JPH06104458B2 - Rear wheel steering control device for vehicle - Google Patents

Description

The present invention relates to a vehicle rear wheel steering control device.

[Prior art]

Conventionally, in this type of vehicle rear wheel steering control device, the rear wheel of the vehicle is controlled in a reverse phase with respect to the front wheel of the vehicle so that a small turn in a low speed region of the vehicle, garage parking, etc. can be performed easily. There is one that has a smaller minimum turning radius.

Therefore, for example, when the vehicle is housed in the garage in the vicinity of its side wall, the rear part of the vehicle body laterally overhangs on the side wall of the garage for antiphase steering control of the rear wheels when the vehicle is out of the garage. May come into contact. For this reason,
As disclosed in Japanese Unexamined Patent Publication No. 56-16756, the steering angle of the rear wheels is set to zero when the vehicle speed is low, and as disclosed in Japanese Unexamined Patent Publication No. 59-81273, the vehicle is started. After that, it is proposed that the steering angle of the rear wheels is set to zero for a certain period of time.

[Problems to be solved by the invention]

However, in such a configuration, there is a strong tendency that the steering angle control of the rear wheels is not performed at a good timing,
For example, there is a drawback in that the steering angle of the rear wheels is not controlled if the turning radius of the vehicle is originally required to be satisfied when the turning radius is required to be reduced.

Therefore, in order to cope with such a situation, the present invention reduces the steering angle of the rear wheels of the vehicle in a vehicle rear wheel steering control device during a small turning at a low vehicle speed of the vehicle, a turning process such as when leaving the garage. It is something that you try to control.

[Means for solving problems]

In solving such problems, the structural features of the present invention are as follows.
As illustrated in FIG. 1, front wheel steering angle detecting means 1a for detecting the steering angle of the front wheels of the vehicle, vehicle speed detecting means 1c for detecting the vehicle speed of the vehicle, and (target steering angle of rear wheel / steering angle of front wheel). )
Is a target steering angle ratio, the denominator and the numerator of the target steering angle ratio have opposite phases in the low speed value region and have the same phase in the high speed value region. A storage unit 2 that stores in advance a steering angle ratio pattern that is determined to change the ratio according to the change in the vehicle speed, and a determination that determines the target steering angle ratio according to the detected vehicle speed based on the steering angle ratio pattern. A rear wheel steering control device for a vehicle, comprising: means 3; and control means 4 for controlling the rear wheels toward the target steering angle according to the determined target steering angle ratio determined by the determination means 3. When each value of the denominator numerator of the determined target steering angle ratio is in the opposite phase, the turning direction determining means 5 for determining the turning direction of the vehicle based on the steering angle detected by the front wheel steering angle detecting means, and the turning direction. Discriminated by the discrimination means 5 A calculating means 6 for determining the vehicle rear portion of the overhang length in the direction opposite to the rotating direction, distance detecting means for detecting a distance between the side walls of the vehicle and the obstacle adjacent thereto
1d, a length discriminating means 7 for discriminating whether or not the overhang length calculated by the arithmetic means 6 is longer than the distance detected by the distance detecting means 1d, and the length discriminating means 7 being long. Correction means 8 for correcting the determined target steering angle ratio in accordance with the difference between the calculated overhang length and the detected distance in response to the determination,
The control means 4 performs rear wheel steering control according to the determined target steering angle ratio or the corrected target steering angle ratio determined by the correction means 8.

Further, rear wheel steering angle detection means 1b for detecting the steering angle of the rear wheels of the vehicle is provided, and the overhang length is the axial distance between the front wheel shaft and the rear wheel shaft and the rear wheel shaft. This is based on a relational expression between the length to the rear end of the vehicle and the steering angle of the front wheels and the steering angle of the rear wheels.

[Action effect]

By configuring the present invention in this way, the turning direction determining means 5 can be used when the vehicle is traveling at a low vehicle speed in the vicinity of the obstacle in a small forward direction or is turning out from the garage. Based on the relational expression, the computing means 6 determines the turning direction of the vehicle in relation to the determined target steering angle ratio and the detected front wheel steering angle, and the computing means 6 determines the overhang length in the direction opposite to the turning direction determination result. Calculation is performed according to the detected front wheel steering angle and the detected rear wheel steering angle. When the calculated overhang length is longer than the detection distance, the length discriminating means 7 discriminates this, and in response thereto, the correcting means 8 determines the determined target according to the difference between the calculated overhang length and the detection distance. The steering angle ratio is reduced and corrected, and the control means 4 performs rear wheel steering control according to the result of the reduction correction. As a result, the steering angle of the rear wheel is controlled so as to be smaller than the target steering angle of the rear wheel in the determined target steering angle ratio, and as a result, when the vehicle is traveling in a small turn or when the vehicle is out of the garage as described above. In the above, under the control of reducing the steering angle of the rear wheels, it is possible to smoothly carry out a small turn and take out the garage without bringing the rear part of the vehicle into contact with an obstacle or a side wall of the garage.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.
The figure shows that the rear wheel steering control device according to the present invention is a four-wheel vehicle (fifth wheel vehicle).
(See the figure). The rear wheel steering control device includes a rear wheel steering mechanism 10.
Controls the steering angles θrl, θrr of the left and right rear wheels Wrl, Wrr of a four-wheel vehicle. In such a case, each steering angle θrl,
θrr is based on the forward direction of the four-wheeled vehicle, and the angle to the right (or the angle to the left) is positive (or negative).

In addition, the rear wheel steering control device, both steering angle sensors 20, 30,
The distance measuring sensor 40 and the vehicle speed sensor 50 are provided, and the steering angle sensor 20 detects the steering angle θs of the steering wheel of the four-wheel vehicle and generates it as a steering angle detection signal. In such a case, the steering angle θs, like the steering angle θrl (or θrr), is positive (or negative) with respect to the forward direction of the four-wheel vehicle as a reference and the angle to the right (or the angle to the left). This means that each of the steering angles θs, θrl, and θrr has the same sign and the same phase, and the opposite signs have the opposite phases. On the other hand, the steering angle sensor 30 measures the average steering angle θ of each steering angle θrl, θrr of the left and right rear wheels Wrl, Wrr corresponding to the displacement of the tie rods of the rear wheel steering mechanism 10.
r is detected and generated as a steering angle detection signal.

The distance measuring sensor 40 is composed of a pair of ultrasonic sensors, and these ultrasonic sensors are provided on the respective left and right side walls of the four-wheel vehicle. Then, the distance measuring sensor 40 detects the distance from the left side wall of the four-wheeled vehicle to the obstacle in the vicinity thereof and the right side wall of the four-wheeled vehicle by the transmission and reception of the ultrasonic waves of the ultrasonic sensors. The distances to other obstacles in the vicinity of are detected and generated as a left side distance detection signal and a right side distance detection signal. The vehicle speed sensor 50 detects the vehicle speed of the four-wheeled vehicle and generates a series of pulse signals at a frequency proportional to this.

The A-D converter 60 sequentially digital-converts the steering angle detection signals from both steering angle sensors 20, 30 and the left side distance detection signal and the right side distance detection signal from the distance measuring sensor 40 to obtain digital steering angle signals, It is generated as a digital left side ranging signal and a digital right side ranging signal. The waveform shaper 70 sequentially shapes each pulse signal from the vehicle speed sensor 50 to generate a shaped signal. The microcomputer 80 executes a computer program stored in advance in its ROM in cooperation with the AD converter 60 and the waveform shaper 70 in accordance with the flowchart shown in FIG. 3, and during this execution, the rear wheel steering mechanism.
The arithmetic processing necessary for controlling the drive circuit 90 connected to 10 is performed. The drive circuit 90 generates a drive signal required for steering control of the left and right rear wheels Wrl and Wrr of the rear wheel steering mechanism 10 under the control of the microcomputer 80.

In the present embodiment configured as described above, it is assumed that the vehicle is accommodated in the garage by moving backward. In this state, when the vehicle is turned and moved forward under the starting operation in order to take out the garage, the microcomputer 80 starts the computer program in step 100 according to the flowchart of FIG. Then, the vehicle speed (hereinafter referred to as the vehicle speed Vs) of the vehicle is calculated in response to each shaping signal generated by the waveform shaper 70 in cooperation with the vehicle speed sensor 50, and the target steering angle ratio pattern P (see FIG. 4).
Based on the above, the target steering angle ratio K is determined according to each digital steering angle signal generated by the cooperation of the steering angle sensors 20 and 30 from the AD converter 60 and the calculated vehicle speed Vs.

In such a case, the target steering angle ratio pattern P is specified by a straight line representing the relationship between the target steering angle ratio K and the vehicle speed Vs, as shown in FIG. Further, the target steering angle ratio K is represented by (target average steering angle θro / steering angle θs of both rear wheels Wrl, Wrr), and becomes positive in a high vehicle speed region where Vs> Vso, and Vs <V
It becomes negative in the low vehicle speed region of so and becomes zero when Vs = Vso. In addition, the target average steering angle θro (that is, both rear wheels Wrl, Wr
Each target steering angle of r) and steering angle θs (that is, both front wheels Wfl, Wfr
Steering angles) are in phase with each other when K> 0, and K <
When 0, they are in opposite phases. The target steering angle ratio pattern P is stored in the ROM of the microcomputer 80 in advance.

When the computer program proceeds to step 102, since K <0 as understood from the above, the microcomputer 80 determines “YES”. If the vehicle is moving forward in the left turning direction, the microcomputer 80 cooperates with the steering angle sensor 20 to determine "YES" in step 103 based on the digital steering angle signal from the AD converter 60. , And the right extension length L is determined in step 103a.
Calculate 1 as follows. In such a case, right extension length L
As shown in FIG. 5, 1 corresponds to the distance between the point on the locus drawn by the right rear end of the vehicle and the right side wall of the vehicle when the vehicle turns left under low vehicle speed.

Therefore, in the calculation in step 103a, the steering angle θfr of the right front wheel Wfr is based on the relational expression θfr = f1 (θs), and the digital steering angle generated by the cooperation of the steering angle sensor 20 from the AD converter 60. The steering angle θrr of the right rear wheel Wrr is calculated according to the signal, and based on the relational expression θrr = f2 (θr),
The calculated steering angle θ is calculated according to the digital steering angle signal generated by the A / D converter 60 in cooperation with the steering angle sensor 30, and the right extension length L1 is based on the following relational expression (1).
It is calculated according to fr, θrr.

However, the symbol Wb represents the axial distance between the axes of the front wheels Wfl, Wfr and the axes of the rear wheels Wrl, Wrr as shown in FIG. 5, and the symbol x represents the axes of the rear wheels Wrl, Wrr. Represents the overhang length of the rear end of the vehicle. However, each relational expression θfr = f1 (θ
s), θrr = f2 (θr) and the relational expression (1) are stored in advance in the ROM of the microcomputer 80.

Rightward extension length in step 103a at this stage
If L1 is longer than the allowable overhang length L0, the microcomputer 80 determines “YES” in step 104. In such a case, the allowable overhang length L0 is set to a value which is predicted that the rear end of the vehicle will not come into contact with an obstacle in the vicinity when the vehicle turns. Then, a microcomputer
In step 104a, the reference numeral 80 reduces and corrects the target steering angle ratio K in step 101 in accordance with (L1-L0), and the reduction correction result is generated in step 105 as a steering angle ratio correction signal.

Then, the drive circuit 90 generates a drive signal in response to the steering angle correction signal from the microcomputer 80, and in response to this, the rear wheel steering mechanism 10 causes the value of the drive signal (that is, the steering angle ratio correction The steering angle θrl, θrr of each rear wheel Wrl, Wrr is determined by the target steering angle ratio K according to the signal value).
Control is performed so as to be smaller than the target steering angles of rl and Wrr. As a result, the vehicle can be smoothly turned out from the garage while turning leftward without being in contact with the side wall of the garage.

Also, as described above, the computer program
When it reaches 103, the determination in step 103 is “NO”.
If it is, the microcomputer 80 steps
At 103b, the left extension length L2 is calculated as follows. In such a case, the left overhang length L2 is substantially the same as the right overhang length L1 and the point on the locus drawn by the left rear end of the vehicle at the time of turning to the right at a low vehicle speed of the vehicle and the vehicle. Corresponds to the distance to the left side wall. Then, in the calculation in step 103b, the steering angle θfl of the left front wheel Wlf is
Based on the relational expression θfl = f3 (θs), the steering angle θrl of the left rear wheel Wrl is calculated according to the digital steering angle signal generated from the AD converter 60 in cooperation with the steering angle sensor 20, and the relational expression θrl = F4 (θr) based on the digital steering angle signal generated by the AD converter 60 in cooperation with the steering angle sensor 30, and the left overhang length L2 is based on the following relational expression (2). It is calculated according to each of the calculated steering angles θfl and θrl.

However, each relational expression θfl = f3 (θs), θrl = f4 (θr) and the relational expression (2) are stored in the ROM of the microcomputer 80 in advance.

At the current stage, the left extension length in step 103b
If L2 is longer than the allowable overhang length L0, the microcomputer 80 determines “YES” in the step 106, and the step 10
In 6a, the target steering angle ratio K in step 101 is set to (L2-L
Decrease correction according to 0), and the decrease correction result is generated in step 105 as a steering angle ratio correction signal. Then, the drive circuit 90 generates a drive signal in response to the steering angle correction signal from the microcomputer 80, and in response to this, the rear wheel steering mechanism 10 causes the value of the drive signal (that is, the steering angle ratio correction Steering angles θrl, θrr of both rear wheels Wrl, Wrr according to the signal value)
Is controlled to be smaller than the respective target steering angles of both rear wheels Wrl, Wrr specified by the target steering angle ratio K. As a result, the vehicle can be smoothly turned out from the garage while turning rightward without being in contact with the side wall of the garage.

Also, as described above, the computer program
If it is determined to be "NO" when 102, 104, or 106 is reached, the microcomputer 80 generates the target steering angle ratio K in step 101 as a determined steering angle ratio signal in step 105, and in response thereto, Wheel steering mechanism 10 drive circuit
In cooperation with 90, each rear wheel Wrl, Wrr is controlled to its target steering angle.

[Brief description of drawings]

1 is a block diagram showing the configuration of the invention described in the claims, FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 3 is a flow chart showing the operation of the microcomputer in FIG. FIG. 4 is a target steering angle ratio pattern diagram, and FIG. 5 is an explanatory diagram of various dimensions in the vehicle. Explanation of symbols Wfl, Wfr …… Front wheel, Wrl, Wrr …… Rear wheel, 10 …… Rear wheel steering mechanism, 20,30 …… Steering angle sensor, 40 …… Distance measuring sensor, 50…
… Vehicle speed sensor, 60 …… AD converter, 80 …… Microcomputer, 90 …… Drive circuit.

Claims (2)

[Claims] 1. A front wheel steering angle detecting means for detecting a steering angle of a front wheel of a vehicle, a vehicle speed detecting means for detecting a vehicle speed of a vehicle, and a target steering angle ratio of (target steering angle of rear wheel / steering angle of front wheel). In this case, the target steering angle ratio is set to the vehicle speed so that the denominator and the numerator of the target steering angle ratio have opposite phases in the low speed value region and have the same phase in the high speed value region. Storage means for pre-storing a steering angle ratio pattern determined to be changed according to the steering angle ratio pattern, deciding means for deciding the target steering angle ratio according to the detected vehicle speed based on the steering angle ratio pattern, and deciding by the deciding means. A control means for controlling the rear wheels toward the target steering angle according to the determined target steering angle ratio, and a rear wheel steering control device for a vehicle comprising: When the value is in the opposite phase, the front wheel A turning direction determining means for determining the turning direction of the vehicle based on the steering angle detected by the angle detecting means, and a protruding length of the rear portion of the vehicle in a direction opposite to the turning direction determined by the turning direction determining means A distance detecting means for detecting a distance between the side wall of the vehicle and an obstacle adjacent to the side wall of the vehicle, and a distance at which the overhang length calculated by the calculating means is detected by the distance detecting means. A length determining means for determining whether or not it is longer, and the determination target according to the difference between the calculated overhang length and the detected distance in response to the determination of the length by the length determining means. Correction means for correcting to reduce the steering angle ratio, and the control means controls the rear wheel steering control according to the determined target steering angle ratio or the corrected target steering angle ratio determined by the correction means. Vehicular rear-wheel steering control system being characterized in that the Migihitsuji. 2. The vehicle rear wheel steering control device according to claim 1, further comprising rear wheel steering angle detection means for detecting a steering angle of a rear wheel of the vehicle, wherein the overhang length is An axial distance between the front wheel shaft and the rear wheel shaft, and the length from the rear wheel shaft to the rear end of the vehicle,
A rear wheel steering control device for a vehicle, which is obtained based on a relational expression between a steering angle of the front wheels and a steering angle of the rear wheels.