JP4046584B2 - Car navigation system and GPS receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a car navigation apparatus that determines a vehicle position using a GPS positioning result and positioning data obtained by self-contained navigation.
[0002]
[Prior art]
Currently, a GPS receiver that obtains a position using information from GPS satellites, that is, GPS navigation, and a self-contained navigation that obtains a position using information from each sensor installed in the vehicle, so-called hybrid navigation Car navigation devices that perform vehicle position determination by the above are widely used.
[0003]
Here, the GPS receiver receives a signal from a GPS satellite orbiting around the earth, obtains the distance from the satellite from the arrival time and the propagation speed of the radio wave, and determines the GPS as the intersection of the distances from a plurality of satellites. Calculate the position of the receiver. Therefore, GPS navigation can be established with a GPS receiver alone. In general, the GPS receiver calculates the estimated error amount for the calculated position simultaneously with the calculation of the position. Due to the nature of GPS positioning, positioning cannot be performed in places where satellite radio waves cannot be received, such as in tunnels.
[0004]
On the other hand, in the self-contained navigation, in general, the vehicle speed is obtained from the vehicle speed pulse, and the traveling direction of the vehicle is obtained from the gyro sensor, and the speed (speed and direction) obtained by these and the position obtained last time are used as Calculate the position. In particular, the unit at some point, the traveling direction ∠V _GYRO faster V _odo the vehicle of the vehicle obtained from the sensors to determine the vehicle velocity V (t), as a product of the V (t) and the unit time Obtain the amount of movement (displacement) of the vehicle per hour. This movement amount is added to the position P _ES (t−1) before the unit time to obtain the current position P _ES (t). In other words, it is assumed that the self-contained navigation has a position before unit time. In the self-contained navigation, since the operation of adding the displacement amount to the previous position is repeated, errors may be gradually accumulated.
[0005]
A schematic flow of position determination in the car navigation apparatus adopting hybrid navigation is shown in the flowchart of FIG. First, when the GPS positioning result (position P _GPS , estimated error amount P _ERR ) by the GPS receiver and the position P _ES by the self-contained navigation are obtained (S31, S32), the position P _ES by the self-contained navigation and the estimation for the GPS positioning position are obtained. Comparison with the error amount P _ERR is performed (S33). When the position P _ES by the self-contained navigation is within the range determined by the GPS positioning position and its estimated error amount P _ERR (S33: YES), the positions of both navigations indicate substantially the same position. but it becomes, in this case, to adopt a position P _ES by autonomous navigation, which can be considered as reflecting the finer the vehicle motion (S34). In contrast, the position _{P ES} by autonomous navigation is, if not within the range defined GPS positioning position and by the estimated error amount _{P ERR} (S33: NO), the error amount accumulated in the position _{P ES} by autonomous navigation Since the GPS positioning position is more accurate, the GPS positioning position is adopted (S35).
[0006]
Further, a map matching process is applied to the position determined in this way to determine the final vehicle position (S36). The vehicle position determined in this way is output on the monitor (S37). A series of processes as described above are repeatedly executed at predetermined time intervals.
[0007]
Next, the estimated error amount calculated by the GPS receiver will be described. The estimation error amount generally has two types of estimation error components. One is a component based on the instantaneous geometrical arrangement of GPS satellites used during positioning. The error based on the geometrical arrangement of GPS satellites is calculated each time the positioning calculation is performed at unit time intervals. For example, if the satellites used for positioning are gathered in one direction on the sky, a large value is obtained. If the satellites are scattered moderately in the sky, it is calculated as a low value.
[0008]
On the other hand, the GPS receiver does not output the positioning position obtained at unit time intervals as it is, but performs a filtering process between the current positioning position and the past positioning position. This filtering process is known as a Kalman filter. That is, another error component for the estimated error amount is a component based on the filtering process.
[0009]
Even if a strange value is unexpectedly calculated by the positioning performed every unit time by this filtering process, the positioning position output from the GPS receiver does not change greatly. However, on the other hand, once the positioning position changes greatly, and so-called position jump occurs, it takes time until the position as the output result of the GPS receiver returns to the correct position. An error component based on the filtering process in the estimated error amount is determined so as to reflect the above-described property of the positioning position accompanying the filtering process. That is, the error component based on the filtering process in the estimated error amount is determined as a large value when the non-positioning state continues for a long time, and when the 2D positioning (two-dimensional positioning) state continues, the 3D positioning ( When 3D positioning) continues, it is determined as a small value.
[0010]
As described above, the estimated error amount P _ERR output from the GPS receiver is highly reliable by including an error component based on the filtering process. Therefore, in the car navigation apparatus, the accuracy of determining the vehicle position can be improved by using the estimated error amount _PERR .
[0011]
[Problems to be solved by the invention]
Thus, although it can be said that the estimated error amount calculated by the GPS receiver has become highly reliable by having two error components, when the two error components work in opposite directions, Although the positioning position P _GPS output from the receiver actually includes a relatively large error, the estimated error amount P _ERR may be a small value. In this case, if the car navigation apparatus determines the vehicle position as in the past (FIG. 3), the GPS actually includes a relatively large error, although the position by the self-contained navigation is more accurate. Positioning position has been adopted. As a result, there is a case where the current position of the vehicle suddenly shifts to the wrong position on the monitor screen of the car navigation device, so-called position jump may occur.
[0012]
Such a situation occurs, for example, when three-dimensional positioning is resumed after a long non-positioning state. Specifically, the positioning conditions (satellite arrangement) when the vehicle passes through a place such as a tunnel where radio waves cannot be received and then the vehicle exits the tunnel are good. After the non-positioning continues, the filtering process is not effective for the GPS positioning position P _GPS , and therefore the error amount included in the GPS positioning position P _GPS from the GPS receiver is actually a large value. At this time, if the estimated error amount P _ERR is sufficient that a large value to reflect this situation, as the vehicle position in a car navigation system, the position P _ES by autonomous navigation is employed, that would cause the position skip problems Will not occur.
[0013]
However, since the satellite arrangement is good, the estimated error amount P _ERR becomes a small value as a result. In this case, the position by the self-contained navigation goes out of the range determined by the GPS positioning position and the estimated error amount P _ERR , and the GPS positioning position P _GPS that actually includes a large error is adopted as the vehicle position. It will cause a situation of being. In this case, a position jump occurs, and therefore the accuracy of determining the vehicle position deteriorates.
[0014]
The present invention has been made in view of the above circumstances. That is, an object of the present invention is to provide a car navigation device and a GPS receiver that can improve the accuracy of an estimation error amount with respect to a GPS positioning position and thereby improve the accuracy of vehicle position determination.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, an estimated error amount changing means having the following function for changing the estimated error amount by the GPS positioning calculation is added to the car navigation device. That is, when it is determined that the vehicle has entered a place where the GPS is not positioned, the estimated error amount changing means determines a positioning start position, which is a position where the vehicle exits from the place where the vehicle is not positioned, based on the map data. When it is determined that the vehicle has exited from a place that is in a non-positioning state, based on the positioning start position, the GPS positioning position after exiting from the place, and the estimated error amount with respect to the GPS positioning position When a predetermined condition is satisfied, a function for changing an estimated error amount with respect to the GPS positioning position is provided. When starting positioning after the GPS non-positioning state continues, the estimated error amount may be small even though the positioning position actually includes a relatively large error. However, if the accurate positioning start position is obtained from the map data, the accuracy of the GPS positioning position at the start of positioning can be determined, so the error amount included in the GPS positioning position must be changed to an estimated error amount that accurately reflects the error. Can do. That is, the accuracy of the estimated error amount can be increased.
[0016]
The estimated error amount changing means is such that the positioning start position is P ₀ , the GPS positioning position after exiting the place is P _GPS , and the estimated error amount with respect to the GPS positioning position is P _ERR .
If | P ₀ −P _GPS |> | P _ERR |, the estimated error amount is changed to | P ₀ −P _GPS |
If | P ₀ −P _GPS | ≦ | P _ERR |, the estimated error amount may be | P _ERR | (claim 2).
[0017]
Further, the estimated error amount changing means sets the positioning start position when there is a lapse of time until the GPS positioning position is obtained after it is determined that the vehicle has exited from the non-positioning state. Further, the vehicle may be configured to be updated based on the amount of displacement of the vehicle with the passage of time, which is obtained by self-contained navigation (claim 3).
[0018]
Further, in the determination by the estimated error amount changing means that the vehicle has exited from the place that is in the non-positioning state, the vehicle exits from the place that is in the non-positioning state when the radio wave from at least one GPS satellite is received. (Claim 4).
[0019]
When the place where the GPS non-positioning state is set is a tunnel, the estimated error amount changing means can determine that the vehicle has entered the tunnel based on the map data.
[0020]
In order to achieve the above object, an estimated error amount changing means having a function for changing the estimated error amount is added to the GPS receiver used in connection with the host system for navigation. In other words, the estimated error amount changing means is provided with a map start position, which is a position where the vehicle exits from the place where the vehicle enters the non-positioning state when it is determined that the vehicle has entered the place where the GPS is not located. Obtained by cooperation with the host system, and when it is determined that the vehicle has exited from a location that is in a non-positioning state, a positioning start position, a GPS positioning position after exiting from the location, and an estimate for the GPS positioning location If a predetermined condition is satisfied based on the error amount, a function of changing the estimated error amount for the GPS positioning position is provided. By using such a GPS receiver, the host system can improve the accuracy of determining the position of the vehicle.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing the overall configuration of a navigation device 10 as an embodiment of the present invention. FIG. 2 is a flowchart showing a process of changing the estimated error amount, which is executed as one function of the GPS receiver 1 in the navigation device 10.
[0022]
First, the configuration of the navigation device 10 will be described with reference to FIG. In FIG. 1, the GPS receiver 1 has a calculation part which performs a positioning calculation based on the GPS signal received from the GPS antenna 9, and performs a filtering process using a Kalman filter. The GPS receiver 1 performs a positioning calculation at a predetermined time interval, and outputs a positioning position and an estimated error amount as a positioning result to the NAVI_CPU 5 having a function as a CPU at a predetermined time interval. The positioning position output from the GPS receiver 1 is represented as P _GPS . Here, as is conventionally known, the GPS receiver 1 calculates an estimated error amount from two components, an error component based on the instantaneous geometric arrangement of GPS satellites and an error component based on filtering processing. This estimated error amount is expressed as P _ERR . The GPS receiver 1 does not directly output P _ERR as an estimated error amount for the GPS positioning result, but provides the NAVI_CPU 5 with a highly accurate estimated error amount determined by the process of FIG. 2 described below. To do.
[0023]
The gyro sensor 2 outputs a DC voltage corresponding to the angular velocity in the turning direction of the host vehicle. The output signal of the gyro sensor 2 is converted from analog to digital by the AD conversion unit 3 and output to the NAVI_CPU 5. The vehicle speed pulse signal 4 is a pulse having a frequency corresponding to the vehicle speed, and is output to the NAVI_CPU 5 as a count value obtained by counting the number of pulses by the logic circuit 12. The output signal of the gyro sensor 2 and the vehicle speed pulse 4 are used for the NAVI_CPU 5 to calculate the position by self-contained navigation. The speed of the vehicle obtained from each sensor is _represented as V _odo , the traveling direction is represented as ∠V _GYRO , the vehicle speed is represented as V (t), and the current position by self-contained navigation is represented as P _ES (t).
[0024]
The NAVI_CPU 5 is a CPU that executes processing such as vehicle position determination and map matching, and manages all functions necessary as a car navigation device. The map matching is executed when the NAVI_CPU 5 reads map data from a medium (not shown) on which map data is recorded via the DVD drive mechanism 8. The memory 7 stores programs and data necessary for the NAVI_CPU 5 to execute processing. The map data and the current position of the vehicle are displayed on the monitor 13 via the graphic control circuit 11 under the control of the NAVI_CPU 5.
[0025]
The NAVI_CPU 5 determines the vehicle position by a process similar to the process shown as the prior art in FIG. 3. At this time, as an estimated error amount with respect to the GPS positioning position for comparison with the position by the self-contained navigation, FIG. A highly accurate estimation error amount obtained by the calculation process shown in FIG.
[0026]
The error estimation value determination process in FIG. 2 will be described. Note that the processing in FIG. 2 is executed in parallel with the vehicle position determination processing by the NVI_CPU 5 while acquiring predetermined information from the NAVI_CPU 5 side under the control of the arithmetic unit in the GPS receiver 1. 2 is assumed to start when it is determined that the navigation device 10 is operating normally and the GPS receiver 1 has not been positioned. First, when it is determined that the vehicle is in a non-positioning state, it is determined from the map data whether the vehicle is currently in a tunnel (or something similar to a tunnel) (S1). As a result, when it is not in the tunnel (S1: NO), the process exits.
[0027]
On the other hand, when the vehicle has entered the tunnel, obtains an exit position P ₀ of the tunnel on the basis of the map data (S2). Since the GPS satellite signal can be received after exiting the tunnel, the determination is repeated until at least one satellite signal can be received in step S3 in order to obtain timing for the vehicle to exit the tunnel. As a result, if even one satellite signal can be received (S3: YES), it is subsequently determined in step S4 whether GPS positioning has been performed. If you're not GPS positioning (S4: NO), the exit location P ₀ of the tunnel, from the time when it is determined that passes through the tunnel, in addition to displacement by the autonomous navigation, obtained by this position new and _{P 0} a. The treatment in step S5 is repeatedly executed until GPS positioning is started. That is, the position P ₀ is set as a solution for the self-contained navigation starting from the exit of the tunnel.
[0028]
Here, when calculating P ₀ , updating may be performed according to the elapsed time since it was determined that the tunnel has been exited as described above, but until the GPS receiver receives a satellite signal after exiting the tunnel. If statistical data or experience values can be used as the time, the time may be added to the elapsed time. Furthermore, the starting point used for the self-contained navigation may be determined by pattern matching between the trajectory of the vehicle after passing through the tunnel and the map data.
[0029]
On the other hand, if it is determined that the GPS positioning is started (S4: YES), the next step S6, taking the difference between the position _{P 0} and the GPS positioning position _{P GPS,} the estimated error amount obtained by this difference and the GPS receiver 1 Compare with _PERR . That means
| P ₀ -P _GPS | >> _PERR |
Determine.
As a result, if the determination in step S6 is YES, | P ₀ -P _GPS | is output to NAVI_CPU 5 as an estimated error amount for the GPS positioning position (S7), and if the determination in step S6 is NO Then, P _ERR is output as an estimated error amount for the GPS positioning position (S8). That is, the larger value of | P ₀ −P _GPS | and | P _ERR | is output as the estimated error amount with respect to the GPS positioning position. This is because P ₀ is an accurate exit position based on the map data, and therefore | P ₀ -P _GPS | accurately reflects an error actually included in the GPS positioning position after the positioning is resumed.
[0030]
In this way, by determining the estimated error amount, the GPS positioning position is determined when the vehicle exits the tunnel after passing through a location where the vehicle cannot receive a satellite signal such as a tunnel and the GPS non-positioning state continues. In a situation where the amount of error actually included is large, this state can be reflected in the estimated error amount to maintain the estimated error amount at a larger value. Therefore, in the situation of starting positioning after non-positioning, a situation in which the GPS positioning position that includes a larger error than the position by the self-contained navigation is adopted in the vehicle position determination process, resulting in a position jump. Can be avoided.
[0031]
The embodiment of the present invention described above is a configuration in which a new estimated error amount is determined on the GPS receiver 1 side, and the determined new estimated error amount is provided to the NAVI_CPU 5 side. It is also possible to realize a configuration in which processing is performed on the NAVI_CPU 5 side. In step S2 of FIG. 2, when the exit position of the tunnel is acquired from the map data, the time and the traveling direction predicted to exit the tunnel are obtained based on the exit position. By using it in 1, it is possible to shorten the time until GPS positioning resumes, that is, the acquisition time of GPS satellites.
[0032]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a highly accurate estimated error amount with respect to the GPS positioning position in a situation where the non-positioning state continues and GPS positioning is resumed thereafter. As a result, it is possible to avoid a situation where a position jump or the like occurs and to improve the accuracy of the vehicle position determination as the car navigation device.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a navigation device according to the present invention.
FIG. 2 is a flowchart showing estimation error amount determination processing executed in the navigation apparatus of FIG. 1;
FIG. 3 is a flowchart showing a flow of vehicle position determination in a conventional navigation device.
[Explanation of symbols]
1 GPS receiver 2 Gyro sensor 4 Vehicle speed pulse 5 NAVI_CPU
10 Navigation device

Claims (6)

GPS that performs GPS positioning calculation and outputs an estimated error amount including an error component based on a geometrical arrangement of GPS satellites at the time of positioning and an error component based on filtering processing as an estimated error amount for the positioning position together with the positioning position Positioning means;
A self-contained navigation means for calculating a position by self-contained navigation based on the output from the sensor;
Map data,
When it is determined that the vehicle has entered a place that is in a GPS non-positioning state, a positioning start position that is a position where the vehicle exits from the place in the non-positioning state is acquired based on the map data, and the non-positioning state A predetermined condition is established based on the positioning start position, the GPS positioning position after exiting the location, and the estimated error amount with respect to the GPS positioning location. When performing the estimation error amount changing means for changing the estimation error amount for the GPS positioning position,
Vehicle position determining means for determining the position of the vehicle based on the GPS positioning position, the estimated error amount acquired from the estimated error amount changing means, and the position by the self-contained navigation means;
A vehicle-mounted navigation device comprising: The estimated error amount changing means includes
When the positioning start position is P ₀ , the GPS positioning position after exiting the place is P _GPS , and the estimated error amount for the GPS positioning position is P _ERR ,
If | P ₀ −P _GPS |> | P _ERR |, the estimated error amount is changed to | P ₀ −P _GPS |
If | P ₀ −P _GPS | ≦ | P _ERR |, the estimated error amount is set to | P _ERR |
The vehicle navigation apparatus according to claim 1. The estimated error amount changing means includes
If it is determined that the vehicle has exited from the non-positioning state and the GPS positioning position is obtained, the positioning start position can be obtained by the self-contained navigation. Updating based on vehicle displacement over time,
The in-vehicle navigation device according to claim 1 or 2, characterized in that. In the determination that the vehicle has exited from the non-positioning state by the estimated error amount changing means, the vehicle has exited from the non-positioning state upon reception of radio waves from at least one GPS satellite. The in-vehicle navigation device according to any one of claims 1 to 3, wherein the in-vehicle navigation device is determined to have been. 5. The place where the GPS non-positioning state is set is a tunnel, and the estimated error amount changing means determines that a vehicle has entered the tunnel based on the map data. The in-vehicle navigation device according to any of the above. A GPS receiver used in connection with a host system for navigation,
Positioning calculation means for outputting an estimated error amount composed of an error component based on a geometrical arrangement of GPS satellites at the time of positioning and an error component based on filtering processing as an estimated error amount for the positioning position together with the positioning position;
When it is determined that the vehicle has entered a place where the GPS is not positioned, a positioning start position, which is a position where the vehicle exits from the place where the vehicle is not positioned, is acquired in cooperation with the host system including map data. In addition, when it is determined that the vehicle has exited from the place that is in the non-positioning state, based on the positioning start position, the GPS positioning position after exiting from the place, and the estimated error amount with respect to the GPS positioning position When the predetermined condition is satisfied, an estimated error amount changing means for changing the estimated error amount with respect to the GPS positioning position;
A GPS receiver comprising:

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