JP2011128138A - Method and system for calculating position - Google Patents

Abstract

An object of the present invention is to make it possible to appropriately perform correlation processing in consideration of fluctuations in Doppler frequency.
The speed calculated by the INS unit and the GPS unit and the speed detected by the speed / direction sensor units are integrated to calculate the speed of the position calculation system. Further, the Doppler error is determined using the speed error calculated by the INS unit 50 and the GPS unit 60 and the speed error detected by the speed / direction sensor units 70 and 80. Then, the Doppler frequency is determined using the speed determined by GPA 15, and the correlation integration time is determined using the determined Doppler error. Then, the positions calculated by the INS unit 50 and the GPS unit 60 are integrated, and the position of the position calculation system 1 is calculated.
[Selection] Figure 1

Description

  The present invention relates to a position calculation method and a position calculation system.

  A GPS (Global Positioning System) is widely known as a positioning system using positioning signals, and is used in a position calculation device built in a mobile phone or a car navigation device. In the GPS, position calculation calculation for obtaining position coordinates and clock error of the position calculation device is performed based on information such as positions of a plurality of GPS satellites and pseudo distances from each GPS satellite to the position calculation device.

  A GPS satellite signal transmitted from a GPS satellite is modulated with a spreading code different for each GPS satellite called a CA (Coarse and Acquisition) code. The position calculation device performs a correlation operation between the received signal and a replica CA code that is a replica of the CA code, and captures a GPS satellite signal based on the correlation value. In this case, when a GPS satellite signal is captured from a weak received signal, the correlation value acquired by the correlation calculation is integrated over a predetermined integration time in order to facilitate detection of the peak of the correlation value. Is used.

  However, since the CA code itself for spreading and modulating the GPS satellite signal is BPSK (Binary Phase Shift Keying) modulated every 20 milliseconds by the navigation message, the polarity of the CA code can be inverted every 20 milliseconds. Therefore, when the correlation values are integrated across the inversion timing, correlation values having different signs may be integrated. As a technique for solving this problem, for example, as disclosed in Patent Document 1, a technique for accumulating correlation values based on information on polarity inversion timing acquired from the outside is known.

JP 2001-349935 A

  According to the technique of Patent Document 1, the correlation integration time can be made longer than 20 milliseconds. However, another problem arises by increasing the correlation integration time. Doppler is one of them. For example, when the moving speed of the position calculating device changes, the Doppler frequency changes. As a result, the search frequency may gradually fluctuate during long-time correlation integration, and may deviate from the initial frequency search range. For example, when the position calculation device is moving at an acceleration of 1 [G], the variation amount of the Doppler frequency is 50 [Hz / s]. That is, when the moving speed varies, the actual search frequency deviates from the originally assumed search frequency.

Theoretically, if the Doppler frequency does not fluctuate, the more integrated the correlation value, the larger the correlation integrated value of a certain frequency, and the specific frequency (= received frequency) with the peak of the correlation integrated value. Should be easily discernable. However, in reality, when the Doppler frequency fluctuates, a deviation occurs between the actual search frequency and the originally assumed frequency, and the specific frequency itself also fluctuates. As a result, if the correlation integration is performed for a certain time or more, a situation occurs in which it is difficult to determine the peak of the correlation integration value.
This leads to the fact that the satellite signal cannot be captured even if the correlation integration time is lengthened.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to make it possible to appropriately perform correlation processing in consideration of fluctuations in Doppler frequency.

  A first mode for solving the above problems is a position calculation unit that performs correlation processing on a received signal that has received a satellite signal, captures the satellite signal, and calculates a position and a velocity, and at least the velocity can be detected. A position calculating method for calculating a position using a sensor unit, calculating a determination speed that is a speed determined using a calculation result by the position calculation unit and a detection result by the sensor unit; The calculation error by the position calculation unit and the detection error by the sensor unit are used to calculate the error of the determination speed, and the Doppler frequency used when the position calculation unit determines a search frequency for searching the satellite signal. Is determined using the determination speed, and the correlation when the position calculation unit performs the correlation process. The computation time, and determining with an error of the determination speed, the position calculating method comprising, and calculating the position using the detection result by the calculation result and the sensor unit by the position calculation unit.

  Further, as another form, a position calculation unit that performs correlation processing on a received signal that has received a satellite signal to acquire the satellite signal and calculates a position and velocity, a sensor unit that can detect at least velocity, and the position Using a determination speed calculation unit that calculates a determination speed that is a speed determined using a calculation result by the calculation unit and a detection result by the sensor unit, a calculation error by the position calculation unit, and a detection error by the sensor unit An error calculation unit for calculating an error of the determination speed; and a Doppler frequency determination unit for determining a Doppler frequency used when the position calculation unit determines a search frequency for searching the satellite signal using the determination speed; , The correlation integration time when the position calculation unit performs the correlation process is determined as the determination speed. A position calculation system comprising: a correlation integration time determination unit that determines using a difference; and a position calculation unit that calculates a position using a calculation result by the position calculation unit and a detection result by the sensor unit; Also good.

  According to the first aspect and the like, the determination speed is calculated using the calculation result by the position calculation unit that calculates the position and speed using the satellite signal and the detection result by the sensor unit that can detect at least the speed. . Further, the determination speed error is calculated using the calculation error by the position calculation unit and the detection error by the sensor unit. Then, the Doppler frequency used when the position calculation unit determines the search frequency is determined using the determination speed, and the correlation integration time when the position calculation unit performs correlation processing is determined using the determination speed error. To do. Then, the position is calculated using the calculation result by the position calculation unit and the detection result by the sensor unit.

  The Doppler frequency resulting from the movement of the position calculation unit can be predicted using the speed detected by the sensor unit. However, the assumed Doppler frequency may vary depending on the movement state of the position calculation unit and the like. In this case, the Doppler frequency error (= variation amount of the Doppler frequency) can be approximated based on the speed error. Therefore, by using an error (determination speed error) that can be included in the determination speed calculated using the calculation result by the position calculation unit and the detection result by the sensor unit, an appropriate correlation integration time that takes into account fluctuations in the Doppler frequency Can be determined.

  Further, as a second mode, in the position calculation method according to the first mode, the determination speed error may be calculated by determining the error of the determination speed with respect to the line-of-sight direction to the positioning satellite that transmits the satellite signal. You may comprise the position calculation method including calculating.

  According to the second embodiment, the error of the determination speed with respect to the line-of-sight direction to the positioning satellite that transmits the satellite signal is calculated. By calculating the determination error with respect to the direction of the line of sight to the positioning satellite, the error of the Doppler frequency can be obtained appropriately.

  Further, as a third mode, in the position calculation method according to the first or second mode, calculating the error of the determination speed includes a calculation error by the position calculation unit and a detection error by the sensor unit. A position calculation method including weighted averaging may be configured.

  In this case, as a fourth mode, the position calculation method is configured so that the weighted average in the position calculation method of the third mode includes changing the weight of the weighted average according to a moving state. It is also possible.

  According to the fourth embodiment, the determination speed error is determined by deciding which of the calculation error by the position calculation unit and the detection error by the sensor unit to be weighted and averaged according to the moving state. Can be obtained more accurately.

  Further, as a fifth form, the weighted average in the position calculation method of the third or fourth form can detect whether the position calculation unit is in a position-computable state, and can be detected by the sensor unit. It is also possible to configure the position calculation method to include changing the weighted average weight according to whether or not the state is present.

  According to the fifth embodiment, the satellite signal is obtained by changing the weighted average weight according to whether the position calculation unit is in a state in which position calculation is possible and whether the sensor unit is in detection state. Thus, it is possible to calculate an appropriate determination speed error according to the reception environment and the detection state of the sensor unit. For example, there may be a case where a satellite signal cannot be temporarily received in a tunnel or the like, and such a state can be appropriately handled.

  Furthermore, as a sixth form, the weighted average in the position calculation method of any one of the third to fifth forms depends on a relative value between a calculation error by the position calculation unit and a detection error by the sensor unit. It is also possible to configure the position calculation method to include changing the weight of the weighted average.

  According to the sixth aspect, the accuracy of the required determination speed error is further improved by changing the weighted average weight according to the relative value of the calculation error by the position calculation unit and the detection error by the sensor unit. To do.

  Further, as a seventh mode, the position calculation method according to any one of the first to sixth modes, wherein the position calculation unit adds the correlation integration value every time the correlation integration time elapses. The unit performs the correlation process and calculates the position by performing the correlation process at a predetermined time interval. Based on the predetermined time interval and the correlation integration time, the correlation is performed once. The position calculation method may further include adjusting an end timing of summation of the correlation integrated values in the processing.

  According to the seventh aspect, the position calculation unit performs the correlation process by adding the correlation integration value every time the correlation integration time elapses. Then, the process of calculating the position by performing the correlation process is performed at a predetermined time interval, and the end timing of the summation of the correlation integrated value in one correlation process is adjusted based on the predetermined time interval and the correlation integrated time. .

  Since the correlation integration time is determined using an error in the determination speed, it is not always constant. However, according to the seventh aspect, even if the correlation integration time varies, the correlation integration value in one correlation process is appropriately summed up each time the correlation integration time elapses. The end timing of the summation is adjusted.

The block diagram which shows an example of a function structure of a position calculation system. The block diagram which shows an example of a function structure of a GPS unit. The figure which shows an example of a data structure of speed / speed error data. The figure which shows an example of the table structure of the table for output type determination. The figure which shows an example of a data structure of weighted average weight pattern data. The flowchart which shows the flow of a Doppler error determination process. The flowchart which shows the flow of a speed error calculation process. Explanatory drawing of the principle of speed error calculation. The flowchart which shows the flow of a position / speed calculation process. The flowchart which shows the flow of a satellite signal acquisition process. The flowchart which shows the flow of a correlation integration process. Explanatory drawing of the principle of correlation integration time determination. The flowchart which shows the flow of a position / speed integration process. The block diagram which shows an example of a function structure of the position calculation system in a modification. The figure which shows an example of the weighted average weight pattern data in a modification. The figure which shows an example of the table structure of the table for correlation integration time determination in a modification.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Of course, embodiments to which the present invention is applicable are not limited to the embodiments described below.

1. System Configuration FIG. 1 is a block diagram showing a functional configuration of a position calculation system 1 (position calculation device) in the present embodiment. The position calculation system 1 is a kind of position calculation device, and in the present embodiment, a description will be given on the assumption that a navigation device mounted on a moving body such as an automobile or a bus is assumed. However, the present invention can also be applied to other electronic devices such as a mobile phone including a smartphone, a notebook computer, and a PDA (Personal Digital Assistant).

  The position calculation system 1 is installed with a fixed relative position with respect to the moving body, and is configured such that the direction sensor unit 80 can detect the traveling direction of the moving body as the traveling direction of the position calculation system 1.

  The position calculation system 1 includes a processing unit 10, an input unit 20, a display unit 30, a communication unit 40, an INS (Inertial Navigation System) unit 50, a GPS (Global Positioning System) unit 60, and a speed sensor unit 70. And a direction sensor unit 80.

  The processing unit 10, the input unit 20, the display unit 30, and the communication unit 40 are connected via a first data bus 45. The processing unit 10, the INS unit 50, the GPS unit 60, the speed sensor unit 70, and the azimuth sensor unit 80 are connected via a second data bus 90.

  The processing unit 10 is a control device that comprehensively controls the position calculation system 1, and includes Doppler error determination unit 11, position / velocity integration processing unit (hereinafter referred to as “GPA (Generic Position Algorithm)”) as its functional units. 15).

  The Doppler error determination unit 11 is a processing circuit block that determines an assumed fluctuation amount (hereinafter referred to as “Doppler error”) of the Doppler frequency caused by the movement of the position calculation system 1. Although the Doppler is generated by the movement of the position calculation system 1, the Doppler frequency in that case varies depending on the movement state of the position calculation system 1 and the like. The Doppler error determination unit 11 calculates the amount of fluctuation of the Doppler frequency as a Doppler error using unit information from each unit.

  The Doppler error determination unit 11 includes a processor such as a digital signal processor (DSP) and a memory, and executes Doppler error determination processing described later as digital signal processing. The Doppler error determination unit 11 includes a storage unit 12 as a memory for storing various data.

  The storage unit 12 includes a storage device such as a ROM (Read Only Memory), a flash ROM, and a RAM (Random Access Memory), and a system program for the processing unit 10 to control the position calculation system 1 or a Doppler error determination unit. 11 stores programs and data for determining the Doppler error. In addition, a work area for temporarily storing various programs executed by the Doppler error determination unit 11, data being processed in various processes, processing results, and the like is formed.

  The storage unit 12 includes, for example, unit data 121 that is unit information data output from each unit, and speed / speed error that is data of speed and speed error of the position calculation system 1 calculated using the unit information. Data 123, an output type determination table 125 for determining an output type of unit information of each unit, weighted average weight pattern data 127 in which a weight pattern for weighted averaging of unit information of each unit is defined, Is memorized.

  FIG. 3 is a diagram showing an example of the data configuration of the speed / speed error data 123. As shown in FIG. In the speed / speed error data 123, a speed / speed error 1233 calculated using the unit information of each unit is stored in time series in association with the time 1231. Based on the unit information stored in the unit data 121, the Doppler error determination unit 11 calculates the speed and speed error in the earth reference orthogonal coordinate system of the position calculation system 1 and stores them in the speed / speed error data 123. . Information output by each of the INS unit 50, the GPS unit 60, the speed sensor unit 70, and the direction sensor unit 80 is referred to as “unit information”.

  In the present embodiment, the GPS unit 60 calculates the position, velocity, and error thereof in the ECEF (Earth Centered Earth Fixed) coordinate system. On the other hand, the INS unit 50 calculates the position, speed, and error in an ENU (East North Up) coordinate system. The speed sensor unit 70 detects the speed of the position calculation system 1 in the traveling direction and its error, and the direction sensor unit 80 detects the direction indicating the traveling direction of the position calculation system 1 and its error. The Doppler error determination unit 11 performs a process of calculating the speed and speed error of the position calculation system 1 in the ECEF coordinate system based on unit information acquired from each unit via the second data bus 90.

The ECEF coordinate system is known as the earth-centered earth-fixed coordinate system. The origin is the center of the earth (the center of gravity of the earth), the Z-axis is the axis of rotation of the earth, and the X-axis is the axis where the Greenwich meridian and equatorial planes intersect. This is a three-axis orthogonal coordinate system in which the axis orthogonal to the axis is the Y-axis. Also, the ENU coordinate system is known as the Tohoku upper coordinate system, with a certain point near the ground surface as the origin, the zenith direction (above the vertical line to the ground surface) is the U axis, the east direction is the E axis, and the north direction This is a three-axis orthogonal coordinate system with an N axis.
The coordinate conversion itself between the ENU coordinate system and the ECEF coordinate system can be performed by matrix calculation or the like.

  FIG. 4 is a diagram illustrating an example of a table configuration of the output type determination table 125. The output type determination table 125 stores the unit information output state 1251 of each unit and the output types 1253 associated with each output state 1251 on a one-to-one basis.

  The output state 1251 is information indicating whether or not unit information is output from each unit. The unit is in a state where the unit information is being output. “X” is stored. The speed sensor unit 70 and the direction sensor unit 80 are collectively shown as “speed / direction” in order to calculate a speed error using the detection results from both sensor units. “○” is stored only when the unit information is output. Therefore, the output state 1251 can be said to be information indicating whether the current state of each unit is a state in which unit information can be calculated or detected.

  For example, a state in which all units of the INS unit 50, the GPS unit 60, and the speed / direction sensor units 70 and 80 output unit information is “type A”. For example, when the position calculation system 1 is located in a place where the sky is open and each unit is operating without any problem, the type A is selected.

  The INS unit 50 and the GPS unit 60 are in the output state, but in the state where the speed / azimuth sensor units 70 and 80 are not outputting, they are “type B”. For example, this type B corresponds to a case in which the speed / direction sensor units 70 and 80 are broken for some reason in a reception environment where satellite signals from GPS satellites can be received.

  When the INS unit 50 and the speed / orientation sensor units 70 and 80 are outputting, but the GPS unit 60 is not outputting, the type is “type C”. For example, the type C is a case where a GPS satellite signal from a GPS satellite cannot be received, such as in a tunnel or a building, and only the GPS unit 60 does not output (cannot output) unit information.

  The Doppler error determination unit 11 identifies the output state 1251 based on the output status of unit information from each unit. Then, the output type determination table 125 is referred to, and the output type 1253 associated with the identified output state 1251 is determined.

  FIG. 5 is a diagram illustrating an example of a data configuration of the weighted average weight pattern data 127. In the weighted average weight pattern data 127, an output type 1271, a movement state 1273, and a weighted average weight pattern 1275 are stored in association with each other.

  The output type 1271 corresponds to the output type 1253 of the output type determination table 125 of FIG. The movement state 1273 is a current movement state of the position calculation system 1, and is, for example, “stop” indicating that it is in a stopped state, “constant speed” indicating that it is in a constant speed movement state, an acceleration state, or a deceleration state. A plurality of movement states such as “acceleration / deceleration” indicating this are stored.

  The weighted average weight pattern 1275 is a weight pattern of each speed error when performing a weighted average calculation of the speed error of the INS unit 50, the speed error of the GPS unit 60, and the speed error of the speed / direction sensor units 70 and 80. is there. That is, a combination of values of the weight “α” for the speed error of the INS unit 50, the weight “β” for the speed error of the GPS unit 60, and the weight “γ” for the speed error of the speed / azimuth sensor units 70 and 80. Defined as a weighted average weight pattern. However, “α + β + γ = 1”.

  When the moving state is “stop”, the unit information of the speed / direction sensors 70 and 80 is trusted, and the weight “γ” for the speed error of the speed / direction sensors 70 and 80 is determined to be large. Yes. This is because in the stopped state, the detection accuracy of the speed / direction sensors 70 and 80 is high, but the calculation accuracy of the INS unit 50 and the GPS unit 60 is considered to decrease.

  When the movement state is “constant speed”, the unit information of the GPS unit 60 is trusted, and the weight “β” for the speed error of the GPS unit 60 is determined to be large. This is because it is considered that the calculation accuracy of the GPS unit 60 is particularly improved in the constant speed state.

When the movement state is “acceleration / deceleration”, the unit information of the INS unit 50 is trusted, and the weight “α” for the speed error of the INS unit 50 is determined to be large. This is because, in the acceleration / deceleration state, the calculation accuracy of the INS unit 50 is improved, but the GPS unit 60 is considered to have poor followability and lower calculation accuracy.
Note that the method of determining these weights is merely an example, and the setting can be changed as appropriate.

  The Doppler error determination unit 11 determines the current output state 1251 of each unit and also determines the current movement state 1273 of the position calculation system 1 based on the unit information history stored in the unit data 121. Then, an output type 1253 (1271) corresponding to the determined output state 1251 of each unit is determined based on the output type determination table 125. Then, the weighted average weight pattern 1275 corresponding to the output type 1271 and the movement state 1273 is determined based on the weighted average weight pattern data 127. Then, the average speed error is calculated by weighted averaging the speed error of each unit calculated by the speed error calculation process using the read weighted average weight pattern 1275. The average speed error is a value corresponding to an error in the determination speed of the position calculation system 1.

  Further, the Doppler error determination unit 11 acquires information such as the satellite position and the satellite speed of the GPS satellite (hereinafter referred to as “satellite information”) from the GPS unit 60 via the second data bus 90, and the GPA 15 The final integrated information of the obtained position calculation system 1 (hereinafter referred to as “integrated terminal information”) is acquired. Then, using the acquired satellite information and integrated terminal information, a line-of-sight direction from the position calculation system 1 to the GPS satellite is obtained, and an average velocity error with respect to the obtained line-of-sight direction is calculated as a Doppler error.

  The GPA 15 calculates the integrated position and the integrated speed, which are the final position and speed of the position calculation system 1, by performing an integrated operation on the position and the speed output from the various sensor units using, for example, a Kalman filter. It is a processing unit. The integrated position and the integrated speed are integrated terminal information. The function of the GPA 15 is realized by a processor such as a CPU or a DSP. The GPA 15 displays the obtained integrated terminal information on the display unit 30 and outputs it to the Doppler error determination unit 11. The integrated speed is a value corresponding to the determination speed of the position calculation system 1.

  The input unit 20 is an input device configured by, for example, a touch panel or a button switch, and outputs a signal of a key or button pressed by the user to the processing unit 10. Various instructions such as a position calculation request are input by an operation input from the input unit 20.

  The display unit 30 is configured by an LCD (Liquid Crystal Display) or the like, and is a display device that performs various displays based on display signals input from the processing unit 10. The display unit 30 displays a position display screen, time information, and the like.

  The communication unit 40 is a communication device for the position calculation system 1 to communicate with an external device under the control of the processing unit 10. This function is realized by, for example, a module for wired communication, a wireless LAN by IEEE802.11, a wireless communication module by a spread spectrum system, or the like. In the case where the position calculation system 1 is applied to a mobile phone, the communication unit 40 may be a communication device for a mobile phone.

  The INS unit 50 is a type of sensor unit, and performs known inertial navigation calculation processing based on acceleration and angular velocity measured by an IMU (Inertial Measurement Unit) 51 to calculate and detect the position and velocity of the INS unit 50. This is an inertial navigation system (position calculation system). Further, based on the acceleration error and the angular velocity error measured by the IMU 51, an error that can be included in the calculated position and velocity is calculated. In the present embodiment, the INS unit 50 calculates a position error and a speed error, which are errors thereof, along with the position and speed in the ENU coordinate system as needed. These pieces of information are output as unit information to the processing unit 10 via the second data bus 90.

  The IMU 51 includes, for example, an acceleration sensor and a gyro sensor, and is configured to be able to detect the axial acceleration of each of the three orthogonal axes of the ENU coordinate system and the angular velocity around the axis of each axis. The acceleration sensor and the gyro sensor are sensors that measure acceleration and angular velocity, respectively. The IMU 51 is configured to calculate and output errors that can be included in the measured acceleration and angular velocity as needed. For example, an elapsed time from the start of measurement and an error that can be included in the measurement value are stored in association with each other, a configuration in which an error corresponding to the elapsed time from the start of measurement is output, the temperature of the measurement environment, A configuration in which an error that can be included in the measurement value is stored in association with each other and an error corresponding to the current environmental temperature is output is conceivable. The acceleration sensor and the gyro sensor may be independent sensors or may be integrated sensors. Moreover, it is good also as detecting and outputting a speed based on the detection result of an acceleration sensor.

  The GPS unit 60 is a kind of position calculation unit, and performs a known position calculation calculation and speed calculation calculation using a GPS satellite signal transmitted from a GPS satellite which is a kind of positioning satellite. In the present embodiment, the GPS unit 60 calculates the position and velocity in the ECEF coordinate system, and the position error and velocity error that are errors that can be included in the calculation results. These pieces of information are output as unit information to the processing unit 10 via the second data bus 90.

  The speed sensor unit 70 is a kind of sensor unit, and is a speed detection unit including a sensor that detects the moving speed of the position calculation system 1. For example, a speed sensor unit using a Doppler effect or a spatial filter may be used. May be used. For example, when the position calculation system 1 is applied to an automobile, a speedometer mounted on the automobile may be used as the speed sensor unit 70.

  In the present embodiment, the speed sensor unit 70 outputs a speed error that can be included in the moving speed and the moving speed with respect to the traveling direction of the position calculation system 1 (moving body). For example, the speed error may be determined according to the elapsed time from the start of measurement, or may be determined in association with the measured environmental temperature, and output according to the elapsed time or the environmental temperature. These pieces of information are output as unit information to the processing unit 10 via the second data bus 90.

  The azimuth sensor unit 80 is a kind of sensor unit, and is a azimuth detection unit including a biaxial geomagnetic sensor composed of, for example, an element whose resistance value or impedance value increases or decreases depending on the strength of the magnetic field.

  In the present embodiment, the azimuth sensor unit 80 detects the traveling direction of the position calculation system 1 (moving body) as the azimuth and outputs an azimuth error that can be included in the detected azimuth. Similar to the speed sensor unit 70, the azimuth error is determined according to, for example, the elapsed time from the start of measurement, or is determined in association with the measured environmental temperature, and is output according to the elapsed time or the environmental temperature. It is done. These pieces of information are output as unit information to the processing unit 10 via the second data bus 90.

2. Configuration of GPS Unit FIG. 2 is a block diagram illustrating an example of a functional configuration of the GPS unit 60. The GPS unit 60 includes a GPS antenna 61, an RF (Radio Frequency) receiving circuit unit 63, and a baseband processing circuit unit 65.

  The GPS antenna 61 is an antenna that receives an RF signal including a GPS satellite signal transmitted from a GPS satellite, and outputs a received signal to the RF receiving circuit unit 63.

  The RF receiving circuit unit 63 is an RF signal processing circuit block, which down-converts the received RF signal into an intermediate frequency signal (hereinafter referred to as “IF (Intermediate Frequency) signal”), amplifies the IF signal, and the like. After that, it is converted into a digital signal by an A / D converter and output to the baseband processing circuit unit 65.

  The RF receiving circuit unit 63 and the baseband processing circuit unit 65 constitute a GPS receiving unit. The RF receiving circuit unit 63 and the baseband processing circuit unit 65 can be manufactured as separate LSIs (Large Scale Integration) or as a single chip.

  The baseband processing circuit unit 65 performs correlation calculation processing on the IF signal output from the RF receiving circuit unit 63 to acquire and extract GPS satellite signals, decodes the data, and displays navigation messages, time information, and the like. It is a circuit part to take out. The baseband processing circuit unit 65 includes a satellite signal acquisition unit 651, a position / velocity calculation unit 653, and a storage unit 655.

  The satellite signal acquisition unit 651 is a circuit unit that acquires a GPS satellite signal from a reception signal that is an IF signal output from the RF reception circuit unit 63, and includes a correlator 6511 and a replica signal generation unit 6513. The

  A correlator 6511 is a correlator (correlator) that performs a correlation operation between the reception signal converted into the IF signal input from the RF reception circuit unit 63 and the replica signal input from the replica signal generation unit 6513. The correlator 6511 outputs the correlation value obtained by performing the correlation calculation to the position / velocity calculation unit 653.

  The replica signal generation unit 6513 is a circuit unit that generates a replica signal of a CA code that is a spreading code of a GPS satellite signal. The replica signal generation unit 6513 generates the replica signal by changing the phase of the replica signal according to the correlation integration time output from the correlation integration time determination unit 6533, and outputs the replica signal to the correlator 6511.

  The position / velocity calculation unit 653 is a circuit unit that calculates the position and velocity of the GPS unit 60 by performing a known position / velocity calculation calculation using the GPS satellite signal captured by the satellite signal acquisition unit 651. The processing circuit block includes a correlation integration processing unit 6531 and a correlation integration time determination unit 6533.

  The correlation integration processing unit 6531 is a processing unit that performs a correlation integration process of integrating the correlation value output from the correlator 6511 of the satellite signal acquisition unit 651 according to the correlation integration time determined by the correlation integration time determination unit 6533. This processing unit is realized by a processor such as a CPU or a DSP.

  The correlation integration time determination unit 6533 is a processing unit that determines the correlation integration time when the correlation integration processing unit 6531 performs the correlation integration process. The correlation integration time determination unit 6533 is also realized by a processor such as a CPU or DSP.

  The correlation integration time determination unit 6533 acquires the Doppler error determined by the Doppler error determination unit 11 from the processing unit 10 via the second data bus 90. Then, a correlation integration time is calculated and determined using the acquired Doppler error, and is output to the correlation integration processing unit 6531.

  The storage unit 655 is configured by a storage device such as a ROM, flash ROM, or RAM, and various programs and data for realizing the system program of the baseband processing circuit unit 65, the correlation integration processing function, the position / speed calculation function, and the like. Etc. are remembered. In addition, it has a work area for temporarily storing data being processed and results of various processes.

  The storage unit 655 stores, for example, bit inversion pattern data 6551, satellite orbit data 6553, and Doppler error 6555.

  Bit inversion pattern data 6551 is data in which a bit inversion pattern of the CA code of the received signal is stored. The bit inversion pattern data 6551 can be acquired as assist data from the assist server of the position calculation system 1, for example. When the position calculation system 1 is applied to a mobile phone, it can be acquired as assist data from the base station of the mobile phone.

  By using the bit inversion pattern data 6551, it is possible to perform the correlation integration process by extending the correlation integration time. The CA code for modulating the GPS satellite signal is BPSK modulated every 20 milliseconds by the navigation message. Therefore, when the correlation integration time exceeds 20 milliseconds, the CA code value is inverted due to the polarity inversion of the navigation message, and the correlation value is changed, thereby canceling the correlation value in the correlation integration process. There is a problem. However, if the bit inversion pattern of the received signal is known, the correlation value signs can be aligned (adjusted) and integrated, and the correlation value can be prevented from canceling.

  The satellite orbit data 6553 is data such as an almanac that stores approximate satellite orbit information of all GPS satellites, and an ephemeris that stores detailed satellite orbit information for each GPS satellite. The satellite orbit data 6553 can be obtained by decoding a GPS satellite signal received from a GPS satellite, or can be obtained from a base station of a mobile phone or an assist server.

  The Doppler error 6555 is a Doppler error acquired from the Doppler error determination unit 11 via the second data bus 90.

3. Flow of processing 3-1. Processing of Doppler Error Determination Unit 11 FIG. 6 is a flowchart showing the flow of Doppler error determination processing executed by the Doppler error determination unit 11 of the processing unit 10.

  First, the Doppler error determination unit 11 determines a unit that outputs unit information (step A1). Then, the output type 1253 associated with the output state 1251 from each unit is determined with reference to the output type determination table 125 of the storage unit 12 (step A3).

  Next, the Doppler error determination unit 11 determines the movement state 1273 of the position calculation system 1 based on the history of each unit information stored in the unit data 121 of the storage unit 12 (Step A5). For example, when the speed of each unit information is the stop equivalent speed ("0" or a value close to this), "stop", constant speed condition (a state where the time change of the speed is small for a predetermined time or longer) It can be determined that “constant speed” is satisfied, and “acceleration / deceleration” is satisfied when acceleration / deceleration conditions (when the change in speed with time is abrupt) are satisfied.

  In addition, when the judgment based on the history of each unit information results in different judgment results, as in the above-described weighted average weight pattern 1275, the “stop” judgment is performed by using the unit information of the speed / direction sensors 70 and 80 as “ The “constant speed” determination can be performed with emphasis on unit information of the GPS unit 60, and the “acceleration / deceleration” determination can be performed with emphasis on unit information of the INS unit 50.

  Then, the Doppler error determination unit 11 refers to the weighted average weight pattern data 127 in the storage unit 12, and the weighted average weight in which the output type 1271 selected in Step A3 and the movement state 1273 determined in Step A5 are associated with each other. A pattern 1275 is selected (step A7). And the Doppler error determination part 11 performs a speed error calculation process (step A9).

FIG. 7 is a flowchart showing the flow of the speed error calculation process.
First, the Doppler error determination unit 11 performs the process of Loop A for each unit determined in Step A1 (Steps B1 to B19). In the process of Loop A, the Doppler error determination unit 11 determines the type of the unit (Step B3). If the unit is the GPS unit 60 (Step B3; GPS), the process proceeds to the next unit. To do. In the present embodiment, since the GPS unit 60 outputs the speed and speed error in the ECEF coordinate system, it is not necessary to perform coordinate conversion.

  On the other hand, when the unit is the speed sensor unit 70 (step B3; speed sensor), the Doppler error determination unit 11 determines whether or not there is an output from the direction sensor unit 80 (step B5). When it determines (step B5; Yes), the speed error in an ECEF coordinate system is calculated using the detection result of the speed sensor unit 70 and the direction sensor unit 80 (step B7-B15).

  FIG. 8 is a diagram for explaining the principle of calculating the speed error in the ECEF coordinate system. In FIG. 8, the horizontal axis indicates the east-west direction with the east direction being positive, and the vertical axis indicates the north-south direction with the north direction being positive. The speed in the traveling direction of the moving body on which the position calculation system 1 is mounted is detected by the speed sensor unit 70, and the direction of the traveling direction is detected by the direction sensor unit 80. Therefore, a speed vector is defined in which the speed detected by the speed sensor unit 70 is the length (size) of the speed vector, and the detected direction detected by the direction sensor unit 80 is the direction of the speed vector. This is the velocity vector V in FIG.

  The detected speed error output from the speed sensor unit 70 is an error in the direction along the direction of the speed vector V, and the detected direction error output from the direction sensor unit 80 is the direction of the speed vector V ( This is an error with respect to the central angle with respect to the coordinate origin in FIG.

  Therefore, first, an error range L1 of the detected speed output from the speed sensor unit 70 is calculated using the end point of the speed vector V as a reference (step B7 in FIG. 7). Since this range L1 is an error range in the front-rear direction (moving forward / backward direction) of the moving body on which the position calculation system 1 is mounted, it is hereinafter referred to as a “front-rear direction speed error range”.

  Next, with reference to the direction of the velocity vector V, a deviation width of the direction of the velocity vector V corresponding to the detection azimuth error range output from the azimuth sensor unit 80 is calculated. This deviation width is calculated as a range L2 in the direction orthogonal to the direction of the velocity vector V from the end point of the velocity vector V (step B9 in FIG. 7). Since this range L2 is a range of the error in the left-right direction with respect to the moving direction of the moving body on which the position calculation system 1 is mounted, it is hereinafter referred to as a “left-right speed error range”.

  Next, a square speed error region S having a larger value of the speed error range “L1” in the front-rear direction and the speed error range “L2” in the left-right direction as a diagonal line is calculated (FIG. 7). Step B11). In FIG. 8, since L1 is larger than L2, a speed error region S having L1 as a diagonal component is calculated. Then, the length in the east-west direction of the calculated speed error region S is calculated as the east-west direction component (E component) of the speed error, and the length in the north-south direction is calculated as the north-south direction component (N component) of the speed error (step in FIG. 7). B13). For example, a fixed value is set for the vertical component (U component) of the speed error. Thus, the speed error in the ENU coordinate system is obtained.

  When the speed error in the ENU coordinate system is obtained in this way, a coordinate conversion calculation is performed to calculate the speed error in the ECEF coordinate system (step B15 in FIG. 7). Then, the process proceeds to the next unit.

  On the other hand, when it is determined that the sensor unit is the INS unit 50 (step B5; INS), the Doppler error determination unit 11 performs a coordinate conversion calculation to calculate the velocity error in the ENU coordinate system detected by the INS unit 50. , Converted into a speed error in the ECEF coordinate system (step B17). Then, the Doppler error determination unit 11 shifts the processing to the next unit.

  After performing the processing of Steps B3 to B17 for all units, the Doppler error determination unit 11 ends the processing of Loop A (Step B19). Thereafter, the Doppler error determination unit 11 stores the speed error in the ECEF coordinate system acquired for each unit in the storage unit 12 as the speed / speed error data 123 (step B21). Then, the Doppler error determination unit 11 ends the speed error calculation process.

  Returning to the Doppler error determination process of FIG. 6, after performing the speed error calculation process, the Doppler error determination unit 11 uses the speed error calculated in Step A9 according to the weighted average weight pattern selected in Step A7 ( The average speed error is calculated by calculating “speed error of INS unit 50” × α + “speed error of GPS unit 60” × β + “speed error obtained from speed / azimuth sensor unit 70, 80” × γ). (Step A11).

  Next, the Doppler error determination unit 11 acquires satellite information from the GPS unit 60 via the second data bus 90 and also acquires integrated terminal information from the GPA 15 (step A13). And the Doppler error determination part 11 calculates the gaze direction from the position calculation system 1 to a GPS satellite using the acquired satellite information and integrated terminal information (step A15).

Specifically, using the integrated terminal position (X _U , Y _U , Z _U ) of the position calculation system 1 and the satellite position (X _SV , Y _SV , Z _SV ) of the capture target satellite, ) To calculate the observation matrix “H”. The observation matrix is a matrix that represents the line-of-sight direction from the position calculation system 1 to the GPS satellite.

In Expression (1), “range” is the geometry between the integrated terminal position (X _U , Y _U , Z _U ) of the position calculation system and the satellite position (X _SV , Y _SV , Z _SV ) of the GPS satellite. It is a scientific distance and is represented by the following formula (2).

式（３）において、「（Ｕ_σ，Ｖ_σ，Ｗ_σ）」は、それぞれＥＣＥＦ座標系における各軸方向の平均速度誤差である。 Next, the Doppler error determination unit 11 calculates the Doppler error by obtaining the average speed error with respect to the line-of-sight direction calculated in Step A15 (Step A17). Specifically, the Doppler error “σ” is calculated according to the following equation (3) using the observation matrix “H” calculated in step A15.

In Expression (3), “(U _σ , V _σ , W _σ )” is an average velocity error in each axial direction in the ECEF coordinate system.

  Next, the Doppler error determination unit 11 outputs the Doppler error “σ” calculated in Step A17 to the GPS unit 60 (Step A19). Then, the Doppler error determination unit 11 ends the Doppler error determination process.

3-2. Processing of GPS Unit 60 FIG. 9 is a flowchart showing a flow of position / velocity calculation processing executed by the position / velocity calculation unit 653 of the GPS unit 60.

  First, the position / velocity calculation unit 653 performs capture target satellite determination processing (step C1). Specifically, a GPS satellite located in the sky at a given reference position at the current time measured by a clock unit (not shown) is determined using the satellite orbit data 6553 of the storage unit 655, and is captured. Satellite. The reference position is, for example, the position acquired from the assist server by so-called server assist in the case of the first position calculation after power-on, and the latest integrated terminal position in the second or subsequent position calculation. It can be set with.

  Next, the position / velocity calculation unit 653 executes the process of loop B for each capture target satellite determined in step C1 (steps C3 to C11). In the process of loop B, the position / velocity calculation unit 653 performs satellite signal acquisition processing (step C5).

FIG. 10 is a flowchart showing the flow of satellite signal acquisition processing.
First, the position / velocity calculation unit 653 calculates satellite information (satellite position, satellite speed) of the capture target satellite based on the satellite orbit data 6553 stored in the storage unit 655 (step D1). Further, the position / speed calculating unit 653 acquires integrated terminal information (integrated terminal position, integrated terminal speed) from the GPA 15 (step D3).

  Next, the position / velocity calculation unit 653 outputs the satellite information and the integrated terminal information acquired in steps D1 and D3 to the Doppler error determination unit 11 (step D5). This is because the Doppler error determination unit 11 can calculate the line-of-sight direction to the capture target satellite.

  Further, the position / velocity calculation unit 653 acquires the drift of the clock built in the GPS unit 60 (step D7). Then, the position / velocity calculation unit 653 determines the Doppler frequency of the capture target satellite using the satellite speed, the integrated terminal speed, and the clock drift (step D9). Since the calculation method of the Doppler frequency is conventionally known, the description thereof is omitted here.

  Next, the position / velocity calculation unit 653 determines the search frequency to be used for the frequency search of the capture target satellite in consideration of the Doppler frequency determined in Step D9 (Step D11). Specifically, the frequency obtained by adding the Doppler frequency to the carrier frequency of the GPS satellite signal is determined as the search frequency.

  Then, the position / velocity calculation unit 653 causes the satellite signal acquisition unit 651 to acquire the GPS satellite signal of the acquisition target satellite at the determined search frequency (step D13). Then, the position / velocity calculation unit 653 ends the satellite signal acquisition process.

  Returning to the position / velocity calculation process of FIG. 9, after performing the satellite signal acquisition process, the correlation integration processing unit 6531 performs the correlation integration process (step C7).

FIG. 11 is a flowchart showing the flow of the correlation integration process.
First, the correlation integration processing unit 6531 sets the next output time of the correlation integration value (step E1). The next output time can be set to an arbitrary time (for example, a time after 4 seconds from the start of correlation integration). Then, the correlation integration processing unit 6531 resets and starts an internal timer (step E3).

  Next, the correlation integration time determination unit 6533 acquires the Doppler error from the Doppler error determination unit 11 via the second data bus 90 (step E5). Then, the correlation integration time determination unit 6533 performs a correlation integration time determination process (step E7).

  Here, the principle of the method for determining the correlation integration time in this embodiment will be described. The inventor of the present application conducted an experiment for obtaining a relationship among a Doppler error, a correlation integration value, and a correlation integration time.

FIG. 12 is a diagram showing the relationship between the Doppler error obtained from the experimental results, the correlation integration value, and the correlation integration time, and the process of integrating the correlation values with the correlation integration time as t (milliseconds) was performed. It is a graph which shows the change of the correlation integrated value in a case. When there is no Doppler error Δf (“0”), since the Doppler frequency f _d does not change, the actual search frequency (= carrier frequency f _c + Doppler frequency f _d ) also does not change. However, when there is a Doppler error Δf (≠ 0), since the Doppler frequency f _d is different from the assumed frequency, the actual search frequency is a frequency that has fluctuated from the assumed search frequency.

  When integrating the correlation values, the correlation values corresponding to the frequencies are integrated. If the integration is performed when there is a Doppler error Δf (≠ 0), the frequency used as a reference for the integration is incorrect. As a result, the peak value of the final correlation integrated value obtained by the integration is lower than the expected value. The reduction of the peak value of the correlation integrated value is greatly reduced as the magnitude of the Doppler error Δf is larger. This is as shown in the graph of FIG.

  On the other hand, the same applies to the correlation integration time t. When there is a Doppler error Δf (≠ 0), the longer the correlation integration time t, the lower the peak value of the final correlation integration value. Although it is difficult to understand in FIG. 12, it is apparent from the relationship between the Doppler error Δf when the correlation integrated value (peak value) becomes “0” and the correlation integrated time t.

  That is, the Doppler error Δf when the correlation integrated value becomes “0” is obtained by 1000 / t. The longer the correlation integration time t, the smaller the Doppler error Δf. This means that as the correlation integration time t becomes longer, the peak value of the final correlation integration value to be obtained decreases rapidly (becomes “0” earlier). Therefore, if correlation integration is performed with a long correlation integration time t, it is difficult to detect the peak of the correlation integration value even with a slight Doppler error.

From this, it is considered appropriate to set the correlation integration time t long when the Doppler error Δf is small, and to set the correlation integration time t short when the Doppler error Δf is large. Therefore, in this embodiment, the correlation integration time t is calculated according to the following equation (4) using the Doppler error Δf.

  According to Expression (4), the correlation integration time t becomes shorter as the Doppler error Δf is larger. The reason for calculating the correlation integration time t using the value 2Δf obtained by doubling the Doppler error is that the Doppler error boundary at which the peak of the correlation integration value (peak value) is not observed is shown in FIG. Since Δf = 1000 / t, it is considered that it is difficult to detect the peak of the correlation integration value when the correlation integration time is determined as t = 1000 / Δf.

  Returning to the description of FIG. 11, when the correlation integration time is determined in this way, the correlation integration processing unit 6531 executes correlation integration for integrating the correlation value output from the correlator 6511 with the determined correlation integration time t. (Step E9). Then, the correlation integration processing unit 6531 determines whether or not the time at which the current correlation value is integrated (hereinafter referred to as “current integration time”) exceeds the output time (step E11).

  If it is determined in step E11 that it has not exceeded (step E11; No), the correlation integration processing unit 6531 refers to the correlation integration value at the current integration time as the latest correlation integration value (hereinafter, “latest correlation integration value”). ) To update the latest correlation integrated value (step E13). Then, after the latest accumulated time is updated with the current accumulated time (step E15), the process returns to step E5.

  On the other hand, if it is determined in step E11 that the current integration time exceeds the output time (step E11; Yes), the correlation integration processing unit 6531 indicates that the time difference between the current integration time and the output time is the latest integration time and the output. It is determined whether or not the time difference is smaller than the time (step E17).

  And when it determines with it being small (step E17; Yes), the newest correlation integrated value is updated by adding the correlation integrated value of this integration time to the newest correlation integrated value (step E19). Then, the correlation integration processing unit 6531 updates the correlation integration value to be output (hereinafter referred to as “output correlation integration value”) with the latest correlation integration value (step E21). Then, the output correlation integrated value is stored in the storage unit 655 (step E23), and the correlation integration process is terminated.

  Returning to the position / velocity calculation process of FIG. 9, after performing the correlation integration process, the position / speed calculation unit 653 detects the reception frequency and code phase based on the output correlation integration value obtained in the correlation integration process ( Step C9). Then, the position / velocity calculation unit 653 shifts the processing to the next acquisition target satellite.

  After performing the processing of steps C5 to C9 for all the acquisition target satellites, the position / velocity calculation unit 653 ends the processing of loop B (step C11). After that, the position / velocity calculation unit 653 executes position / velocity calculation calculation to calculate the position and speed of the position calculation system 1, and the position error and speed error (step C13).

  The position calculation calculation can be realized, for example, by performing a known convergence calculation using, for example, a least square method or a Kalman filter using a pseudo distance between the position calculation system 1 and the acquisition target satellite. Further, the speed calculation calculation can be realized based on a known method in the same manner using a time change of the reception frequency of the GPS satellite signal received from the capture target satellite, for example.

  Then, the position / velocity calculation unit 653 outputs the calculated position, position error, velocity, and velocity error to the processing unit 10 via the second data bus 90 (step C15). Then, the position / velocity calculation unit 653 determines whether or not to end the process (step C17). If it is determined that the process is not yet ended (step C17; No), the process returns to step C1.

  When it is determined that the process is to be ended (step C17; Yes), the position / speed calculation unit 653 ends the position / speed calculation process.

3-3. Processing of GPA 15 FIG. 13 is a flowchart showing a flow of position / speed integration processing executed by the GPA 15.
First, the GPA 15 acquires the position from the INS unit 50 and the GPS unit 60 via the second data bus 90 (step F1). Moreover, the speed of each unit is acquired from the Doppler error determination part 11 (step F3).

  Next, the GPA 15 performs a filtering process on the position and speed acquired in Steps F1 and F3 (Step F5). In the present embodiment, position and velocity integration processing using a Kalman filter is executed as filter processing.

  Specifically, the position and speed of the INS unit 50 are set as a state (state vector) “X” in the Kalman filter. Further, the observation value “Z” as an external observation amount in the Kalman filter is the position and velocity acquired from the GPS unit 60 and the velocity obtained from the velocity / orientation sensor units 70 and 80. Then, a prediction calculation for predicting the state “X” and a correction calculation for correcting the predicted state “X” using the observation value “Z” are performed. Then, the position and speed included in the state “X” corrected by the correction calculation are determined as the integrated terminal position and terminal speed.

  Next, the GPA 15 outputs the integrated terminal position and the integrated terminal speed integrated by the filtering process to the Doppler error determination unit 11 as integrated terminal information and also outputs to the GPS unit 60 via the second data bus 90 (step). F7). Then, the GPA 15 ends the position / speed integration process.

4). In the position calculation system 1, the speed calculated by the INS unit 50 and the GPS unit 60 and the speed detected by the speed / direction sensor units 70 and 80, which are a kind of sensor unit, are integrated by the GPA 15, and the position is calculated. The speed of the calculation system 1 is calculated. Further, the Doppler error determination unit 11 determines the Doppler error using the speed error calculated by the INS unit 50 and the GPS unit 60 and the speed error detected by the speed / direction sensor units 70 and 80.

  In the GPS unit 60, the Doppler frequency is determined using the speed determined by the GPA 15, and the correlation integration time for performing the correlation process is determined using the Doppler error determined by the Doppler error determination unit 11. Is done. Then, the positions calculated by the INS unit 50 and the GPS unit 60 are integrated by the GPA 15 to calculate the position of the position calculation system 1.

  Since the position calculation system 1 moves, the influence of Doppler accompanying the movement cannot be ignored. The Doppler frequency in this case can be predicted using the speed of the position calculation system 1, but the assumed Doppler frequency varies depending on the movement state of the position calculation system 1 and the like. In the present embodiment, the variation amount of the Doppler frequency is calculated as a Doppler error using the speed error of the position calculation system 1. Then, the correlation integration time is determined using the calculated Doppler error. As a result, it is possible to perform correlation processing by determining an appropriate correlation integration time in consideration of fluctuations in the Doppler frequency.

  More specifically, a weighted average weight pattern, which is a weight pattern for weighted averaging the speed error of each unit, based on the output state of the unit information from each unit and the moving state of the position calculation system 1 is obtained. select. Then, using the selected weighted average weight pattern, the speed error from each unit is weighted and averaged to calculate the average speed error. Then, the line-of-sight direction to the GPS satellite that transmits the GPS satellite signal is obtained, and an average speed error with respect to the obtained line-of-sight direction is calculated as a Doppler error.

  Depending on factors such as whether each unit is in a state where unit information can be detected and output, and factors such as the movement state of the position calculation system 1, unit information output from any unit should be emphasized and trusted. It changes. Therefore, the Doppler error can be obtained more accurately by performing the weighted average by changing the weight of the speed error of each unit according to these factors.

  For example, when the position calculation system 1 is located in an environment where a GPS satellite signal such as inside a tunnel cannot be received, the unit information of the GPS unit 60 cannot be used, so the speed calculation accuracy is reduced. However, the speed error gradually increases. In this case, since the Doppler error becomes large, the correlation integration time is shortened by the equation (4). However, as shown in FIG. 12, if the correlation integration time is shortened, the peak of the correlation integration value can be detected even if the Doppler error is a large value. Therefore, when the position calculation system 1 returns through a tunnel to a state in which GPS satellite signals can be received, the GPS satellite signals can be quickly and appropriately captured.

  Further, in the correlation integration process, the GPS unit 60 performs the correlation process by adding the correlation integration value at each integration time with the time when the correlation integration time has elapsed as the integration time. If the current integration time exceeds the output time of the correlation integration value (for example, every 4 seconds), the time difference between the current integration time and the output time, and the previous integration time and the output time The magnitude of the time difference is determined, and the integration time with the smaller time difference is determined as the end time of the summation of the correlation integration values.

  In this embodiment, since the correlation integration time is determined using the Doppler error, the correlation integration time is not a constant value but a discrete value. For this reason, the output timing of the predetermined correlation integration value and the integration timing of the correlation integration time do not always coincide with each other. Therefore, the integration time closest to the output time of the correlation integration value is adjusted to be the end timing of the addition of the correlation integration value.

  In this embodiment, the fluctuation amount of the Doppler frequency is defined as “Doppler error”. However, the fluctuation amount of the Doppler frequency is defined as “Doppler accuracy” in terms of the accuracy of the Doppler frequency. Also good. Other “errors” can also be referred to as “accuracy”.

5). Modified example 5-1. Types of Units The units that can be mounted on the position calculation system 1 are not limited to the units described above. For example, a sensor unit such as an acceleration sensor unit or a gyro sensor unit can be incorporated as a unit capable of detecting a physical event that can be used for calculation of position and velocity. A unit that detects a position using RFID (Radio Frequency IDentification) can also be incorporated as a position detection unit.

  FIG. 14 is a block diagram showing an example of the configuration of the position calculation system 2 in this modification. The position calculation system 2 is a system in which an IMU 51 is mounted instead of the INS unit 50. In FIG. 14, the same components as those of the embodiment described above are denoted by the same reference numerals as those of FIG. 1 described above, and detailed description thereof is omitted.

  In the position calculation system 2, an IMU 51 is provided instead of the INS unit 50. Further, the processing unit 10 is provided with an IMU position / velocity calculation unit 13 that calculates a position and velocity, a position error and a velocity error using unit information output from the IMU 51. In this case, the Doppler error determination unit 11 is calculated from the speed error calculated by the IMU position / speed calculation unit 13, the speed error calculated by the GPS unit 60, and the detection results of the speed / direction sensor units 70 and 80. The Doppler error is calculated and determined using the speed error. In addition, the position / speed integration processing unit 15 is configured to output the position and speed output from the GPS unit 60, the speed output from the speed / direction sensor units 70 and 80, and the position calculated by the IMU position / speed calculation unit 13. And integrated terminal information is calculated by integrating the speed.

  Note that the speed sensor unit 70 and the azimuth sensor unit 80 are omitted, and the Doppler error is calculated using the speed error calculated by the IMU position / speed calculation unit 13 and the speed error calculated by the GPS unit 60. Also good. In this case, the integrated terminal information is calculated by integrating the position and speed calculated by the IMU position / speed calculating unit 13 and the position and speed calculated by the GPS unit 60.

5-2. Unit Coordinate System In the above-described embodiment, the INS unit 50 is assigned with the ENU coordinate system as the calculation coordinate system, and the GPS unit 60 is described with the ECEF coordinate system assigned as the calculation coordinate system. However, the setting of the coordinate system assignment can be changed as appropriate. For example, the INS unit 50 can be designed to calculate the position and velocity in the ECEF coordinate system. In any case, by performing the coordinate conversion calculation, the position and speed can be calculated by unifying the coordinate system.

5-3. Changing the weighted average weight according to the relative value of the speed error Depending on the relative value of the speed error of the INS unit 50, the speed error of the GPS unit 60, and the speed error of the speed / direction sensor units 70 and 80, the speed You may decide to change the weight at the time of carrying out a weighted average of an error.

  FIG. 15 is a diagram showing an example of the data configuration of the weighted average weight pattern data in this case. For simplification of explanation, the output type of each unit is not shown, and the weighted average weight pattern for each moving state is shown.

  In this weighted average weight pattern data, a pattern is defined in which a value obtained by multiplying a value predetermined for each unit by a parameter value normalized by the speed error of each unit is used as a weight. However, the speed error of the INS unit 50 is “σi”, the speed error of the GPS unit 60 is “σg”, and the weight of the speed / direction sensor units 70 and 80 is “σs”. The Doppler error can be obtained more accurately by setting the weighted average weight in consideration of the relative value of the speed error of each unit.

5-4. Calculation of Doppler error In the above-described embodiment, the average speed error is calculated by weighted averaging the speed error of each unit, and the Doppler error is calculated using this average speed error. The method is just an example.

  For example, the average speed error may be calculated using a simple arithmetic average instead of the weighted average, and the Doppler error may be calculated using the average speed error. Alternatively, the speed error having the smallest value among the speed errors output from each unit may be selected, and the Doppler error may be calculated using the selected speed error.

5-5. Determination of Correlation Integration Time In the embodiment described above, the correlation integration time is calculated according to the equation (4). However, as shown in FIG. 16, for example, a table that defines the correspondence between Doppler error and correlation integration time May be prepared. Then, the correlation integration time associated with the Doppler error determined by the Doppler error determination unit 11 may be read from the table to determine the correlation integration time.

5-6. Position / velocity integration processing In the above-described embodiment, the position / velocity integration processing executed by the GPA 15 has been described as performing the filtering process using the Kalman filter by using the calculation result of the GPS unit 60 as an observation value. Filter processing using a Kalman filter may be performed using the calculation result of the INS unit 50 as an observation value.

5-7. Filter Processing In the above-described embodiment, an example in which the position is calculated by the Kalman filter processing has been described. As a filter to be used, a particle filter (particle filter), a sigma point filter (sigma point filter), and a filter using the least square method Etc. may be adopted, and the filter processing using these filters may be performed to integrate the position / velocity.

5-8. In the above-described embodiment, the GPS unit has been described as an example of the position calculation unit. However, WAAS (Wide Area Augmentation System), QZSS (Quasi Zenith Satellite System), GLONASS (GLObal NAvigation Satellite System), A position calculation unit using another satellite positioning system such as GALILEO may be used.

DESCRIPTION OF SYMBOLS 1 Position calculation system, 10 process part, 11 Doppler error determination part, 13 IMU position / velocity calculation part, 15 Position / speed integration process part (GPA), 20 input part, 30 display part, 40 communication part, 45 1st data Bus, 50 INS unit, 51 IMU, 60 GPS unit, 70 Speed sensor unit, 80 Direction sensor unit, 90 Second data bus

Claims (8)

A position calculation method for calculating a position using a position calculation unit that performs correlation processing on a received signal that has received a satellite signal, captures the satellite signal, calculates a position and velocity, and a sensor unit that can detect at least the velocity Because
Calculating a determination speed that is a speed determined using a calculation result by the position calculation unit and a detection result by the sensor unit;
Calculating an error of the determination speed using a calculation error by the position calculation unit and a detection error by the sensor unit;
Determining a Doppler frequency to be used when the position calculating unit determines a search frequency for searching the satellite signal, using the determination speed;
Determining a correlation integration time when the position calculation unit performs the correlation process using an error of the determination speed;
Calculating a position using a calculation result by the position calculation unit and a detection result by the sensor unit;
Position calculation method including Calculating the error in the determination speed includes calculating the error in the determination speed with respect to the line-of-sight direction to the positioning satellite that transmits the satellite signal.
The position calculation method according to claim 1. Calculating the error of the determination speed includes a weighted average of the calculation error by the position calculation unit and the detection error by the sensor unit.
The position calculation method according to claim 1 or 2. The weighted average includes changing a weight of the weighted average according to a moving state.
The position calculation method according to claim 3. The weighted average includes changing the weighted average weight according to whether the position calculation unit is in a state capable of position calculation and whether the sensor unit is in a detectable state.
The position calculation method according to claim 3 or 4. The weighted average includes changing a weight of the weighted average according to a relative value between a calculation error by the position calculation unit and a detection error by the sensor unit.
The position calculation method as described in any one of Claims 3-5. The position calculation unit performs the correlation process by adding the correlation integrated value every time the correlation integration time elapses, and performs the process of calculating the position by performing the correlation process at a predetermined time interval. Unit,
Adjusting the end timing of the summation of the correlation integration values in one correlation process based on the predetermined time interval and the correlation integration time;
The position calculation method according to any one of claims 1 to 6, further comprising: A position calculation unit that performs correlation processing on the received signal that has received the satellite signal to acquire the satellite signal and calculate the position and velocity;
A sensor unit capable of detecting at least the speed,
A determination speed calculation unit that calculates a determination speed that is a speed determined using the calculation result by the position calculation unit and the detection result by the sensor unit;
An error calculation unit that calculates an error of the determination speed using a calculation error by the position calculation unit and a detection error by the sensor unit;
A Doppler frequency determining unit that determines a Doppler frequency used when the position calculating unit determines a search frequency for searching the satellite signal using the determination speed;
A correlation integration time determination unit for determining a correlation integration time when the position calculation unit performs the correlation process using an error of the determination speed;
A position calculation unit that calculates a position using a calculation result by the position calculation unit and a detection result by the sensor unit;
Position calculation system with

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