Positioning system

Abstract

To provide a satellite positioning system with which it is made possible to acquire a position and speed with higher accuracy and motion information about acceleration, etc.SOLUTION: The positioning system comprises: a position information acquisition unit 21 for acquiring position information of a mobile station 3 on the basis of the distance between a plurality of satellites 2a and a stationary station 2b and the mobile station 3; a first speed calculation unit 22 for calculating a first speed by differentiating the position information by a first sampling time; a gyro sensor 41 and an acceleration sensor 42 provided to the mobile station 3; a conversion unit 5 for converting, using the gyro sensor 41, the coordinate system of acceleration detected by the acceleration sensor 42 into acceleration based on an absolute coordinate system; a second speed calculation unit 6 for differentiating the acceleration converted by the conversion unit 5 by a second sampling time and thereby calculating a second speed of the mobile station; and a speed correction unit 7 for calculating a correction speed corrected from these first and second speeds.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a positioning system that uses a satellite positioning system (hereinafter referred to as "GNSS") such as an RTK system to enable accurate measurement of the motion state, such as the speed, of a mobile station. [Background technology]

[0002] Currently, GNSS such as GPS is commonly used to measure the position of a mobile station such as an automobile. This GPS measures the distance to multiple satellites using radio waves, and makes it possible to measure the position of an object based on the distance to each of the radio waves (see Patent Document 1).

[0003] However, with this GPS, the sampling frequency for positioning is coarse, ranging from 10 Hz to 100 Hz, and not only is it unable to handle minute movements, but the position measurement is also off by within a few meters.

[0004] In contrast, a satellite positioning system using the RTK method has a fixed station on the ground for multiple satellite stations, and determines the position of a mobile station based on its distance from the multiple satellite stations, and can measure the position information of the mobile station with an error of a few centimeters based on correction information from the fixed station.For this reason, it is beginning to be used as a system that can accurately measure the movement of a mobile station with small position changes. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-173190 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, even with this RTK method, there is an error of several centimeters, so it is not possible to detect the position of a mobile station more precisely, and it is difficult to apply it to the analysis of the movement of, for example, a human hand or foot. Furthermore, when detecting speed or acceleration based on the measured position, the position information with error must be differentiated at the sampling period for positioning to calculate the speed, and the speed must be further differentiated to detect the acceleration, resulting in a large error.

[0007] SUMMARY OF THEINVENTION In order to solve the above problems, an object of the present invention is to provide a satellite positioning system that is capable of measuring motion conditions such as speed with higher accuracy. [Means for solving the problem]

[0008] In other words, in order to solve the above-mentioned problems, the present invention comprises a position information acquisition unit that acquires position information of a mobile station based on a plurality of satellites, or the plurality of satellites and the distance between a fixed station and a mobile station, a first velocity calculation unit that calculates a first velocity by differentiating the position obtained from the position information acquisition unit with respect to a first sampling time, a gyro sensor and an acceleration sensor provided in the mobile station, a conversion unit that uses the gyro sensor to convert a coordinate system of the acceleration detected by the acceleration sensor into an acceleration based on an absolute coordinate system, and a second velocity calculation unit that calculates a second velocity of the mobile station by integrating the acceleration converted by the conversion unit with a second sampling time, and a velocity correction unit that calculates a corrected velocity of the mobile station using the first velocity obtained by the first velocity calculation unit and the second velocity obtained by the second velocity calculation unit.

[0009] With this configuration, the coordinate system of the acceleration sensor is aligned with an absolute coordinate system based on position information from a satellite, and the final corrected velocity is calculated using the first velocity obtained by differentiating the position information from the satellite and the second velocity obtained by integrating the acceleration detected by the acceleration sensor over the sampling time, making it possible to measure velocity more accurately.

[0010] In addition, in such an invention, the apparatus may further include a second position calculation unit that integrates the second velocity obtained by the second velocity calculation unit over the second sampling time to calculate a second position of the mobile station, and a position correction unit that calculates a corrected position of the mobile station using the position acquired by the position information acquisition unit and the second position acquired by the second position calculation unit.

[0011] With this configuration, the final corrected position is calculated using the second position obtained by integrating the acceleration detected by the acceleration sensor twice at the second sampling time and the position information obtained from the satellite, making it possible to measure the position more accurately.

[0012] Furthermore, the mobile station may be configured to include a first acceleration calculation unit that calculates a first acceleration by differentiating the position obtained from the position information output unit twice with respect to the first sampling time, and an acceleration correction unit that calculates a corrected acceleration of the mobile station from the first acceleration obtained by the first acceleration calculation unit and the acceleration converted by a conversion unit.

[0013] With this configuration, the acceleration from the acceleration sensor and the second acceleration based on the displacement of the position information from the satellite are used to calculate the final corrected acceleration, making it possible to measure acceleration more accurately. Effect of the Invention

[0014] According to the present invention, the coordinate system of the acceleration sensor is aligned with an absolute coordinate system based on position information from a satellite, and a final corrected velocity is calculated using a first velocity obtained by differentiating the position information from the satellite and a second velocity obtained by integrating the acceleration detected by the acceleration sensor over a second sampling time, thereby making it possible to measure velocity more accurately. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is an external view of a positioning system according to an embodiment of the present invention. [Diagram 2] Functional block diagram of the same configuration [Diagram 3] Example of calculating the corrected speed in the same configuration [Figure 4] Example of calculating the corrected speed in the same configuration [Diagram 5] Example of calculating the corrected speed in the same configuration [Figure 6] Example of calculating the corrected speed in the same configuration [Figure 7] FIG. 1 is a flowchart showing the process according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] The positioning system 1 of this embodiment is configured to use satellites 2a and fixed stations 2b to locate the position of a mobile station 3 and detect the motion state of the mobile station 3, such as its speed, from the position, and is configured to include, as hardware, a plurality of satellites 2a, fixed stations 2b, and an inertial sensor 4 attached to the mobile station 3. Characteristically, the position of the mobile station 3 is detected using the plurality of satellites 2a and fixed stations 2b, and a first speed is calculated based on the detected position, while the acceleration of the mobile station 3 is detected using the inertial sensor 4 attached to the mobile station 3, and a second speed is calculated using the detected acceleration. Then, a corrected speed is estimated using the calculated first speed and second speed. The positioning system 1 of this embodiment will be described in detail below.

[0018] First, the position information acquisition unit 21 is configured to be able to measure the position of the mobile station 3 using radio waves from four or more satellites 2a. At this time, the GNSS system used may be a GPS system, but since the detection accuracy of the GPS system includes an error of several meters, here, a fixed station 2b is provided on the ground, and an RTK system is used in which the position of the mobile station 3 is corrected according to the distance between the fixed station 2b and the mobile station 3. With such an RTK system, it is possible to detect the position information with an error of several centimeters. Note that the position information is acquired at a sampling period (every first sampling time) of about 10 Hz to 100 Hz. At this time, the position information of the mobile station 3 acquired by the position information acquisition unit 21 is acquired as position information based on an absolute coordinate system.

[0019] The first velocity calculation unit 22 calculates a first velocity of the mobile station 3 based on the absolute coordinate system, based on the displacement of the position information acquired by this position information acquisition unit 21, and calculates the first velocity of the mobile station 3 in the absolute coordinate system from the displacement of the position information acquired at each first sampling time using the following equation.

[0020]

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[0021] In addition, since the position information acquired by the position information acquisition unit 21 has an error of several centimeters, and the first sampling time is also relatively long, the calculated first velocity has poor accuracy when analyzing fine movements such as the movements of human hands and feet. Therefore, the inertial sensor 4 provided in the mobile station 3 is used here to enable the final corrected velocity to be calculated.

[0022] The inertial sensor 4 is composed of a gyro sensor 41 and an acceleration sensor 42 attached to the mobile station 3, and detects angular velocities around three axes and accelerations along the three axis directions of a coordinate system based on the inertial sensor 4 at a second sampling period (every second sampling time) of the inertial sensor 4. The second sampling period of the inertial sensor 4 is longer than the first sampling period of the GNSS, and is detected at a period of about 1000 Hz.

[0023] However, since the acceleration detected by the acceleration sensor 42 in this manner is different from a value based on the absolute coordinate system of the GNSS, it is necessary to match the direction of the acceleration with the absolute coordinate system. Therefore, the conversion unit 5 is used to convert the acceleration in the coordinate system of the acceleration sensor 42 into the acceleration in the absolute coordinate system.

[0024] When the conversion unit 5 converts the coordinate system of the inertial sensor 4 into values ​​of the absolute coordinate system, the conversion unit 5 uses the angular velocities obtained from the gyro sensor 41 to detect angular velocities around three axes that are the coordinate system in the inertial sensor 4. In general, the relationship shown in Equation 2 is established between the differential value of the roll angle, the differential value of the pitch angle, and the differential value of the yaw angle in the absolute coordinate system and the angular velocities of the gyro sensor 41.

[0025]

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[0026] On the other hand, when the yaw angle is obtained from the angular velocity of the yaw angle, the yaw angle is obtained by integrating the angular velocity as shown in the following equation.

[0027]

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[0028] That is, when Equation 3 is calculated using the sampling time Ts, the yaw angle expressed by the following equation is obtained.

[0029]

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[0030] Taking this relational expression into consideration, when the yaw angle of Equation 2 is calculated using the sampling time Ts, the yaw angle is expressed by Equation 5.

[0031]

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[0032] At this time, as the initial value, the mobile station 3 with the inertial sensor 4 attached is made to face north in a horizontal state in advance, and the value in the state where it is close to the absolute coordinate system is input as the initial value.

[0033] Similarly, the roll angle and pitch angle are calculated from Equation 2 to calculate the roll angle, which is a rotation around the X-axis based on the coordinate system of the inertial sensor 4, the pitch angle, which is a rotation around the Y-axis, and the yaw angle, which is a rotation around the Z-axis, which is the orientation.

[0034] Then, using the roll angle, pitch angle, and yaw angle calculated sequentially from the initial values ​​input in advance, the acceleration (Ax, Ay, Az) based on the coordinate system of the acceleration sensor 42 is converted into acceleration (ax, ay, az) in an absolute coordinate system based on the north azimuth.

[0035] Incidentally, since the acceleration in the z-axis direction in this absolute coordinate system includes the acceleration of gravity, the acceleration of gravity is subtracted from the acceleration in the z-axis direction in the converted absolute coordinate system.

[0036] Next, the second velocity calculation unit 6 integrates the acceleration A in the x, y and z-axis directions based on the converted absolute coordinate system over the second sampling time to calculate a first velocity V along the x, y and z-axis directions. In the following equation, V and A represent vectors.

[0037]

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[0038] When this relational expression is calculated using the second sampling time Ts, a first velocity obtained by converting the information from the acceleration sensor 42 into the absolute coordinate system is obtained.

[0039] Then, a corrected velocity of the mobile station 3 is calculated using a velocity correction unit 7 based on a first velocity based on the displacement of the position detected by the position information acquisition unit 21 and a second velocity calculated from the acceleration converted into the absolute coordinate system by the conversion unit 5.

[0040] Various methods can be used to calculate this corrected speed.

[0041] <First correction method>

[0042] As a first correction method, when there is a first velocity based on information obtained from the GNSS and a second velocity based on information obtained from the acceleration sensor 42, the average value of the first velocity and the second velocity can be calculated as the corrected velocity as shown in Fig. 3. According to this method, it is possible to reduce the error compared to a velocity calculated from only one side.

[0043] <Second correction method>

[0044] As a second correction method, when the first sampling time based on the GNSS and the second sampling time based on the acceleration sensor 42 are approximately the same, as shown in FIG. 4, a value (e.g., an average value) between the first velocity based on information obtained from the GNSS and the second velocity based on information obtained from the acceleration sensor 42 is calculated as the corrected velocity, while at the second sampling time that does not match the first sampling time, the second velocity based on information obtained from the acceleration sensor 42 can also be calculated as the corrected velocity.

[0045] <Third correction method>

[0046] As a third correction method, when a large acceleration is detected by the acceleration sensor 42, it is assumed that a sudden, small change in speed has occurred, and the proportion of the influence of the second speed based on the information obtained from the acceleration sensor 42 is increased and conversely, the proportion of the influence of the first speed based on the information obtained from the GNSS is decreased according to the magnitude of the acceleration of the acceleration sensor 42, to calculate the corrected speed, as shown in Fig. 5. In this way, when a sudden movement is detected by the acceleration sensor 42, the influence of the second speed based on the acceleration obtained from the acceleration sensor 42 is increased, making it possible to bring the speed closer to the actual speed.

[0047] <Fourth correction method>

[0048] As a fourth correction method, when there is a first velocity based on information obtained from the acceleration sensor 42 and a second velocity based on information obtained from the GNSS, the corrected velocity can be calculated using an extended Kalman filter as shown in Fig. 6. According to such a method, calculation can be performed at high speed, and the corrected velocity can be estimated with high accuracy.

[0049] Next, a method for estimating speed in the positioning system 1 configured as above will be described with reference to the flowchart of FIG.

[0050] First, the position information obtained from the GNSS is obtained using the position information acquisition unit 21 (step S1). Then, the difference of this position information is taken for each first sampling time, and a first speed based on the information obtained from the GNSS is calculated (step S2). Note that the first speed calculated at this time is the speed in an absolute coordinate system based on the north azimuth.

[0051] Meanwhile, the acceleration based on the coordinate system of the mobile station 3 is measured by the acceleration sensor 42 provided in the mobile station 3 (step S3).

[0052] Then, in order to convert this measured acceleration into acceleration based on an absolute coordinate system, the yaw angle, pitch angle, and roll angle are calculated using the gyro sensor 41, and based on these calculated angles, the acceleration obtained by the acceleration sensor 42 is converted into acceleration based on the absolute coordinate system (step S4).

[0053] The acceleration of the acceleration sensor 42 thus converted is then integrated over the second sampling time, and a second velocity is calculated from the information based on the acceleration sensor 42 (step S5).

[0054] Next, a corrected speed is calculated from the first speed calculated based on the information from the GNSS and the second speed based on the acceleration sensor 42 (step S6).

[0055] In this case, when the corrected speed is calculated by the first correction method, the average value of the first speed and the second speed is calculated, and when the corrected speed is calculated by the second correction method, the intermediate value is used as the corrected speed only when the respective sampling times match, and when they do not match, the second speed is used as the corrected speed. When the corrected speed is calculated by the third correction method, the proportion of the speed based on the information from the acceleration sensor 42 is increased depending on the magnitude of the acceleration of the acceleration sensor 42 to calculate the corrected speed. Furthermore, when the corrected speed is calculated by the fourth correction method, the corrected speed is calculated using an extended Kalman filter.

[0056] As described above, according to the embodiment, the mobile station 3 is provided with a position information acquisition unit 21 that acquires position information of the mobile station 3 based on the distance between the mobile station 3 and a plurality of satellites 2a, or the distance between the mobile station 3 and the plurality of satellites 2a and the fixed station 2b, a first velocity calculation unit 22 that calculates a first velocity by differentiating the position obtained from the position information acquisition unit 21 with respect to a first sampling time, a gyro sensor 41 and an acceleration sensor 42 provided in the mobile station 3, a conversion unit 5 that uses the gyro sensor 41 to convert the coordinate system of the acceleration detected by the acceleration sensor 42 into an acceleration based on an absolute coordinate system, and a second velocity calculation unit 6 that calculates a second velocity of the mobile station 3 by integrating the acceleration converted by the conversion unit 5 with respect to a second sampling time, and a velocity correction unit 7 that calculates a corrected velocity using the first velocity obtained by the first velocity calculation unit 22 and the second velocity obtained by the second velocity calculation unit 6, so that the velocity of the mobile station 3 can be measured more accurately.

[0057] The present invention is not limited to the above-described embodiment, but can be embodied in various forms.

[0058] For example, in the above embodiment, the first velocity is calculated by differentiating the position information based on the information from the GNSS, and the second velocity is calculated by integrating the acceleration based on the information from the acceleration sensor 42. However, the acceleration based on the information from the acceleration sensor 42 may be integrated twice to calculate the position information (second position), and the position information may be corrected in the position correction unit using this second position and the position information from the position information acquisition unit 21. Alternatively, conversely, the displacement of the position information from the GNSS may be differentiated twice at the first sampling time to calculate the acceleration (first acceleration), and the acceleration correction unit may calculate the corrected acceleration using this first acceleration and the acceleration obtained by converting the value of the acceleration sensor 42 into the acceleration in the absolute coordinate system. In this case, after the value of the acceleration sensor 42 is converted into the acceleration in the absolute coordinate system, the influence of the gravitational acceleration remains to some extent, so that a more accurate acceleration can be calculated by correcting the acceleration using the acceleration obtained from the position information of the GNSS.

[0059] In the above embodiment, the velocity of the mobile station 3 is calculated, but the angular velocity etc. may be output. At this time, the angular velocity around the xyz axes in the absolute coordinate system is output as the angular velocity.

[0060] Furthermore, in the above embodiment, the correction speed is calculated using an average value, an intermediate value, or a value obtained using a Kalman filter. However, as a method other than the above, the correction speed may be calculated using a complementary filter or the like.

[0061] Furthermore, in the above embodiment, the angle is calculated using the gyro sensor 41, but other than this, the angle may be calculated using a geomagnetic sensor. [Explanation of symbols]

[0062] 1. Positioning system 2a...satellite 2b...Fixed station 21...Location information acquisition unit 22...First speed calculation section 3. Mobile station 4. Inertial sensor 41 Gyro sensor 42 Acceleration sensor 5. Conversion section 6...Second speed calculation section 7...Speed ​​correction section

Claims

1. a location information acquisition unit that acquires location information of the mobile station based on a plurality of satellites or the plurality of satellites and a distance between the mobile station and the fixed station; a first velocity calculation unit that calculates a first velocity by differentiating the position obtained from the position information acquisition unit with respect to a first sampling time; a gyro sensor and an acceleration sensor provided in the mobile station; a conversion unit that converts a coordinate system of the acceleration detected by the acceleration sensor into an acceleration based on an absolute coordinate system using the gyro sensor; a second velocity calculation unit that calculates a second velocity of the mobile station by integrating the acceleration converted by the conversion unit over a second sampling time; a speed correction unit that calculates a corrected speed of the mobile station by using the first speed obtained by the first speed calculation unit and the second speed obtained by the second speed calculation unit; A mobile station positioning system comprising:

2. The mobile station positioning system of claim 1, further comprising: a second position calculation unit that calculates a second position of the mobile station by integrating the second velocity obtained by the second velocity calculation unit over the second sampling time; a position correction unit that calculates a corrected position of the mobile station by using the position acquired by the position information acquisition unit and the second position acquired by the second position calculation unit; A mobile station positioning system comprising:

3. The mobile station positioning system of claim 1, further comprising: a first acceleration calculation unit that calculates a first acceleration by differentiating the position obtained from the position information output unit twice with respect to the first sampling time, an acceleration correction unit that calculates a corrected acceleration of the mobile station from the first acceleration obtained by the first acceleration calculation unit and the acceleration converted by the conversion unit; A mobile station positioning system comprising:

4. acquiring location information of the mobile station based on a plurality of satellites or the plurality of satellites and a distance between the mobile station and the fixed station; calculating a first velocity by differentiating the acquired position information with respect to a first sampling time; converting a coordinate system of acceleration detected by an acceleration sensor provided in the mobile station into acceleration based on an absolute coordinate system using a gyro sensor provided in the mobile station; calculating a second velocity of the mobile station by integrating the converted acceleration over a second sampling time; calculating a corrected velocity of the mobile station using the first velocity and the second velocity; A mobile station positioning method comprising:

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