JP2523187B2 - Vehicle steering angle control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a steering angle control device for a vehicle, and more particularly to controlling an auxiliary steering angle when auxiliary steering one of a front wheel and a rear wheel during main steering by a steering wheel. It relates to a useful device.

(Prior Art) This type of steering angle control device is configured in a closed loop so that the actual steering angle matches the target steering angle obtained by calculation. As an example, the applicant of the present application proposes it in Japanese Patent Application No. 63-154308. There is something like that shown in Fig. 7.

In FIG. 7, the steering actuator is composed of a current amplifier, an electric motor, a rotary encoder, and a tachogenerator. The ratio of the motor rotation amount to the steering angle, that is, the ratio N of the motor rotation amount to the unit steering angle is multiplied by the target steering angle δ to obtain the motor rotation amount θ _S0 corresponding to the target steering angle, and this motor rotation amount θ _S0 The target motor rotation amount θ _S1 obtained by multiplying by the gain k ₂ is input to the subtractor. This subtracter subtracts the motor rotation correction amounts θ _C1 , θ _C2 , and θ _C3 from the target motor rotation amount θ _S1 and outputs a motor rotation amount signal I. The current amplifier receives this signal and outputs a corresponding drive current i. Supply to the motor,
The motor executes auxiliary steering with a rotation amount θ _M according to the current i.

The rotary encoder detects the motor rotation amount θ _M (actual steering angle), and the tachogenerator detects the motor rotation speed α. On the other hand, the detected motor rotation amount θ _M is multiplied by the same gain k ₂ as the above to become the correction amount θ _C1 , and this correction amount is input to the subtractor. The motor rotation speed α is multiplied by the gain k ₁ to obtain a correction amount θ _C2 , and this correction amount is input to the subtractor. On the other hand, the detected motor rotation amount θ _M is used to calculate the correction amount θ _C3 as follows.

That is, motor rotation amount signal (steering actuator input)
I and the motor rotation amount (steering actuator output) θ _M are the low-pass filter of the transmission characteristic H and the transmission characteristic H /
It is passed through a filter of P ₀ (however, the transfer characteristic of P ₀ steering actuator) and input to another subtractor, and this subtractor sets the difference between both inputs as a correction amount θ _C3 . The motor rotation correction amount θ _C3 based on this steering actuator input / output corresponds to a signal for compensating the steering angle error due to the disturbance, and it is possible to prevent the execution angle from deviating from the target steering angle due to the disturbance.

(Problems to be Solved by the Invention) However, when the motor rotation correction amount θ _C3 is large due to excessive disturbance or the like, and the motor rotation signal I becomes a value exceeding the current maximum value of the current amplifier or the torque maximum value of the motor, Since the motor cannot function as instructed and the steering angle control corresponding to the instruction cannot be performed, the control becomes unstable. For example, the sixth
The actual steering angle may be opposite to the target steering angle δ shown by the dotted line a with respect to the target steering angle δ shown by the solid line in the figure.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems by devising a system for creating a correction document according to input / output of a steering actuator so that the steering actuator is not input with information exceeding the functional limit. .

(Means for Solving the Problem) The present invention for this purpose responds to the difference between the input and output of a steering actuator and a first signal generator that produces a first signal according to a target steering angle and an actual steering angle. A second signal generator that produces a second signal, and a steering angle control device for a vehicle that uses the difference between the first signal and the second signal as the input of the steering actuator. Actuator input
A limiter is provided to limit the value to a value less than the value corresponding to the functional limit of the steering actuator.

(Operation) The first signal generator produces a first signal according to the difference between the target steering angle and the actual steering angle, and the second signal generator produces a second signal according to the input / output of the steering actuator. The steering actuator functions by using the difference between the first signal and the second signal as an input, and controls the steering angle so as to bring the actual steering angle to the target steering angle. Therefore, the actual rudder angle follows the target rudder angle even due to disturbance or the like, and the control accuracy can be improved.

By the way, when the input of the steering actuator exceeds the functional limit due to an excessive disturbance or the like, the limiter suppresses the steering actuator input toward the second signal generating unit to a value corresponding to the functional limit. For this reason, it is possible to eliminate the inconvenience that the steering angle control becomes unstable and the steering angle becomes the steering angle in the opposite direction to the target steering angle of the actual steering angle in the occurrence part of such a situation.

(Example) Hereinafter, the Example of this invention is described in detail based on drawing.

1 and 2 show an embodiment of the device of the present invention. In FIG. 1, 1L and 1R are left and right steering wheels, respectively, which are supported by knuckle arms 2L and 2R so as to be steerable. The knuckle arms 2L and 2R are connected by a tie rod 3, and a ball nut 4 is screwed onto this tie rod. The ball nut 4 is rotatably supported with its axial position fixed.
It is drivingly coupled to the output shaft of the motor 6 via the gear set 5.

The controller 7 inputs the motor rotation amount signal I corresponding to the target steering angle δ to the current amplifier 8, which in turn outputs the battery 9
The electric current i corresponding to the signal I is supplied to the motor 6 with the electric power from. The motor 6 is rotated by an angle θ _M corresponding to the drive current i, and this rotation is transmitted to the ball nut 4 via the gear set 5,
The steered wheels 1L, 1R are steered by the target rudder angle δ via the stroke of the tie rod 3. The rotary encoder 10 detects the motor rotation amount θ _M (actual steering angle) and feeds it back to the controller 7.

As shown in FIG. 2, the motor 6, the current amplifier 8 and the rotary encoder 10 form a steering actuator 11. The controller 7 includes a multiplier 12, a subtractor 13, a PID calculator 14, a subtractor 15, a limiter 16, and a low pass filter 1.
7, the functional blocks of the filter 18 and the subtractor 19 are shown, but the following control is repeatedly performed at every instant T (n) = Δt × n (n is the number of calculations) in each calculation cycle Δt.

For each instant T (n), the multiplier 12 multiplies the target steering angle δ (n) by the gear ratio N to obtain the motor target rotational speed θ _S (n). Here, the gear ratio N represents the ratio between the rotation angle of the motor 6 and the steering angle due to the rotation of the motor 6, and is a constant determined by the gear ratio of the gear set 5, the pitch of the ball nut 4, and the arm lengths of the knuckle arms 2L and 2R. Is. Therefore, θ _S (n) corresponds to the theoretical rotation angle of the motor 6 for obtaining the target steering angle δ (n), that is, the motor target rotation angle.

The calculator 13 calculates the motor rotation angle θ _M (n) detected by the rotary encoder 10 from the motor target rotation angle θ _S (n) to calculate the deviation signal (fifth signal) u ₅ = θ _S (n) −θ _M ( n)
Ask for. The PID calculator 14 uses the motor rotation angle deviation signal u
_{From 5} (n) to the next PID (P is proportional, I is integral, D is differential)
First signal u ₁ (n) for eliminating the above deviation by calculation
Ask for.

∴u ₁ (n) = u ₁ (n-1) + K ₀ · u ₅ (n) + K ₁ · u ₅ (n) + K ₂ · u ₅ (n-1) The subtracter 15 outputs the first signal u ₁ The second signal u from (n)
₂ (n) is subtracted to obtain the motor rotation angle signal I (n). The second signal u ₂ (n), which will be described in detail later, indicates the motor rotation correction amount corresponding to the deviation between the input and output of the actuator 11 due to the disturbance T _d to the motor 6. Motor rotation angle signal I
(N) causes the current amplifier 8 to output the corresponding motor drive current i (n) to the motor 6, and the motor 6 steers the steered wheels 1L, 1R by this rotation. By the way, since the rudder angle is feedback-controlled in the calculator 13 and the disturbance is compensated in the subtractor 15, the rudder angle can be exactly matched with the target rudder angle and the feedback control is influenced by the disturbance. Can be accomplished without

Next, the second signal u ₂ (n) will be described. The limiter 16 obtains the motor rotation angle limit value I _L (n) from the motor rotation angle signal I (n) (actuator input). This limit value is I _L (n) = I (n) if the motor rotation angle signal I (n) is a value corresponding to the functional limit of the actuator 11, for example, less than the current output upper limit value I _{max of the} current amplifier 8, If the rotation angle signal I (n) is greater than or equal to I _max, 1 _L (n) = I _max . In this way, the motor rotation angle limit value I _L (n), which is limited so as not to exceed I _max , is transferred to the transfer characteristic H.
Pass the low-pass filter 17 of
Obtain the third signal u ₃ (n + 1) for (n + 1). Here, the third signal u ₃ (n + 1) is (B _H1 = 1 + A _H1 ) On the other hand, it is assumed that the filter 18 has a transfer function of H / P ₀ when the transfer characteristic of the steering actuator is P ₀ , and the motor rotation angle θ _M (n) detected by the rotary encoder 10, that is, the steering actuator output is Pass through to obtain a fourth signal u ₄ (n) indicative of the actuator input corresponding to this output. This fourth signal u ₄ (n) is Can be represented by

The subtractor 19 subtracts the third signal u ₃ (n) from the fourth signal u ₄ (n) to obtain the second signal u ₂ (n) corresponding to the shift between the input and output based on the disturbance T _{d of the} actuator 11. Then, this is input to the subtractor 15 as a motor rotation correction amount signal corresponding to the disturbance.

Due to the above, the actuator 11 causes the disturbance T _{d as} described above.
It is possible to perform feedback control that brings the actual steering angle to the target steering angle δ (n) without being affected by. By the way, if the actuator input I becomes a value that exceeds the functional limit of the actuator 11 due to external disturbance (I>
I _max), the limiter 16 suppresses I _L = second signal form and I _max u _2. Therefore, in the next calculation cycle, it is possible to prevent the actuator input I from entering the range of the functional limit and the steering angle control from becoming unstable. For example, the target rudder angle δ
Even if an excessive disturbance is input in the case where is shown by the solid line in FIG. 6, the actual steering angle only decreases in the steering angle amount as shown by the one-dot chain line b, and the actual steering angle is in the opposite direction to the target. There is no steering angle, which is advantageous for stability.

FIG. 3 shows another example of the method of generating the second signal u ₂ . In this example, the transfer function described above the signal I _L from the limiter 16.
Passed through a filter 20 is P _0, obtains the actuator output theta _i of the target to naturally obtained with the current actuator input, the error between the actuator output theta _i of the actual actuator output theta _M and the target by the subtractor 21 theta _{Find D.} This error is due to the disturbance T _d to the motor 6,
This is passed through the filter 22 whose transfer function is H / P ₀ described above to obtain the second signal u ₂ for disturbance component correction.

_{Here, u 2 = (H / P} 0) from the third figure seek u ₂ is a · θ _M -H · I _L. Next, θ _i of the instant T (n) is calculated from I _L as follows.

Therefore, θ _i (n + 1) = − A _P1 · θ _i (n) −A _P2 · θ _i (n−
1) + B _P1 · I _L (n) + B _P2 · I _L (n-1). Similar to u _{3 in} FIG. 2, θ _i is a value used at the next calculation instant T (n + 1) at the instant T (n).

Next, in order to obtain θ _D of the instant T (n), θ _D (n) = θ _M (n) −θ _i (n). On the other hand, the second signal u ₂ at the instant T (n) is And θ _D (n) is θ _D (n) = P ₀ · I _L (n) −θ _M (n), Next, it was evidenced in this example is equivalent to the second signal u ₂ of the second signal u ₂ in Figure 2.

According to the PID calculation in both embodiments, the ratio between the actual value θ _M of the motor rotation angle and the target value θ _S , that is, the transfer characteristic of the steering angle control device Therefore, by properly selecting the gains K ₀ , K ₁ , and K ₂ , the responsiveness of θ _M to θ _S can be secured.

FIG. 4 shows still another example of the present invention. In this example, the motor target rotation angle θ _S (target rudder angle command) is passed through the predistorter 23 having the transfer characteristic E to generate the sixth signal u ₆ . Motor rotation angle θ
_M (actual steering angle signal) is passed through the filter 24 having the transfer characteristic G to obtain the seventh signal, and the subtracter 25 uses the sixth signal u ₆ to the second signal.
The value obtained by subtracting u _{2 from} the seventh signal u ₇ is the first signal u ₁ .
Then, the filter 26 whose transfer function is 1 / F
To the actuator 11 and the limiter 16.

In this example, the transfer characteristic θ _M / θ _S of the steering angle control device is Therefore, by setting the transfer functions E, 1 / F, and G as described below, θ _M can be made to follow θ _{S with a} sufficiently small delay.

F (Z ^-1 ) A _P (Z ^-1 ) = A _M (Z ^-1 ) -B _P (Z ^-1 ) G (Z ^-1 ) ・ Z ^-1 The limiter 16 based on the idea of the present invention is the fifth one.
As shown in the figure, the same object can be achieved by applying it to the system of FIG. 7 as it is. In this case, the motor rotation speed α can be set to a desired value by feeding back the poles of the loop surrounded by the dotted line by k ₁ and k ₂ .

(Effect of the Invention) Thus, as described above, the steering angle control device of the present invention uses the input I of the steering actuator so as to deal with an excessive disturbance due to disturbance or the like.
Limiter 16
Is configured to suppress the steering actuator input I toward the second signal (u ₂ ) generating portion to a value Imax corresponding to the functional limit, the steering angle control becomes unstable even when such a situation occurs, and the actual steering angle is reduced. It is possible to eliminate the inconvenience that the target steering angle is opposite to the target steering angle.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a steering angle control device of the present invention, FIG. 2 is a block diagram of a controller in the same example, and FIGS. 3 to 5 show other three examples of the present invention. 2 is a block diagram similar to FIG. 2, FIG. 6 is a time chart showing the time series change of the actual steering angle with respect to the target steering angle in comparison between the device of the present invention and the conventional device, and FIG. 7 is the block line of the conventional device. It is a figure. 1L, 1R …… Steering wheel, 3 …… Tie rod 4 …… Ball nut, 6 …… Motor 7 …… Controller, 8 …… Current amplifier 10 …… Rotary encoder 11 …… Steering actuator 12 …… Multiplier 13,15 , 19,21,25 …… Subtractor 14 …… PID calculator, 16 …… Limiter 17 …… Low-pass filter 18,20,22,24 …… Filter 23 …… Predistorter

Claims (4)

(57) [Claims] 1. A first signal generator for producing a first signal according to a difference between a target steering angle and an actual steering angle, and a second signal generator for producing a second signal according to an input / output of a steering actuator. In a steering angle control device for a vehicle, wherein a difference between a first signal and a second signal is taken as an input of the steering actuator, a steering actuator input to the second signal generation unit is less than a value corresponding to a functional limit of the steering actuator. A steering angle control device for a vehicle, which is provided with a limiter for limiting the steering angle. 2. The reduction pass filter of the transfer characteristic H, wherein the second signal generator passes the signal from the limiter into a third signal, and the transfer characteristic of the steering actuator is P ₀ . Of the vehicle, which has a transmission characteristic of H / P ₀ and passes a steering actuator output to obtain a fourth signal, and a subtractor which takes a difference between the third signal and the fourth signal to obtain a second signal Steering angle control device. 3. The subtraction device according to claim 1 or 2, wherein the first signal generation unit uses a difference between the target steering angle and the actual steering angle as a fifth signal, and a gain K for the fifth signal. A steering angle control device for a vehicle configured by a PID calculator that multiplies by to obtain a first signal. 4. The front compensator for transmitting the target steering angle command with a predetermined transmission characteristic to form a sixth signal, and the first steering signal for transmitting the actual steering angle signal according to claim 1 or 2. A steering angle control device for a vehicle, which is configured by a filter that passes a characteristic and outputs a seventh signal, and a subtractor that uses a difference between the sixth and seventh signals as a first signal.