JPH0867261A - Control device for electric power steering device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a control device for an electric power steering device that does not cause a feeling of strangeness in the steering wheel operation even if steering torque is generated due to steering wheel operation after the ignition key is turned from ON to OFF. [Structure] When the ignition key is turned off, a steering angular velocity detector 32 detects a steering angular velocity ω _a by differentiating the pulse detected by a pulse generator 31 provided on the shaft of the motor 10 with respect to time. To do. The proportional calculator 33 multiplies the input steering angular velocity ω _a by a predetermined constant k and calculates −kω _a as a current command value I2 corresponding to the steering angular velocity at that time. The motor 10 is controlled by the current command value I2, so that the steering wheel operation after turning off the ignition key does not give a feeling of strangeness.

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, and more particularly, to an electric power steering device that performs an improved control operation that does not cause a driver to feel uncomfortable when the ignition key is turned from ON to OFF. The present invention relates to a device control 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 wheel, and drives a motor based on the detection signal to drive the steering wheel. It assists the steering force of. The control of such an electric power steering apparatus is executed by an electronic control circuit. The outline of the control is based on the steering torque detected by the torque sensor and the vehicle speed detected by the vehicle speed sensor. The magnitude of the supplied current is calculated, and the current supplied to the motor is controlled based on the calculation result.

That is, the electronic control circuit supplies a large steering assist force when the detected vehicle speed is zero or a low speed when the steering wheel is operated and steering torque is generated, and the detected vehicle speed is supplied. When the steering speed is fast, the motor is operated according to the steering force of the steering wheel and the vehicle speed so that a small steering assist force is supplied.
By controlling the current supplied to the steering wheel, the optimum steering assist force according to the traveling state can be given.

In this type of device, an electromagnetic clutch is provided between the motor and the steering shaft, and normally the motor and the steering shaft are connected so that the auxiliary steering force by the motor is transmitted to the steering shaft. When the ignition key is turned off, the coupling by the electromagnetic clutch is released.

Therefore, while the steering handle is being operated and the steering torque is being generated, the ignition key is pressed.
When is turned from ON to OFF, the steering assist force suddenly becomes zero, the elastic energy stored in the steering mechanism is released at once, and is transmitted to the steering wheel, so that the driver receives an impact force from the steering wheel. There was inconvenience such as receiving.

As a countermeasure against this, the ignition key is turned off.
When it is turned off from N, the coupling by the electromagnetic clutch is not immediately released, but the steering assist force is gradually reduced by gradually lowering the motor current control value over a predetermined time, and then the electromagnetic clutch. There has been proposed a method of releasing the binding of the above (see Japanese Patent Application Laid-Open No. 62-181958).

[0007]

According to the above-described method of gradually decreasing the current control value, the ignition key is turned off.
If the steering wheel is not operated after setting to F, the steering assist force can be gradually reduced. However, when the steering force is set to zero by once releasing the steering handle within a predetermined time to gradually decrease the current control value and then the steering handle is rotated again, steering torque is generated and the ignition key is turned on. Despite the fact that − was turned off, the steering assist force was generated, and the driver felt uncomfortable with the operation of the steering wheel.

The present invention solves the above problems and, after the ignition key is turned off, the control of the electric power steering apparatus does not give the driver a feeling of discomfort regardless of the operation of the steering wheel. The purpose is to provide a device.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above problems by calculating a motor current command value at least in accordance with the magnitude of steering torque generated in the steering shaft, and based on the calculation result. -In a control device for an electric power steering apparatus having a control means for controlling a control current, a steering angular velocity detecting means for detecting a steering angular velocity is provided, and the control means, when the ignition key is turned from ON to OFF, Calculating a motor current command value proportional to the steering angular velocity detected by the steering angular velocity detecting means and controlling the motor current based on the motor current command value proportional to the steering angular velocity for a predetermined time. Is characterized by.

And, as the steering angular velocity detecting means,
It is possible to use one that obtains the steering angular velocity by differentiating the detection value of the rotation sensor connected to the motor shaft.

The steering angular velocity detecting means may be one that estimates the steering angular velocity based on the motor current, the motor current control value, and the battery voltage.

Further, as the steering angular velocity detecting means,
The steering angular velocity may be estimated based on the motor current and the voltage between the motor terminals.

[0013]

After the ignition key is switched from ON to OFF, the current control value is controlled based on the motor current command value proportional to the steering angular velocity within a predetermined time, and the elastic energy stored in the steering mechanism is controlled. Absorb.

[0014]

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. 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.

The electronic control circuit 13 for controlling the power steering device is supplied with electric power from the battery 14 via the ignition switch 11. The electronic control circuit 13
Steering torque detected by torque sensor 3 and vehicle speed sensor 1
A current command calculation is performed based on the vehicle speed detected in step 2, and the current i supplied to the motor 10 is controlled based on the calculated current command value.

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 ignition key is off and when the electronic control circuit 13 determines that the power steering device has failed. This will be described in detail later.

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 to enhance the stability of the steering system, and is input to the current command calculator 22. The vehicle speed detected by the vehicle speed sensor 12 is also input to the current command calculator 22.

The current command calculator 22 is a motor 1 according to a predetermined calculation formula based on the input torque signal and vehicle speed signal.
The current command value I1 which is the control target value of the current supplied to 0 is determined.

The adder 30 adds the current command value I1 from the current command calculator 22 and the current command value I2 from the proportional calculator 33, which will be described later, to obtain a control target value of the current supplied to the motor 10. An adder that outputs a certain current command value I actually outputs either the current command value I1 or the current command value I2 as the current command value I. This will be described in detail later.

The circuit composed of the comparator 23, the differential compensator 24, the proportional calculator 25 and the integral calculator 26 is arranged so that the actual motor current value i matches the above-mentioned current command value I. This is a circuit that performs feedback control.

The proportional calculator 25 outputs a proportional value proportional to the difference between the current 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.

In the differential compensator 24, the current command calculator 22
In order to increase the response speed of the motor current value i actually flowing to the motor with respect to the current command value I calculated in step 1, the differential value of the current command value I is output.

The differential value of the current command value I output from the differential compensator 24, the proportional value proportional to the difference between the current command value output from the proportional calculator 25 and the actual motor current value i, and the integral The integrated value output from the calculator 26 is added and calculated in the adder 27, and the current control value 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 converter 44 for separating and converting the current control value input from the adder 27 into a PWM signal and a current direction signal, FET1 to FET4, and gates thereof.
It is composed of an FET gate drive circuit 45 and the like for driving the gate to open and close. The step-up power supply 46 is a power supply for driving the high side of FET1 and FET2.

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

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 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 which 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 FET3 is in a conducting state, a current flows through the FET1, the motor 10, the FET3 and the resistor R1 and a forward current flows through the motor 10. In addition, FET
When 4 is conducting, the current is FET2, motor 1
0, FET4, and resistor R2, and a negative current flows through the motor 10.

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

The electronic control circuit described above, when the steering wheel is operated and the steering torque is generated, the detected steering torque is large, and when the detected vehicle speed is zero or low, a current command is issued. When the value I is set large, the detected steering torque is small, and the detected vehicle speed is fast, the current command value I is set small, so that the optimum steering assist force according to the traveling state can be given.

Next, the ignition key according to the present invention.
The configuration and operation for controlling the current control value by the steering angular velocity after the switch is turned off will be described with reference to FIG.

A pulse generator 31 for detecting the rotation angle of the motor 10 is provided on the shaft, and the detected pulse is input to the steering angular velocity detector 32. The steering angular velocity detector 32 detects the steering angular velocity ω _a by differentiating the detected pulse number with respect to time and outputs it to the proportional calculator 33.

The proportional calculator 33 receives the input steering angular velocity ω
multiplied by a predetermined constant k to _a, it is calculated as the current command value I2 corresponding to -Keiomega _a to steering angle speed at that time. The steering angular velocity detector 32 and the proportional calculator 33 are keyed to be described later.
When the OFF detector 35 detects that the ignition key is OFF, it operates for a predetermined time.

On the other hand, I. G. The key-off detector 35 is
ON / OFF of the ignition key is detected, and when the ON of the ignition key is detected, the contact 35a is closed, the contact 35b is opened, and the current command value I1 output from the current command calculator 22 is output to the adder 30. , Proportional calculator 3
The output circuit of 3 is cut off. When the ignition key is detected to be OFF, the steering angular velocity detector 32 and the proportional calculator 33 are operated, the contact 35b is closed, the contact 35a is opened, and the current command value I2 output from the proportional calculator 33 is changed. Output to the adder 30 and shut off the output circuit of the current command calculator 22. Needless to say, the contacts 35a and 35b can be configured by logic circuits.

The adder 30 receives the input current command value I1,
Alternatively, the current command value I2 is output as the current command value I which is the control target value of the current supplied to the motor 10.

FIG. 4 shows the I.D. G. 6 is a flowchart for explaining the operation of the key-off detector 35. First, the ON / OFF state of the ignition key is detected (step P
1), if it is ON, it immediately returns to the main routine, but it is OFF
In the case of, the current command value I (the current command value I1 has been set) which is the control target value until then is reset and the timer T is reset (step P2). The timer T is a timer that measures a predetermined time for controlling the current control value by the steering angular velocity after the ignition key is detected to be turned off.

Next, the steering angular velocity detector 32 and the proportional calculator 33 are operated to detect the steering angular velocity ω _a , and the constant k
Is multiplied by to calculate a current command value I2 = -k [omega] _a corresponding to the steering angular velocity at that time, and the current command value I2 is set as the current command value I which is a new control target value (step P3). It is determined whether the timer T has timed (step P
4) If the time measurement has not ended, the process returns to step P2 and the processes of steps P2 and P3 are repeated, but if the time measurement has ended,
The clutch drive signal is output to the clutch drive circuit 36 to turn off the clutch (release the coupling of the clutch), turn off the power supply of the control circuit (CPU) (step P5), and finish the process.

After the ignition key is turned off by the above processing, the current command value proportional to the steering angular velocity is defined as a new current command value, and the ignition key OF is set.
After F, the motor control is continued for a predetermined time based on the new current command value, and the elastic energy stored in the steering mechanism can be absorbed.

Next, a second embodiment of the present invention will be described. In the first embodiment described above, the steering angular velocity ω _a of the motor is detected by the pulse generator, but in the second embodiment,
The rudder angular velocity ω _a of the motor is set to the battery voltage and the motor current value i.
The steering angular velocity estimated value ω _b estimated from is used.

The relationship between the motor terminal voltage value V, the actual motor current value i, and the motor rotation angular velocity ω is given by the following equation (1).

[0042]

[Equation 1] Here, L is the inductance of the motor, s is the Laplace operator, R is the resistance between the motor terminals, and K _T is the back electromotive force constant of the motor.

The rotational angular velocity ω of the motor can be obtained from the equation (1), but the resistance R between the motor terminals and the counter electromotive force constant K _T of the motor fluctuate under the influence of temperature. .

That is, the resistance R between the motor terminals is represented by the following equation (2), and the back electromotive force constant K _T of the motor is represented by the following equation (3).

[0045]

[Equation 2]

[0046]

(Equation 3) Where R ₀ is the resistance between the motor terminals at the reference temperature, K
_T0 is the back electromotive force constant of the motor at the reference temperature, and t is the temperature difference from the reference temperature.

As is clear from the equations (2) and (3), the mode
Data inter-terminal resistor R algicidal - counter electromotive force constant K _T of the motor varies due to the influence of temperature. Accordance connexion, motor - between data terminal resistor R algicidal - counter electromotive force constant K _T of the motor, for example may be corrected by measuring the temperature at that point.

Since the current rising time constant defined by L / R is sufficiently small when estimating the motor rotation angular velocity ω, the motor rotation angular velocity ω is obtained from the above equation (1). The equation can be expressed by the following equation (4).

[0049]

[Equation 4] Further, the voltage V between the terminals of the motor has a relationship with the current control value (duty ratio of the PWM signal) shown by the following equation (5).

[0050]

(Equation 5) Here, V _BAT is the battery voltage D _DTY is the duty ratio of the PWM signal.

Therefore, the equation (4) can be expressed by the following equation (6).

[0052]

(Equation 6) Since the rotation angular velocity of the motor is proportional to the steering angular velocity of the motor, the equation (6) can be regarded as the steering angular velocity of the motor. Therefore, the steering angular velocity ω _a in the first embodiment is
Instead of, the steering angle velocity estimated value ω expressed by the following equation (7)
_b can be used.

[0053]

(Equation 7) Second embodiment described below, the formula (7) in the represented based on the steering angular velocity estimate omega _b, is what determines the current command value I2.

FIG. 5 is a block diagram of the electronic control circuit according to the second embodiment of the present invention. The second embodiment is different from the first embodiment only in that the motor 10 does not have the pulse generator 31 but is provided with a battery voltage detector 38 for detecting battery voltage and a steering angular velocity estimator 39. Therefore, elements common to the block diagram (FIG. 2) of the electronic control circuit of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. Only the differences will be described.

The rudder angular velocity estimator 39 has a battery voltage value V _BAT detected by the battery voltage detector 38, a duty ratio D _{DTY of} an input signal to the motor drive circuit, that is, a PWM signal, and a current detection circuit 42. The actual mode detected by
With the input current value as the input signal, the steering angular velocity estimated value ω _b is calculated based on the equation (7).

[0056] proportional calculator 33 multiplies a predetermined constant k to the input steering angular velocity estimate omega _b, is calculated as a current instruction value I2 corresponding to -Keiomega _b to the steering angular velocity at that time. Subsequent processing is the same as that in the first embodiment, and therefore its explanation is omitted here.

In the second embodiment described above, the rudder angular velocity estimator 39 uses the voltage V between the terminals of the motor as the battery voltage value V.
It is calculated from the duty ratio D _{DTY of BAT} and PWM signal, but it is also possible to directly detect the voltage V between the terminals of the motor and calculate the estimated steering angular velocity ω _b based on the equation (4). it can.

[0058]

As described above, according to the present invention, after the ignition key is switched from ON to OFF, the motor current command value proportional to the steering angular velocity is maintained for a predetermined time. The current is controlled, and even if steering torque is generated by operating the steering wheel, the steering torque causes the motor to operate.
Current is not controlled. Thus, after the ignition key is turned from ON to OFF, the elastic energy stored in the steering mechanism is absorbed even when the steering wheel is operated, and the driver does not feel discomfort from the steering wheel operation.

[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 the electronic control circuit according to the first embodiment of the present invention.

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

FIG. G. Flow chart explaining the operation of the key-off detector

FIG. 5 is a block diagram of an electronic control circuit according to a second embodiment of the present invention.

[Explanation of symbols]

 3 Torque Sensor 10 Motor 12 Vehicle Speed Sensor 13 Electronic Control Circuit 21 Phase Compensator 22 Current Command Calculator 23 Comparator 24 Differential Compensator 25 Proportional Calculator 26 Integral Calculator 27 Adder 30 Adder 31 Pulse Generator 32 Rudder Angular velocity detector 33 Proportional calculator 35 I. G. Key-off detector 38 Battery voltage detector 39 Steering angular velocity estimator 41 Motor drive circuit 42 Motor current detection circuit

Front Page Continuation (72) Inventor Kuga Kogai 78 Toba-cho, Maebashi-shi, Gunma Nippon Seiko Co., Ltd.

Claims (4)

[Claims] 1. An electric power steering system having a control means for calculating a motor current command value according to at least a steering torque generated in a steering shaft and controlling the motor current based on the calculation result. The control device of the apparatus comprises a steering angular velocity detecting means for detecting a steering angular velocity, and the control means is characterized in that the ignition key is turned from ON to OFF.
When it is set to, the motor current command value proportional to the steering angular velocity detected by the steering angular velocity detecting means is calculated, and the motor current command value proportional to the steering angular velocity is calculated for a predetermined time. -A control device for an electric power steering device, which is characterized by controlling a control current. 2. The electric power steering apparatus according to claim 1, wherein the rudder angular velocity detecting means obtains a rudder angular velocity by differentiating a detection value of a rotation sensor coupled to the motor shaft. Control device. 3. The electric power according to claim 1, wherein the rudder angular velocity detecting means estimates the rudder angular velocity based on a motor current, a motor current control value and a battery voltage. Steering device control device. 4. The electric power steering apparatus according to claim 1, wherein the steering angular velocity detecting means estimates the steering angular velocity based on a motor current and a voltage across the motor terminals. Control device.