JP2605356B2 - Vehicle steering angle control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering angle control device, and in particular, the stability and control characteristics of a vehicle are impaired even when disturbance is input from a road surface or the like. It was made not to be.

[Conventional technology]

As a conventional vehicle steering angle control device, for example, there is one as shown in FIG. 8, which is a control system of a rear wheel steering angle control device that steers rear wheels according to a front wheel steering angle and a vehicle speed. FIG. 2 shows a block diagram.

That is, the wheel steering angle calculation section 50 after the operation and outputs the target steering angle _R of the rear wheels in accordance with the front-wheel steering angle θ and vehicle speed V, the target steering angle _R that is output from the rear wheel steering angle calculating unit 50 The proportional elements 51, 52 multiplied by the constant (K _SR , K ₁ ) and the comparison elements 51, 52
An adder 53 that adds the output of the adder 52 and a negative feedback obtained by multiplying the output of an integration element described later by a constant, a proportional element 54 that multiplies the output T of the adder 53 by a constant (1 / I _KR ), An adder 55 for adding the output of the element 54 and a negative feedback obtained by multiplying the output of an integration element to be described later by a constant, and the adder 55
55, an integration element 56 for integrating the output _R ,
Is proportional to a constant (K ₂ ) when negatively feeding back the output _R to the adder 53, and the output _{R of the} integration element 56
Is fed back to the adder 55 by a constant (D _KR / I
_KR) and multiplied by the proportional element 58, an integral element 59 for integrating the output _R of the integral element 56, which fold constant (K ₁₎ at the time of negative feedback the output [delta] _R of the integral element 59 to the adder 53 a proportional element 60, and a proportional element 61 is multiplied by a constant (K _SR / I _KR) when negative feedback to the adder 55 the output [delta] _R of the integral element 59, the output of the integral element 59 [delta] _R Corresponds to a driving amount of an actuator (not shown) that drives a rear wheel steering angle varying device that generates a steering angle for the rear wheels, that is, an actual rear wheel steering angle.
S is a Laplace operator, K ₁ and K ₂ are gain constants, I _KR and D
_KR and _KSR are the inertia, viscosity and spring constant of the actuator converted to the wheel end, respectively.

Here, the transfer function G (S) of this control system is represented by the following equation (1).

Here, ω _n is a natural angular frequency, and ξ is an attenuation coefficient, which are represented by the following equations (2) and (3), respectively.

ω _n = ｛(K ₁ + K _SR ) / I _KR ｝ ^1/2 (2) ξ = (K ₂ + D _KR ) / (2I _KR ω _n ) (3) Based on the steering angle θ of the front wheels and the vehicle speed V, for example, the turning control of the vehicle is improved by setting the front wheels and the rear wheels in opposite phases during low-speed running, and the running stability of the vehicles is controlled by setting the front wheels and the rear wheels in phase during high-speed running. sex is calculated by the target steering angle _R is rear-wheel steering angle calculation unit 50 so as to increase the target steering angle _R of the calculated, depending on the actual steering angle [delta] _R and the feedback signal of the actual steering angular speed of the rear wheel since wheel steering angle control is performed after, so the actual steering angle [delta] _R converges quickly target steering angle _R.

[Problems to be Solved] However, the above in the conventional art control system, since the compensation means to the disturbance transmitted from a road surface or the like was not provided, for example, the cornering force C _R reaction force 2ξC by _R If various disturbances q such as changes in the road surface friction coefficient μm are input, the influence of the disturbances is transmitted to the actuator that drives the rear wheel steering angle mechanism, and the steered wheels fluctuate and the running vehicle becomes improper. There was an unsolved problem of becoming stable.

That is, as shown in FIG. 8, when the disturbance q (Q (S)) is further added to the output T of the adder 53, the input of the conventional control system is U (S), and the output is X ( S), these functions are as shown in the following equation (4).
Output X (S) Sokuchi actual steering angle [delta] _R becomes unstable.

Further, a control system that is strong against disturbance q may be designed by increasing the proportional gains K ₁ and K _{2. In} this case,
The natural angular frequency ω _n and the damping coefficient ξ
Since it fluctuates with K ₁ and K ₂ (see the above equations (2) and (3)), it becomes difficult to realize a control system having a desired natural angular frequency ω _n and damping coefficient ξ. Even so, if the compensation for the disturbance is performed during the low-speed running (the vehicle speed is safe even if the wheels slightly fluctuate), the energy consumed increases, which is uneconomical.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned unsolved problems in the related art, and provides a vehicular steering angle control device that does not impair running stability of a vehicle even when disturbance is input from a road surface or the like. The purpose is to do.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a steering angle variable mechanism for generating a steering angle on a wheel, an actuator for driving the steering angle variable mechanism in accordance with a control signal, and the control in accordance with a running condition of a vehicle. An actuator control device that outputs a signal, a vehicle steering angle control device including: a driving state detection unit that detects a driving state of the actuator;
Disturbance provided in the actuator control device, which impairs the driving of the actuator, is compensated based on the detection result of the driving state detecting means, and the strength of the compensation is made variable in accordance with at least a running condition including a vehicle speed and a steering angle. And a disturbance compensating means, wherein the disturbance compensating means reduces the strength of the compensation when the vehicle speed is low, and reduces the strength of the compensation when the steering angle is small.

[Action]

A drive state detecting means for detecting a drive state of the actuator is provided, and a disturbance compensating means for compensating for a disturbance harming the drive of the actuator based on a detection result of the drive state detecting means is provided in an actuator control device for outputting a control signal to the actuator. With this arrangement, even if a disturbance is input from a road surface or the like, the disturbance compensating means operates so as to compensate for the behavior of the actuator due to the disturbance, so that the influence of the disturbance is not transmitted to the actuator. It is stable and the running stability of the vehicle is improved.

Moreover, the strength of the disturbance compensation means against disturbance is
Since it is reduced when the vehicle speed is low as the traveling condition and is small when the steering angle is small as the traveling condition, wasteful energy is not consumed and the vehicle steering angle control device is economical.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1 to 7 show an embodiment of the present invention, which is an example in which the present invention is applied to a rear wheel steering angle control device of a vehicle.

First, the configuration will be described. In FIG. 1, a rear wheel 5 capable of turning around a kingpin shaft 4a via a ball joint 3 and a knuckle arm 4 is provided at an end (one end is omitted) of a tie rod 2 forming a part of a rear wheel steering system. Are linked.

A worm 2a is formed integrally with the outer peripheral portion of the tie rod 2 at a substantially central portion in the longitudinal direction.
A ball nut 6 that can only rotate and is prevented from moving in the axial direction is screwed.

The ball nut 6 has an assist gear 8a fixed to the outer periphery thereof by the same rotating shaft, and an assist gear 8a
The rotational force of the motor 7 is transmitted through a reduction mechanism 8 constituted by a drive gear 8b fixed to an output shaft of a rear wheel steering motor 7 as an actuator. When the ball nut 6 is rotated by the rotational force of the motor 7, the tie rod 2 integrally formed with the worm 2a meshing with the ball nut 6 moves in the longitudinal direction, and as a result, a steering angle is generated at the rear wheel 5. I do.

Here, tie rod 2, worm 2a, ball joint
3, the knuckle arm, the ball nut 6, and the speed reduction mechanism 8 constitute the rear wheel steering device 1 as a variable steering angle mechanism.

A coil spring 10 for urging the tie rod 2 so as to maintain the rear wheel 5 in a straight state, and a tie rod 10 between a member 9 supported by a vehicle body (not shown) and a member 2b fixed to the tie rod 2 2 and a shock absorber 11 for generating a damping force according to the rear wheel turning speed. Further, another coil spring and a shock absorber having the same configuration as above are also provided near the other end of the tie rod 2 located on the right side (not shown) of FIG.

Numeral 12 denotes a steering angle sensor for detecting a steering angle of a front wheel steering system (not shown), which detects a turning position of the steering wheel and outputs a steering angle detection signal θ corresponding to the steering angle.

Reference numeral 13 denotes a vehicle speed sensor for detecting a vehicle speed, for example, detecting a rotation speed of an output shaft of a transmission and outputting a vehicle speed detection signal V including a periodic pulse signal corresponding thereto.

Reference numeral 14 denotes a target steering of the rear wheels 5 based on a steering angle detection signal θ as a driving condition (steering condition) supplied from the steering angle sensor 12 and a vehicle speed detection signal V as a driving condition supplied from the vehicle speed sensor 13. A rear-wheel steering angle calculation unit that calculates and outputs an angle _R. For example, the vehicle has improved turning performance by using the front and rear wheels 5 in opposite phases during low-speed running, and uses the front and rear wheels 5 in phase during high-speed running. running stability of calculating the target steering angle _R as improved.

Reference numeral 15 includes, for example, an interface circuit and a microcomputer, and a detection signal supplied from a rotary encoder 7a that outputs a target steering angle _R supplied from the rear wheel steering angle calculation unit 14 and a rotation position of the motor 7. Is a motor control device as an actuator control device that calculates and outputs a control signal for the motor 7 in accordance with the actual steering angle δ _R and the steering angular velocity _{R of the} rear wheel obtained based on the following. Further, the Lori encoder 7a, by an operation processing for obtaining the actual steering angle [delta] _R and the steering angular velocity _R of the rear wheels based on the detection signal, the driving state detecting means is constructed.

16 includes a pulse width modulation circuit, a left rotation power element, a right rotation power element, and the like, and performs pulse width modulation control according to a control signal supplied from the motor control device 15,
This is a drive circuit that drives the motor 7.

That is, when the motor drive device 15 performs a predetermined calculation to calculate a control signal for the motor 7, the drive circuit 16 performs pulse width modulation control in accordance with the control signal. The rotating power element supplies a current to the motor 7, and as a result, a predetermined rotational force is generated in the motor 7, so that the rear wheel steering device 1 is driven as described above, and the steering angle to the rear wheel 5 is increased. Occur.

FIG. 2 shows a block diagram of this control system.
In the figure, S is a Laplace operator, K ₁ and K ₂ are gain constants, Z is a gain coefficient, and I _KR , D _KR , and K _SR are the inertia, viscosity, and spring constant of the motor 7 each converted to a wheel end. In addition,
Elements that are the same as those in the above-described conventional control system (FIG. 8) are denoted by the same reference numerals, and redundant description is omitted.

That is, in the control system of FIG. 2, the configuration shown in dashed lines is the disturbance compensator 20 as disturbance compensation means of the present invention, wheel actual steering angle [delta] _R constant after the driving state of the actuator or motor 7 ( K _SR ), a proportional element 22 for multiplying the rear wheel steering angular velocity _R as another driving state of the motor 7 by a constant (D _KR ), and a rear element steering angular velocity _R for a constant (I _KR ) A proportional element 23 for doubling, an adder 24, an integral element 25 for integrating the output of the adder 24, and an integral element 25
And an output of the proportional element 23, and a proportional element 27 for multiplying the output of the adder 26 by a factor (Z). The adder 24 calculates the negative feedback of the output values of the proportional elements 21 and 22 and the proportional element 27 and the output value T of the adder 62 that adds the output value of the adder 53 and the output value of the proportional element 27. Positive feedback is supplied, and these are added and output.

A linear filter is constituted by the integral element 25 and the proportional element 27, and the gain coefficient Z
Is a coefficient that corresponds to the bandwidth of the filter and determines the strength of the disturbance compensator 20 against disturbance, as will be described later, and is variable according to the steering angle detection value θ and the vehicle speed detection value V of the front wheel steering system. And is determined based on the following equation (5).

Z = K _S × θ + K _V × V (5) where K _S and K _V are proportional constants.

 Next, the operation of the above embodiment will be described.

Now, assuming that the disturbance transmitted from the road surface to the motor 7 via the rear wheel 5 and the like is q (see FIG. 3), the equation of motion of this control system is as shown in the following equation (6).

T + q = I _{KR R} + D _{KR R} + K _SR δ _R (6) Here, the disturbance compensation value V _T shown in the following equation (7) is added to the above equation (6) to remove the disturbance q ( 4).

V _T = −q = T−I _{KR R} −D _{KR R} −K _SR δ _R (7) However, since it is difficult to detect the rear wheel steering angular acceleration _R , in this embodiment, the rear wheel steering angular velocity _R In a low-pass filter to calculate the rear wheel steering angular acceleration _R in a pseudo manner.

Therefore, the disturbance compensation value V _T, utilizing the disturbance compensation value V _T 'shown in (8) below (see Figure 5).

[Z / (S + Z)] (broken line in FIG. 5) in the equation (8) is the primary filter 30, and the frequency characteristic of the primary filter 30 is as shown in FIG. disturbance compensation value V _T and V _T 'is substantially identical at lower place than the bandwidth Z.

Therefore, in the control system (see FIG. 2) of the present embodiment in which the disturbance compensation value V _T 'shown in the above equation (8) is added to the above equation (6), the motion is calculated as shown in the following equation (9). This is equivalent to removing the disturbance from the equation.

_{T + q + V T '=} T + q + V T = I KR R + D KR R + K SR δ R + (T-I KR R -D KR R -K SR δ R) = T ...... (9) that is, as shown in Figure 2 In the present embodiment including the control system, even when disturbance q is input from the road surface, the disturbance compensator 20 compensates for the disturbance q, so that the rear wheel steering angle control device is strong against disturbance. .

FIG. 7 compares the results of simulating fluctuations in the rear wheel steering angle and yaw rate when a predetermined disturbance is given to the control system of the rear wheel steering angle control device, with a device with a disturbance compensating unit and a device without the disturbance compensating unit. FIG. That is, the rear wheel 5
When a torque disturbance q as shown in FIG. 1A is input, the rear wheel steering angle control device of the present embodiment including the disturbance compensation unit 20
While little variation in the steering angle (see FIG. 7 (b) L _1), in devices without a disturbance compensation unit deviates greatly from the target steering angle (FIG. 7 (b) refer to L _2), the vehicle Running stability is impaired. Also, the change in yaw rate at the time, the apparatus comprising a disturbance compensation unit (see FIG. 7 (c) L ₃₎ fluctuations from the target value converges to a slight and and quickly target value but does not include In the device, the fluctuation from the target value is large and the convergence requires a long time (No. 7).
Figure (c) refer to L _4). From this simulation result, it can be seen that the rear wheel steering angle control device including the disturbance compensating unit 20 according to the present embodiment has a strong compensation force against disturbance.

The transfer function G '(S) of the control system shown in FIG.
Equation (10) below is obtained.

That is, the disturbance compensating unit 20 calculates the transfer function G (S) of the control system.
Since not any influence, because the control characteristic of the control system by the disturbance compensator 20 is not impaired, can be a control system having a desirable natural angular frequency omega _n and attenuation coefficient ξ like.

In the above embodiment, the bandwidth Z of the primary filter 30
That is, since the strength of the disturbance compensation by the disturbance compensating unit 20 is made variable based on the above equation (5) according to the steering angle detection value θ and the vehicle speed detection value V as the driving conditions, the vehicle speed in a low vehicle speed or a straight traveling state is determined. In such a state in which disturbance is unlikely to occur, unnecessary power is not consumed, and the rear wheel steering angle control device is economical.

Further, in the above embodiment, the coil spring 10 and the shock absorber 11 are interposed between the tie rod 2 constituting the rear wheel steering device 1 and the member 9 on the vehicle body side.
In addition to the characteristics of the control system described above, the fluctuation of the rear wheel steering angle can be further suppressed, the convergence to the target steering angle can be improved, and the motor 7 and the motor control device 15 fail and the rear wheel Even when the steering angle control cannot be executed, the rear wheel steering device 1 can be stabilized by the urging force of the coil spring 10 and the damping force of the shock absorber 11.

In the above-described embodiment, the case where the present invention is applied to the rear wheel steering angle control device has been described. However, the present invention is not limited to this, and may be a front wheel steering system steering angle control device.

Further, in the above embodiment, the target steering angle _{R of the} rear wheel 5 is set.
Has been described based on the steering angle θ of the front wheels and the vehicle speed V, but is not limited thereto.
Instead or together with this, for example, the target steering angle is calculated in consideration of other traveling conditions such as the steering speed of the front wheels and the steering torque generated in the front wheel steering system, and the friction coefficient of the traveling road surface. Is also good.

Further, in the above embodiment, the steering angle θ of the front wheels and the vehicle speed V
In accordance with the above equation (5), the strength of the compensation for the disturbance of the outer ring compensator 20, that is, the bandwidth Z of the primary filter 30 is made variable, but the present invention is not limited to this.
Along with the vehicle speed V, it is also possible to consider other driving situations as in the case of determining the target steering angle.

〔The invention's effect〕

As described above, in the vehicle steering angle control device of the present invention, the disturbance that hinders the driving of the actuator is compensated based on the driving state of the actuator in the control device of the actuator that drives the variable steering angle mechanism. Since the compensation means is provided, even if disturbance from a road surface or the like is input, the disturbance compensation means compensates for the disturbance, so that the vehicle steering angle control device can be made strong against the disturbance. Driving stability can be improved, and the strength of the disturbance compensation means against disturbances should be reduced in situations where the vehicle speed is low as the driving situation, and should be reduced in situations where the steering angle as the driving situation is small. As a result, useless energy is not consumed, so that an economical vehicle steering angle control device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a block diagram showing a control system of this embodiment, FIG. 3 is a block diagram explaining the equation of motion of this control system, FIG. Figure 3
A block diagram obtained by adding a disturbance compensation value to the block diagram of FIG.
FIG. 5 is a block diagram illustrating a disturbance compensator, FIG. 6 is a Bode diagram illustrating a frequency characteristic of a primary filter forming a part of the disturbance compensator, and FIG. 7 is a graph illustrating an effect of the present embodiment. 9A shows a rear wheel torque disturbance, FIG. 9B shows a change in the rear wheel steering angle, and FIG. 9C shows a change in the yaw rate of the vehicle. FIG. 8 is a block diagram showing a conventional control system. DESCRIPTION OF SYMBOLS 1 ... Rear wheel steering device (variable steering angle mechanism) 2, ... Tie rod, 6 ... Ball nut, 5 ... Rear wheel, 7 ... Motor (actuator), 12 ... Steering angle sensor, 13 ... Vehicle speed Sensor, 15: Motor control device (actuator control device), 20: Disturbance compensation unit (disturbance compensation means).

Claims (1)

(57) [Claims] 1. A variable steering angle mechanism for generating a steering angle on a wheel, an actuator for driving the variable steering angle mechanism in response to a control signal, and an actuator control device for outputting the control signal in accordance with a running condition of a vehicle A driving state detecting means for detecting a driving state of the actuator; and a detection result of the driving state detecting means for detecting a disturbance provided in the actuator control apparatus and impairing the driving of the actuator. Disturbance compensating means for compensating based on the vehicle speed and varying the strength of the compensation at least in accordance with the driving conditions including the vehicle speed and the steering angle, wherein the disturbance compensating means performs the compensation when the vehicle speed is low. Reduce the strength,
A steering angle control device for a vehicle, wherein the magnitude of the compensation is reduced when the steering angle is small.