JPH0234469A - Electric power steering device - Google Patents

Abstract

PURPOSE:To eliminate inertial feeling of steering due to inertia of a rotor by allowing a differential gain of differential calculation unit for differentiating a torque signal from a torque sensor to respond to a car speed so that the differential gain is reduced on the low speed side and increased on the high speed side. CONSTITUTION:By a torque output signal obtained on MPU49 of a motor control device receiving output signals from a torque sensor 3 for detecting steering torque acting on the input shaft 2 connected to a handle, and a car speed sensor 4, the device inscribed in the caption drives a motor M to give its power to a steering mechanism as a steering auxiliary power. In this instance, a car speed induction circuit 59 receiving a car speed signal processed by a car speed processing circuit 46 connected to the speed sensor 4 is provided. This circuit processes a differentiation signal from a differentiation circuit 17 receiving torque signals and obtaining the rate of change of torque as a function of car speed, using the car speed signal, and controls the differential gain so that it is reduced on the low speed side and increased on the high speed side.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electric steering device that eliminates rotor inertia of an electric motor and prevents vibration.

(Prior Art) The conventional electric power steering device shown in FIG. 7 has a torque sensor 3 connected to a steering wheel 1, and this torque sensor 3 is connected to a function generator 16 and a differentiation circuit 17. A vehicle speed sensor 4 is also connected to the function generator 1B, so that the function generator 16 outputs a torque signal corresponding to the vehicle speed.

The output signal of the function generator 18 and the output signal of the differentiation circuit 17 are added and input to the steering angle correction circuit on the same day. This steering angle correction circuit 18 includes a steering angle sensor 15.
is connected, and the difference between the actual steering angle and the steering angle of the steering wheel 1 is corrected.

The steering angle signal corrected as described above is determined by the forward/reverse direction determining circuit 18 as to whether it is forward or reverse, and is transmitted to the electric motor M. When the steering angle signal is transmitted to the electric motor M, the electric motor M is driven in accordance with the signal and steers the tires 14 via the speed reducer 7.

(Problems to be Solved by the Invention) The conventional device configured with the above circuit produces a steering feeling as if a weight is attached to the tip of the steering shaft due to the effect of the rotor inertia of the electric motor M. This feeling is especially noticeable at medium and high speeds. Therefore, in order to correct the delay due to the inertia of the rotor of the electric motor M in this conventional device, it is conceivable to increase the differential gain.

However, when the gain of the torque derivative is increased, the reaction to sudden changes becomes excessive, and therefore vibrations are more likely to occur during steering, and this vibration becomes particularly intense when the vehicle is stopped or at low speeds. In order to eliminate the inertial path of the steering, it is desirable to increase the differential gain, but on the other hand, increasing the differential gain causes vibration. Therefore, there is a problem in that a differential gain sufficient to cancel out the rotor inertia of the electric motor cannot be obtained, and a steering inertia path remains.

An object of the present invention is to provide a device that eliminates the steering inertia path caused by rotor inertia and prevents vibrations when the vehicle is stopped or at low speeds.

(Means for Solving the Problems) The present invention provides an electric power steering device that includes a function generation circuit that outputs an output torque signal according to driving conditions such as vehicle speed, and that controls an electric motor using the output signal of the function generation circuit. This is based on the premise that

Based on the above device, the present invention includes a torque sensor that detects steering torque, a torque signal processing circuit that outputs a voltage signal according to the output of the torque sensor,
A vehicle speed sensor that detects vehicle speed, a vehicle speed signal processing circuit that outputs a voltage signal according to the output of the vehicle speed sensor, and a differential processing section that differentiates the output signal of the torque sensor, and a differential gain of the differential processing section. is sensitive to vehicle speed, and the differential gain is small on the low speed side and large on the high speed side.

(Operation of the present invention) Since the present invention is configured as described above, the torque signal detected by the torque sensor is subjected to differential processing, and the differential gain is made responsive to vehicle speed.

(Effects of the Present Invention) According to the electric power steering device of the present invention, the gain of torque differentiation is made responsive to vehicle speed, and the gain is small on the low speed side and large on the high speed side, thereby reducing the steering inertia path at high speeds. This cancels out vibrations and also prevents vibrations from occurring in the steering wheel at low speeds.

(Embodiment of the present invention) In the first embodiment shown in FIGS. 1 to 5, a pinion 9 is connected to the tip of a steering input shaft 2 connected to a handle l, and this pinion 9 is engaged with a rack 5. . Both sides of the rack 5 are connected to knuckle arms 10 of a tire 14 via side rods 11. Further, a speed reducer 7 is connected to the electric motor M which is capable of forward and reverse rotation. A pinion 13 is connected to the tip of the output shaft of this speed reducer 7, and this pinion 13 is engaged with the rack 5.

Further, the input shaft 2 is provided with a torque sensor 3 that detects the steering torque acting on the input shaft 2. Additionally, a vehicle speed sensor 4 is provided to detect the vehicle speed of the vehicle.
Each of these sensors is connected to a motor control device 6.

The torque signal Tin detected by the torque sensor 3 is sent to a torque signal processing circuit 41 provided in the motor control device 6,
It is input to the torque sensor abnormality detection circuit 45.

The torque signal vl outputted from the torque signal processing circuit 41 is sent to a forward/reverse direction determination circuit 19 that determines the direction of the torque, an absolute value converting circuit 43, and a differential value C, which differentiates the torque signal v1, and and a differentiating circuit 17 for converting it into V, respectively. Then, a torque forward/reverse signal T is outputted from the determination circuit 18.

is input to the input port A+ of the microprocessor 49 which corresponds to the function generating circuit of the present invention.

The differentiation circuit 17 is connected to a vehicle speed sensitive circuit 59.

Further, the signal v1 input to the absolute value conversion circuit 43 is converted into an absolute value therein, and this absolute value 1v11 is converted into a digital value by the A/D conversion circuit 44.

The torque level signal TI converted into a digital value is input to the input port A2 of the microprocessor 43.
7) If IVll=O is zero, lVII=m a x
corresponds to 255.

The vehicle speed signal V detected by the vehicle speed sensor 4 is input to a vehicle speed signal processing circuit 46 and a vehicle speed sensor abnormality detection circuit 45.

The vehicle speed signal VS processed by the vehicle speed signal processing circuit 4B is sent to an interrupt port l of the microprocessor 48.
It is input to the vehicle speed sensitive circuit 59 as well as to the NTl.

Note that the vehicle speed signal processing circuit 48 outputs a pulse train according to the vehicle speed, for example, O pulses/second when the vehicle speed is Ok/h;
40 pulses/second at 40km/h.

At 100ks/h, a pulse train of 100 pulses/second is output. Then, when this pulse signal rises or falls, interrupt baud)
An interrupt is generated in lNTl.

Furthermore, the output signals of each of the abnormality detection circuits 45 and 47 described above are inputted to the interrupt port INT2 of the microprocessor-49 via an OR gate 48.

The output port C1 of the microprocessor 48 outputs a forward/reverse signal MO specifying the rotational direction of the electric motor M, and the output port C2 outputs a digital output level signal Ml. Level signal MO
.

In other words, the torque output signal output from this D/A conversion circuit 50 is configured to change depending on the steering torque and vehicle speed.

The vehicle speed sensitive circuit 59 processes the differential signal C,*1 sent from the differentiating circuit 17 using the vehicle speed signal Vs sent from the vehicle speed signal processing circuit as shown in the following equation.

G+v1=(+V+XF(Vs)) Here, Fffs is a function determined by the vehicle speed, and changes as shown in the curve shown in FIG. 3, for example.

, that is, the output signals C', G from the vehicle speed sensitive circuit 58
, depends on both the rate of change of torque and the vehicle speed, and it is possible to control the torque differential gain by decreasing it on the low speed side and increasing the gain on the high speed side.

The output signal voltages d and Q and the torque signal voltage v2 sent from the D/A conversion circuit 50 and subjected to vehicle speed sensing are added in a first addition circuit 54.

i'J pressure V3=C'lt1+V2 is obtained.

A signal v3 for controlling the motor drive circuit 52 is output from the first addition circuit 54, and the electric motor M is controlled by this signal V3.

Further, the output capacitor C3 outputs a pulse indicating that the program is running normally, and this output signal is input to the OR gate 48 via the watch spike processing circuit 51.

The sensitive circuit 58 includes a second adder circuit 54 in addition to the first adder circuit 54
Although it is also connected to an adder circuit 57, this second adder circuit 5
7 is also connected to the torque signal processing circuit 41, so that the output signal v1 of the torque signal processing circuit 41 is input to the second addition circuit 57.

Therefore, from this second addition circuit 57, the signal v
1 and the differential signal (', 9.), a signal v4 is output.

An input/output check circuit 58 is connected to the second addition circuit 57, and this input/output check circuit 58 is connected to the current sensor 55 via a current signal processing circuit 58. The current sensor 55 detects the current supplied to the electric motor M, and the current signal processing circuit 5
6 outputs a signal v5 in accordance with the output signal of the current sensor 55. The input/output check circuit 58 configured as described above uses the output signal v4 of the second addition circuit 57 as the input signal X, and the output signal v5 of the current signal processing circuit 56 as the output signal y, as shown in FIG. These x and y coordinate points are in the normal range N
l, N2, dead band F+, F2, first output abnormality area Ul, U2 or second output abnormality area U3,
It is determined which of Ua it is located in.

The dead bands Fl and F2 appear in the first and second quadrants, respectively, and the dead band F1 in the second quadrant is
is in the range where the input signal
0, the output signal y is in the range y>−To.

The above-mentioned first output abnormality castles U, , U2 are in the ① quadrant and ②
Appears in each of the quadrants, and the second output abnormal area U3, U
4 appears in the I-quadrant and the I-quadrant.

In other words, in the first output abnormality region U1, the input signal X is x<
0, the output signal y is in the range Y>To, and the second output abnormal area U3 is such that the input signal
It is in the range of l.

Further, in another first output abnormality castle U2, the input signal X is
, the output signal y is in the range of y<-yo, and the second output abnormal region U4 is such that the input signal X is in the range of X>-XO and the output signal y is in the range of 7<-
-71 range.

As mentioned above, when the x, y coordinate point is in either of the above 1.2 output abnormality castles U, -04, it is determined that the output y is abnormal with respect to the input X, and the motor drive circuit 52 to stop the electric motor M. When the input/output coordinate points x, y are in a range other than the first and second output abnormality areas U, -04, it is not determined to be abnormal, and the power steering state is continued.

Further, the output port C3 outputs a pulse indicating that the program is running normally, but this output signal is sent to the OR via the watch spike processing circuit 51.
The signal is input to gate 48.

Thus, the signal V output from the torque signal processing circuit 41 is combined with the output signals C and G from the vehicle speed sensing circuit 59.

The input/output check circuit 58 checks the signal V4=x which is the sum of the signals V4=x and the signal V5=y detected by the current sensor 55, and when the direction of the output signal y differs from the direction of the input signal X, In other words, when the input/output coordinates X, 7 are in the first output abnormality range Ul, U2, the abnormality signal H is output, the motor drive circuit 52 is controlled, and the electric motor M is stopped.

Furthermore, when the input signal The output signal controls the motor drive circuit 52 and stops the electric motor M.

Note that in this embodiment, a second adder circuit 57 is provided to
= vl+c, v, is found, ko (7) V a (7)
(I) The reason why the signal v5 on the output side is compared is that the signal v3 outputted from the first addition circuit 54 has already been converted into the differentiated signal C1*1 by the vehicle speed sensitive circuit 59,
Since the value converted to 1 is added, the purpose is to balance it with that.

FIG. 6 shows a second embodiment, in which torque differentiation is performed by software of the microprocessor 49 rather than by a hard differentiation circuit. Here, the input forward/reverse signal To and level signal TI are converted into a signed torque signal T, and the differential value T thereof is 7== ("r (ten Δt) - T (t)) / Δt
This is obtained by adding the output value after sensing the vehicle speed, resulting in M=M+klT, which is divided into an output forward/reverse signal Mo' and an output level signal Ml'.

Note that 1 is a constant determined by the vehicle speed.

(See Figure 4) Therefore, the voltage after D/A conversion is V2 =
It will have the content of G+V+ + V2. Here, C and V outputted from the port C4 are differential components for matching the input and output of the input/output check circuit.

As mentioned above, in this second embodiment as well, the differential gain is made dependent on the vehicle speed, and the gain is made smaller at low speeds and increased at high speeds, thereby preventing vibrations at low speeds and reducing the feeling of rotor inertia at high speeds. It can be eliminated.

[Brief explanation of the drawing]

Drawings 1 to 5 show a first embodiment of this invention.
Figure 1 is a mechanism diagram, Figure 2 is a circuit diagram, Figure 3 is a graph showing an example of the characteristics of the function F (Vs) depending on vehicle speed, and Figure 4
The figure is a graph showing the relationship between output level and steering torque.
In FIG. 5, there is an input signal X. L... Handle, 2... Steering input shaft, 3... Steering torque sensor, 4... Vehicle speed sensor, M... Electric motor, 10... Knuckle arm, 17... Differential circuit,
49...Microprocessor, 54...First addition circuit, 59...Vehicle speed sensitive circuit.

Claims (1)

[Claims] In an electric power steering device that includes a torque signal processing circuit that outputs an output torque signal according to driving conditions such as vehicle speed and controls an electric motor using the output signal of this function generation circuit, a torque sensor that detects steering torque and a torque sensor that detects steering torque are used. , a torque signal processing circuit that outputs a voltage signal according to the output of the torque sensor, and a vehicle speed sensor that detects vehicle speed.
It includes a vehicle speed signal processing circuit that outputs a voltage signal according to the output of the vehicle speed sensor, and a differentiation processing section that differentiates the output signal of the torque sensor, and the differentiation gain of the differentiation processing section is made responsive to vehicle speed, and on the low speed side, This electric power steering device is characterized by reducing the gain and increasing it at high speeds.