JPH08150954A - Controller for motor-driven power steering device - Google Patents

Abstract

PURPOSE: To smoothly change a steering assisting command value to change in the speed of a vehicle. CONSTITUTION: In a steering assisting command value calculating unit 22 of an electronic control circuit 13 constituting a controller 13, a steering assisting command value I is calculated on the basis of a torque signal input from a torque sensor 3 and a vehicle velocity signal input from a vehicle velocity sensor 12. In a memory 28 additionally provided to the calculator 22 the value I is included which is corresponding to steering torque T in a plurality of typical vehicle velocity V=0, Va, Vb. In the case that detected vehicle velocity V is not V=0, V=Va, V=Vb, based on the condition where the velocity is between the three values, the value I is obtained by compensation calculation according to the steering assisting command value corresponding to the steering torque in the typical vehicle velocity near the former velocity and a compensation coefficient preliminarily set according to the velocity of vehicle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an electric power steering device.

[0002]

2. Description of the Related Art An electric power steering apparatus for a vehicle detects a steering torque and a vehicle speed generated in a steering shaft by operating a steering handle, calculates a steering assist command value based on the detection signal, and calculates the steering assist command value. According to the steering assist command value, the motor is driven to assist the steering force of the steering wheel, and the microcomputer is used for calculating the steering assist command value and controlling the motor based on the command value. An electronic control circuit is used, including

The steering torque has a component corresponding to a road surface load generated by steering and a component corresponding to a frictional force of the steering mechanism. Therefore, the product of the control value corresponding to the road surface load determined based on the detected steering torque and the vehicle speed coefficient corresponding to the vehicle speed that decreases in accordance with the increase in the detected vehicle speed and becomes zero at a predetermined speed or more. Is proposed, and a control value corresponding to the frictional force of the steering mechanism is added to this to calculate a steering assist command value.

In this structure, the road surface load control value corresponding to the steering torque, the frictional force control value corresponding to the steering torque, and the vehicle speed coefficient corresponding to the vehicle speed are respectively predetermined and stored in the memory and detected. The required data is read from the memory according to the steering torque and the vehicle speed, and the steering assist command value is calculated (Japanese Patent Publication No. 5-10).
271).

[0005]

In the control means for calculating the steering assist command value as described above, the road surface load control value and the frictional force control value are determined in advance according to the steering torque. Once determined, the steering assist command value will change only in response to the vehicle speed.

Therefore, if a steering assist command value corresponding to the steering torque is preset for a plurality of vehicle speeds and stored in the memory, the steering assist command value can be immediately obtained from the detected steering torque and vehicle speed. You can

However, it is not an appropriate method to change the steering assist command value only in response to the vehicle speed when the steering torque is determined. For example,
As shown in FIG. 8, at the vehicle speed V1, the dead zone width is set to B1 and
When the vehicle speed is V2 (V2> V1), the width of the dead zone is set to B2, and the width of the dead zone of the steering assist command value is changed according to the vehicle speed in the area where the steering torque is small. The better the steering feel. Also,
The steering feeling is further improved by changing the curve of the steering assist command value curve with respect to the steering torque according to the vehicle speed.

For this purpose, the steering assist command value is finely set in advance corresponding to the steering torque and the vehicle speed. That is,
Even if the steering torque is the same, different steering assist command values are set in correspondence with the slow vehicle speed, and a plurality of different steering assist command values are set in correspondence with the slow vehicle speed and the magnitude of the steering torque. It should be stored in memory. However, this method results in increased cost because the required memory capacity is significantly increased, and is not a desirable method.

Further, instead of the above-mentioned method of reading the steering assist command value from the memory, a steering assist command value arithmetic expression having steering torque and vehicle speed as variables is set and the steering assist command value is calculated. Although a method can be considered, this method complicates the arithmetic expression, and therefore a micro computer capable of high-speed operation must be adopted, which also results in an increase in cost and is not a desirable method. The present invention aims to solve the above problems.

[0010]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems, and to calculate a steering assist command value based on at least a steering torque and a vehicle speed generated in a steering shaft, and the calculated steering assist. The motor current control means for controlling the motor current based on the command value is provided,
In a control device for an electric power steering device that applies a steering assist force corresponding to a steering torque and a vehicle speed to a steering mechanism, a plurality of typical vehicle speeds are set as parameters in the calculation means.
Storage means for storing a steering assist command value corresponding to the steering torque set as a parameter is provided, and the computing means determines that the detected vehicle speed is in the middle of the representative vehicle speeds stored in the storage means. In this case, the steering assist command value corresponding to the steering torque at a representative vehicle speed before and after the detected vehicle speed is read from the storage means, and based on the difference and the vehicle speed correction coefficient, the detected vehicle speed and the steering torque are handled. The steering assist command value is calculated.

[0011]

When the detected vehicle speed is in the middle of the representative vehicle speed stored in the storage means, the steering assist command value corresponding to the steering torque at the representative vehicle speed before and after the detected vehicle speed is read from the storage means. , The difference between the steering assist command values corresponding to the steering torque at two typical vehicle speeds,
A steering assist command value corresponding to the detected vehicle speed and steering torque is calculated based on the difference and the vehicle speed correction coefficient.

Since the steering assist command value for the vehicle speed is stored in the storage means in advance, there is a degree of freedom in setting the steering assist command value. Further, since the steering assist command value corresponding to the steering torque is stored only for a typical vehicle speed, the storage capacity of the storage means is small, and the steering assist command value can be calculated by a simple calculation algorithm. it can.

[0013]

Embodiments of the present invention will be described below.
FIG. 1 is a view for explaining the outline of the configuration of an electric power steering apparatus suitable for carrying out the present invention, in which a shaft 2 of a steering handle 1 has a reduction gear 4, a universal joint 5a,
5b, through a pinion rack mechanism 7, it is connected to a steering wheel 8 of a steering wheel. The shaft 2 is provided with a torque sensor 3 for detecting the steering torque of the steering wheel 1, and a motor 10 for assisting the steering force is connected to the shaft 2 via a clutch 9 and a reduction gear 4. There is.

An electronic control circuit 13 for controlling the power steering device is provided from the battery 14 to the ignition key-1.
Power is supplied via 1. The electronic control circuit 13 calculates a steering assist command value based on the steering torque detected by the torque sensor 3 and the vehicle speed detected by the vehicle speed sensor 12, and the motor 10 is operated based on the calculated steering assist command value. Control the current supplied to.

The clutch 9 is controlled by the electronic control circuit 13. The clutch 9 is connected in a normal operation state, and is disconnected when the electronic control circuit 13 determines that the power steering device has a malfunction and when the power is off.

FIG. 2 is a block diagram of the electronic control circuit 13. In this embodiment, the electronic control circuit 13 is mainly a CP.
Although it is composed of U, the function executed by the program inside the CPU is shown here. For example, the phase compensator 21 does not represent the phase compensator 21 as an independent hardware, but the phase compensator function executed by the CPU. It goes without saying that the electronic control circuit 13 may not be configured by a CPU, but these functional elements may be configured by independent hardware (electronic circuit).

The function and operation of the electronic control circuit 13 will be described below. The steering torque signal input from the torque sensor 3 is phase-compensated by the phase compensator 21 in order to enhance the stability of the steering system, and is input to the steering assist command value calculator 22. The vehicle speed detected by the vehicle speed sensor 12 is also input to the steering assist command value calculator 22.

The steering assist command value calculator 22 determines the steering assist command value I, which is the control target value of the current supplied to the motor 10, on the basis of the input torque signal and vehicle speed signal. 28 is attached. The memory 28 has a plurality of memory cells (three memory cells in this embodiment, which will be described in detail later).
The steering assist command value corresponding to the steering torque is stored with the vehicle speed V of the type) as a parameter, and is used for the calculation of the steering assist command value I by the steering assist command value calculator 22.

The circuit composed of the comparator 23, the differential compensator 24, the proportional calculator 25, the integral calculator 26 and the adder 27 ensures that the actual motor current value i coincides with the steering assist command value I. It is a circuit for performing feedback control.

The proportional calculator 25 outputs a proportional value proportional to the difference between the steering assist command value I and the actual motor current value i. Further, the output signal of the proportional calculator 25 is integrated by the integral calculator 26 to improve the characteristics of the feedback system, and the proportional value of the integrated value of the difference is output.

The differential compensator 24 increases the response speed of the motor current value i actually flowing to the motor with respect to the steering assist command value I calculated by the steering assist command value calculator 22.
The differential value of the steering assist command value I is output.

The derivative value of the steering assist command value I output from the differential compensator 24, the proportional value proportional to the difference between the steering assist command value output from the proportional calculator 25 and the actual motor current value, and The integrated value output from the integration calculator 26 is added and calculated in the adder 27, and the current control value E as the calculation result is output to the motor drive circuit 41 as a motor drive signal.

FIG. 3 shows an example of the configuration of the motor drive circuit 41. The motor drive circuit 41 includes a conversion unit 44 for separating and converting the current control value E input from the adder 27 into a PWM signal and a current direction signal, FET1 to FET4, and FEs thereof.
It is composed of a FET gate drive circuit 45 for opening and closing the gates of T1 to FET4. The step-up power supply 46 is FET1.
, A power supply for driving the high side of FET2.

The PWM signal (pulse width modulation signal) is a signal for driving the gates of FET (field effect transistor) switching elements FET1 to FET2 connected to the H-bridge, and the current control value E calculated in the adder 27. The duty ratio (time ratio for turning on / off the gate of the FET) of the PWM signal is determined by the absolute value of.

The current direction signal is a signal indicating the direction of the current supplied to the motor, and is a signal determined by the sign (positive or negative) of the current control value E calculated by the adder 27.

FET1 and FET2 are switching elements whose gates are turned on / off based on the duty ratio of the PWM signal, and are switching elements for controlling the magnitude of the current flowing to the motor. . Also, FET3
And FET4, the gate is turned on or off based on the above-mentioned current direction signal (when one is on, the other is OF
The switching element is a switching element that switches the direction of the current flowing through the motor, that is, the rotation direction of the motor.

When the FET4 is in the conducting state, the current flows through the FET1, the motor 10, the FET4 and the resistor R1, and the current in the positive direction flows through the motor 10. FET3
Is conductive, current is FET2, motor 1
Current flows through 0, FET3, and resistor R2, and the motor 10
A negative current flows through.

The motor current detection circuit 42 detects the magnitude of the positive direction current based on the voltage drop across the resistor R1 and detects the negative direction current based on the voltage drop across the resistor R2. Detect size. The detected actual motor current value i is fed back to the comparator 23 and input (see FIG. 2).

Next, the steering assist command value calculator 2 of the present invention
Calculation of the steering assist command value by 2 will be described. As described above, the memory 28 is attached to the steering assist command value calculator 22. In this embodiment, the memory 28 stores three values when the steering wheel is stationary (vehicle speed V = 0), at low speed traveling (vehicle speed V = Va), and at medium and high speed traveling (vehicle speed V = Vb).
The steering assist command value corresponding to the steering torque is stored for each type of representative vehicle speed. The representative vehicle speed is not limited to three types.

FIG. 4 shows the steering assist command value I corresponding to the steering torque T for the three representative vehicle speeds stored in the memory 28, and the horizontal axis shows the steering torque T.
Is plotted on the vertical axis. In the figure, the vehicle speed V = 0, the steering assist command value I in the steering torque value T ₁ is I0 (T1), when the vehicle speed V = Va, the steering assist command value I in the steering torque value (T1) is Ia (T1 ), Vehicle speed V = Vb
Cases, the steering assist command value I in the steering torque value T ₁ is Ib (T
1) is shown.

Although shown in a curve in FIG. 4, the steering torque T and the steering assist command value I stored in the memory 28 are, of course, digital values, and are set finely within a range that does not hinder practical use.

The detected vehicle speed is the above-mentioned vehicle speed V = 0,
When the vehicle speed V = Va and the vehicle speed V = Vb, the steering assist command corresponding to the detected steering torque is obtained from the table of steering assist command values corresponding to the preset steering torque for the vehicle speed read from the memory 28. The value can be calculated.

The detected vehicle speed is the above-mentioned vehicle speed V = 0,
For vehicle speeds other than vehicle speed V = Va and vehicle speed V = Vb, a steering assist command value corresponding to the steering torque at the representative vehicle speeds before and after the detected vehicle speed depending on which of the three representative vehicle speeds is present. Then, a correction calculation is performed based on a correction coefficient preset according to the vehicle speed.

That is, when the detected vehicle speed V is 0≤V≤Va (when the vehicle speed V is in the low speed range), the steering assist command value I (T1) is calculated by the following equation (1).

Further, the detected vehicle speed V is Va <V≤Vb
In the case of (when the vehicle speed V is in the medium speed range), the steering assist command value I (T) is calculated by the following equation (2).

I (T) = γ {I0 (T) −Ia (T)} + Ia (T) (1) I (T) = γ {Ia (T) −Ib (T)} + Ib (T ) (2) FIG. 5 is a flow chart for explaining the correction calculation for obtaining the steering assist command value described above. First, the detected vehicle speed V
Is compared with the representative vehicle speed Va to determine whether 0 ≦ V ≦ Va (step P1). If 0≤V≤Va, that is, if the vehicle speed V is in the low speed region, the process proceeds to step P4.

Then, the correction coefficient γ in the low speed region is read from the memory (step P4), and the steering assist command value I0 (T) corresponding to the steering torque T when the detected vehicle speed V = 0.
Then, the steering assist command value Ia (T) when the vehicle speed V = Va is read from the steering assist command value table (step P5). further,
The steering assist command value I (T) is calculated based on the above equation (1) (step P6), and the process is ended.

In step P1, the vehicle speed V is 0≤V≤.
If it is not Va, it is determined whether Va <V≤Vb (step P2). When Va <V ≦ Vb, that is, the vehicle speed V
Is in the medium speed range, the routine goes to Step P7.

Then, the correction coefficient γ in the medium speed range is read from the memory (step P7), and the detected steering torque T
Steering assist command value Ia (T) when the vehicle speed V = Va corresponding to
Then, the steering assist command value Ib (T) when the vehicle speed V = Vb is read from the steering assist command value table (step P8). further,
The steering assist command value I (T) is calculated based on the above equation (2) (step P9), and the process is terminated.

In step P2, the vehicle speed V is Va <V.
If ≤Vb is not satisfied, V> Vb, that is, the vehicle speed V is in the high speed region, so Ib (T) is adopted as the steering assist command value I (T) (step P3), and the process is terminated.

The correction coefficient γ is preset according to the vehicle speed. FIG. 6 is a diagram showing an example of the relationship between the vehicle speed and the correction coefficient. The horizontal axis represents the vehicle speed and the vertical axis represents the correction coefficient. In the range where the vehicle speed V is Va <V ≦ Vb, that is, in the medium speed range, the correction coefficient γ changes along the curve p. A value that changes along with it is set in advance.

In order to obtain the optimum steering assist force according to the vehicle speed, the shapes of the curves p and q, that is, the values of the correction coefficient γ are set to the most appropriate values by a running experiment or the like.

For example, FIG. 7 is a diagram showing the relationship between the vehicle speed and the steering reaction force when the vehicle is traveling in a state where the steering angle is kept constant and no steering assist force is applied. The horizontal axis represents the vehicle speed and the vertical axis represents the steering. There is a reaction force. The steering reaction force is TR1 when the vehicle speed starts to move from zero, but thereafter the steering reaction force decreases rapidly as the vehicle speed increases, and when the vehicle speed is 10 km / h or more, the change in the steering reaction force is small. Even when the steering assist force is applied, if the steering assist force is applied based on the curve indicating the relationship between the vehicle speed and the steering reaction force, the steering wheel operation will not be uncomfortable.

Therefore, in the present invention, when the correction coefficient γ is set, the correction coefficient γ is set so that the relationship between the vehicle speed and the steering reaction force shown in FIG. It does not give a feeling of strangeness.

[0045]

As described above, in the control device for the electric power steering apparatus of the present invention, the steering torque in which a plurality of representative vehicle speeds are set as parameters in the calculating means for calculating the steering assist command value. Is attached to the storage means for storing the steering assist command value corresponding to the steering assist command value, and the calculation means detects that the detected vehicle speed is in the middle of the representative vehicle speed stored in the storage means. The steering assist command value corresponding to the steering torque at a typical vehicle speed before and after the vehicle speed is read from the storage means, and the steering assist command value corresponding to the detected vehicle speed and steering torque is interpolated based on the difference and the vehicle speed correction coefficient. It is something that is calculated.

In the storage means, steering assist command values corresponding to the steering torque are determined and stored in advance for a plurality of vehicle speeds. At this time, the steering assist command values corresponding to the steering torque differ depending on the vehicle speed. In this case as well, the steering assist command value can be set according to the vehicle speed, so there is a degree of freedom in setting the steering assist command value. When the detected vehicle speed is in the middle of the representative vehicle speeds stored in the storage means, the steering assist command value is obtained by interpolation calculation. In this case also, the steering assist command value corresponding to the vehicle speed is stored in the storage means. Since it is read out and calculated, the steering assist command value can be changed smoothly in response to changes in the vehicle speed, the steering wheel operation can be performed smoothly, and there is no discomfort.

Further, since the steering assist command value corresponding to the steering torque is stored only for a typical vehicle speed, the storage capacity of the storage means is small, and the steering assist command value is calculated by a simple calculation algorithm. You can
The calculation of the steering assist command value can be performed at high speed and easily without relying on an expensive CPU.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an outline of a configuration of an electric power steering device.

FIG. 2 is a block diagram of an electronic control circuit according to an embodiment of the present invention.

FIG. 3 is a circuit block diagram showing the configuration of a motor drive circuit.

FIG. 4 is a diagram illustrating a relationship between a representative vehicle speed and a steering assist command value I corresponding to a steering torque T.

FIG. 5 is a flowchart for explaining a calculation operation of a steering assist command value executed by an electronic control circuit.

FIG. 6 is a diagram showing an example of a relationship between a vehicle speed and a correction coefficient.

FIG. 7 is a diagram showing a relationship between a vehicle speed and a steering reaction force when the vehicle travels in a state where a steering angle is kept constant and a steering assist force is not applied.

FIG. 8 is a diagram illustrating setting of a dead zone of a steering torque and a steering assist command value according to a vehicle speed.

[Explanation of symbols]

 3 torque sensor 10 motor 11 ignition key 12 vehicle speed sensor 13 electronic control circuit 21 phase compensator 22 current command calculator 23 comparator 24 differential compensator 25 proportional calculator 26 integration calculator 27 adder 28 memory 41 motor Drive circuit 42 Motor current detection circuit 44 Conversion unit 45 FET gate drive circuit

Claims (1)

[Claims] 1. A calculating means for calculating a steering assist command value based on at least a steering torque generated in a steering shaft and a vehicle speed, and a motor for controlling a motor current based on the calculated steering assist command value. Equipped with current control means,
In a control device for an electric power steering device that gives a steering assisting force corresponding to a steering torque and a vehicle speed to a steering mechanism, a steering corresponding to a steering torque set with a plurality of typical vehicle speeds as parameters to the arithmetic means. A storage unit for storing the auxiliary command value is attached, and when the calculation unit determines that the detected vehicle speed is in the middle of the representative vehicle speeds stored in the storage unit,
A steering assist command value corresponding to the steering torque at a typical vehicle speed before and after the detected vehicle speed is read from the storage means, and based on the difference and the vehicle speed correction coefficient, the steering assist command value corresponding to the detected vehicle speed and steering torque. A control device for an electric power steering device, characterized in that: