JP2012127899A - Positioning accuracy determining device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positioning accuracy determining device capable of determining a magnitude of a position error of GPS positioning.SOLUTION: The positioning accuracy determining device includes: a moving distance operation unit 9 that calculates moving distances by a velocity sensor-derived velocity by a velocity sensor 2, a satellite positioning velocity by a satellite positioning velocity operation unit 6, a Doppler velocity by a Doppler velocity operation unit 7, and an acceleration sensor-derived velocity by an acceleration sensor-derived velocity operation unit 8 respectively; and an accuracy determining unit 10 that calculates a difference between a moving distance obtained by the satellite positioning velocity and other moving distances and, when the difference is larger than a threshold, determines that the GPS positioning accuracy is lowered.

Description

  The present invention relates to a positioning accuracy determination device capable of determining the size of a position error of GPS positioning.

  As a positioning device for detecting the current position of a moving body, a positioning device using a GPS (Global Positioning System) in the United States has been known. The positioning accuracy of GPS is evaluated by a degradation factor (Dilution of Precision; hereinafter referred to as “DOP”), which takes into account the arrangement of GPS satellites, the reception sensitivity based on the GPS satellite, the ionospheric state, and the like. The larger the DOP, the lower the positioning accuracy. Therefore, the position error is estimated based on the size of DOP. For example, when DOP is 1, it is said that there is a position error of about 5.6 m. The DOP is provided from the GPS satellite to the receiver.

Japanese Patent Laid-Open No. 9-304096 JP 2010-8095 A

  When GPS positioning accuracy is evaluated by DOP, a position error relatively proportional to DOP can be obtained in an open area where there is no obstacle such as a building that blocks radio waves from GPS satellites. However, in places where there are obstacles, the multipath resulting from the irregular reflection of radio waves by the obstacles affects the positioning accuracy, and the position error is often not proportional to DOP. In addition, since multipath is a local phenomenon, even if a correction signal from a system other than GPS is used, a decrease in positioning accuracy due to multipath may not be improved. For this reason, in general systems using GPS positioning information, it is an issue to improve the GPS positioning accuracy degradation due to multipath.

  In addition, high sensitivity receivers that have been put into practical use in recent years have been easier to receive radio waves from GPS satellites than before, so it is difficult to estimate the size of the position error using only DOP.

  In general, when various services are performed on a moving body, it is important that the current position recognized by the moving body is accurate. However, as described above, in the conventional technology, the current position error of GPS positioning is small or large. Therefore, it is difficult to perform position correction in real time.

  Therefore, an object of the present invention is to provide a positioning accuracy determination device that can solve the above-described problems and can determine the size of a position error of GPS positioning.

  To achieve the above object, the present invention provides a speed sensor that is mounted on a moving body and detects the speed of the moving body, an acceleration sensor that is mounted on the moving body and detects the acceleration of the moving body, and the movement A receiver mounted on the body for receiving a signal from a positioning satellite, a satellite positioning unit for positioning the position of the moving body based on a received signal of the receiver, and a plurality of positions determined by the satellite positioning unit A satellite positioning speed calculator that calculates the speed (referred to as satellite positioning speed) by differentiating the distance between the two and a Doppler speed calculator that calculates the speed of the moving body (referred to as Doppler speed) based on the received signal of the receiver And an acceleration sensor-derived speed calculation unit that calculates a speed (referred to as an acceleration sensor-derived speed) from the acceleration detected by the acceleration sensor, and a speed (referred to as a speed sensor-derived speed) generated by the speed sensor. Obtained from the satellite positioning speed, the moving distance calculating section for calculating the moving distance for the satellite positioning speed by the satellite positioning speed calculating section, the Doppler speed by the Doppler speed calculating section, and the acceleration sensor derived speed by the acceleration sensor derived speed calculating section. And an accuracy determination unit that calculates a difference between the travel distance and another travel distance and determines that the GPS positioning accuracy is lowered when the difference is greater than a threshold value.

  The movement distance calculation unit calculates a movement distance in a plurality of different time widths, and the accuracy determination unit calculates a difference between the movement distances for each time width, and the difference is larger than a threshold in any time width. Sometimes, it may be determined that the GPS positioning accuracy is degraded.

  The present invention exhibits the following excellent effects.

  (1) The position error of GPS positioning can be determined.

It is a block diagram of the positioning accuracy determination apparatus which shows one Embodiment of this invention. It is a block diagram which shows the flow of the calculation by the positioning accuracy determination apparatus of FIG. It is a graph which shows the time change and time width of a vehicle speed. It is a graph which shows the example of actual measurement of the time change of vehicle speed.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, a positioning accuracy determination apparatus 1 according to the present invention is mounted on a moving body (not shown) and detects a speed of the moving body, and a moving body mounted on the moving body. An acceleration sensor 3 for detecting the acceleration of the receiver, a receiver 4 mounted on the moving body for receiving a signal from a positioning satellite, and a satellite positioning unit 5 for positioning the position of the moving body based on a received signal of the receiver 4; The satellite positioning speed calculator 6 calculates the satellite positioning speed by time-differentiating the distances between the plurality of positions obtained by the satellite positioning section 5, and calculates the Doppler speed of the mobile body based on the received signal of the receiver 4. Doppler speed calculation unit 7, acceleration sensor-derived speed calculation unit 8 that calculates acceleration sensor-derived speed from the acceleration detected by acceleration sensor 3, speed sensor-derived speed calculated by speed sensor 2 and satellite positioning speed calculation unit 6 When The movement distance calculation unit 9 that calculates the movement distance for the Doppler velocity by the puller velocity calculation unit 7 and the acceleration sensor-derived speed by the acceleration sensor-derived speed calculation unit 8, and the movement distance obtained from the satellite positioning speed and other movement distances The difference is calculated, and when the difference is larger than the threshold value, the accuracy determination unit 10 that determines that the GPS positioning accuracy is lowered, and the correction value of the position error is calculated from the difference between the movement distances obtained by the accuracy determination unit 10 And a position correction calculation unit 11 that corrects the position obtained by the satellite positioning unit 5.

  In the present embodiment, an automobile (hereinafter referred to as a vehicle) is used as the moving body. The speed sensor 2, the acceleration sensor 3, and the receiver 4 are conventionally mounted on a vehicle, and the distance, speed, and acceleration are calculated by differentiating or integrating the speed, acceleration, and position obtained directly from these with time. It is also possible conventionally. The satellite positioning unit 5, the satellite positioning speed calculation unit 6, the Doppler speed calculation unit 7, the acceleration sensor-derived speed calculation unit 8, the movement distance calculation unit 9, and the accuracy determination unit 10 are connected to an electronic control unit (ECU) 12. Can be installed as software. A GPS satellite is used as a positioning satellite. The receiver 4, the satellite positioning unit 5, the satellite positioning speed calculation unit 6, and the Doppler speed calculation unit 7 are already incorporated in the commercially available GPS positioning device 13 (see FIG. 2), and can be used. is there.

  Hereinafter, the principle and specific operation of the positioning accuracy determination apparatus 1 of the present invention will be described.

  In order to estimate a position error in GPS positioning and perform correction easily, it is preferable that there is an index other than DOP provided by a GPS satellite. For example, a relative movement distance using a vehicle speed pulse signal detected by a speed sensor (vehicle speed sensor) 2 or an acceleration signal detected by an acceleration sensor 3 as a system capable of performing positioning calculation using members conventionally mounted on a vehicle. There is a measurement system (also called a self-contained navigation system). Self-contained navigation has relatively high accuracy in the short term, and can also be used in places where the positioning accuracy by GPS decreases due to the influence of multipath. It is conceivable to use this characteristic to compare the distance traveled by the self-contained navigation and the distance traveled from the received signal of the positioning satellite and to estimate the position error in GPS positioning from the result. It is desired that the position by GPS positioning can be corrected using this position error as a correction value.

  Conventionally, when comparing GPS positioning and autonomous navigation, there are cases where GPS positioning has better positioning accuracy and autonomous navigation has better positioning accuracy, so switch to the more accurate one based on DOP. It is carried out. However, as described in the problem column, there are cases where the DOP cannot estimate the size of the position error.

  Therefore, in the positioning accuracy determination apparatus 1 of the present invention, the movement distances are obtained by integrating the speeds derived from the sensors and the received signals, and compared with each other. For example, the difference between the movement distance obtained from the speed sensor-derived speed and the movement distance obtained from the satellite positioning speed, or the difference between the movement distance obtained from the acceleration sensor-derived speed and the movement distance obtained from the satellite positioning speed is obtained. Since this difference is theoretically 0, if the difference is sufficiently small, it can be determined that the positioning accuracy is high. When the difference is larger than a preset threshold value, it is determined that the GPS positioning accuracy is lowered. At this time, a time width (also referred to as a time constant) that is a multiple of the constant is defined using the GPS positioning cycle, and is used for calculating the movement distance. A plurality of time constants are used so as to respond to the difference in speed change during constant speed traveling or rapid acceleration / deceleration traveling.

  Specifically, as shown in FIG. 2, the speed sensor 2 detects the speed of the moving body (speed derived from the speed sensor). The acceleration sensor 3 detects the acceleration of the moving body, and the acceleration sensor-derived speed calculation unit 8 calculates the acceleration sensor-derived speed from the acceleration. From the GPS positioning device 13, the satellite positioning speed and the Doppler speed can be obtained. The satellite positioning speed is obtained by dividing the distance between positioning positions for each positioning cycle by the positioning cycle. The Doppler velocity was calculated by calculating the relative velocity between the positioning satellite and the moving object from the difference between the signal transmission interval (known) in the positioning satellite and the signal reception interval in the receiver 4, and using the velocity (known) of the positioning satellite. The speed of the moving object. Whereas the positioning position can be detected only by simultaneous reception from three, four to five or more positioning satellites, the Doppler velocity can be detected if there is reception from one or two positioning satellites.

  The moving distance calculation unit 9 has a speed sensor-derived speed by the speed sensor 2, a satellite positioning speed by the satellite positioning speed calculation unit 6, a Doppler speed by the Doppler speed calculation unit 7, and an acceleration sensor-derived speed by the acceleration sensor-derived speed calculation unit 8. Calculate the travel distance. This operation is specifically integration. In the present embodiment, three types of time width (time constant) to be integrated are used: small time constant, medium time constant, and large time constant.

  As shown in FIG. 3, the speed of the vehicle varies from when the temporal change is large to when it is small. Here, for simplicity of explanation, the velocity ignores the direction component and handles only the magnitude component. When the temporal change in speed is large, the characteristic appears in a short time, and when observed for a long time, it is averaged and the change becomes gradual. On the other hand, when the temporal change in speed is small, the feature becomes more prominent as the observation is continued for a long time. Therefore, when calculating the moving distance, which is a feature value, by integrating the speed, the time constant is small if the speed change is large (acceleration is large), and the time constant is small if the speed change is small (acceleration is small). It is preferable to make it large. The time constant may be two types from small to large, three types, or four or more types. In real-time measurement, it is unknown how the current speed will change thereafter, so integration with all time constants is performed simultaneously.

  The accuracy determination unit 10 calculates a difference between the moving distances, and determines that the GPS positioning accuracy is lowered when the difference between the moving distance obtained from the satellite positioning speed and the other moving distance is larger than the threshold value. . Since the movement distance calculation unit 9 calculates the movement distances in a plurality of different time widths (time constants), the accuracy determination unit 10 calculates the difference between the movement distances for each time width, and in any time width When the difference is larger than the threshold value, it is determined that the GPS positioning accuracy is lowered.

  For example, as shown in FIG. 4, it is assumed that the speed sensor-derived speed 41 indicated by a solid line and the satellite positioning speed 42 indicated by a broken line are different at the time of rapid acceleration of the vehicle. In this case, since a significant difference appears between the travel distances obtained with a small time constant, it can be determined that the GPS positioning accuracy is degraded. Although not shown in the figure, if the GPS positioning accuracy decreases due to multipath when the vehicle is traveling at a constant speed, a significant difference appears between the travel distances obtained with a large time constant. It can be determined that it has decreased.

  In addition, the speed sensor-derived speed detected by the speed sensor 2 uses a vehicle speed pulse signal that accurately represents the rotation of the tire. Therefore, the travel distance obtained from the speed sensor-derived speed basically represents an accurate travel distance. However, it becomes inaccurate if the tire slips or locks due to the frictional condition of the road surface. In this case, the movement distance obtained from the acceleration sensor-derived speed may be compared with the movement distance obtained from GPS positioning.

  Further, a decrease in GPS positioning accuracy can also be seen by comparing the satellite positioning speed by the satellite positioning speed calculator 6 and the Doppler speed by the Doppler speed calculator 7.

  As described above, the positioning accuracy determination device 1 of the present invention evaluates the GPS positioning accuracy by comparing the movement distance obtained from the satellite positioning speed with the movement distance obtained from other speeds. Not only when the positioning accuracy is known to be low due to the large size, but also when the movement of the moving object is changing even if the DOP is small, or when multipath is locally generated, etc. It can be known in real time that the GPS positioning accuracy is lowered in the moving body.

  In the present embodiment, when it is determined that the GPS positioning accuracy is lowered, the position correction calculation unit 11 corrects the position obtained by the satellite positioning unit 5. Since the difference between the movement distances is calculated in the accuracy determination unit 10, the position correction calculation unit 11 may use the difference between the movement distances as a correction value for the position error.

  At this time, there are four moving distances: a moving distance obtained by integrating the speed derived from the speed sensor, a moving distance obtained by integrating the speed derived from the acceleration sensor, a moving distance obtained by integrating the satellite positioning speed, and a moving distance obtained by integrating the Doppler speed. There are values obtained by integration in three ways: small time constant, medium time constant, and large time constant. To determine which time constant is used to calculate the correction value for the combination of travel distances derived from which speed, the relationship between the speed change magnitude and the combination of travel distance and the time constant is examined in advance through experiments. It is preferable to select a combination of moving distances and a time constant according to the speed change. Further, the correction value may be obtained by weighting the difference between the moving distances according to the speed change.

  As described above, when the current position by GPS positioning is corrected to an accurate position by the correction value, various services can be suitably provided to the moving body. Further, since it is possible to determine a decrease in GPS positioning accuracy, it is possible to adjust the level and timing of the service provided according to the degree of decrease, the size of the position error, and the like.

  The positioning accuracy determination device 1 of the present invention further detects tire idling or tire lock from a comparison between the acceleration sensor-derived speed obtained by integrating the acceleration detected by the acceleration sensor 3 and the speed sensor-derived speed detected by the speed sensor 2. Can be detected. When tire idling or tire lock is detected, the movement distance obtained from the speed sensor-derived speed may be corrected.

DESCRIPTION OF SYMBOLS 1 Positioning accuracy determination apparatus 2 Speed sensor 3 Acceleration sensor 4 Receiver 5 Satellite positioning part 6 Satellite positioning speed calculating part 7 Doppler speed calculating part 8 Acceleration sensor origin speed calculating part 9 Moving distance calculating part 10 Accuracy determining part 11 Position correction calculating part 11 12 ECU
13 GPS positioning device

Claims (2)

A speed sensor mounted on the moving body for detecting the speed of the moving body;
An acceleration sensor mounted on the moving body for detecting the acceleration of the moving body;
A receiver mounted on the mobile body for receiving signals from positioning satellites;
A satellite positioning unit for positioning the position of the moving body based on a reception signal of the receiver;
A satellite positioning speed calculation unit that calculates a speed (referred to as a satellite positioning speed) by differentiating the distance between a plurality of positions obtained by the satellite positioning unit;
A Doppler speed calculator that calculates the speed of the moving body (referred to as Doppler speed) based on the received signal of the receiver;
An acceleration sensor-derived speed calculation unit that calculates a speed (referred to as an acceleration sensor-derived speed) from the acceleration detected by the acceleration sensor;
The movement distances of the speed (speed sensor-derived speed) by the speed sensor, the satellite positioning speed by the satellite positioning speed calculation section, the Doppler speed by the Doppler speed calculation section, and the acceleration sensor-derived speed by the acceleration sensor-derived speed calculation section, respectively. A moving distance calculation unit to calculate,
An accuracy determining unit that calculates a difference between a moving distance obtained from a satellite positioning speed and another moving distance and determines that the GPS positioning accuracy is lowered when the difference is larger than a threshold value. Positioning accuracy determination device. The moving distance calculation unit calculates moving distances in different time widths,
The accuracy determination unit calculates a difference in moving distance for each time width, and determines that the GPS positioning accuracy is lowered when the difference is larger than a threshold value in any time width. The positioning accuracy determination device according to 1.

Images