JPS61122078A - Controller of motor type power steering device - Google Patents

Abstract

PURPOSE:To finely set the power shift by moving an assist direction motor current commanding value curve for the torsion torque signal of a steering shaft in parallel in response to vehicle speed, and loosening the gradient. CONSTITUTION:An adding arithmetic constant function portion 13 is constituted to generate a sensor voltage adding factor signal So, which is gradually decreased as vehicle speed increases. A signal S+ or -So is determined by an arithmetic portion 14, of which signal is obtained by adding or subtracting a voltage adding factor signal So to the torsion torque signal S of a torsion torque sensor 21. It is possible to move in parallel an assist direction motor current commanding value i in response to vehicle speed by inputting this signal S+ or -So to an output torque value indicating function portion 15. Further, it is possible to loose the gradient of functions i0-i2 by multiplying a vehicle speed factor signal from a multiplying arithmetic constant function portion 16 by functions i0-i2 of an assist direction motor current commanding value by means of an arithmetic portion 17, as the vehicle speed increases.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a control device for an electric power steering device for an automobile.

BACKGROUND ART In order to reduce the need for steering wheel operations during steering in automobiles, a torque sensor is provided to detect steering torque during steering operations, and the steering torque detected by the torque sensor is converted into an electrical quantity. An electric power steering device has already been developed in which the output of an electric motor is variably controlled according to changes in the amount of electricity, and the electric motor performs puff assist in the steering direction according to the steering torque. (See, for example, Japanese Patent Publication No. 45-41246).

Problems to be Solved by the Invention In the electric power steering cover as described above,
It has various problems as described below.

(1) If an attempt is made to provide sufficient puff assist when driving at low speeds, the steering force will become lighter when driving at high speeds, leading to slippage and excessive turning of the steering wheel.

(2) Due to a phase delay or the like in the electric circuit, a time delay occurs between when the torsional torque sensor detects the steering torque and when the electric motor generates the power assist. In such a case, the steering system becomes vulnerable to disturbances, and self-excited imaging is likely to occur during stationary steering.

Furthermore, since the electric motor provides power assist to the steering mechanism via the speed reducer, the responsiveness of the steering wheel becomes poor due to the inertia of the electric motor and the 7-force of the speed reducer.

(2) If the torsional torque sensor that detects the steering torque while driving is malfunctioning or the torque signal of the torsional torque sensor becomes abnormally large due to a short circuit in the wiring, etc., the torque signal from the torsional torque sensor becomes abnormally large and is not proportional to the steering force of the steering wheel. Excessive power assist is given, making it difficult for humans to operate the steering wheel by hand.

An object of the present invention is to provide an electric power steering device that can eliminate the drawbacks of the conventional devices as described above. In an electric power steering device that controls current to an electric motor according to the torsional torque of the shaft and provides power assist in the steering direction by the motor, the torque is determined based on the vehicle speed based on the steering shaft torsional torque signal. The assist direction motor current command value of the assist direction motor current instruction section that issues the assist direction motor current command value drives a control circuit that performs power assist control by the electric motor, and also differentiates the torsional torque signal of the steering shaft. A phase compensation unit is provided with a phase compensation unit that generates a signal proportional to the value, and the signal of the phase compensation unit is added to the torsional torque signal of the steering shaft, or a phase compensation current command value is generated in accordance with the signal of the phase compensation unit. Either or both of adding the assist direction motor current command value to the assist direction motor current command value via an instruction function section, and comparing the absolute value of the addition signal of the assist direction motor current command value and the phase compensation current command value with the vehicle speed. An output torque limit value determination section that determines the magnitude relationship between the vehicle speed limit command value and the vehicle speed limit command value, which issues a vehicle speed limit command value that gradually becomes smaller as the vehicle speed limit command value increases, and outputs the smaller one as an output signal. The present invention is characterized in that the power assist by the 10 motors is limited by the output signal.

Operation The present invention operates as follows by employing the above configuration.

(11. The assist direction motor current command value curve for the steering shaft torque signal is moved in parallel and tilted according to the vehicle speed, so the assist direction motor current command value increases as the vehicle speed increases.As the vehicle speed increases, the assist direction motor current command value curve gradually decreases as the vehicle speed increases.) This allows it to provide a suitable amount of power assistance when driving at high speeds.

(2) Adding a signal proportional to the differential value of the torsional torque signal of the steering shaft to the torsional torque signal K
It is possible to detect changes in the torsional torque signal and improve the responsiveness of the steering system.

(3) The magnitude relationship between the assist direction motor current command value that provides power assist and the vehicle speed limit value is determined, and the smaller signal controls the power assist by the electric motor, so the output of the torsional torque sensor is abnormal. Power assist can be limited even if the power is increased.

Example The present invention will be explained in detail with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes an assist direction motor current indicating section, which detects the torsional torque of the steering shaft and emits a torsional torque signal S proportional to the torsional torque, and detects the vehicle speed and emits a vehicle speed signal. A vehicle speed sensor 12, an addition calculation constant function section 13 that generates a sensor voltage addition coefficient signal So that gradually decreases as the vehicle speed increases, as shown in FIG. 2, and a senna obtained by the addition calculation constant function section 13. an addition calculation unit 14 that adds the voltage addition coefficient signal So and the torsional torque signal S of the torsional torque sensor 11; and an output torque value instruction function unit that issues an assist direction motor current command value t in response to the output signal of the addition calculation unit 14. 15, a multiplication constant function section 16 that generates a single continuous coefficient signal that gradually decreases as the vehicle speed increases, as shown in FIG. 4, a single continuous coefficient signal of the multiplication constant section 16, and the assist direction motor. 2 is a torsion ')) A phase compensation section consisting of a differentiating circuit or the like that differentiates the torque signal in place of the lux sensor 110 and extracts the change;
For example, as shown in FIG. The electric motor 4 is driven via the control circuit 3 with a μ signal obtained by adding the assist direction motor current command value and the phase compensation current of the phase compensation instruction function unit 21, and power assist is given to the coffee fire mechanism 5. It has become.

The control circuit 3 includes a positive/negative determination ff1s31 that determines whether the added signal of the assist direction motor current command value i and the phase compensation current command value ip is positive or negative, and the absolute value of the added signal +i+
An absolute value conversion unit 33 that takes ip +, and the positive/negative determination unit 31
An electric motor 4 drive unit 32 that determines the rotation direction of the electric motor based on the signal and drives the electric motor 4 based on the current command value of the absolute value conversion unit 33, and an electric motor detected by the armature current detection unit 35. and a duty control section 34 that performs duty control by comparing the armature current with the current command value of the absolute value conversion section 33.

Reference numeral 6 denotes an output current limiter, and the output current limiter 6 issues a vehicle speed limit command value that gradually decreases as the vehicle speed signal from the vehicle speed sensor 12 increases, as shown in FIG. The instruction function section 61 is interposed between the absolute value conversion section 33 and the duty control section 34 of the side circuit 3 to convert the current command value of the absolute value conversion section 33 and the vehicle speed limit value instruction function section 61. Determine the magnitude relationship with the vehicle speed limit command value,
The first feature of the present invention configured as described above is to provide the steering mechanism with an appropriate power assist according to the vehicle speed. The assist direction motor current command value curve corresponding to the torsional torque signal from the torsional torque sensor 11 of the steering shaft is moved in parallel and tilted in accordance with the vehicle speed.

That is, as shown in FIG. 2, the addition calculation constant function section 13 is energized so as to generate a sensor pressure addition coefficient signal S0 that gradually decreases as the vehicle speed increases.
4, a signal S±Sa is obtained by adding or subtracting the sensor voltage addition coefficient signal So to the torsion torque signal S of the torsion torque sensor 21 (subtracted when the torsion torque signal is negative). The above signal S±80 is outputted by the torque value instruction function section 15.
By inputting the auxiliary direction motor current command value i, which has one basic function as shown by the dashed line in Fig. 3, in response to the complex torque signal S, in parallel according to the vehicle speed, as shown by the solid line in Fig. 3. can be done.

That is, in FIG. 3, number a represents the assist direction motor current command value when the vehicle speed is zero Va, and as the vehicle speed increases, V
, , As it becomes V2, it gradually becomes L2. ii, the assist direction motor flow command value for a certain value of the torsional torque signal gradually decreases as the vehicle speed increases, making it possible to provide appropriate power assist at high speeds.

Further, when the sensor voltage addition coefficient signal So is a function that increases with vehicle speed, a signal 8 is obtained by subtracting or adding the sensor voltage addition coefficient signal So to the torsional torque signal S.
By inputting this into the output torque value instruction function unit 15, the same torsional torque signal versus assist direction motor current command value characteristic as described above can be obtained (however, l S l (Se
At 2 o'clock, S+''So = 0).

As shown in FIG. 4, the multiplication constant function section 16 is configured to issue a vehicle speed coefficient signal that gradually decreases as the vehicle speed increases, and the multiplication operation section 17 uses the vehicle speed coefficient signal to output the output torque value instruction. Each function Lo of the assist direction motor current command value is shifted in parallel with the vehicle speed by multiplying each function 'Or'++'2 (shown by solid line in FIG. 3) of the assist direction motor current command value of the function section 15.

As the vehicle speed increases, the slope of 'I + L2 can be made gentler as shown in the figure 3.

In the above embodiment, the assist direction motor current command value is determined based on the addition signal of the torsion torque signal and the senna voltage addition coefficient signal, and control is performed using a multiplication signal obtained by multiplying the assist direction motor current command value by the vehicle speed coefficient signal. Although an example has been given in which the circuit 3 is controlled, the control circuit 3 may be driven by the flow command value of the assist direction motor based on the addition signal of the torsion torque signal and the sensor voltage addition coefficient signal, or the control circuit 3 may be driven by the flow command value based on the addition signal of the torsion torque signal and the sensor voltage addition coefficient signal. Of course, the assist direction motor current command value may be obtained and the control circuit 3 may be controlled by a signal multiplied by the assist direction motor current command value and the vehicle speed coefficient signal.

The second feature of the present invention is a phase compensator 2 that compensates the phase of the torsional torque signal of the torsional torque sensor 11 in order to cope with the response delay of the steering string, and a phase compensation current command based on the output of the phase compensator 2. This is because a phase compensation indicating function unit 21 that emits a value is provided.

That is, in the conventional electric power steering device,
When the torsional torque signal reaches a predetermined value during steering of the steering wheel, the control circuit starts operating based on that signal.Therefore, there is a dead zone in which no output voltage is generated on both the left and right sides when the vehicle is traveling straight, and the electric Due to reasons such as delays in signal transmission in the circuit, the power assist may not work until after the steering wheel is operated, causing the driver to feel discomfort when steering, or causing vibrations when steering the vehicle stationary. There is.

To address these problems, the present invention uses phase compensation fi
! is2 to obtain a signal proportional to the differential value of the torsional torque signal of the steering shaft, and add this signal to the torsional torque signal. An assist direction motor current command value given by the output torque value instruction function section 15 based on the signal;
For example, as shown in FIG. 5, the control circuit uses an addition signal obtained by adding the phase compensation current command value of the oral function unit 21 to the phase compensation unit 21 which generates the phase compensation current command value according to the output signal of the phase compensation unit 2. 3.

By adopting the above configuration, it is possible to not only improve the followability of the power assist by the electric motor, but also to prevent the occurrence of self-excited vibrations when stationary, and to absorb the effects of inertia of the electric motor during high-speed driving. It is possible to remove the discomfort of

In the above embodiment, the assist direction motor i [command value is determined by the output torque value instruction function section 15 based on the addition signal of the torsional torque signal of the torsional torque sensor 1 and the output signal of the phase compensation section 2. Furthermore, the assist direction motor electric current is 0.
An example was given in which the control circuit 3 is controlled by the addition signal obtained by adding the command value and the phase compensation current command value of the phase compensation instruction function unit 210. The rear neck is mainly used to absorb the inertia of the electric motor during high-speed driving and eliminate the discomfort during steering, so one or more of the two or only one of the two can be used as necessary. Of course, it is possible.

A fifth feature of the present invention is that a safety device is provided for the case where an excessive power assist that is not proportional to the steering of the steering wheel is provided due to a failure of the torsional torque sensor that detects the torsional torque of the steering shaft while driving. That's true.

That is, in the present invention, a vehicle speed limit value instruction function section 61 is provided which gives a vehicle speed limit command value that gradually decreases as the output of the vehicle speed sense 12 becomes larger, and the vehicle speed limit command value and the assist direction motor flow ratio are an output torque limit value determining unit that determines the magnitude relationship with the assist direction motor current command value of the display unit 1, and outputs the vehicle speed limit command value when the assist direction motor current command value is smaller than the vehicle speed limit command value; 62 is provided, and the output torque limit value determination section 62 is connected to the control circuit 3.
It is interposed between the absolute value converting section 33 and the duty system @1 section 34.

In the conventional device, the relationship between the torsional torque signal of the torsional torque sensor 11 and the assist direction motor current command I of the assist direction motor current instruction section 1 that provides power assist is W, as shown by the curve in Figure 6. As the torsional torque signal increases, the assist direction motor current command value gradually increases, so if the output becomes abnormally large due to a failure of the torsional torque sensor 11, the assist direction motor current command value also increases accordingly, resulting in a large power output. In contrast, the present invention sets a vehicle speed limit command value that gradually decreases as the vehicle speed increases, as shown in the curve shown in FIG. When the assist direction motor current command value becomes larger than the vehicle speed restriction command value, the control circuit 3 is controlled by the vehicle speed restriction command value.

In Figure gg6, when the vehicle is stationary and the vehicle speed is zero, a motor current with an upper limit of vehicle speed limit command value A is given as power assist, so the torsional torque signal becomes abnormally large due to a failure of the torque sensor 21, etc. mentioned above. Even when)
The motor radio wave given as a brake assist never exceeds A when the vehicle is stationary, and never exceeds B when the vehicle speed is V.

Effects of the Invention By employing the above configuration, the present invention can bring about many practical effects as described below.

(11. The assist direction motor current command value curve for the torsional torque signal of the steering shaft is moved in parallel according to the vehicle speed, and its slope is made gentle, so the magnitude of the power assist due to the rotation of the electric motor is reduced. It can be set in detail according to the vehicle speed.

(2) A signal proportional to the differential value of the steering shaft torque signal is obtained, and based on the signal added to the above-mentioned torsional torque signal, the assist direction motor given by the output torque value instruction function section is set as the flow command value. Since the electric motor is rotated by the addition signal obtained by adding the phase complement @ current command value according to the signal proportional to the differential value of the above-mentioned torsional torque signal, the delay due to the transmission of M4'y in the electric circuit In addition to improving the followability of power assist, it also prevents vibrations from occurring when the vehicle is stationary, and eliminates the strange feeling of steering caused by the inertia of the electric motor during high-speed driving.

(3) Set a vehicle speed limit command value that gradually decreases as the vehicle speed increases, and when the assist direction motor current command value becomes larger than the vehicle speed limit command value, the vehicle speed limit command value is set to Since the power assist is controlled by one torque, even if the output of the torsional torque sensor becomes abnormally large due to a malfunction of the steering shaft bias torque sensor, an upper limit can be given to the power assist, so manual steering is no longer required. It can be prevented from making things difficult.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a sensor voltage addition coefficient signal characteristic diagram, FIG. 3 is an explanatory diagram showing changes in assist direction motor current command value curve depending on vehicle speed, and FIG. The figure is a characteristic diagram of a single continuous coefficient signal, Figure 5 is a characteristic diagram of the phase compensation chamber n, command (11), and Figure 6 is a characteristic diagram of the vehicle speed limit command I. . . . Phase compensation unit, 3. Control circuit, 4. Electric motor, 5.
... Steering mechanism, 6... Output current limiting section. that's all

Claims (4)

[Claims] (1) In an electric power steering device that controls the current to an electric motor according to the torsional torque of the steering shaft and uses the motor to provide power assist in the steering direction, the torsional torque signal of the steering shaft is Based on the assist direction motor current command value of the assist direction motor current instruction section that issues an assist direction motor current command value determined based on the vehicle speed, a control circuit that performs power assist control by the electric motor is driven, and the torsion of the steering shaft is A phase compensation section that emits a signal proportional to the differential value of the torque signal is provided, and the signal of the phase compensation section is added to the torsional torque signal of the steering shaft, or a phase compensation current command value is determined according to the signal of the phase compensation section. The absolute value of the addition signal of the assist direction motor current command value and the phase compensation current command value is added to the assist direction motor current command value through a phase compensation instruction function unit that generates An output that determines the magnitude relationship between the vehicle speed limit command value and the vehicle speed limit command value of the vehicle speed limit value instruction function section that issues a vehicle speed limit command value that gradually decreases as the vehicle speed increases, and outputs the smaller one as an output signal. A control device for an electric power steering device, characterized in that power assist by an electric motor is limited based on the output signal of the torque limit value determining section. (2) The assist direction motor current instruction section includes a torsional torque sensor that emits a torsional torque signal of the steering shaft, and an addition calculation constant function section that emits a sensor voltage addition coefficient signal that gradually decreases as the vehicle speed increases; Claim 1, further comprising: an output torque value instruction function section that issues an assist direction motor current command value based on the addition signal of the torsion torque signal and the sensor voltage addition coefficient signal. Control device for electric power steering device. (3) The assist direction motor current instruction section includes a torsional torque sensor that issues a torsional torque signal of the steering shaft, an output torque value instruction function section that issues an assist direction motor current command value based on the torsional torque signal, and a and a multiplication calculation function section that generates a multiplication signal of the assist direction motor current command value and the vehicle speed coefficient signal. A control device for an electric power steering device according to claim 1. (4) The assist direction motor current instruction unit includes a torsional torque sensor that generates a torsional torque signal of the steering shaft, and an addition calculation constant function unit that generates a sensor voltage addition coefficient signal that gradually decreases as the vehicle speed increases; An output torque value instruction function section that issues an assist direction motor current command value based on the addition signal of the above-mentioned torsion torque signal and the sensor voltage addition coefficient signal, and a multiplier that issues a vehicle speed coefficient signal that gradually decreases as the vehicle speed increases. The electric power steering according to claim 1, comprising a calculation constant function section and a multiplication calculation section that generates a multiplication signal of the assist direction motor current command value and the vehicle speed coefficient signal. Device control device.