JPH04140608A - Navigation apparatus - Google Patents

Abstract

PURPOSE:To improve the certainty in determination of the advancing azimuth of a vehicle by calculating the relative azimuth of the vehicle from the steering angle of rear wheels and the tread of the rear wheels obtained from the difference of the running distance of the rear wheels and outputs of a front wheel steering angle sensor with reference to the curve of a predetermined steering ratio. CONSTITUTION:In a vehicle with four-wheel drive, the difference of the running distance of the rear wheels is obtained from the difference of the integrated values of outputs of speed sensors 23, 24 which detect the speed of the respective rear wheels. The relative azimuth of a vehicle body is operated from the obtained difference of the running distance, he steering angle of rear wheels obtained from the outputs of a front wheel steering angle sensor 5 with reference to the curve of a predetermined steering ratio, and the tread of the rear wheels. The azimuth data of a terrestrial magnetism sensor 22 is corrected by the relative azimuth thereby to obtain the absolute azimuth. The advancing azimuth of the vehicle is determined by the absolute azimuth. Therefore, errors of the absolute azimuth data obtained from the terrestrial magnetism sensor 22 or the like can be compensated even in the four-wheel driving vehicle, so that the advancing azimuth of the vehicle can be determined with improved certainty.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a navigation device for a vehicle, and particularly in a vehicle having a four-wheel steering (hereinafter referred to as 4WS) device, the turning angle (hereinafter referred to as yaw angle) of the vehicle body. Find it correctly,
The present invention relates to a navigation device that can create data regarding the traveling direction of a vehicle.

[Conventional technology]

2. Description of the Related Art Conventionally, a geomagnetic sensor that detects the direction of the earth's magnetic field to determine the direction has been generally used as an absolute direction sensor for self-contained navigation in a navigation device for a car or the like.

However, if the distribution of geomagnetism is disturbed by buildings, railroads, other vehicles, etc., the geomagnetic sensor may indicate a direction different from the actual direction of travel of the vehicle.

Therefore, in the navigation devices that are in practical use,
In order to more accurately determine the direction in which the vehicle is traveling, the relative azimuth, or yaw angle, of the vehicle body is determined from the travel difference determined from the wheel speeds of the left and right rear wheels of the vehicle, relative to the absolute azimuth determined from the geomagnetic sensor. A method is used to correct errors in the geomagnetic sensor.

In the case of a two-wheel steering (2WS) vehicle, since the rear wheels are not steered, it is relatively easy to determine the yaw angle.

FIG. 8 explains the method of determining the yaw angle of the vehicle from the difference in travel between the wheels, where 31.32 is the front wheel, 33.34
indicates the rear wheel, and O is the turning center.

Now, let's assume that the rear wheel tread is a, the rear right wheel travel determined as the integral value of the wheel speed of the rear right wheel is X, and the rear left wheel travel determined as the integral value of the rear left wheel wheel speed is y. θ
Assuming r-0, the yaw angle θ can be easily determined from the relationship −y θ−(1).

[Problem to be solved by the invention]

In the case of a ZWS vehicle, the yaw angle can be easily determined from the wheel speeds of the left and right rear wheels as described above, and this can be used to correct the geomagnetic sensor.

However, in the case of a dWS vehicle, θ,
Since ≠0, the yaw angle is different from the value obtained from equation (1). Therefore, even if the conventionally known azimuth correction method for 2WS vehicles was used to correct errors in geomagnetic sensors, there was a problem in that the errors were too large to be used.

[Purpose of the invention]

The present invention aims to solve the problems of the prior art, and is capable of accurately determining the yaw angle even in JWS vehicles, correcting the azimuth data from the geomagnetic sensor, etc., and determining the vehicle's traveling azimuth. The objective is to provide a navigation device that can improve the accuracy of decisions.

[Means to solve the problem]

In the present invention, in a four-wheel steered vehicle, there is provided a means for determining the distance difference between the two rear wheels from the difference in the integral values of the outputs of the two rear wheel speed sensors (23, 24), and a means for determining the distance difference between the two rear wheels determined thereby. the stroke difference and the rear wheel steering angle determined from the output of the front wheel steering angle sensor (5) with reference to a predetermined steering ratio curve, or the rear wheel steering angle determined from the rear wheel steering angle sensor (12); means for calculating the relative orientation of the vehicle body from the rear wheel trend, and calculates the traveling direction of the vehicle from the absolute orientation obtained by correcting the orientation data of the geomagnetic sensor (22) based on the determined relative orientation. It is structured. This aims to achieve the above-mentioned purpose.

[Effect]

The distance difference between the two rear wheels is determined from the difference in the integral values of the outputs of the two rear wheel speed sensors. From this determined travel difference between the two rear wheels and the rear wheel steering angle determined by referring to a predetermined steering ratio curve from the output of the front wheel steering angle sensor, or from the measured rear wheel steering angle and rear wheel tread. Calculate the relative orientation of the vehicle body. Then, the absolute direction is obtained by correcting the direction data of the geomagnetic sensor, etc. using the obtained relative direction, and the traveling direction of the vehicle is determined based on this absolute direction. By compensating for errors in the determined absolute azimuth data, it is possible to improve the accuracy of determining the vehicle's heading.

[Embodiment] FIG. 1 shows the overall configuration of a 4WS system according to a first embodiment of the present invention, and shows an open-loop control 4WS system.

In FIG. 1, reference numeral 1 denotes a front wheel gearbox, which moves a front wheel tie rod 3 based on the operation of a steering handle 2, thereby turning the front wheels 4. A front wheel steering angle sensor 5 is attached to the front wheel tie rod 3 and detects the steering angle of the front wheel 4. 6 is a vehicle speed sensor, which detects the speed of the vehicle body. A 4WS controller 7 drives a rear wheel steering motor 8 based on detection signals from the front wheel steering angle sensor 5 and the vehicle speed sensor 6.

Reference numeral 9 denotes a rear wheel actuator section, which is connected to a rear wheel tie rod 10 by a neutral holding mechanism using a centering spring.
is held in a neutral state, and when the motor 8 is driven, the rear wheel tie rod 1o is moved to turn the rear wheel 11.

The operation of the 4WS system shown in FIG. 1 is performed as follows.

(2) Front wheel steering angle θ detected by the front wheel steering angle sensor 5;

Then, the vehicle speed V detected by the vehicle speed sensor 6 is input.

(2) Determine the target rear wheel steering angle θ from the front wheel steering angle θ, the vehicle speed (2), and the steering ratio (K) curve.

Fig. 2 is an example of a steering ratio curve showing the relationship between vehicle speed and steering ratio, where the target rear wheel steering angle θ is calculated from the steering ratio and the front wheel steering angle θ, and θ,= ×θ, ・−(2)
It is determined by the relationship.

(2) The rear wheels 11 are turned through the rear wheel actuator 9 to achieve the target rear wheel steering angle θ.

(2) The rear wheel actuator 9 includes, for example, a hydraulic piston type and a type using an electric motor and a rack and pinion.

■, θ, -〇, rear wheel actuator output is 0.
, the rear wheel steering angle θ is set to 0 by the rear wheel neutral holding mechanism.
Make it.

FIG. 3 is a block diagram showing the system configuration of the 4WS vehicle navigation device according to the first embodiment of the present invention,
Components that are the same as in FIG. 1 are designated by the same numbers. This third
In the figure, reference numeral 21 denotes a rear wheel steering mechanism that steers the rear wheels;
Reference numeral 22 is a geomagnetic sensor, reference numerals 23 and 24 are wheel speed sensors that detect the wheel speed of the rear wheels, reference numeral 25 is a navigation controller that performs navigation control of the vehicle, and reference numeral 26 is a CR.
a visual display device such as a T display or an LCD display;
Reference numeral 27 is an input device such as a keyboard, and reference numeral 28 is a pre-stored map database.

In this embodiment, in a four-wheel steering vehicle, the stroke difference between the two rear wheels is determined from the difference in the integral values of the outputs of the rear wheel speed sensors 23 and 24, and the stroke difference between the two rear wheels thus determined is The relative orientation of the vehicle body is calculated from the rear wheel steering angle determined from the output of the front wheel steering angle sensor 5 with reference to a predetermined steering ratio curve and the rear wheel trend, and the geomagnetic sensor 22 uses the calculated relative orientation.
The heading direction of the vehicle is determined by the absolute heading obtained by correcting the heading data.

The operation of the dWS car navigation system shown in FIG. 3 is performed as follows.

■, Front wheel steering angle θf determined by front wheel steering angle sensor 5
is input to the 4WS controller 3.

(2) The 4WS controller 3 uses the steering ratio K uniquely determined from the steering ratio curve illustrated in FIG.
The rear wheel steering angle θ is determined from the relationship of the formula, and the rear wheel steering motor 8 is
．． The rear wheels 11 are turned through a rear wheel steering mechanism 21 consisting of a rear wheel actuator 9 and the like.

(2) The 4WS controller 3 communicates the rear wheel steering angle θ to the navigation controller 25.

(2) The navigation controller 25 determines the yaw angle θ of the vehicle body from the travel difference xy obtained from the right and left wheel speed sensors 23, 24 and the rear wheel steering angle θ according to the following relationship.

θ= (x-y)/acos θ,
-(3) Note that a is the rear wheel tread. This yaw angle θ
is used to correct the absolute orientation of the geomagnetic sensor 22.

Now, when the vehicle body rotates by θ (rad) with respect to the turning center 0, the trajectories drawn by the rear left and right wheels become as shown in FIG. 8, and the strokes of the two wheels are expressed as follows.

Rear right wheel travel x = (R + acos θr) θ - (4)
Rear left wheel stroke y=Rθ − (5) Therefore, the stroke difference xy between both rear wheels is: x y = a cos θ,·θ Therefore, the yaw angle θ is determined by the following equation.

Note that the strokes X and y are obtained by integrating the output of the wheel speed sensor 2324, and R is the turning radius of the inner wheel.

In the operation of this device described above, the rear wheel steering angle θ is calculated inside the 4WS controller 7, but the steering ratio is stored in advance in the navigation controller side, the vehicle speed signal V is input, and the rear wheel steering angle θ is calculated inside the 4WS controller 7. The rear wheel steering angle θ may be determined within 25.

In addition, in the above-mentioned embodiment, the explanation was centered on the example of the relative azimuth sensor that uses the stroke difference to correct the data of the geomagnetic sensor 22, but it can also be used as an independent relative azimuth sensor without using the geomagnetic sensor together. May be used.

FIG. 4 shows the overall configuration of a 4WS system according to a second embodiment of the present invention, in which the same components as in FIG. 1 are designated by the same numbers, and 12 detects the steering angle of the rear wheels. This is a rear wheel steering angle sensor.

FIG. 5 is a block diagram showing the system configuration of a navigation device for a 4WS vehicle according to a second embodiment of the present invention, in which the same parts as in FIG. 3 are designated by the same numbers.
2 is a rear wheel steering angle sensor.

In the embodiment shown in FIG. 5, the 4WS controller 7 operates like the embodiment shown in FIG.
A target rear wheel steering angle θ1 is determined from the front wheel steering angle θ determined from the front wheel steering angle θ and the vehicle speed 2 determined from the vehicle speed sensor 6, and the rear wheels are turned through the rear wheel steering mechanism 21.

The rear wheel steering angle sensor 12 detects the actual steering angle θ,'' of the rear wheels, and
Notify the 4WS controller 7. The 4WS controller 7 performs feedback control so that θr'-〇.

The 4WS controller 7 communicates the steering angle θ to the navigation controller 25.

The navigation controller 25, similar to the embodiment shown in FIG. From the wheel steering angle θ1 and the rear wheel tread a held as data in advance, the yaw angle θ (relative azimuth) is determined from the relationship in equation (6), and the absolute azimuth obtained from the geomagnetic sensor 22 is corrected. .

FIG. 6 shows the overall configuration of a 4WS system according to a third embodiment of the present invention, and the same parts as in FIGS. 1 and 4 are designated by the same numbers.

FIG. 7 is a block diagram showing the system configuration of a 4WS vehicle navigation device according to a third embodiment of the present invention,
The same parts as in FIG. 5 are indicated by the same numbers.

In the embodiment shown in FIG. 7, the 4WS controller 7 operates like the embodiment shown in FIG.
The target rear wheel steering angle θ is determined from the front wheel steering angle θ determined from the front wheel steering angle θ and the vehicle speed 2 determined from the vehicle speed sensor 6, and the rear wheels are turned through the rear wheel steering mechanism 21.

The rear wheel steering angle sensor 12 detects the rear wheel steering angle θ, and communicates it to the navigation controller 25.

The navigation controller 25, similarly to the embodiment shown in FIG.
The yaw angle θ (relative azimuth) is determined from the rear wheel steering angle θ obtained by the equation (6) and the rear wheel tread a stored in advance as data, and the absolute azimuth obtained from the geomagnetic sensor 22 is Correct the direction.

In each of the above embodiments, the absolute orientation is determined by the geomagnetic sensor 22, but the absolute orientation may be determined by inputting the initial orientation and using the integrated value of the relative orientation without using the geomagnetic sensor. .

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to determine the yaw angle even in a dWS vehicle, and therefore it is possible to correct the absolute azimuth data determined by the geomagnetic sensor etc. to improve the accuracy of the vehicle's heading. Therefore, it becomes possible to improve the marketability of the navigation system.

In the first embodiment of the present invention, there is no need for a sensor to detect the steering angle of the rear wheels, the mechanism is simple and inexpensive, and the detection of the steering angle of the rear wheels can be performed using software, so multiple sensors can be used. It becomes possible to respond to vehicle models with minimal changes, improving development productivity.

In the second embodiment of the present invention, the 4WS controller communicates the rear wheel steering angle to the navigation controller, so there is no need to connect the rear wheel steering angle sensor to the navigation controller.

In the third embodiment of the present invention, since the navigation controller determines the rear wheel steering angle, it can be made independent of the 4WS system, and even if the 4WS controller fails, it will not affect the operation of the navigation system. There is no.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a first embodiment of the present invention, FIG. 2 is a diagram illustrating a steering ratio curve showing the relationship between vehicle speed V and steering ratio, and FIG. 3 is a diagram showing a first embodiment of the present invention. FIG. 4 is a block diagram showing the system configuration of a 4WS vehicle navigation device according to the second embodiment of the present invention, and FIG. 5 is a diagram showing the overall configuration of the 4WS system according to the second embodiment of the present invention. A block diagram showing the system configuration of a 4WS vehicle navigation device, FIG. 6 is a diagram showing the overall configuration of a 4WS system according to a third embodiment of the present invention, and FIG. 7 is a block diagram showing a system configuration of a 4WS vehicle navigation device according to a third embodiment of the present invention. Block diagram showing the system configuration of the car navigation device, No. 8
The figure is a diagram illustrating a method for determining the yaw angle of the vehicle from the travel difference between the wheels. Front wheel steering angle sensor, geomagnetic sensor, 3°...wheel speed sensor.

Claims (1)

[Claims] (1). means for determining the stroke difference between the two rear wheels from the difference in the integral values of the outputs of the two rear wheel speed sensors, and a means for determining a predetermined steering ratio curve from the determined stroke difference between the two rear wheels and the output of the front wheel steering angle sensor. It has means for calculating the relative orientation of the vehicle body from the rear wheel steering angle determined by reference and the rear wheel tread, and the absolute direction calculated by correcting the orientation data of the geomagnetic sensor based on the determined relative orientation. A navigation device characterized by determining the traveling direction of a vehicle based on a direction.