JPS61261166A - Car speed responsive controlling method in power steering device - Google Patents

Abstract

PURPOSE:To prevent a wheel from getting steering delayed or oversteered, by performing steering control on the bass of a car speed signal when the car speed signal out of a car speed sensor normally varies but when it abnormally varies, performing the existing control as it is. CONSTITUTION:A car speed sensor 10 outputs a pulse signal, and this output pulse is inputted into a microcomputer 12 by way of a waveform shaping circuit 11. The microcomputer 12 outputs a control signal corresponding to a car speed when the car speed normally varies on the basis of this signal. With this control signal, an actuator 14 is operated via a drive circuit 13 whereby a power steering 15 is controlled according to the car speed. At the time of an abnormal car speed signal at wheel racing or locking, etc., the microcomputer 12 maintains the output of a control signal being outputted prior to the abnormal car speed. Therefore, the power steering 15 is controlled by this control signal independently of the abnormal car speed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a power steering device for a vehicle, that is, a vehicle speed response control method in a power steering device.

(Prior art) A power steering device supplements the steering force provided by steering wheel operation with the steering force provided by hydraulic pressure or an electric motor, so it is effective when stopped or driving at low speeds, but when driving at high speeds. When driving, the steering force becomes too light and there is no response, making it impossible to obtain stable steering operation. A vehicle speed response control type power steering device solves this problem, but the conventional vehicle speed response control method obtains a speed signal from the axle or vehicle speedometer, generates hydraulic pressure according to the signal, and then transmits it to the power steering device. A reaction force chamber provided in a part of the vehicle generates a reaction force that corresponds to the speed of the vehicle, giving a responsive feel to the steering wheel. By the way, since the conventional vehicle speed response control method uses vehicle speed signals obtained from the axle, transmission, speedometer, etc. as they are, it is not always possible to obtain a signal proportional to the vehicle speed. That is, when the drive shaft of the vehicle is idling, the vehicle speed signal indicates a value faster than the actual vehicle speed, and when the drive shaft is locked due to sudden braking, etc., the vehicle speed signal indicates a slower value. As a result, the steering force is not controlled in response to the vehicle speed, and when the vehicle is idling, the reaction force from steering becomes too large, causing a delay in turning the steering wheel.When the vehicle is locked, the reaction force is too small, causing the steering wheel to be too light. There is a possibility of cutting too much, which poses a safety problem.

(Purpose) The present invention aims to solve the above-mentioned problems by preventing the steering wheel from being turned too late or too much, and even if the vehicle speed sensor fails, the vehicle can be controlled to the state immediately before the failure. .

(Configuration) In order to solve the above-mentioned problems, the present invention does not directly use the signal obtained from the vehicle speed sensor for control.
The amount of change is compared with the standard fluctuation width, and if the change is within a predetermined range, control is performed according to the vehicle speed signal, but if the change exceeds the predetermined range, the control is performed before the change occurs. maintain control of. As means for determining whether or not the change is within the reference fluctuation range, there are methods using a microcomputer and methods using a low-pass filter.

If the amount of change in the signal obtained from the vehicle speed sensor exceeds the predetermined range when compared with the standard fluctuation range, that is, the change is not normal, which means that the above-mentioned idling acid lock condition has occurred. However, in this case, the previous normal control is maintained, so there is no risk of incorrect control.

Next, a detailed description will be given based on an example.

FIG. 1 shows an example of the control system of the present invention. 10
The vehicle speed sensor is composed of a reed switch, and outputs, for example, four pulses per rotation of the output shaft of the transmission. This output pulse is given to the microcomputer 12 via the waveform shaping circuit 11, where it undergoes predetermined processing and becomes a control signal, which is then supplied to the actuator 14 via the drive circuit 13. The actuator 14 acts on the power steering device 15 to control its steering force or reaction force in accordance with the vehicle speed.

FIG. 2 shows the signal processing performed by the microcomputer 12. In other words, if the pulse signal (pulse frequency) P from the vehicle speed sensor 10 gradually increases or decreases or shows a constant value, it can be considered that it is proportional to the vehicle speed, but it is indicated by point a. If there is a sudden increase in
If there is a sudden decrease as shown at point b, it should be detected that a lock has occurred. Therefore, in these cases, the vehicle speed response control of the power steering device 15 should not be performed based on the peak value, and the control should be performed based on the values at points A and B before those changes, instead of points a and b. It is. The microcomputer 12 performs such signal processing, and FIG. 3 is a flowchart thereof, in which (A) is an overall diagram, (B) is a detailed diagram of the control vehicle speed data determination routine, and (C) is a control diagram. FIG. 3 is a detailed diagram of a data input routine.

The pulse signal output from the vehicle speed sensor 10 is shaped into a square wave by a waveform shaping circuit 11 and then input to the microcomputer 12 .

The microcomputer 12 calculates the vehicle speed from the input pulse signal in a vehicle speed calculation routine 31 and stores it. This memory is an example.

The past three samplings (sampling is done at regular intervals) 1. C2. ν, is.

Based on these, the predicted value ν of the current vehicle speed. is required and it is also memorized. Needless to say, this predicted value ν. is rewritten every sampling. The loop arrows in FIG. 3(A) indicate that sampling is repeated one after another and control is performed using new data each time.

Normally, the flag V is reset, so the processing by the microcomputer goes to the No side in the determination section 33, and the vehicle speed data ν, which was input from the vehicle speed calculation routine 31 to the control vehicle speed data determination routine 32 in this sampling, is , predicted value ν. compared with ν, −ν. = Δ is calculated (the previous data ν3 may be used instead of the predicted value ν). This difference Δ is compared with a preset reference variation width α in the discrimination unit 34, and its absolute value 1ΔI If is not larger than α (there is no rapid change in vehicle speed), the process passes through the No side and the vehicle speed data ν is directly provided to the control data input routine 35 as control vehicle speed data. As shown in FIG. 3(C), the control data input routine 35 determines control data from the control vehicle speed booter and sets output data. This output data is given to the next stage drive circuit 13.

If the determination result of the determination unit 34 is 1Δ1>α, that is, if the change in vehicle speed is rapid as shown in FIG. 4, the microcomputer's processing passes to the YES side and the reflag V is set. Then, as the control vehicle speed data, the current control vehicle speed Y is maintained as it is (the expected value ν may be used as the control vehicle speed data). Since the flag V is set at the time of the next sampling, the determination unit 33 is set to the YES side. Then, the difference γ=T, -ν3 between the vehicle speed data v5 obtained by sampling and the current control vehicle speed data data is calculated. This difference γ
The feed value 1γ1 of - is compared with a predetermined reference value E in the determining section 36.

If 1γ1≦E (this means that the sudden change in vehicle speed has stopped), the flag V is reset and the current input vehicle speed data ν is output as control vehicle speed data. Therefore, during the next sampling, the determining section 33 opens to the No side. If 1γ1≦ε, the 1 discriminator 36 exits from the No side.

At this time, two methods may be used depending on the case. The first method is the flow shown by the broken line, and in this case, the current vehicle speed γ, (orγ.) is maintained as it is as the control vehicle speed data. Therefore, the current control state of vehicle speed control is maintained until 1γ1≦ε. The second method is the flow shown by the solid line, and the input vehicle speed data γ.

is compared with the previous input vehicle speed data ν, and their difference β=
ν,−ya, is calculated. The predicted value ν between this difference β and the previous vehicle speed booter. Each sign of the difference Δ from the discriminator 37
They are compared and have different signs (Figure 4 A, where the sudden change in vehicle speed is starting to subside).

B), the vehicle speed data is YE of the discriminator 37.
Exit from the S side, reset the flag V, and set the control vehicle speed data ν
, is output with a roar. If Δ and β have the same sign (in the case of Fig. 4C where the sudden change in vehicle speed is still continuing),
The vehicle speed data γ, is output from the No side of the determining unit 37, and is not used as the control vehicle speed data, but the current control vehicle speed data γ, (or ν) is output as is as the control vehicle speed data.

FIG. 5 shows an embodiment of the second invention.

In the second example, the pulse signal obtained by the vehicle speed sensor 10 is converted into a voltage according to the vehicle speed by the frequency-voltage conversion circuit 16, and then passed through the low-pass filter 17 to the drive circuit 1.
given to 3.

As shown in Fig. 6, if the output of the frequency-voltage converter 16, which is supposed to indicate the vehicle speed, suddenly changes discontinuously, this is due to slipping, locking, etc., and does not indicate the actual vehicle speed. 17 is such a sudden change,
In other words, since high frequency components are cut, the output signal does not include the effects of idling, locking, etc. The cutoff frequency of the 0-mouth, 1-pass filter 17 is determined by the expected maximum acceleration when the vehicle accelerates or decelerates. This achieves the same purpose as the means for setting the standard fluctuation range of the first invention.

(Effects) As described above, in the case where the change in the vehicle speed signal obtained from the vehicle speed sensor is greater than a predetermined width, the present invention does not regard it as the actual vehicle speed and maintains the previous control state. Therefore, unlike control based on the apparent vehicle speed, delays in turning the steering wheel or turning the steering wheel too much can be prevented, and safety can be improved. In addition, if the output of the vehicle speed sensor is cut off due to some kind of failure while driving at high speed, conventional control methods determine that the vehicle speed is zero and control the steering wheel to become too light, which is dangerous, but according to the present invention, at least The previous control state can be maintained, the steering force will not be reduced, and danger can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an example of the control system of the first invention, Fig. 2 is a graph showing temporal changes in vehicle speed signals, Fig. 3 is a flowchart of control vehicle speed data processing by a microcomputer, and Fig. 4 is a vehicle speed It is a graph showing the relationship between signal changes and control vehicle speed data, and A and C show the slip that occurred during acceleration. B indicates a lock that occurs during deceleration, and C indicates a case where the idle period is long. FIG. 5 shows an example of the control system of the second invention,
FIG. 6 is a graph showing temporal changes in the output voltage of the frequency-voltage conversion circuit. 10...Vehicle speed sensor 12...Microcomputer 15...Power steering device 17...Low pass filter 32...Control vehicle speed data determination routine ν2. Ya,
...Vehicle speed signal ν. ...Expected vehicle speed signal Δ...Amount of change α...Reference fluctuation width -τ (during acceleration), (R1 Fig. 4 (R1)

Claims (4)

[Claims] (1) In a vehicle speed response control method in a power steering device that inputs a vehicle speed signal and controls steering force as a function of vehicle speed,
It is determined whether the amount of change of the vehicle speed signal from the vehicle speed sensor at each sampling or the difference from the expected vehicle speed signal exceeds a reference fluctuation range, and if it does not exceed the reference fluctuation range, control is performed based on the vehicle speed signal. A vehicle speed response control method characterized in that the current control is maintained at least until the next sampling if the vehicle speed is exceeded. (2) In a state where the current control is maintained, normal control is returned to when the vehicle speed signal at the next sampling becomes approximately equal to the vehicle speed signal corresponding to the maintained state. The vehicle speed response control method according to item 1. (3) The feature is that while the current control is maintained, it is detected that the direction of change in the vehicle speed signal during the next sampling is opposite to the direction of change in the previous vehicle speed signal, and the control returns to normal. A vehicle speed response control method according to claim 1 or 2. (4) In a vehicle speed response control method in a power steering device that inputs a vehicle speed signal and controls steering force as a function of vehicle speed,
A vehicle speed response control method characterized in that an analog electrical signal is used as a vehicle speed signal and is used as a control signal through a low-pass filter whose cutoff frequency is determined by the maximum expected acceleration of the vehicle.