JP2010143518A - Apparatus and method for controlling steering - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain both of improvement of response in the early period of steering operation, and avoidance of entanglement phenomenon of a vehicle due to a yaw rate in the latter period of steering operation. <P>SOLUTION: For the speed ratio that is a ratio of steered speed of steered wheels 7 to steering speed θ' of a steering wheel 1, the speed ratio in the early period of steering operation is controlled to be larger than the speed ratio in the latter period of steering operation. The speed ratio in the early period of steering operation is corrected by a value proportional to an absolute value of the steering speed θ' of the steering wheel 1, and the speed ratio in the latter period of steering operation is corrected by a value proportional to an absolute value of a steering acceleration θ'' of the steering wheel 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for controlling steering of steered wheels with respect to steering of a steering wheel.

As a steering control device, for example, there is a technique described in Patent Document 1. This device steers the rear wheels in phase with the front wheels as the front wheels are steered. When the steering speed of the steering wheel is low, the turning angle of the rear wheel is increased. As a result, the speed of the vehicle in the yaw direction is reduced to avoid sudden changes in the vehicle posture due to sudden turning during high-speed traveling or the like, so that the occupant feels stable. On the other hand, when the steering speed of the steering wheel is high, the turning angle of the rear wheel is reduced. Accordingly, in the lane change or the like, the speed in the yaw direction of the vehicle is increased to improve the response.
JP-A-5-85385

The above prior art can improve the responsiveness at the initial stage of the steering operation when the steering speed of the steering wheel is high. However, during turning with a high steering speed, the turning angle of the rear wheels remains small, so the speed of the vehicle in the yaw direction continues to increase. As a result, in a later stage of the steering operation, the speed of the vehicle in the yaw direction increases, and the movement of the vehicle in the steering direction increases, so-called the phenomenon of the vehicle being involved by yaw rate occurs.
The present invention pays attention to such points, and it is an object of the present invention to make it possible to achieve both improvement in responsiveness at the initial stage of steering operation and avoidance of a vehicle entanglement phenomenon due to yaw rate in the later stage of steering operation. To do.

  In order to solve the above-described problem, the present invention relates to a speed ratio, which is a ratio of a steered wheel steered speed to a steering speed of a steering wheel, such that a speed ratio at an initial stage of steering operation is larger than a speed ratio at a later stage of steering operation. To control. The speed ratio at the initial stage of the steering operation is corrected with a value proportional to the absolute value of the steering speed of the steering wheel, and the speed ratio at the latter stage of the steering operation is corrected with a value proportional to the absolute value of the steering acceleration of the steering wheel.

In the initial stage of the steering operation, the steering speed of the steered wheels is relatively high with respect to the steering speed of the steering wheel, so that the response of the steering direction displacement (yaw direction change) of the vehicle can be improved. Further, in the latter half of the steering operation, the steered wheel turning speed relative to the steering speed of the steering wheel of the driver is relatively reduced, so that an increase in the speed of the vehicle in the yaw direction in the latter half of the steering operation is suppressed. Can be avoided.
In this way, it is possible to achieve both improvement in the responsiveness at the initial stage of the steering operation and avoidance of the yaw rate entrainment phenomenon in the later stage of the steering operation.

Next, embodiments according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram for explaining the steering device according to the present embodiment.
(Constitution)
The steering device of the present embodiment will be described by taking a by-wire type steering device as an example.
Reference numeral 1 denotes a steering wheel operated by a driver. The steering shaft includes an upper steering shaft 2 and a lower steering shaft 3. Under normal conditions, the upper steering shaft 2 and the lower steering shaft 3 are separated from each other. When an abnormality is detected, the upper steering shaft 2 and the lower steering shaft 3 are connected.

The upper steering shaft 2 is connected to the steering wheel 1 at the top. As a result, the upper steering shaft 2 rotates with the rotation of the steering wheel 1.
The lower steering shaft 3 is connected at its lower portion to the rack shaft 4 via a rack-pinion mechanism. The ends of the rack shaft 4 are connected to the knuckle 6 via tie rods 5 respectively. The knuckle 6 rotatably supports the steering wheel 7. As a result, when the lower steering shaft 3 is rotationally displaced, the rack shaft 4 is displaced in the vehicle width direction by a predetermined gear ratio. Then, the left and right steering wheels 7 are steered.

As a steering control device, a steering angle sensor 10, a turning actuator 12, and a turning controller 11 are provided. A vehicle speed sensor 13 is also provided.
The vehicle speed sensor 13 detects the vehicle speed based on wheel rotation information and the like. The detected vehicle speed information is output to the steering controller 11.
The steering angle sensor 10 detects the steering angle θ of the steering wheel 1. In the present embodiment, the operation angle sensor detects the rotation angle of the upper steering shaft 2. Note that the steering speed θ ′ of the steering wheel 1 may be directly detected. The steering angle sensor 10 outputs the detected steering angle signal to the steering controller 11.

The steered actuator 12 drives the lower steering shaft 3 to rotate. The steered actuator 12 rotationally displaces the lower steering shaft 3 so that the steered and steered turning angle becomes a turning angle corresponding to the turning angle signal from the turning controller 11.
The turning controller 11 calculates a turning angle correction amount θr ^* (steering angle command value) based on the steering speed θ ′ of the steering wheel 1, and a turning angle signal corresponding to the calculated turning angle correction amount θr ^*. Is output to the steering actuator 12.

Next, the process of the turning controller 11 will be described with reference to FIG.
The steered controller 11 operates at a predetermined control cycle. It should be noted that “0” is set as an initial value in a turning angle correction amount θr described later.
First, in step S10, the current steering angle θ and vehicle speed V are input.
Next, in step S20, an initial gain K1 is obtained. In the present embodiment, the initial gain K1 is calculated using the map or function as shown in FIG. 3 and the input vehicle speed V as a variable. As shown in FIG. 3, the initial gain K1 decreases as the vehicle speed V increases.

Next, in step S30, a late gain K2 is obtained. In the present embodiment, the late gain K2 is calculated using the input vehicle speed V as a variable using a map or function as shown in FIG. As shown in FIG. 4, the late gain K2 increases as the vehicle speed V increases.
Next, in step S50, the steering speed θ ′ and the steering acceleration θ ″ are obtained based on the steering angle θ. That is, the steering angle θ is differentiated to calculate the steering speed θ ′ (steering angular speed). 'Is differentiated to calculate a steering acceleration θ ″ (steering angular acceleration).

Next, in step S60, it is determined whether the steering operation is in the initial stage or the steering operation is in the late stage. As a result of the determination, if it is determined that the steering operation is initial, the process proceeds to step S60. If it is determined that the steering operation is late, the process proceeds to step S70.
In the present embodiment, the determination as to whether the steering operation is early or the steering operation is late is performed as follows. That is, the determination is made based on whether the direction of change of the steering speed θ ′ has changed, that is, whether the sign of the steering acceleration θ ″ has changed.

  In the present embodiment, the sign of the steering speed θ ′ and the sign of the steering acceleration θ ″ are compared to determine whether the steering operation is early or late. Specifically, the sign of the steering speed θ ′ and the steering speed are determined. When the sign of the acceleration θ ″ is the same sign, it is determined that the steering operation is in the initial stage. On the other hand, when the signs of the steering speed θ ′ and the steering angle θ speed are different, it is determined that the steering operation is late.

In step S60, the turning angle correction amount θr ^* is calculated based on the following formula, and the process proceeds to step S80.
θr ^* = θr + K1 × | θ ′ |
On the other hand, in step S70, the turning angle correction amount θr ^* is calculated based on the following formula, and the process proceeds to step S80.
θr ^* = θr−K2 × | θ ″ |
In step S80, a control signal (steering angle signal) corresponding to the turning angle correction amount θr ^* is output to the turning actuator 12, and the process proceeds to step S90.
In step S90, the turning angle correction amount θr ^* is input to the turning angle correction amount θr to return.
θr = θr ^*

(Operation / Action)
In the initial stage of the steering operation, the turning angle is corrected so as to increase by an amount proportional to the absolute value of the steering speed θ ′. On the other hand, in the latter half of the steering operation, the turning angle is corrected so as to decrease by an amount proportional to the absolute value of the steering acceleration θ ″.
As a result, the ratio of the steering speed of the steered wheels 7 to the steering speed θ ′ is a larger value in the initial stage of the steering operation than in the latter stage of the steering operation.
That is, at the initial stage of the steering operation, the steered wheel 7 is steered at a relatively high speed relative to the steering speed θ ′ in accordance with the driver's operation of the steering wheel 1. For this reason, the responsiveness of the steering direction displacement (yaw direction change) of the vehicle in the initial stage of the steering operation can be improved.

  In accordance with the further operation of the steering wheel 1 by the driver, the steered speed of the steered wheels 7 with respect to the steering speed θ ′ is reduced in the later stage of the steering operation. For this reason, an increase in the speed in the yaw direction of the vehicle in the latter half of the steering operation is avoided, and an increase in the speed in the yaw direction of the vehicle in the second half of the steering is suppressed. As a result, it is possible to reliably avoid the vehicle posture from becoming unstable.

With the above operation, it is possible to achieve both improvement in the responsiveness at the initial stage of the steering operation and avoidance of the phenomenon of the yaw rate involving the steering operation.
Further, as shown in FIGS. 6A to 6C, the absolute value of the steering speed θ ′ decreases with the passage of time from the start of the steering operation in the initial stage of the steering operation. Further, the steering acceleration θ ″ increases with the passage of time from the start of the steering operation in the latter stage of the steering operation.

  Thereby, the correction amount with respect to the turning angle gradually decreases in the initial stage of the steering operation. On the other hand, the correction amount for the turning angle gradually increases in the latter half of the steering operation. As a result, the change in the correction amount at the time of transition from the initial steering operation to the latter steering operation is prevented from becoming large. That is, a sudden change in steering characteristics is avoided. That is, at the initial stage of the steering operation, by using the correction amount based on the steering speed θ ′, the connection between the rising of the steering angle θ and the later stage of the steering operation at the switching point can be made smooth. Further, by using a correction amount based on the steering acceleration θ ″ in the latter half of the steering operation, the yaw rate in the latter half of the steering operation can be reduced and the steering control can be smoothly converged at the end of the steering. Since the gap can be reduced, a sudden change in steering characteristics can be avoided, and a natural steering feeling without a sense of incongruity can be obtained.

  Further, the initial gain K1 is set smaller as the vehicle speed V is higher, and the late gain K2 is set larger as the vehicle speed V is higher. This increases the effect of improving the responsiveness at the initial stage of the steering operation when the vehicle speed V is on the low speed side. On the other hand, when the vehicle speed V is on the high speed side, the effect of avoiding the phenomenon of yaw rate entrainment in the latter half of the steering operation is set large. That is, on the low speed side, the initial gain K1 at the initial stage of the steering operation is increased with respect to the high speed to increase the steering angle θ correction amount at the initial stage of the steering operation. On the high speed side, by increasing the late gain K2 in the latter half of the steering operation with respect to the low speed, it is possible to increase the amount of correction of the steering angle θ in the latter half and reliably reduce the high speed yaw rate.

Here, the steering angle sensor 10 and step S40 constitute a steering speed acquisition means. The steered actuator 12 constitutes a steered device. The steered controller 11 constitutes a steered control means. Step S40 constitutes a steering acceleration acquisition means. Step S50 constitutes an operation time determination means. Steps S60 and S70 constitute correction means.
The absolute value of the steering speed θ ′ constitutes the initial operation correction amount. The absolute value of the steering acceleration θ ″ constitutes the later-stage correction amount. The turning angle correction amount θr constitutes the target turning angle.

(Effect of this embodiment)
(1) The steering control means has a speed ratio, which is a ratio of the steering speed of the steered wheels 7 to the steering speed θ ′ of the steering wheel 1, greater than the speed ratio in the late stage of the steering operation. Control to value.
Thereby, in the initial stage of the steering operation, the responsiveness of the vehicle turning direction displacement (yaw direction change) can be improved. Furthermore, in the latter half of the steering operation, avoiding the vehicle speed in the yaw direction from continuing to increase, suppressing an increase in the speed of the vehicle in the yaw direction in the second half of steering, and making the vehicle posture unstable. It can be avoided reliably.
As a result, it is possible to achieve both improvement in the responsiveness at the initial stage of the steering operation and avoidance of the yaw rate entrainment phenomenon in the later stage of the steering operation.

(2) The operation time determining means determines the operation initial stage and the operation late stage of the steering operation. Based on the determination result of the operation timing determination means, the correction means adds a correction amount for initial operation when it is determined that the steering operation is early, and corrects to reduce the correction amount for late operation when it is determined that the steering operation is late. Do.
As a result, the speed ratio, which is the ratio of the steering speed of the steered wheels 7 to the steering speed θ ′ of the steering wheel 1, can be set to a larger value than the speed ratio in the late stage of the steering operation. It becomes.
That is, at the initial timing of the steering operation, the turning angle is increased and adjusted with respect to the steering operation, and the initial response amount of the yaw rate is increased. Also, at the timing of the latter half of the steering operation, the turning angle is adjusted to decrease with respect to the initial steering operation to suppress the second half of the yaw rate (increase).

(3) The operation initial correction amount decreases with the passage of time from the start of the steering operation. In addition, the late operation correction amount increases with the passage of time from the start of the steering operation.
Accordingly, it is possible to suppress an increase in the correction amount at the time of transition from the initial steering operation to the latter steering operation. As a result, it is possible to avoid a sudden change in the steering characteristics at the time of transition from the initial steering operation to the latter steering operation, and to obtain a natural steering feeling without any sense of incongruity.

(4) The initial operation correction amount is a value proportional to the absolute value of the steering speed θ ′. The late operation correction amount is a value proportional to the absolute value of the steering acceleration θ ″.
Thus, the operation initial correction amount can be set so as to decrease with the passage of time from the start of the steering operation. Further, the later operation correction amount can be set so as to increase with the passage of time from the start of the steering operation.

(5) An initial gain K1 for multiplying the initial operation correction amount and a late gain K2 for multiplying the late operation correction amount are provided. The initial gain K1 is set to a smaller value as the vehicle speed V is higher. The late gain K2 is set to a larger value as the vehicle speed V is higher.
Following this, it is possible to improve the responsiveness in the initial stage of the steering operation when the vehicle speed V is the low speed side, and the effect of avoiding the yaw rate entrainment phenomenon in the late stage of the steering operation when the vehicle speed V is the high speed side. That is, the balance between the responsiveness at the initial stage of the steering operation and the stability at the latter stage of the steering operation can be adjusted on the low speed side and the high speed side of the vehicle speed V.

(6) The operation time discrimination means discriminates the initial steering operation and the late steering operation based on the direction of change in the steering speed θ ′ of the steering wheel 1.
This makes it possible to distinguish between the initial steering operation and the latter steering operation.
(7) The operation time discrimination means discriminates the steering operation initial stage and the steering operation late stage by comparing the sign of the steering speed θ ′ and the sign of the steering acceleration θ ″.
This simplifies the discrimination process between the initial steering operation and the later steering operation. Further, it can be easily determined regardless of whether the steering direction is normal or reverse.

It is a mimetic diagram showing vehicles provided with a steering control device concerning an embodiment based on the present invention. It is a figure explaining the process of the steering controller which concerns on embodiment based on this invention. It is a figure explaining the initial stage gain K1 which concerns on embodiment based on this invention. It is a figure explaining the latter gain K2 which concerns on embodiment based on this invention. It is a figure explaining the effect | action which concerns on embodiment based on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Upper steering shaft 3 Lower steering shaft 4 Rack shaft 7 Steering wheel 10 Steering sensor 11 Steering controller (steering control means)
12 Steering actuator (steering device)
13 Vehicle speed sensor K1 Initial gain K2 Late gain V Vehicle speed θ Steering angle θ ′ Steering speed (operation initial correction amount)
θ ″ Steering acceleration (correction amount for later operation)
θr Turning angle correction amount (target turning angle)
θr ^* Steering angle correction amount

Claims (6)

Steering speed acquisition means for acquiring the steering speed of the steering wheel, a steering device for steering the steered wheels, and a steering control means for controlling the steered angle of the steered wheels via the steering device. ,
The steering control means is
An operation timing determination means for determining an initial operation phase and a later operation phase of the steering operation;
Based on the determination result of the operation timing determination means, the operation initial correction amount is added to the target turning angle when it is determined that the steering operation is initial, and the operation late correction amount is determined when it is determined that the steering operation is late. Correction means for performing a reduction correction;
The speed ratio, which is the ratio of the steering speed of the steered wheels to the steering speed of the steering wheel, is controlled to a value greater than the speed ratio in the late stage of the steering operation.
The steering initial correction amount is a value proportional to the absolute value of the steering speed of the steering wheel, and the late operation correction amount is a value proportional to the absolute value of the steering acceleration of the steering wheel. Control device.   2. The initial operation correction amount decreases with a lapse of time from the start of steering operation, and the late operation correction amount increases with a lapse of time from the start of steering operation. The steering control device described.   It has an initial gain that is multiplied by the initial operation correction amount and an late gain that is multiplied by the late operation correction amount. The initial gain is set to a smaller value as the vehicle speed increases, and the late gain is The steering control device according to claim 1 or 2, wherein a higher value is set as the value is higher.   The steering according to any one of claims 1 to 3, wherein the operation time determination means determines an initial steering operation and a late steering operation based on a direction of a change in a steering speed of the steering wheel. Control device. Steering acceleration acquisition means for acquiring the steering acceleration of the steering wheel;
5. The steering control device according to claim 4, wherein the operation timing determination means determines the initial steering operation and the late steering operation by comparing the sign of the steering speed and the sign of the steering acceleration.   A steering control method, wherein a speed ratio, which is a ratio of a steering speed of a steered wheel to a steering speed of a steering wheel, is controlled to a value larger than a speed ratio at an early stage of steering operation.

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