JP2002120743A - Motor-driven power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor-driven power steering device capable of suppressing dispersion in the control of the assist steering torque and farther enhancing the stability. SOLUTION: The steering angle θ of a steering wheel 1 sensed by a steering angle sensor 6 and the car speed V sensed by a car speed sensor 9 are fed to a controller 7, and a target steering torque presuming means 10 presumes the target steering torque Tm while a steering torque sensor 2 senses the steering torque T, and a deviation calculating means 11 calculates the deviation εof the steering torque T from the target steering torque Tm. Using the deviation ε, a proportioning term control means 12 and differential term control means 14 of a first assist steering torque command amperage control means decide the command amperages Tca and Tcb for the torque, respectively, and they are added by an adder 15 and the sum is fed to a motor control part 16 as the command amperage Tc1 for the first assist steering torque.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus for assisting a steering force of an automobile steering apparatus with an electric motor.

[0002]

2. Description of the Related Art A conventional electric power steering apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. 11-49000.

This electric power steering apparatus has a means for obtaining a reference rack shaft load of a steered wheel from a steering angle and a vehicle speed, and a means for detecting an actual rack shaft load. The steering resistance is set in accordance with the deviation from the shaft load, and the steering resistance is increased as the deviation increases. Therefore, when the vehicle is traveling on a road surface where the road surface reaction force fluctuates, such as a partially frozen road, particularly during turning, the rack shaft load changes, that is, even if the road surface reaction force changes, the steering resistance is adjusted to reduce the steering holding force. By reducing the change, it is possible to prevent the steering angle from being cut due to the imbalance between the steering holding force and the road surface reaction force, and it is possible to secure the stability of the vehicle to some extent.

[0004]

However, in the above-described apparatus, when the actual rack shaft load is detected, the rack shaft load corresponding to the motor output varies due to the influence of temperature change and manufacturing variation. When the reference rack shaft load in the controller is changed or the reference rack shaft load is calculated, the side rod and knuckle arm There is a problem that the control configuration in the controller becomes complicated because the link efficiency due to the bend angle is considered.

[0005] In view of the above-mentioned problems of the prior art, an object of the present invention is to provide an electric power steering apparatus capable of suppressing control variations and further improving stability.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a first aspect of the present invention is a steering torque detecting means for detecting a steering torque of a driver, a steering angle detecting means for detecting a steering angle of a steering wheel, and Vehicle speed detecting means for detecting a vehicle speed, a motor for generating a first auxiliary steering torque with respect to the steering torque, and a first auxiliary steering torque for controlling a command current value of the first auxiliary steering torque generated by the motor In an electric power steering apparatus for controlling the first auxiliary steering torque generated by the motor based on a command current value control means, a steering angle detected by the steering angle detection means and a vehicle speed detected by a vehicle speed detection means Target steering torque estimating means for estimating a target steering torque from the target steering torque estimated by the target steering torque estimating means and the steering torque detecting means. Deviation calculating means for calculating a deviation from the detected steering torque, wherein a first auxiliary steering torque command current value control means controls a command current value of the first auxiliary steering torque based on the deviation. It is characterized by doing.

According to a second aspect of the present invention, in the electric power steering apparatus according to the first aspect, a second auxiliary control device for controlling a command current value of the steering torque and a second auxiliary steering torque generated by the motor based on the vehicle speed. A steering torque command current value control means for adding a command current value of the second auxiliary steering torque to a command current value of the first auxiliary steering torque, and setting a command current value of the first auxiliary steering torque; It is characterized by controlling.

According to a third aspect of the present invention, in the electric power steering apparatus according to the first or second aspect, the first auxiliary steering torque command current value control means controls the first auxiliary steering torque command with respect to the deviation. A proportional term control means for determining a current value, wherein the gain of the command current value of the first auxiliary steering torque with respect to the deviation decreases in a region near zero deviation. is there.

According to a fourth aspect of the present invention, in the electric power steering apparatus according to the third aspect, the first auxiliary steering torque command current value control means controls the first auxiliary steering torque with respect to a differential value of the deviation. The differential term control means determines the command current value of the first auxiliary steering torque, and the gain of the command current value of the first auxiliary steering torque with respect to the differential value of the difference is small in an area near zero of the differential value of the difference. It is characterized by becoming.

[0010] The invention of claim 5 is the invention of claims 1 to 4.
In the electric power steering apparatus described in the above, a steering angular velocity calculating means for calculating a steering angular velocity from a steering angle detected by the steering angle detecting means, and a command current value of a damping torque generated by a motor based on the steering angular velocity is controlled. Torque command current value control means for controlling the command current value of the first auxiliary steering torque by adding the command current value of the damping torque to the command current value of the first auxiliary steering torque. It is characterized by doing.

According to a sixth aspect of the present invention, in the electric power steering apparatus according to the fifth aspect, a damping constant determined by a gain of a command current value of the damping torque with respect to the steering angular velocity is detected by the vehicle speed detecting means. It is characterized in that it changes so as to increase as the vehicle speed increases.

The invention of claim 7 is the first to sixth aspects of the present invention.
Wherein the gain of the command current value of the first auxiliary steering torque is corrected based on the vehicle speed and the deviation in the proportional term control means.

According to an eighth aspect of the present invention, in the electric power steering apparatus according to the seventh aspect, the gain of the command current value of the first auxiliary steering torque increases as the vehicle speed increases when the deviation is positive. On the contrary, when the deviation is negative, the correction is made so as to decrease as the vehicle speed increases.

[0014]

According to the first aspect of the present invention, since the driver's steering torque determined by the steering force by which the driver steers the steering wheel and the turning radius of the steering wheel is detected, the motor temperature changes and manufacturing variations. Can completely eliminate the influence on torque. Further, since the target steering torque is set without considering the vehicle weight or the link efficiency, the control in the controller can be simplified.

According to the second aspect of the present invention, even when the steering angle cannot be detected due to the failure of the steering angle detecting means, the control is not stopped and the second auxiliary steering torque command is obtained based on the steering torque and the vehicle speed. It can be controlled by current value control means.

According to the third aspect of the invention, in addition to the effects of the first or second aspect, when the deviation between the target steering torque and the steering torque is small, that is, when it is not necessary to generate much auxiliary steering torque, Control can be stabilized by effectively reducing the gain and suppressing hunting.

According to the invention of claim 4, in addition to the effect of claim 3, hunting can be prevented and control can be further stabilized.

According to the invention of claim 5, claims 1 to
In addition to the effect of 4, when the driver releases the steering torque during steering, the steering angular speed at which the steering angle at which the vehicle goes straight is neutral is maximized, the damping torque is also maximized at that position, and the steering angle is reduced to the neutral angle. It is easier to converge to the position.

According to the invention of claim 6, in addition to the effect of claim 5, since the damping constant increases as the vehicle speed increases, the damping constant is required at high speed running by increasing the damping gain at high speed turning. It is possible to improve the performance of converging the steering angle to the neutral position. On the other hand, when the vehicle is turning at a low speed, the gain of the damping is reduced to improve the return performance of the steering wheel required at the time of low speed traveling. be able to. Therefore, it is possible to easily achieve conflicting performance requirements at high speed and at low speed.

According to the seventh and eighth aspects of the present invention, in addition to the effects of the first to sixth aspects, the gain of the proportional term can be corrected by the vehicle speed. It is possible to provide a steering feeling that meets the needs. When the steering torque is smaller than the target steering torque, for example, when the vehicle turns and the steering torque decreases due to the road surface reaction force due to the change in the road surface μ (when the deviation is positive), if the vehicle is turning at high speed, the gain is increased. By doing so, a firm steering feeling can be given. Conversely, when the vehicle is at a low speed, the gain is reduced to make it easier for the driver to understand the change in the steering torque when, for example, the road surface μ changes suddenly.
Can help with danger prediction. On the other hand, when the steering torque is larger than the target steering torque (when the deviation is negative),
During high-speed turning, reducing the gain can leave the driver with a certain level of steering feeling,
On the other hand, when turning at low speed, increasing the gain
For example, when a garage is to be placed, the steering load of the driver can be reduced by reducing the stationary steering torque.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 is an overall system diagram showing an electric power steering control device according to the present invention. In FIG. 1, 1 is a steering wheel, 2 is a steering torque sensor (steering torque detecting means), 3 is a speed reducer, 4 is a rack and pinion steering mechanism, 5 is a motor, 6 is a steering angle sensor, 7 is a control unit, and 8 is The steering shaft 9 is a vehicle speed sensor (vehicle speed detecting means).

Sensor signals are sent to the control unit 7 from the steering torque sensor 2, the steering angle sensor 6 and the vehicle speed sensor 9. The command current value of the torque generated in the motor is calculated based on these sensor signals, and the command current value of the torque is output to the motor control unit 16. The motor 5 is driven under the control. The driving force of this motor is transmitted to the rack & pinion steering mechanism 4 via the speed reducer 3, and is configured to assist (including increase in torque) the steering torque of the driver with respect to the steering wheel 1.

FIG. 2 is a control block diagram showing the control contents in the control unit 7 of the first embodiment. In FIG. 2, 11 is a subtractor (deviation calculating means), and 15 is
It is an adder. The steering angle θ of the steering wheel 1 is detected by a steering angle sensor 6 attached to the center of the steering wheel 1, and the vehicle speed V of the vehicle is detected by a vehicle speed sensor 9. Both detection results are input to the controller 7, and the target steering torque estimating means 10
Is used to estimate the target steering torque Tm. Here, the estimated value of the target steering torque is shown in FIG. Here, the steering angle θ and the target steering torque Tm are defined as positive (+) in the right direction.
The gain of the target steering torque Tm tends to increase as the vehicle speed V increases with respect to the steering angle θ. On the other hand, when the steering wheel 1 is steered, the steering torque T is detected by the steering torque sensor 2 with respect to the steering angle θ, and the subtractor (deviation calculating means) 11
Then, the deviation ε between the target steering torque Tm and the steering torque T is calculated. Here, Tm-T = ε is defined.

Next, the command current value of the first auxiliary steering torque is controlled by the proportional term control means 12 and the differential term control means 14 of the first auxiliary steering torque command current value control means 24 based on the calculated deviation ε. Is done. The details will be described below. In the proportional term control means 12, the command current value Tca of the first auxiliary steering torque is determined as shown in FIG. The deviation is positive (+) and the torque command current value Tca is negative (-). When the deviation is positive (+), the steering torque T is smaller than the target steering torque Tm.
The command current value Tca is set to a negative value (-) to apply a torque in the reverse direction. With respect to the differential term, a differential value ε of the deviation ε with respect to time is calculated by the differential differential operation circuit 13, and the command current value Tcb of the second auxiliary steering torque with respect to the differential value ε is calculated by the differential term control means 14. 5 is determined. The Tca and Tcb are added by the adder 15 and output to the motor control unit 16 as a first auxiliary steering torque command current value Tc1. Since the content of this control is the control for the steering torque, there is no need to consider the temperature change of the motor, the manufacturing variation, the vehicle weight, and the link efficiency as in the conventional control of the rack shaft load.

FIG. 6 is a control block diagram showing the control contents of the control unit 7 in the second embodiment. The second embodiment shows an embodiment in which the present invention is applied to the control of the auxiliary steering torque. In FIG. 6, reference numeral 18 denotes an adder. Explaining the difference from the first embodiment, the vehicle speed V detected by the vehicle speed sensor 9 and the steering torque T detected by the steering torque sensor 2 are input to the controller 7 and are controlled by the second auxiliary steering torque control means. A certain second
Is input to the auxiliary steering torque command current value control means 17,
The command current value Tco of the second auxiliary steering torque is determined.
FIG. 7 shows the determination of the command current value of the second auxiliary steering torque. Here, the command current value Tco of the steering torque T and the second auxiliary steering torque defines the right direction as positive (+). As the vehicle speed V increases, the gain of the command current value Tco of the second auxiliary steering torque tends to decrease. The second
The command current value Tco of the first auxiliary steering torque is the command current value Tc of the first auxiliary steering torque determined in the same manner as in the first embodiment.
The command current value Tc2 of the first auxiliary steering torque is added to 1 by the adder 18 and is output to the motor control unit 16. Therefore, even when the steering angle cannot be detected, the control current does not stop and the command current value of the first auxiliary steering torque is controlled by the second auxiliary steering torque command current value control means based on the steering torque and the vehicle speed. Can be.

FIG. 8 shows a third embodiment in which the proportional term control means 12 of the above-described first and second embodiments has the first auxiliary steering torque in the region where the deviation ε is near zero (between -ε1 and + ε1). This shows a case where the gain of the command current value Tca decreases. When the deviation ε is equal to or more than ε1 in absolute value, the gain of the torque command current value Tca rises sharply, and when the deviation ε is large, the command current value Tca becomes small and the motor torque becomes insufficient. Preventing. Therefore, when the deviation is small, that is, when it is not necessary to generate much motor torque, it is possible to effectively reduce the gain, suppress hunting, and stabilize the control.

FIG. 9 shows a fourth embodiment in which the differential term control means 14 of the third embodiment has a command current of the first auxiliary steering torque in a region where the differential value ε of the deviation is near zero (between -ε1 and + ε1). The case where the gain of the value Tcb becomes small is shown.
In the same manner as the proportional term control means 12, the ε is an absolute value ε
When it becomes 1 or more, the command current value Tcb of the first auxiliary steering torque
Suddenly rises, the command current value Tcb becomes small when the differential value ε of the deviation is large, and together with the proportional term control means 12, the motor torque is prevented from becoming insufficient. As a result, when the deviation is small, in addition to the effect of the third embodiment, hunting can be prevented and control can be further stabilized.

FIG. 10 is a control block diagram showing the control contents of the control unit 7 in the fifth embodiment.
The fifth embodiment shows an embodiment in which damping torque command current value control means is added to each of the first to fourth embodiments. In FIG. 10, reference numeral 21 denotes an adder. The steering angle θ detected by the steering angle sensor 6 is used as the steering angle differential operation circuit 1
9, a derivative value θ of the steering angle θ with respect to time is calculated, and the damping torque command current value control means 20 calculates the derivative value θ.
, A command current value Tcc of the damping torque is determined. FIG. 11 shows the determination of the command current value of the damping torque. Here, the differential value θ and the command current value Tcc of the damping torque are defined as positive (+) in the right direction. The derivative value θ and the command current value Tcc of the damping torque are in a proportional relationship. The command current value Tcc of the damping torque is added to the command current value Tc1 or Tc2 of the first auxiliary steering torque output to the motor control unit 16 in each of the first to fourth embodiments.
And the command current value Tc3 of the first auxiliary steering torque.
Is output to the motor control unit 16. Therefore, when the driver releases the steering torque during steering, the steering angular velocity at which the steering angle at which the vehicle goes straight is neutral is maximized, the damping torque is maximized at that position, and the steering angle converges to the neutral position. It will be easier.

FIG. 12 is a control block diagram showing the control contents of the control unit 7 in the sixth embodiment.
The sixth embodiment differs from the fifth embodiment in that the damping torque command current value control means 20 is variable with respect to the vehicle speed V.
In FIG. 12, a time-dependent differential value θ of the steering angle θ calculated in the same manner as in the fifth embodiment and the vehicle speed V detected by the vehicle speed sensor 9 are input to the vehicle speed variable damping torque command current value control means 22. Thus, the command current value Tcc of the damping torque is determined. Here, the determination of the command current value of the vehicle speed variable damping torque is shown in FIG. As the vehicle speed increases, the gain of the command current value Tcc of the damping torque tends to increase. This makes it possible to improve the performance of converging the steering angle required during high-speed running to the neutral position by increasing the damping gain when the vehicle is turning at high speed. , The return performance of the steering wheel in steering required during low-speed running can be improved. Therefore, it is possible to easily achieve conflicting performance requirements at high speed and at low speed.

FIG. 14 is a control block diagram showing the control contents of the control unit 7 in the seventh embodiment.
In the seventh embodiment, the proportional term control means 12 is variable with respect to the vehicle speed V in each of the first to sixth embodiments. In FIG. 14, the vehicle speed V detected by the vehicle speed sensor is input to the vehicle speed variable proportional term control means 23 simultaneously with the deviation ε, and the command current value Tca of the first auxiliary steering torque is determined. Here, the determination of the proportional term that is variable depending on the vehicle speed is shown in FIGS. FIG. 15 shows a state in which the gain increases and decreases depending on the vehicle speed in FIG. 4, and FIG. 16 shows a case similar to FIG. When the deviation ε is positive (+), the command current value Tca of the first auxiliary steering torque increases in the negative (−) direction by increasing the gain in the negative (−) direction as the vehicle speed V increases. By generating a command current value of a large reaction torque, a firm steering feeling can be given to the driver. Conversely, as the vehicle speed V decreases, the command current value Tca of the torque decreases in the negative (-) direction and the reaction torque generated with respect to the steering torque T is small. Can predict the danger to some extent. When the deviation ε is negative (−), the command current value Tca of the first auxiliary steering torque decreases in the positive (+) direction by decreasing the gain in the positive (+) direction as the vehicle speed V increases. The command current value of the small assist torque will be generated,
If the vehicle is turning at high speed, the driver can have a certain feeling of steering. Conversely, as the vehicle speed V decreases, the command current value Tca of the first auxiliary steering torque increases in the positive (+) direction, and the assist torque generated with respect to the steering torque T increases. In this case, the steering load of the driver can be reduced by reducing the stationary steering torque.

[Brief description of the drawings]

FIG. 1 is an overall system diagram showing an electric power steering control device according to an embodiment of the present invention.

FIG. 2 is a control block diagram showing control contents in a control unit 7 of the first embodiment.

FIG. 3 is a diagram showing a relationship between a steering angle θ, a target steering torque Tm, and a vehicle speed V in a target steering torque estimating means 10;

FIG. 4 is a diagram showing a relationship between a deviation ε and a command current value Tca of a first auxiliary steering torque by a proportional term control means 12.

FIG. 5 is a diagram illustrating a relationship between a differential value ε of a deviation and a command current value Tcb of a first auxiliary steering torque by a differential term control unit 14.

FIG. 6 is a control block diagram showing control contents in a control unit 7 of the second embodiment.

FIG. 7 shows a second auxiliary steering torque command current value control unit 17.
And the command current value T of the steering torque T and the second auxiliary steering torque
It is a figure showing the relationship between co and vehicle speed V.

FIG. 8 is a diagram showing a case where the relationship between the deviation ε and the command current value Tca of the first auxiliary steering torque by the proportional term control means 12 is such that the deviation ε is small in a region near zero.

FIG. 9 is a graph showing the relationship between the differential value ε of the deviation and the command current value Tcb of the first auxiliary steering torque by the differential term control means 14;
Is a diagram showing a case where is small in a region near zero.

FIG. 10 is a control block diagram showing control contents in a control unit 7 of a fifth embodiment.

FIG. 11 is a diagram showing a relationship between a differential value θ of the steering angle θ with respect to time and a damping torque command current value Tcc by the damping torque command current value control means 20.

FIG. 12 is a control block diagram showing control contents in a control unit 7 of a sixth embodiment.

FIG. 13 shows a differential value θ and a damping torque command current value T by a vehicle speed variable damping torque command current value control means 22.
It is a figure showing the relationship between cc and vehicle speed V.

FIG. 14 is a control block diagram showing control contents in a control unit 7 of a seventh embodiment.

FIG. 15 is a diagram illustrating a relationship with a vehicle speed V in FIG. 4;

FIG. 16 is a diagram showing a relationship with a vehicle speed V in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 steering wheel 2 steering torque sensor 3 reduction gear 4 rack & pinion steering mechanism 5 motor 6 battery 7 control unit 8 steering shaft 9 vehicle speed sensor 10 target steering torque estimating means 11 deviation calculating means 12 proportional term controlling means 13 deviation differential operation circuit 14 differentiation Term control means 15 Adder 16 Motor controller 17 Second auxiliary steering torque command current value control means 18 Adder 19 Steering angle differential operation circuit 20 Damping torque command current value control means 21 Adder 22 Vehicle speed variable damping torque command current Value control means 23 vehicle speed variable proportional term control means 24 first auxiliary steering torque command current value control means

Claims (8)

[Claims] 1. A steering torque detecting means for detecting a steering torque of a driver, a steering angle detecting means for detecting a steering angle of a steering wheel, a vehicle speed detecting means for detecting a vehicle speed, and a first auxiliary to the steering torque. A motor for generating a steering torque;
An electric power steering device for controlling a first auxiliary steering torque generated by the motor based on first auxiliary steering torque command current value control means for controlling a command current value of the first auxiliary steering torque generated by the motor; A target steering torque estimating means for estimating a target steering torque from a steering angle detected by the steering angle detecting means and a vehicle speed detected by a vehicle speed detecting means; and a target steering estimated by the target steering torque estimating means. A deviation calculating means for calculating a deviation between the torque and the steering torque detected by the steering torque detecting means;
An electric power steering apparatus, wherein the command current value of the first auxiliary steering torque is controlled by the auxiliary steering torque command current value control means. 2. The electric power steering apparatus according to claim 1, wherein a second auxiliary steering torque command current value for controlling a command current value of the steering torque and a second auxiliary steering torque generated by a motor based on the vehicle speed. Control means for adding a command current value of the second auxiliary steering torque to a command current value of the first auxiliary steering torque to control the command current value of the first auxiliary steering torque. Electric power steering device. 3. The electric power steering apparatus according to claim 1, wherein the first auxiliary steering torque command current value control means controls a command current value of a first auxiliary steering torque with respect to the deviation. An electric power steering apparatus, further comprising proportional term control means for determining, wherein the gain of the command current value of the first auxiliary steering torque with respect to the deviation decreases in a region near zero deviation. 4. The electric power steering apparatus according to claim 3, wherein the first auxiliary steering torque command current value control means determines a first auxiliary steering torque command current value based on a differential value of the deviation. A differential term control means, wherein the gain of the command current value of the first auxiliary steering torque with respect to the differential value of the deviation decreases in a region near the differential value of zero. Power steering device. 5. The electric power steering apparatus according to claim 1, wherein a steering angular velocity calculating means for calculating a steering angular velocity from a steering angle detected by the steering angle detecting means, and a steering angular velocity based on the steering angular velocity. A damping torque command current value control means for controlling a command current value of a damping torque to be generated in the motor, wherein the command current value of the damping torque is added to the command current value of the first auxiliary steering torque. An electric power steering apparatus, wherein a command current value of an auxiliary steering torque is controlled. 6. The electric power steering apparatus according to claim 5, wherein a damping constant determined by a gain of a command current value of the damping torque with respect to the steering angular velocity increases as the vehicle speed detected by the vehicle speed detection unit increases. An electric power steering device, comprising: 7. The electric power steering apparatus according to claim 1, wherein the proportional term control means corrects a gain of a command current value of the first auxiliary steering torque based on the vehicle speed and a deviation. An electric power steering device, comprising: 8. The electric power steering device according to claim 7, wherein the gain of the command current value of the first auxiliary steering torque increases as the vehicle speed increases when the deviation is positive, and conversely, the gain of the command current value of the first auxiliary steering torque increases. When the deviation is negative, the electric power steering device is corrected so as to decrease as the vehicle speed increases.