JP2625583B2 - Rear wheel steering system for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention uses at least the traveling speed of a vehicle, and in some cases, a signal from a yaw rate sensor or a signal from a steering sensor.
The present invention relates to an apparatus for controlling a steering angle of a rear wheel of a vehicle.

[0002]

2. Description of the Related Art Hitherto, various rear wheel steering devices have been proposed for improving the steerability and stability of a vehicle. As disclosed in Japanese Patent Application Laid-Open No. 62-146775, there is known a concept of selecting a vehicle speed larger than a plurality of vehicle speeds as a countermeasure in the event of an abnormality of a sensor that detects a vehicle speed used as a parameter of the rear wheel steering angle. I have. That is, it has a selecting means for selecting the highest vehicle speed. In a rear wheel steering system that adjusts a steering ratio of a rear wheel to a front wheel, the vehicle speed selecting means is generally considered to be a safe side if a high speed side, that is, a higher vehicle speed is selected. Although the vehicle running posture, that is, the behavior of the vehicle during high-speed running is stable and safe, it can be said that the rear wheel steering angle θr is directly equal to the vehicle speed Vr such that θr = f (V). In the rear wheel steering system having a function of the following equation, when the vehicle speed changes due to a disturbance, the rear wheels may be moved unnecessarily, and as a result, the stability of the vehicle may be impaired.

In other words, when the rear wheel steering angle θr cannot be directly changed greatly by the vehicle speed V as in the conventional system, the change in the vehicle speed due to disturbance does not matter so much, but the rear wheel steering angle θr is directly changed by the vehicle speed. In the case of a system in which the vehicle speed is largely controlled, there is a problem that vehicle speed stability becomes more important.

[0004]

However, even in order to stabilize the value of the vehicle speed, that is, the value of the sensor, it is necessary to prevent abnormal fluctuations in the output of the vehicle speed sensor due to obstacles caused by radio waves coming from the outside or failure of the sensor itself. Is extremely difficult. The present invention has been made in view of the above problems, and an object of the present invention is to provide a vehicle rear wheel steering device capable of eliminating a sudden change in vehicle speed due to a disturbance or the like and suppressing unnecessary rear wheel behavior to ensure stability. It is assumed that.

[0005]

According to the present invention, control means is provided in a device for providing a control signal to an actuator for steering a rear wheel, and the control means includes the following means. That is, the first vehicle speed (V ₁ ) from the first vehicle speed sensor
Means for comparing the second vehicle speed (V ₂ ) with the second vehicle speed (V ₂ ) from the second vehicle speed sensor to select a large value (A) and a small value (B), the control vehicle speed (Vt-1) detected last time and the large value And the smaller value, the last control vehicle speed (Vt−
1) is compared with the small value (B). If the small value (B) is larger, the first adoption means adopting the small value (B) as the current control vehicle speed (Vt), Vehicle speed (Vt-1) is greater than the small value (B),
When it is determined that the vehicle speed is smaller than the large value (A), the second adopting means for directly adopting the previous control vehicle speed as the current control vehicle speed, and the previous control vehicle speed (Vt-1) When the vehicle speed is larger than the small value (B) and the large value (A), a third adoption unit that adopts the large value (A) as the current control vehicle speed is provided.

[0006]

The present invention first has two vehicle speed sensors.
A large value and a small value are selected by comparing vehicle speed signals from two vehicle speed sensors. Then, the previous control vehicle speed is compared with the small value, and when the small value is larger, that is, when the vehicle is accelerating, the small value (B) is adopted as the current control vehicle speed. That is, when the vehicle speed signal rises differently between the first vehicle speed and the second vehicle speed during acceleration, even if the first vehicle speed rises sharply, the control vehicle speed selects the second vehicle speed with a small increase in speed. In addition, the rapid fluctuation of the control vehicle speed is suppressed.

Next, when it is determined that the previous control vehicle speed is larger than the small value and smaller than the large value, that is, when the vehicle is running stably, the previous control vehicle speed is directly used as the current control vehicle speed. I am trying to adopt it. As described above, since the previous control vehicle speed is used as it is, even if the disturbance from the first vehicle speed sensor and the second vehicle speed sensor causes some disturbance, the control vehicle speed itself does not change. .

Further, when the control vehicle speed becomes larger than the low value and the large value last time, that is, when the vehicle enters the deceleration running state, a large value is adopted as the control vehicle speed. That is, during deceleration, the stability of the rear wheel steering is ensured by adopting the higher vehicle speed and adopting the one with the smaller vehicle speed fluctuation.

[0009]

As described above, in the present invention, at least two vehicle speed sensors are provided, and the first vehicle speed from the first vehicle speed sensor and the second vehicle speed from the second vehicle speed sensor are taken into consideration in comparison with the previous control vehicle speed. As the control vehicle speed can be the stable vehicle speed, even if the vehicle speed signal is disturbed due to disturbances such as external radio waves or failure of the sensor itself, the control vehicle speed Since there is no large disturbance, unnecessary movement of the rear wheels of the vehicle is suppressed, so that there is an effect that stable rear wheel steering control for the vehicle can be performed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. This device determines the rear wheel steering angle θr from the equation θr = (θf, ω, Vt), where the rear wheel steering angle is θr, the steering angle is θf, the yaw rate is ω, and the vehicle speed is Vt. At this θr, a system for directly controlling the rear wheels using an actuator is used. In FIG. 1, 1 and 2 are front wheels of the vehicle, and 3 and 4 are rear wheels of the vehicle. The front wheels 1 and 2 are provided with wheel speed sensors 5 and 6, from which signals are input to vehicle speed calculating means 7 which calculates the first vehicle speed. Reference numeral 8 denotes a speedometer of the vehicle, and a second vehicle speed calculating means 9 calculates a second vehicle speed based on a signal from the speedometer. In this way, the speed of the vehicle is detected by different mechanisms, and is set as the first vehicle speed and the second vehicle speed, respectively. Note that the vehicle speed calculation means 7 and 9 are actually constituted by a program inside one ECU. A steering sensor 10 detects a steering angle θf of the steering operated by the driver. The signal from the steering sensor is input to the control ECU 11. A yaw rate sensor 12 converts a yaw rate ω (yaw angular velocity) at the time of turning the vehicle into an electric signal and inputs the electric signal to the control ECU 11. The control ECU constitutes the control device of the present invention, and includes a microcomputer and an input / output control circuit such as a driver for driving a motor. An actuator 13 is provided with a motor or a hydraulic mechanism for controlling the steering angle of the rear wheels. Actually, a microcomputer in the control ECU 11 performs a control process and a vehicle speed calculation for calculating the first vehicle speed and a vehicle speed calculation for calculating the second vehicle speed.

Next, a control flow performed in the microcomputer in the control device will be described. 2, the process proceeds to step 101 when started first, in step 100, if the first vehicle speeds V ₁ to the second speed V ₂ is compared, and the better of the first vehicle speed is greater than the second vehicle speed step 102 Proceeds to step 10 if the first vehicle speed is equal to the second vehicle speed or the second vehicle speed is higher.
Proceed to 3. In step 102, the first vehicle speed is stored as a large value (A), and the second vehicle speed is stored as a small value (B). When the process proceeds to step 103, the second vehicle speed is stored as a larger value (A) and the first vehicle speed is stored as a smaller value (B). Next, at step 104, the previous control vehicle speed Vt-1 obtained by the previous calculation is compared with the aforementioned small value. If the value smaller than the previous control vehicle speed Vt-1 is larger or equal, the process proceeds to step 106. If the previous control vehicle speed Vt-1 is larger than the small value, the routine proceeds to step 105.

That is, at step 104, it is determined whether or not the vehicle is accelerating. That is, when the value (B) smaller than the previous control vehicle speed Vt-1 is larger, the vehicle is in an accelerating state, and the process proceeds to step 106 at that time. When the vehicle is not in the acceleration state, the process proceeds to step 105,
The previous control vehicle speed Vt-1 is compared with a large value (A). When the value (A) larger than the previous control vehicle speed is larger, the process proceeds to step 107. That is, the process proceeds to step 107 when the previous control vehicle speed is smaller than the large value but larger than the small value (B). At this time, it is determined that the vehicle is in the stable traveling region and the process proceeds to step 107.

Next, when it is determined in step 105 that the previous control vehicle speed Vt-1 is equal to or larger than the large value, it is determined that the vehicle is in a deceleration driving state, and the routine proceeds to step 108. That is, in this case, both the first vehicle speed and the second vehicle speed are the previous control vehicle speed Vt.
Since it is smaller than -1, it is in a state of deceleration. As described above, in the acceleration state, a small value is adopted as the current control vehicle speed Vt in step 106. When the vehicle is in a stable running state, the previous control vehicle speed is used as it is in step 107 as the current control vehicle speed. Further, when the vehicle is in the deceleration state, a large value is adopted as the control vehicle speed this time. Then, the process proceeds to step 109 and ends.

As described above, in this embodiment, a large value and a small value are obtained from two vehicle speeds, and these values are compared with the previous control vehicle speed to determine three states of acceleration, stability, and deceleration. Accordingly, a more stable state is selected as the control vehicle speed this time in accordance with each. That is, a small value is adopted during acceleration, and even if one of the vehicle speed sensors shows a large value, the smaller value is adopted to suppress abrupt rear wheel steering. Also, if it is determined that it is in a stable state, by adopting the previous value as it is,
Even if the first vehicle speed and the second vehicle speed are disturbed by the influence of disturbance, the control vehicle speed itself is not disturbed at all. Further, at the time of deceleration, a large value is adopted as the control vehicle speed this time, and even if the speed signal of one vehicle speed sensor indicates a large deceleration, that value is not adopted, and the signal from the more stable speed sensor, that is, The adoption of a large value stabilizes the steering of the rear wheels.

FIG. 3 shows an example of the above-mentioned vehicle speed selection. In FIG. 3, the horizontal axis represents the elapsed time t, and the vertical axis represents the vehicle speed and the control vehicle speed indicated by the respective vehicle speed sensors. Region a is when the vehicle is accelerating. In this case, when the first vehicle speed indicated by the broken line indicates a high vehicle speed, and when the second vehicle speed indicated by the one-dot chain line indicates a lower vehicle speed, the smaller one is indicated. Has adopted. As a result, the control vehicle speed follows a trajectory like a solid line, and stable rear wheel steering is performed without using a sudden change in the vehicle speed during the acceleration period as the control vehicle speed. Area b is a stable running area where the vehicle is not significantly accelerating or decelerating. In this case, even if the first vehicle speed and the second vehicle speed fluctuate greatly as indicated by broken lines and dashed lines, respectively, An extremely stable control vehicle speed is obtained by employing the control vehicle speed.

Next, in a region d, the signal of one vehicle speed sensor (in this case, the second vehicle speed sensor) is abnormal, and if such an abnormality is recognized, the signal of the other vehicle speed sensor is detected. The control vehicle speed is selected so as to follow the vehicle speed. Next, a region c is when the vehicle is decelerating. In this case, the higher vehicle speed is selected as the stable vehicle speed.

In the area d, immediately after the vehicle enters the area d, the previous control vehicle speed is adopted as before, but after the abnormality of one of the vehicle speed sensors is definitely recognized, the other vehicle speed sensor is used. If the control is performed so as to follow the signal, it is ensured that the abnormality of one of the vehicle speed sensors is recognized, that is, after the abnormality is determined, the vehicle follows the other vehicle speed sensor. You.

Although the first vehicle speed sensor and the second vehicle speed sensor have different structures in the above-described embodiment, two sensors having the same structure may be used. In addition, two of the first vehicle speed sensor and the second vehicle speed sensor
It is only necessary to include at least these two. For example, when there are three vehicle speed sensors, the largest value is adopted as the large value (A), and the small value (A) is adopted. As B), the smallest value may be adopted.
Further, at the beginning of the control, the previous control vehicle speed is set to zero.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the apparatus of the present invention.

FIG. 2 is a flowchart illustrating processing of a microcomputer representing control means in a control ECU according to the embodiment.

FIG. 3 is a graph showing an example of vehicle speed selection in the embodiment.

[Explanation of symbols]

5,6,7 The right front wheel speed sensor 5 and the left front wheel speed sensor 6 and the first
Vehicle speed calculating means 78, 9 The vehicle speed sensor 8 in the meter and the second vehicle speed calculating means 9 constituting the first vehicle speed sensor 1 1 front right wheel 2 front left wheel 3 rear right wheel 4 rear left wheel 11 ECU 13 for controlling actuator 13 actuator V ₁ 1 vehicle speed V2 _2nd vehicle speed Vt-1 Previous control vehicle speed A Large value B Small value Vt Current control vehicle speed 104, 106 Steps 105, 107 constituting the first adopted means Steps 105, 108 constituting the second adopted means Steps constituting the third adopting means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication B62D 137: 00 (72) Inventor Tetsushi Haseda 1-1-1 Showa-cho, Kariya-shi, Aichi Japan Japan Denso Stock In-company (72) Inventor Hitoshi Iwata 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-62-146775 (JP, A) JP-A-62-241772 (JP, A)

Claims (1)

(57) [Claims] A first vehicle speed sensor for detecting a running speed of the vehicle and a second vehicle speed sensor, wherein a control signal is transmitted to an actuator for steering rear wheels of the vehicle based on a control vehicle speed detected from the vehicle speed sensor. A control device for controlling the first vehicle speed (V ₁ ) from the first vehicle speed sensor and a second vehicle speed (V ₂ ) from the second vehicle speed sensor. Value (A) and small value (B)
And the vehicle speed for the last control (Vt
-1) and means for storing the large value and the small value, comparing the previous control vehicle speed (Vt-1) with the small value (B), and if the small value (B) is larger, this time First adopting means for adopting the small value (B) as the control vehicle speed (Vt), the previous control vehicle speed (Vt-1)
When it is determined that is larger than the small value (B) and smaller than the large value (A), the second adoption means adopting the previous control vehicle speed as it is as the current control vehicle speed; and A vehicle including third adopting means for adopting the large value (A) as the current control vehicle speed when the control vehicle speed (Vt-1) is greater than the small value (B) and the large value (A); Rear wheel steering device.