation unit, as a detection result that has to be synchronized.