JPH04216410A - Navigation apparatus on board vehicle - Google Patents

Abstract

PURPOSE:To obtain a superior navigation apparatus on board a vehicle which can operate the correct position even when the vehicle runs for a long time without a stop by providing a road map memory means, a second memory means, a reliability operating means and a control means. CONSTITUTION:The navigation apparatus is provided with a memory means 13 for storing the road map data, a reloadable second memory means 14 for storing output coefficients of a distance sensor 11 which detects the running distance of a vehicle and a direction sensor 12 which detects the running direction of the vehicle, and the position of the vehicle on the road map, a reliability operating means 16 for calculating the position of the vehicle and the optimum value of the output coefficient based on the data stored in the second memory means 14 and the output results from the distance sensor 11 and the direction sensor 12, and a control means 17 for storing the optimum value in the second memory means 14 in accordance with the degree of reliability.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-vehicle navigation system.

0002

2. Description of the Related Art FIG. 3 is a block diagram showing an example of a conventional in-vehicle navigation system. In FIG. 3, 1 is a mileage sensor, 2 is a rate gyro which is a direction sensor, and 3 is a direction sensor.
is a calculation means for calculating the current position of the vehicle, etc., and the mileage sensor 1 and the rate gyro 2 are connected to the calculation means 3. 4 is an auxiliary storage means for storing map data, etc.; 5 is a control means; this control means 5 includes a calculation means 3;
, auxiliary storage means 4 are connected. Reference numeral 6 denotes a display means such as a CRT connected to the control means 5.

Next, the operation of the above conventional example will be explained using FIG. 4. In the conventional example described above, when the vehicle travels (step (hereinafter referred to as ST) 1), the position calculating means 33 calculates the current position of the vehicle according to the outputs of the mileage sensor 1 and the rate gyro 2 (ST2). The control means 5 displays the vehicle's current position data from the calculation means 3, the map data from the auxiliary storage means 4, etc. on the display means 6, and informs the driver of the current position.

Here, a rate gyro that detects angular velocity is used as the direction sensor, and in this case, the direction of the vehicle is given by integrating the detected angular velocity. In this case, since the zero drift changes, errors accumulate in the vehicle direction obtained by integration. Therefore, when the stop detection means 31 detects a stop of the vehicle, the drift calculation means 32 calculates a zero drift (ST3), and calculates the current position while subtracting the drift while the vehicle is running (ST3).
T1, ST2).

[0005]

[Problems to be Solved by the Invention] However, since the conventional in-vehicle navigation device using a rate gyro calculates drift only when the vehicle is stopped, changes in drift are not calculated when driving a long distance without stopping. There was a problem in that it could not be grasped, direction errors would accumulate, and correct position calculation could not be performed.

SUMMARY OF THE INVENTION The present invention is intended to solve these conventional problems, and it is an object of the present invention to provide an excellent in-vehicle navigation system that can calculate the correct position even when driving for a long time without stopping.

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a first storage means that stores road map information, a distance sensor that detects the traveling distance of the vehicle, and a distance sensor that detects the traveling direction of the vehicle. a second storage means that stores and is rewritable a direction sensor to detect, a position of the vehicle on the road map, and output coefficients of each of the distance sensor and the direction sensor; calculation means for calculating the optimal values of the vehicle position and output coefficient based on the information obtained by the vehicle and the output results of the distance sensor and the direction sensor, and storing the optimal values in the second storage means according to their certainty. The device is equipped with a memory rewriting means.

[0008]

According to the present invention, the output coefficients of the distance sensor and the direction sensor are always maintained at optimum values while referring to the traveling position, so that highly accurate vehicle position information can be calculated. Further, by using a piezoelectric vibration angular velocity sensor as the orientation sensor, an inexpensive in-vehicle navigation device can be provided.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an in-vehicle navigation system according to an embodiment of the present invention. In FIG. 1, 11
is a mileage sensor (hereinafter referred to as distance sensor) that calculates the number of rotations of the axle and detects the distance traveled by the vehicle. If the number of rotations of the axle is N and the distance traveled is S, then S = a0N (
a0 is an output coefficient), and a0 is not completely constant because it depends on the tire diameter, but it is almost stable.

Reference numeral 12 denotes a direction sensor which is composed of a piezoelectric vibration type angular velocity sensor and which detects the running direction of the vehicle by integrating its output.If the output is V, the sampling time is t, and the rotation angle is θ, then , θ=Σ(a1Vt
+a2t) (a1, a2 are output coefficients)
where a1 and a2 are called sensitivity and offset, respectively.

13 is a storage means storing road map information;
14 is a second storage means that stores the position on the road map stored in the storage means 13 and the output coefficients of the distance sensor 11 and the direction sensor 12; 15 is the second storage means 1;
4 and the output results of the distance sensor 11 and the direction sensor 12, respectively, to calculate a possible position of the vehicle at that point in time; The distance sensor 11 and the direction sensor 12 calculate possible routes based on the road map information stored in the storage means 13, and measure the certainty that the routes can be traveled.
Accuracy calculation means 17 calculates the certainty of each output coefficient, and 17 displays the most reliable current location calculated by the accuracy calculation means 16 on the display means 18, and the accuracy calculation means 1
The position of the vehicle on the road map calculated in step 6 and the distance sensor 11
and the output coefficient of each direction sensor 12,
This is a control means for rewriting information stored in the second storage means 14 regarding things that can be confirmed or corrected.

Next, the operation of the above embodiment will be explained with reference to FIG. According to the above embodiment, the position calculation means 15 always performs the following operations based on the outputs of the distance sensor 11 and the direction sensor 12 and the information stored in the second storage means 14.
All possible positions of the vehicle are calculated by allowing the maximum error (ST11), and based on this information, all possible routes are calculated from the storage means 13 (ST12). The accuracy calculating means 16 calculates the certainty of all of these possible routes, and at the same time calculates the certainty of the output coefficients of the distance sensor 11 and the direction sensor 12 when taking that route. The final end of the route indicates the vehicle's current position, so the vehicle's position and
The certainty of the output coefficients of each of the distance sensor 11 and the direction sensor 12 is calculated at the same time (ST13). The control means 17 displays the most reliable route among these routes calculated by the accuracy calculation means 16 on the display means 18, a map,
Displays the current location and driving route to inform the driver of the current driving status. Further, the control means 17 judges whether the optimum route can be used as the starting point for subsequent route calculations depending on the certainty of the optimum route (ST14), and if it is sufficiently certain, the second
The location information of the vehicle is newly stored in the storage means 14 of the vehicle, and the information is rewritten (ST15). Here, reliable position information is not limited to the final end of the route, that is, the vehicle position at that point, but if it can be determined up to the middle of the route, it can be determined as the vehicle position at that retroactive time. Then, it can be used as a starting point for calculating subsequent travel routes. The respective output coefficients of the distance sensor 11 and the direction sensor 12, which are obtained simultaneously with this vehicle position information, are corrected to their most reliable values and stored in the second storage means 14 (ST16-1
7). If the vehicle position cannot be determined in ST14, it is determined whether the direction can be corrected (ST1
8) If correction is possible, correct it (ST17). This is to ensure the reliability of the output coefficient of the orientation sensor 12 when the road does not have any characteristic curves that would allow the vehicle to determine its position, such as when the vehicle is traveling on a straight road for a long time.

[0013] In ST11-12, all possible vehicle positions and travel routes are calculated, and the accuracy of the road map information is increased and the fluctuation width of the output coefficients of the distance sensor 11 and direction sensor 12 is reduced. If it can be predicted, the number of calculations will be reduced, and the calculations after ST13 will be performed quickly. In this way,
Even on roads where the vehicle stops frequently, such as on expressways, the sensor output coefficients are corrected as needed while driving, allowing accurate position calculations.

[0014] Normally, the sensor output coefficient changes greatly at the time of rise. In particular, in the case of piezoelectric vibration type angular velocity sensors, the offset fluctuations are large and the accuracy of position calculation decreases, so conventional in-vehicle navigation devices
Although it was not functioning satisfactorily, in the present invention, the sensor output coefficient is corrected as needed, so accurate position calculation can be performed.

[0015]

Effects of the Invention As is clear from the above explanation, according to the present invention, the reliability of the sensor output coefficient is calculated at the same time as the position calculation, and the sensor output coefficient is corrected at the same time as the position is determined. Even if the vehicle continues to drive without stopping for a certain period of time, it will be possible to accurately calculate the position.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an in-vehicle navigation device according to an embodiment of the present invention.

[Figure 2] Flowchart showing an example of the operation of the in-vehicle navigation device

[Figure 3] Block diagram showing a conventional in-vehicle navigation device

[Fig. 4] Flowchart showing an example of the operation of the in-vehicle navigation device.

[Explanation of symbols]

11 Distance sensor 12 Direction sensor 13 Road map storage means 14 Second storage means 15 Position calculation means 16 Accuracy calculation means 17 Control means 18 Display means

Claims (1)

[Claims] 1. A first storage means storing road map information; a distance sensor for detecting a travel distance of a vehicle; a direction sensor for detecting a travel direction of the vehicle; and a position of the vehicle on the road map. and a second storage means that stores and is rewritable the output coefficients of the distance sensor and the orientation sensor, and the information stored in the second storage means and the output results of the distance sensor and the orientation sensor, respectively. an in-vehicle navigation device comprising: calculation means for calculating the position of the vehicle and the optimum value of the output coefficient based on the vehicle position; and memory rewriting means for storing the optimum value in the second storage means according to its reliability. .