JPH0633369Y2 - Car navigation system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an on-vehicle navigation device with improved navigation accuracy by a map matching method.

[Prior Art] An in-vehicle navigation device that displays the current location of a vehicle along with a road map on a display device in a vehicle compartment to help guide the vehicle to the destination uses radio waves from a satellite or geomagnetism. It can be included in a broad-based navigation system that estimates the current location of a moving body.

The conventional vehicle-mounted navigation device 1 shown in FIG.
This is based on the estimation of the current position by the central processing unit 4 to which the mileage sensor 3 and the like are connected. The road map read from the road map information recording medium 6 such as a CD-ROM via the reading device 5 called a media controller,
After being temporarily stored in the buffer memory 7, it is displayed on the screen of the display device 8 together with the estimated current position. The display device 8 controlled by the display control device 9 can display the road map data near the current position stored in the image memory 10, and the key operation on the keyboard device 11 connected to the central processing unit 4 can be performed. Through, it is possible to display the route closest to the line connecting the departure point and the destination with the shortest distance. Therefore, the driver can select the route to the destination while comparing the shortest distance route to the destination displayed on the screen of the display device 8 with the estimated current position.

[Problems to be Solved by the Invention] The above-described conventional vehicle-mounted navigation device 1 has slightly different estimation accuracy depending on whether a highly accurate gyroscope is used as the direction sensor 2 or a geomagnetic sensor or a steering angle sensor. However, the mileage sensor also has a problem of unavoidable deterioration of detection accuracy due to wheel slips, etc., and it is necessary to somehow compensate for the deterioration of estimation accuracy caused by such sensor detection errors. It was Actively utilizing road information as an effective method for this kind of compensation,
Attention has been paid to map matching, which verifies whether the estimated travel path matches the actual road. However, even with such a map matching method, there is a problem of how to change the actual road information into data suitable for quantitative processing. For example, all of the road maps described in the past have been described. In the method of formulating the road of 2 as a straight line or a curve on a two-dimensional plane,
It requires a very large capacity recording medium and is far from practical use.

[Means for Solving Problems] The present invention solves the above problems, and at least a direction sensor, a mileage sensor, a display device, a road map information recording medium, a road map and A reading device that reads the road information table created by regarding the road described in the road map as a set of straight lines connecting the nodes at both ends, and estimates the current position of the vehicle from the output of the azimuth sensor and the mileage sensor, The display device includes a central processing unit that displays both a road map and the current position of the vehicle, and the central processing unit considers that the vehicle has changed course and entered a new road based on the data from the road information table. If the difference between the derived road angle and the stable driving direction of the vehicle is within a certain range, the nearest node is judged to be the passing node If there is no nearest node, a map matching means for making a similar judgment for the next nearest node and matching the estimated traveling locus with the actual road is provided.

[Operation] According to the present invention, a road information table created by regarding a road described in a road map as a set of straight lines connecting nodes at both ends to a map matching means for matching an estimated traveling locus with an actual road. When it is considered that the vehicle has changed course and entered a new road, the nearest node where the difference between the derived road angle and the stable driving direction of the vehicle is within a certain range is determined to be the passing node, and If there is no nearest node, then the same judgment is made as to the nearest node, and the estimated traveling locus and the actual road are matched to improve the estimation accuracy of the current position of the vehicle and the traveling locus.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is a circuit configuration diagram showing an embodiment of a vehicle-mounted navigation device of the present invention, and FIGS. 2 and 3 are road information tables necessary for the central processing unit shown in FIG. 1 and this road information table. 7 is a flowchart for explaining a map matching operation using the.

In FIG. 1, an in-vehicle navigation device 21 is a central processing unit 22 having a map matching function, and a road information recording medium 23 includes normal road map data and node data used for map matching. Is recorded by adding a road information table in which As shown in FIG. 2, the road information table regards the roads described in the road map as a set of straight lines connecting the nodes at both ends, and each node has its coordinates, the number of roads passing therethrough, and each road. The central processing unit 22 is created by digitizing angles and connecting nodes, and the central processing unit 22 is enumerated as a candidate for passing the vehicle as a part of the traveling locus estimation operation based on the outputs of the azimuth sensor 2 and the traveling distance sensor 3. As for, the node with the most realistic relevance is selected, and the estimated travel locus of the vehicle is matched with the road leading to the selected node.

In the embodiment, as the azimuth sensor 2, a geomagnetic sensor 2a that detects the vehicle azimuth from the horizontal component of the geomagnetism and a steering angle sensor 2b that detects the vehicle azimuth from the steering angle of the steered wheels are used. The geomagnetic sensor 2a is used as the azimuth sensor 2 only when detecting the absolute azimuth necessary when the vehicle starts traveling, and the steering angle sensor 2b is used as the azimuth sensor 2 for subsequent estimation operations.

By the way, the nodes put on the road information table are digitized in accordance with a predetermined format in which the node number, the absolute position coordinates, the number of roads branching, and the connecting nodes are digitized. That is, regarding the node numbers, for example, a map of 1 / 25,000 is decomposed into several units in a grid pattern, and a maximum of 65536 consecutive numbers (0000
~ FFFF _H ) is attached. In that case, the nodes on the map are
A method of sorting along the Y coordinate from the north to the south, and those having the same Y coordinate along the X coordinate from the west to the east, and numbering according to the sort order is adopted. Also, regarding the absolute coordinates of the nodes, 32 bits are used for both the XY coordinates, and 1 bit has a resolution equivalent to 0.5 mm in the actual distance. The number of roads branching from a node is 0001 for dead ends, 0002 for simple inflection points, and 0003
Is a T or Y junction, 0004 is a normal intersection, and 0005 is a five-way intersection. In addition, the road angle is expressed in the range of 0 to 359 degrees from the true east, and a total of 16
Of the angle bits of the bits, the lower 12 bits represent the actual angle, and the upper 4 bits can be used as a pointer when the connecting node does not exist in the same table. The connecting node is the other node of the road leading to the node to be digitized, and one or more connecting nodes are always attached with the node number.

The map matching operation by the central processing unit 22 will be described below with reference to FIG.

In this embodiment, each time the traveling distance sensor 3 detects traveling of a vehicle at a predetermined fixed distance (for example, π / 8 m),
The central processing unit 22 is configured to execute an interrupt processing program for current position estimation. This interrupt processing is supported by a total of four types of processing programs, namely, basic processing as a base and straight traveling processing, curved traveling processing, and branch traveling processing derived from the basic processing.

First, as shown in step (101) of FIG. 3 (A), the basic processing program first saves and protects the main register, and changes the function to the interrupt register. next,
In step (102), a change amount of the traveling angle of the vehicle, that is, a yaw angle is calculated from the steering angle detected by the steering angle sensor 2b, and in the following step (103), the vehicle goes straight according to the detected yaw angle. State, that is, whether the steered wheels are in a neutral state.

Next, in step (104), it is determined whether or not the output of the geomagnetic sensor 2a is taken in as an azimuth angle. If the vehicle is starting to travel, as shown in step (105),
The azimuth angle is calculated based on the output of the geomagnetic sensor 2a, and if the traveling has already started, the azimuth angle is calculated from the yaw angle and the azimuth angle (initial angle) immediately before the interrupt process.

When the calculation of the azimuth angle of the vehicle is completed, the determination steps (107), (108) and (109) for selecting three types of programs derived from the basic processing program are executed at any time,
Finally, the step (110) of restoring the main register is reached, and a series of interrupt processing is completed. In this case, each of the determination steps (107) to (109) is executed by checking the state of the corresponding flag.

When it is determined in the decision step (107) that the vehicle is traveling straight ahead, first, as shown in step (111) of FIG. 3 (B), the estimated current position (Xp, Yp) of the vehicle is ahead of the route. It is judged whether or not the coordinates (Xf, Yf) of the nodes to be saved are almost the same. When it is determined that the estimated current position is the front node, the branch traveling flag is set in step (112), and the process proceeds to step (110). However, if it is determined that the estimated current position is not a node, then it is determined in step (113) whether the vehicle has turned. This judgment is based on the difference between the azimuth angle θd of the vehicle and the azimuth angle θf when the vehicle is completely bent and stabilized, and a reference angle θt for judging whether the vehicle has bent (for example, 25
Judgment is made based on whether or not Then, in the case of the affirmative judgment result, the curving traveling flag is set in step (114), and the process proceeds to step (110).

When it is determined that the vehicle is traveling straight ahead, the absolute coordinates are updated in step (115). The updating of the absolute coordinates is performed by Xp ← Xp ₋₁ + Vcos θr Yp ← Yp ₋₁ + Vsin θr. However, Xp _-1 , Yp _-1 are the absolute coordinates of the current position at the time of the previous estimation, and V is the scalar quantity of the unit distance vector (= π /
8m), θr is the road angle.

When the absolute coordinates are updated in this way, the following steps (11
In step 6), the yaw angle clear flag indicating that the yaw angle has been cleared is set, or in step (117), the stable straight-ahead flag indicating that the vehicle is traveling straight ahead over a certain distance is set. In step (118) of making these judgments and receiving these judgments,
A flag is set to indicate that the steering angle sensor 2b is to be used instead of the geomagnetic sensor 2a to detect the direction. Next, in step (119), the yaw angle is cleared to zero, then the initial angle θi is replaced with the road angle θr, and finally the yaw angle clear flag is set in step (120), and the process proceeds to step (110). Transition.

On the other hand, in the judgment step (108), if it is found that the vehicle is traveling in a curve, first, in the step (121) shown in FIG. 3 (C), by the same method as the above step (115), Update the absolute coordinates of your estimated current location. Next, in step (122), it is determined whether or not the estimated current position is a front node, and if it is a front node, a branch traveling flag is set in step (123), and if the front node is not reached, the step ( After confirming that the vehicle's direction of travel is at rest in (124), follow the steps (12
In 5), the azimuth angle is updated with the stable angle θf. After updating the azimuth, this time, in step (126),
It is determined whether or not the difference between the stable angle θf and the previous stable angle θf ₋₁ exceeds an angle θt that is a criterion for determining whether the vehicle has bent. In this judgment step, it is checked whether or not there are lane changes due to overtaking or overtaking. If these lane changes do not apply, then in step (127), the presence or absence of a U-turn is checked. If it is determined that there is a U-turn, the front node and the rear node are rewritten in step (128). Also, if it turns out that it was not a U-turn,
In step (129), the nearest node is selected according to whether the estimated current position is closer to the front node or the rear node.

When the selection of the nearest node is completed, next, in step (130) of FIG. 3D, it is determined whether the number of roads leading to the selected nearest node is two or less. If the number of roads is 2 or less, it is known that the nearest node is an inflection point, and in order to refrain from map matching during curving, it is checked in step (131) whether the vehicle is in a stable straight line. Only when it is determined that the vehicle is traveling straight in a stable direction, the process proceeds to the same step (132) as when the determination in step (130) is denied. If the vehicle is not traveling in a straight line and is traveling on a curved road to some extent, map matching will be given to the next opportunity.

In step (132), the diverging road angle and the azimuth angle are compared, and the diverging road having the closest angle is selected. Then, in the next step (133), it is checked whether or not the difference between the selected branch road and the azimuth is less than or equal to a predetermined angle θk (for example, 20 degrees). It is determined that the user has entered the road, and necessary data is rewritten in step (134).
If the difference between the divergence angle and the divergence road exceeds the angle θk, in step (135), is the number of roads connecting to the nearest node next to the nearest node selected in step (129) two or less? Make a decision.

This determination step (135) includes steps (136) to (13) having the same contents as those of steps (131) to (133) already described.
8) continues, and after receiving the positive judgment result of step (138),
After performing steps (139) to (143), the process proceeds to step (110). In step (140), the stable straight ahead flag is turned down, and in the next step (141), the coordinates of the front node (X
pf, Ypf) to rewrite the estimated current location (Xp, Yp),
Map matching is executed by so-called warp processing.

Also, when it is determined in the judgment step (119) that the vehicle is branching, the absolute coordinates are first updated in step (151) shown in FIG. 3 (E), and estimated in step (152). After determining whether your current location is within the intersection,
Similar steps (153) to (159) are performed to execute the required map matching, and the process proceeds to step (110).

Thus, the vehicle-mounted navigation device 21, the central processing device 22 is a map matching means for matching the estimated travel path and the actual road, the road described in the road map,
Given the road information table created by considering it as a set of straight lines connecting the nodes at both ends, and when thinking that the vehicle has changed course and entered a new road, perform steps (126) to (13).
As shown in 4), if the difference between the derived road angle and the stable driving direction of the vehicle is within a certain range, the nearest node is judged to be a passing node, and if there is no corresponding nearest node, step ( As shown in (135) to (139), the same judgment is made next for the nearest node to match the actual road with the estimated travel path. , It is possible to collect a huge amount of road information as the minimum required nodal data, and even if a cumulative error is accumulated in the estimation result based on the outputs of the azimuth sensor 2 and the travel distance sensor 3, when the vehicle changes its course, It is possible to estimate the current position with the most realistic relevance by determining the passing nodes from the nearest nodes that satisfy a certain matching condition, and even the azimuth sensor 2 and the mileage sensor 3 with a certain accuracy are available. If so, it is possible to obtain the estimation accuracy sufficiently exceeding the practical level.

[Advantage of Device] As described above, the device of the present invention is a set of straight lines connecting the nodes at both ends of the road described in the road map to the map matching means for matching the estimated traveling locus and the actual road. Given that the road information table created by considering that the vehicle has changed course and entered a new road, the nearest node where the difference between the derived road angle and the stable driving direction of the vehicle is within a certain range Is determined as a passing node, and if there is no corresponding nearest node, the same judgment is made for the nearest node next, and the configuration is designed to match the actual road with the estimated travel path. The huge amount of road information can be aggregated in the road information table of No. 1 as the minimum required nodal data, and the accumulated error is accumulated in the estimation results based on the outputs of the direction sensor and mileage sensor. Even if they try to pile up, when the vehicle changes its course, it is possible to estimate the current position with the most realistic validity by determining the passing node from the nearest node that satisfies a certain matching condition, and with a direction sensor with a certain accuracy. As long as there is a mileage sensor, it is possible to obtain an excellent effect that it is possible to obtain an estimation accuracy that is sufficiently higher than a practical level.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of a vehicle-mounted navigation device of the present invention, and FIGS. 2 and 3 are road information tables necessary for the central processing unit shown in FIG. 1 and this road information table. FIG. 4 is a circuit diagram showing an example of a conventional vehicle-mounted navigation device, which is a flowchart for explaining the map matching operation using the. 2 ... Direction sensor, 3 ... Odometer, 21 ... In-vehicle navigation device, 22 ... Central processing unit, 23 ... Road information recording medium.

Claims (1)

[Scope of utility model registration request] 1. At least a direction sensor, a traveling distance sensor, a display device, and a road map information recording medium, and regards the road map and the roads described in the road map as a set of straight lines connecting nodes at both ends. A reading device that reads the created road information table; a central processing unit that estimates the current position of the vehicle from the outputs of the direction sensor and mileage sensor and displays both the road map and the current position of the vehicle on the display device; The central processing unit, based on the data from the road information table, when it is considered that the vehicle has changed course and entered a new road, the difference between the angle of the derived road and the stable traveling direction of the vehicle is Judge that the nearest node within a certain range is a passing node,
If there is no corresponding nearest node, the vehicle-mounted navigation device is provided with map matching means for making a similar judgment on the next nearest node and matching the estimated travel path with the actual road. .