JP2001106103A - Vehicle steering unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the dynamic characteristics of a vehicle during running at a low speed. SOLUTION: A steering control part 33 controls a steering actuator 2 in accordance with a desired steering angle δ* which is obtained from a desired steering angle δG* based upon a lateral acceleration and desired steering angle δγ*based upon a yaw rate. A gain setting part 35 sets a gain of the desired steering angle δG* with respect to a desired lateral acceleration Gy* and a gain of the desired steering angle δγ* with respect to a desired yaw rate γ*. That is, the gain setting part 35 sets the gain so that the gain is nonlinearly changed with a vehicle speed and a stability factor in a middle and high speed range, but the gain is linearly changed in a low speed range. Since the gain does not increases in the low speed range, the posture of the vehicle can be controlled while lateral oscillating of the vehicle is restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering apparatus for a vehicle capable of changing the relationship between the operation of an operating means such as a steering wheel and the steering of a steered wheel.

[0002]

2. Description of the Related Art A mechanical connection between a steering wheel and a steering mechanism for turning a steering wheel is eliminated, and the operation direction and the operation amount of the steering wheel are detected. 2. Description of the Related Art There has been proposed a vehicle steering system that applies a driving force from an actuator such as an electric motor (see, for example, Japanese Patent Application Laid-Open No. 9-142330).

[0003] By adopting such a configuration, there is no need to mechanically connect the steering mechanism and the steering wheel, so that it is possible to prevent the steering wheel from being pushed up at the time of a collision, and to simplify the configuration of the steering mechanism, and The weight can be reduced. Further, the degree of freedom of the arrangement position of the steering wheel is increased, and further, other operation means such as a lever or a pedal other than the steering wheel can be adopted.

In the vehicle steering apparatus having the above-described structure, the relationship between the operation of the steering wheel and the operation of the steering mechanism can be freely changed by electrical control, so that the driving performance of the vehicle is dramatically improved. It is expected that it can be improved. For example, by obtaining a target yaw rate or a target lateral acceleration corresponding to the operating torque or the operating angle of the steering wheel, and controlling the operation of the steering mechanism based on these, the attitude control of the vehicle can be performed. Motion characteristics can be optimized.

[0005] The target turning angle of the steering mechanism is calculated using a target yaw rate or a target lateral acceleration, a parameter (stability factor) and a vehicle speed obtained from the specifications of the vehicle and the like. Alternatively, the gain of the target turning angle with respect to the target lateral acceleration is set to be non-linear with respect to the vehicle speed. Therefore, there is no problem in the medium speed range and the high speed range, but in the low speed range, the gain increases exponentially as the vehicle speed decreases, the tire angle changes greatly, and the roll of the vehicle increases. Occurs. Therefore, conventionally, the vehicle speed region in which the attitude control is performed is limited to, for example, a middle and high speed region of 30 km / h or more.

[0006]

However, in this case,
Since the posture control in the low speed range will not be performed,
For example, when suddenly braking or suddenly accelerating on a straddle road,
There is a problem that the kinetic performance of the vehicle at the time of low-speed running is not always good, for example, the vehicle attitude becomes unstable. Therefore, an object of the present invention is to solve the above-described technical problem and to provide a vehicle steering device capable of improving the kinetic performance of a vehicle during low-speed running.

[0007]

According to the first aspect of the present invention, there is provided a vehicle for driving a steering mechanism in accordance with an operation of an operation means. Behavior variable calculating means (31) for calculating a target behavior variable, which is a reference value of a behavior variable representing the behavior of a vehicle, in accordance with the operation content of an operation means; Vehicle speed detecting means (14) for detecting the vehicle speed of the vehicle to be operated, and a target turning angle of the steering mechanism based on the target behavior variable calculated by the target behavior variable calculating means and the vehicle speed detected by the vehicle speed detecting means. And a gain of the target turning angle with respect to the target behavior variable, a vehicle speed and a stability factor in a middle or high speed range equal to or higher than a predetermined vehicle speed (boundary vehicle speed). Based on (e.g., the non-linear with respect to the vehicle speed) determined, wherein the gain with decreasing vehicle speed in the low speed range below a predetermined vehicle speed to vary linearly (preferably, independently of the stability factor)
A gain setting means (35) to be determined, and steering control means (20, 33) for driving and controlling the steering mechanism based on the target turning angle set by the target turning angle setting means. This is a vehicle steering device. In addition,
Alphanumeric characters in parentheses indicate corresponding components and the like in embodiments described later. Hereinafter, the same applies in this section.

Preferably, there is no mechanical connection between the operating means and the steering mechanism, and the steering mechanism is electrically controlled in accordance with the operation of the operating means. According to the present invention, in the low speed range, the gain of the target turning angle with respect to the target behavior variable is determined so as to change linearly with a decrease in the vehicle speed. This prevents an exponential gain increase in the low-speed range,
Even in a low-speed range, the posture control can be favorably performed. Thereby, the kinetic performance of the vehicle during low-speed running can be improved. Needless to say, the attitude control in the middle to high speed range can also be performed well, so that good vehicle motion performance can be realized in the entire vehicle speed range.

The steering control means includes a behavior variable detecting means (1) for detecting a behavior variable representing an actual behavior of the vehicle.
Preferably, the steering mechanism is feedback-controlled using the output of (5, 16). Further, it is preferable that the gain setting means determines the gain so that a rate of increase of the gain with a decrease in the vehicle speed is equal to or less than a predetermined value in a low speed range. More specifically, the increase rate is determined using a vehicle speed and a stability factor in a medium to high speed range equal to or higher than the predetermined vehicle speed (for example,
It is preferable that the gain curve determined in a non-linear manner with respect to the vehicle speed is equal to or less than a value in the case of a tangent at the predetermined vehicle speed.

[0010] More specifically, for example, the predetermined vehicle speed V ^* in the above, and to define a gain in the non-linear according to the following equation (1), wherein the predetermined vehicle speed V ^* of less than the low speed range, below the (2 It is preferable to determine the gain linearly according to the expression (3).

[0011]

(Equation 1)

[0012] The behavior variable of the vehicle may include a lateral acceleration of the vehicle. Further, the behavior variable of the vehicle may include a yaw rate of the vehicle. That is, by setting the gain of the target turning angle with respect to the target lateral acceleration and / or the target yaw rate linearly in the low-speed range, good attitude control in the low-speed range becomes possible, and the kinetic performance of the vehicle during low-speed running is improved. can do.

According to a second aspect of the present invention, the steering control means executes control of the steering mechanism based on the target behavior variable on condition that deceleration or acceleration satisfies a predetermined condition in the low speed range. Means to do (S4, S5)
The vehicle steering system according to claim 1, further comprising: According to the invention of claim 1, the kinetic performance of the vehicle at the time of low-speed traveling can be improved. However, when the characteristics of the vehicle change due to a change in the number of occupants or changes in tire air pressure,
Rolling may occur.

Therefore, according to the present invention, when traveling at low speed,
Attitude control is performed under a condition that is satisfied when the attitude control is particularly necessary, that is, for example, at the time of rapid acceleration or rapid deceleration at which the acceleration or deceleration is equal to or more than each predetermined value. The invention according to claim 3 is characterized in that the steering control means controls the steering mechanism based on the target behavior variable on condition that an operation angle or an operation angular velocity of the operation means satisfies a predetermined condition in the low speed range. 3. The vehicle steering system according to claim 1, further comprising means for executing (S2, S3).

[0015] In the present invention, as in the case of the second aspect of the invention, the condition that is satisfied when the attitude control is particularly necessary,
That is, the attitude control is performed on condition that the operation angle or the operation angular velocity indicates a large value equal to or more than each predetermined value. According to the second or third aspect of the present invention, while performing the posture control at the time of low-speed traveling,
Rolling of the vehicle can be prevented, and as a result, the kinetic performance of the vehicle can be further improved.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a conceptual diagram illustrating a basic configuration of a vehicle steering system according to an embodiment of the present invention. In this vehicle steering system, the operation of a steering actuator 2 driven in accordance with a rotation operation of a steering wheel (operation means) 1 is controlled by a steering gear 3 to front left and right wheels 4 (steering wheels).
Thus, the steering is achieved without mechanically connecting the steering wheel 1 and the steering gear 3 to each other. In this case, a steering mechanism is constituted by the steering actuator 2 and the steering gear 3.

The steering actuator 2 can be constituted by an electric motor such as a known brushless motor. The steering gear 3 controls the rotational movement of the output shaft of the steering actuator 2 by using a steering rod 7.
A motion conversion mechanism (such as a ball screw mechanism) that converts the motion into a linear motion in the axial direction (vehicle width direction). The movement of the steering rod 7 is controlled by a knuckle arm 9 via a tie rod 8.
To cause the knuckle arm 9 to rotate. Thereby, the wheel 4 supported by the knuckle arm 9
Is achieved.

The steering wheel 1 is connected to a rotating shaft 10 rotatably supported on the vehicle body. A reaction force actuator 19 for applying a steering reaction force to the steering wheel 1 is attached to the rotating shaft 10. Specifically, the reaction force actuator 19
Can be constituted by an electric motor such as a brushless motor having an output shaft integrated with the rotating shaft 10. An elastic member 3 made of a spiral spring or the like is provided at an end of the rotating shaft 10 opposite to the steering wheel 1.
0 is connected to the vehicle body. This elastic member 30
Is that the reaction force actuator 19 is the steering wheel 1
When no torque is applied to the steering wheel 1, the steering wheel 1 is returned to the straight steering position by its elastic force.

In order to detect an operation input value of the steering wheel 1, an angle sensor 11 for detecting an operation angle δh corresponding to a rotation angle of the rotating shaft 10 is provided. The rotating shaft 10 is provided with a torque sensor 12 for detecting an operating torque T applied to the steering wheel 1. On the other hand, as an output value sensor for detecting an output value of the steering actuator 2, a turning angle sensor 13 for detecting a turning angle δ of the wheel 4 is provided. The steering angle sensor 13 can be constituted by a potentiometer or the like that detects the amount of operation of the steering rod 7 by the steering actuator 2.

The angle sensor 11, the torque sensor 12, and the steering angle sensor 13 are connected to a steering system control device 20 (steering control means) including a computer.
The control device 20 is further connected with a lateral acceleration sensor 15 for detecting the lateral acceleration Gy of the vehicle, a yaw rate sensor 16 for detecting the yaw rate γ of the vehicle, and a speed sensor 14 for detecting the vehicle speed V. I have. As a variable correlated with the lateral acceleration Gy and the yaw rate γ, for example, a sensor that detects a wheel speed may be connected to the control device 20 in addition to the operation angle δh and the vehicle speed V.

The control device 20 includes a steering actuator 2 and a reaction force actuator 19 via driving circuits 22 and 23.
And control. FIG. 2 is a block diagram for explaining the control contents of the control device 20. The control device 20 realizes the operation of each functional unit shown in FIG. 2 by a program process by a computer. Explaining the symbols in the figure, Gy is the lateral acceleration of the vehicle detected by the lateral acceleration sensor 15, Gy ^* is the target value of the lateral acceleration, γ is the yaw rate of the vehicle detected by the yaw rate sensor 16, δ
Is a turning angle of the steering mechanism detected by the turning angle sensor 13, δ ^* is a target value of the turning angle, δh is an operation angle detected by the angle sensor 11, V is a vehicle speed detected by the speed sensor 14, T is the operating torque detected by the torque sensor 12, T ^* is the target value of the operating torque, i ^* is the target value of the drive current of the steering actuator 2, and ih ^* is the target value of the drive current of the reaction force actuator 19. .

The target lateral acceleration calculating section 31 calculates the target lateral acceleration Gy ^* based on the operation angle δh by Gy ^* = K1 · δh ^.
Ask for. K1 is a target lateral acceleration Gy with respect to the operation angle δh.
^* The gain is adjusted so that optimal control can be performed. Since the lateral acceleration that can be generated decreases as the vehicle speed decreases, the gain K1 is a function of the vehicle speed V. On the other hand, based on the operation angle δh detected by the angle sensor 11, the target torque T ^* is obtained by the target torque calculation unit 25. Specifically, the target torque T ^* is T ^* = K2 · δh
(However, K2 is a gain of the target torque T ^* with respect to the operation angle δh.) This target torque T
^* Deviation of the operation torque T with respect to (T ^* -T) is found,
Based on this, the reaction force actuator control unit 26 sets the target drive current ih ^* of the reaction force actuator 19.
This target drive current ih ^* is determined by ih ^* = G4 · (T ^* −T). Here, G4 is a transfer function, for example, G4 = Kd (1 + 1 / (Td · s)). Kd is a gain, Td is a time constant, and s is a Laplace operator.

The target turning angle calculation unit 32 obtains a target steering angle [delta] ^* is the target turning angle based on the lateral acceleration [delta] _G ^*, by adding the target steered angle [Delta] [gamma] ^* based on the yaw rate, the target rolling determine the steering angle _{^{δ * = δ G * + δγ}} *. The target turning angle δ _G ^* based on the lateral acceleration is given by δ _G ^* = G 1 · (Gy ^* ) by the deviation (Gy ^* −Gy) of the actual lateral acceleration Gy of the vehicle 50 from the target lateral acceleration Gy ^* and the transfer function G 1 ^. -Gy).
On the other hand, the target steering angle δγ based on the yaw rate
^* Is the deviation (Gy ^* −γ ·) of the integrated value γ · V of the actual yaw rate γ of the vehicle 50 and the vehicle speed V from the target lateral acceleration Gy ^* .
V), and using this deviation and the transfer function G2, δγ
^* = G2 · (Gy ^* −γ · V) Between the target yaw rate γ ^* and the target lateral acceleration Gy ^* , γ ^* V = G
y ^* holds, the deviation (Gy ^* −γ ·
V) = (γ ^* −γ) V corresponds to the deviation of the actual yaw rate γ from the target yaw rate γ ^* .

Based on the target turning angle δ ^* obtained in this way, the steering control unit 33 executes drive control of the steering actuator 2. Specifically, the steering control unit 33
Deviation of actual turning angle δ from target turning angle δ ^* (δ ^* −
δ), and using this deviation (δ ^* −δ) and the transfer function G3, a target drive current i ^* = G3 · (δ ^* −δ) is calculated.
The steering actuator 2 is feedback-controlled based on the target drive current i ^* .

The above-mentioned transfer functions G1, G2, G3 are determined, for example, as in the following equations (3), (4) and (5), respectively.

[0026]

(Equation 2)

Gains Ka, Kb, Kc and time constant T
a, Tb, and Tc are appropriately adjusted so as to perform optimal control. In particular, in this embodiment, the attitude control of the vehicle 50 is optimally controlled by controlling the yaw rate γ and the lateral acceleration Gy. Therefore, the target lateral acceleration Gy ^*
And each target turning angle with respect to the target yaw rate γ ^* δ _G ^*,
A gain setting unit 35 for setting the gains Ka and Kb of δγ ^* is provided.

The gain setting section 35 divides the area of the vehicle speed V according to the boundary vehicle speed V ^* (for example, 30 km / h), and sets the gains Ka and Kb according to the following equations (6) and (7).

[0029]

(Equation 3)

FIG. 3 shows the gain K according to the above equations (6) and (7).
It is a figure showing an example of setting of a and Kb. That is, the gain K
a, Kb change with the change of the vehicle speed V. Specifically, the gains Ka and Kb gradually and non-linearly increase with the increase of the vehicle speed V in the middle and high speed range (V ≧ 30 km / h). Then, in the low speed range (V <30 km / h), the vehicle speed changes gradually and linearly as the vehicle speed V decreases. The above (7)
The equation is a point on the curve AH corresponding to the value of the equation (6) at the boundary vehicle speed V ^* , and a gain K0 at the minimum vehicle speed (0 km / h).
Represents the straight line AL connecting the point corresponding to
In this embodiment, the tangent of the curve AH at the point (V ^* , K ^* ) is shown.

In FIG. 3, the straight line AL indicates that the gains Ka and Kb increase as the vehicle speed V decreases.
In the low-speed range, for example, Ka = Kb = K ^* may be used to keep the gains Ka and Kb constant, or the straight line AL may be set so that the gains Ka and Kb decrease as the vehicle speed V decreases. May be determined. In any case, it is preferable to determine the straight line AL so that the rate of increase in the gains Ka and Kb with the decrease in the vehicle speed V is smaller than that in the case of the tangent to the curve AH at the boundary vehicle speed V ^* .

As shown by reference numeral A, when the above equation (6) is applied to a low speed range, the gain K
Since a and Kb increase exponentially and cause a sudden change in the tire angle, the vehicle 50 becomes heavily rolled.
In this embodiment, since the straight line AL represented by the above equation (7) is adopted, such a problem does not occur. Therefore,
In this embodiment, the control device 20 controls the lateral acceleration Gy and the yaw rate γ not only in the middle and high speed ranges but also in the low speed range.
Is performed, that is, the attitude control is performed. Even if the attitude control in such a low-speed range is performed, the vehicle 50 is controlled.
No large rolls occur.

FIG. 4 is a flowchart for explaining the operation of the vehicle steering system according to the second embodiment of the present invention. Since this embodiment relates to an improvement of the first embodiment, the above-described FIG. 1 to FIG. 3 will be referred to as necessary. According to the first embodiment, it is possible to perform the attitude control in the low-speed range to a certain extent. However, when the characteristics of the vehicle change due to the number of occupants or changes in the tire pressure, the roll in the low-speed range is reduced. It may be difficult to completely prevent this.

Therefore, in this embodiment, the posture control (control of the lateral acceleration and / or the yaw rate) in the low speed range is performed on the condition that a certain condition is satisfied. More specifically, the control device 20 first determines whether or not the vehicle speed V belongs to the low-speed range by determining whether or not the vehicle speed V is equal to or higher than 30 km / h (step S1). If it is in the middle / high speed range (V ≧ 30 km / h), steering control based on the target lateral acceleration Gy ^* and the target yaw rate γ ^* , that is, attitude control is performed (step S6).

If the vehicle speed V belongs to the low speed range (step S
At 1 (NO), it is determined whether the operation angle δh detected by the angle sensor 11 is equal to or larger than a predetermined value (for example, about 90 degrees) (step S2). When the steering wheel 1 is largely operated and the operation angle δh is equal to or larger than the predetermined value (YES in step S2), the posture control (step S6) is performed. If the operation angle δh is smaller than the predetermined value (NO in step S2), it is further determined whether or not the operation angular velocity δh 'is equal to or more than a predetermined value (for example, about 180 degrees / second) (step S3). Operating angular velocity δh '
At the time of sudden steering such that is equal to or larger than the predetermined value (YES in step S3), the posture control (step S6) is executed. The operation angular velocity Δh ′ can be obtained by differentiating the operation angle Δh with respect to time.

If the operation angular velocity δh ′ is less than the predetermined value (NO in step S3), it is then determined whether the acceleration is equal to or more than a predetermined value (for example, 0.2 g) (step S4). At the time of rapid acceleration such that the acceleration becomes equal to or more than the predetermined value (YES in step S4), the posture control (step S6) is executed. When the acceleration is not equal to or more than the predetermined value (N in step S4)
Next, in O), it is determined whether or not the deceleration (here, the absolute value of the negative acceleration) is equal to or more than a predetermined value (for example, 0.3 g) (step S5). If the vehicle is suddenly decelerated so that the deceleration becomes equal to or more than the predetermined value (step S5).
YES), posture control (step S6) is performed. On the other hand, when the deceleration is less than the predetermined value (NO in step S5), the posture control (step S6) is not performed.

For detecting the acceleration and the deceleration, an acceleration sensor may be used, or the acceleration or the deceleration may be calculated by differentiating the vehicle speed V with respect to time. As described above, according to this embodiment, in the low-speed range, when attitude control is particularly necessary, that is, when a large steering operation is performed, when sudden steering is performed, when sudden acceleration is performed, or When sudden deceleration is performed, attitude control is performed. Therefore, it is possible to prevent the vehicle from rolling in the low-speed range, and it is possible to satisfactorily perform necessary attitude control.

The determinations in steps S2 to S5 may be performed in any order. Further, any of the conditions (conditions for performing the posture control in the low-speed range) represented by these determination steps S2 to S5 may be used alone, or any two or three may be used in combination. You may do it. That is, for example, the condition (step S2) for the operation angle δh and the operation angular velocity δ
The condition relating to h '(step S3) may be omitted.

Although the two embodiments of the present invention have been described above, the present invention can be embodied in other forms. For example, in the embodiment described above, the gain Ka for target turning angle [Delta] [gamma] ^* of the calculation based on the target steering angle [delta] _G ^* and the yaw rate based on the lateral acceleration, although the invention is applied for both Kb, The setting of either one of the gains Ka and Kb may be switched between a low speed region and a medium high speed region. Further, in the above-described embodiment, a case has been described in which two wheels of a four-wheel vehicle can be steered as steering wheels. However, the present invention is applied to a four-wheel steering system in which all four wheels are steered. Is also good.

Further, in the above-described embodiment, the example in which the steering wheel 1 is used as the operating means has been described. However, other operating means such as a lever and a pedal may be used. In addition to these, various design changes can be made within the scope of the matters described in the claims.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating a basic configuration of a vehicle steering system according to an embodiment of the present invention.

FIG. 2 is a block diagram for explaining the contents of steering control.

FIG. 3 is a characteristic diagram showing an example of setting a steering angle gain with respect to a target lateral acceleration and a target yaw rate.

FIG. 4 is a flowchart for explaining steering control by a vehicle steering system according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering actuator 11 Angle sensor 12 Torque sensor 13 Steering angle sensor 14 Speed sensor 15 Lateral acceleration sensor 16 Yaw rate sensor 20 Steering system control device 31 Target lateral acceleration calculation unit 32 Target steering angle calculation unit 33 Steering control unit 35 Gain setting section

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Takamatsu 3-5-8 Minamisenba, Chuo-ku, Osaka-shi Koyo Seiko Co., Ltd. (72) Inventor Masaya Segawa 3-58 Minamisenba, Chuo-ku, Osaka-shi F term in Seiko Co., Ltd. (reference) 3D032 CC01 DA03 DA04 DA15 DA23 DA29 DA33 DB02 DB03 DC03 DC33 DC34 DC40 DD02 DD06 DD07 DD17 EA01 EB04 EB11 EB12 EB17 EC23 EC29 GG01

Claims (3)

[Claims] 1. A vehicle steering device for driving a steering mechanism in accordance with an operation of an operation means, wherein a target behavior variable which is a reference value of a behavior variable representing a behavior of a vehicle is calculated in accordance with the operation content of the operation means. Target behavior variable calculating means, vehicle speed detecting means for detecting a vehicle speed of a vehicle on which the vehicle steering device is mounted, and a target behavior variable calculated by the target behavior variable calculating means and detected by the vehicle speed detecting means. Target turning angle setting means for setting a target turning angle of the steering mechanism based on a vehicle speed, and a gain of the target turning angle with respect to the target behavior variable,
Gain setting means that is determined based on the vehicle speed and the stability factor in a medium to high speed region equal to or higher than a predetermined vehicle speed, and that the gain changes linearly with a decrease in the vehicle speed in a low speed region lower than the predetermined vehicle speed; A steering control unit for driving and controlling the steering mechanism based on the target turning angle set by the target turning angle setting unit. 2. The steering control means includes means for executing control of the steering mechanism based on the target behavior variable on condition that deceleration or acceleration satisfies a predetermined condition in the low speed range. The vehicle steering system according to claim 1, wherein 3. The steering control means executes the control of the steering mechanism based on the target behavior variable on condition that an operation angle or an operation angular velocity of the operation means satisfies a predetermined condition in the low speed range. The vehicle steering system according to claim 1 or 2, further comprising: