JP2772031B2 - Electric power steering controller - Google Patents

Description

The present invention relates to an electric power steering controller for a motor vehicle, and more particularly to a protection circuit for checking a torque detection signal taken into the controller. The present invention relates to an electric power steering controller with improved safety.

(Prior Art) An electric power steering apparatus for an automobile has a torque sensor that detects a steering torque according to a torsional force of a steering shaft, and adjusts an output torque of the electric motor in accordance with the torque detection signal to perform steering operation. The torque assist control is performed so as to reduce the operation of the steering wheel.

Normally, the torque detection signal is detected as an analog amount, and the torque assist control is performed by a CPU such as a microcomputer. Therefore, the torque detection signal is once converted into a digital amount of torque detection signal by the A / D converter, and then various signal processing is performed.

(Problems to be Solved by the Invention) There is no problem if the torque detection signal taken into the CPU as described above is correctly A / D converted. However, the torque detection signal becomes abnormal due to any cause such as disconnection or failure. In particular, when a digital amount of torque detection signal is generated even though no steering torque is applied, the motor generates output torque on its own and is in a dangerous state. Further, if the motor torque is generated in the opposite direction to the direction in which the steering torque is applied, it becomes extremely dangerous for safe driving of the automobile.

The present invention provides an electric power supply having improved protection for driving a vehicle by providing a protection means for stopping a torque assist control when an abnormal state is detected by always checking a torque detection signal of an A / D converted digital amount. The aim is to get a steering controller.

[Configuration of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an electric motor that detects a steering torque of a steering system and generates an assist torque in accordance with the detected analog torque detection signal. An electric power steering controller having an assist torque control means for controlling, an amplification means having a limiter function and amplifying the analog torque detection signal at a constant amplification factor, and an analog torque detection signal amplified by the amplification means. Into a digital signal.
A / D conversion means, second A / D conversion means for converting the analog torque detection signal into a digital signal, and the first A / D conversion means.
The first digital signal converted by the A / D converter and the second digital signal converted by the second A / D converter are input, and the absolute value of the analog torque detection signal is amplified by the amplifier. If the value is equal to or greater than the limiter value of the means, the second digital signal is selectively output, and if the absolute value of the analog torque detection signal is smaller than the limiter value of the amplifying means,
First comparison output means for selectively outputting the first digital signal, D / A conversion means for converting the digital signal output by the comparison output means into an analog signal, and conversion by the D / A conversion means. A second comparison output means for comparing the analog signal with the analog torque detection signal and outputting a stop signal for reducing the assist torque to zero when a certain deviation occurs. Construct a steering controller.

(Operation) With the above configuration, the amplifying means having a limiter function amplifies the analog torque detection signal at a constant amplification factor, and converts the amplified analog torque detection signal into the first A / A signal.
It is converted to a digital signal by the D conversion means. Also, the second
A / D conversion means converts an analog torque detection signal into a digital signal. Then, in the first comparison output means,
The first digital signal converted by the first A / D converter and the second digital signal converted by the second A / D converter are input, and the analog torque detection signal is input. If the absolute value is greater than or equal to the limiter value of the amplification means,
The second digital signal is selectively output, and when the absolute value of the analog torque detection signal is smaller than the limiter value of the amplifying means, the first digital signal is selectively output. Thereafter, the D / A conversion means converts the digital signal output by the comparison output means into an analog signal, and the converted analog signal is compared with the analog torque detection signal by the second comparison means, and is converted to a constant value. If the deviation of
A stop signal for reducing the assist torque to zero is output.

(Embodiment) An embodiment of the present invention is shown in FIG. In the figure, 1
Outputs a torque detection signal T _R in accordance with the torsional force of the steering shaft (not shown) by the torque sensor. 2 was amplified torque detection signal T _R a preamplifier with a constant amplification factor signal
Output T _A. 3 outputs the control signal CS in response to the signal T _A control circuit made by the CPU. Reference numeral 4 denotes a motor drive circuit including a PWM control circuit and a power amplifier, reference numeral 5 denotes a current detector, reference numeral 6 denotes a motor, and reference numeral 7 denotes a steering mechanism for transmitting a motor output to a steering shaft as assist torque. Control circuit 3
A / D converters 10 and 15 for converting analog torque detection signals T _A and T _R into digital quantities, coefficient units 11 and 16, and a torque for determining a current reference I ^* according to the torque detection signal. current conversion means 12, a / D converter 14 for converting the analog current detection signal I _a into a digital quantity of the current detection signal I _F, I ^* and I _F compare the direction in which the deviation is reduced control signal CS Current control means 13 which outputs a switch 18 according to the torque detection signals T ₁ and T _2.
And a D / A converter 19 that switches the selected torque detection signal to an analog signal _Trc . 20 signal T _R and T by a comparator
_The stop signal STP is output to the motor drive circuit 4 when the _rc is compared and a predetermined deviation occurs.

In the above configuration, the output T _A of the preamplifier 2 is limited by the torque required for control, and the torque detection signal T ₁ via the A / D converter 10 and the coefficient unit 11 is ± T _L as shown in FIG. Output in range. Meanwhile, the torque detection signal T ₂ through the A / D converter 15 and the coefficient multiplier 16 is outputted while maintaining a proportional relationship.

To the A / D converters 10 and 15 and the same number of bits N torque detection signal T _1, a resolution of T ₂ are ^{_{T 0/2 N-1,}} T M / 2 N-1 towards the next T ₁ is highly accurate Thus, the torque within the control range of ± T ₀ can be detected with high accuracy. The torque detection signal T torque / current converting means in response to ₁ 12 determines the current reference I ^*. Various methods have been proposed and published for the decision method,
The description is omitted because it is not directly related to the present invention. Current reference
According to I ^* , the current control means 13 outputs a control signal CS, and the motor drive circuit 4 causes a current to flow through the motor 6. This current is detected by the current detector 5, and the current detection signal I is output through the A / D converter 5.
It is fed back as _F. As a result, the electric motor 6
A torque corresponding to ^* is generated, and the assist torque is transmitted to a steering shaft (not shown) via the steering mechanism 7.

Normally, the switch 18 selects the torque detection signal T ₁ , which is converted by the D / A converter 19 again into the analog value signal T 1.
Converted to _rc . The signal T _rc preamplifier 2, A / D converter 10, coefficient multipliers 11 is equal to the torque detection signal T _R in the torque in the control range of ± T ₀ if operating normally. Accordingly, the comparator 20 deviation Δe of T _R and T _rc enters the error range does not output a stop signal STP. If the deviation Δe exceeds a predetermined value for some reason, the comparator
Reference numeral 20 determines that an abnormality has occurred, outputs a stop signal STP, stops the operation of the motor drive circuit 4, and reduces the current of the motor 6 to zero.

The switch 18 comparator 17 when the torque detection signal T _R becomes large enough to exceed the range of ± T ₀ detects this is switched towards the torque detection signal T _2. This allows
Signal T _R and T _rc When operating normally even when exceeding the control range of T ₀ is equal comparator 20 stops the signal S
Do not output TP.

Incidentally, the comparator 17 the signal T ₂ reaches the level of ± T ₀ has a condition to enable its function, the value of the signal T ₁ is to prevent switching even exceed the ± T ₀ within the range ing.

Further, a pulse width modulation type can be used for the D / A converter 19.

According to the present embodiment, it is possible to A / D convert the torque detection signal in the control range with high accuracy.

In this embodiment, the motor drive circuit 4 is controlled by the stop signal STP.
As described above, the reliability and safety can be further improved if the power supply to the electric motor is cut off by an electromagnetic switch and the torque transmission of the clutch and the like is cut off at the same time. Can be.

〔The invention's effect〕

According to the present invention, the operation state of a series of signals of the input system until the detection signal of the torque sensor is taken into a control circuit such as a CPU and converted into a substantial torque detection signal is constantly checked, so that control reliability is improved. When an abnormality occurs in the flow of the signal, the assist torque is set to zero, and the steering operation is performed manually only, so that the safety of driving the vehicle can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
FIG. 4 is a characteristic diagram for explaining the operation of the present invention. 1 torque sensor 2 preamplifier 3 control circuit (CPU) 4 electric motor drive circuit 5 current detector 6 electric motor 7 steering mechanism 10,14,15 A / D converters 11, 16 Coefficient unit 12 Torque / current control means 13 Current control means 17 Comparator (1) 18 Switch 19 D / A converter 20 Comparator ( 2)

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shigeo Nishimura 3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka Inside Koyo Seiko Co., Ltd. (56) References JP-A-64-56274 (JP, A) JP-A-61-254829 (JP, A) JP-A-61-222869 (JP, A) Japanese Utility Model Showa 62-152880 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B62D 5 / 04 B62D 6/00

Claims (1)

(57) [Claims] An electric power steering controller comprising an assist torque control means for detecting a steering torque of a steering system and controlling an electric motor to generate an assist torque in accordance with the detected analog torque detection signal. Amplifying means having a function and amplifying the analog torque detection signal at a constant amplification factor; first A / D conversion means for converting the analog torque detection signal amplified by the amplification means into a digital signal; A second A / D converter for converting the analog torque detection signal into a digital signal; a first digital signal converted by the first A / D converter and the second A / D converter If the absolute value of the analog torque detection signal is greater than or equal to the limiter value of the amplifying means,
A second digital signal is selectively output, and when the absolute value of the analog torque detection signal is smaller than the limiter value of the amplifying means, the first digital signal is selectively output.
Comparison output means, D / A conversion means for converting a digital signal output by the comparison output means into an analog signal, and an analog signal converted by the D / A conversion means and the analog torque detection signal. And a second comparing means for outputting a stop signal for reducing the assist torque to zero when a certain deviation occurs.