JPH0667739B2 - Motor control device for electric power steering device - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a motor control device for an electric power steering device that applies an auxiliary steering force (power assist) by a motor drive to a steering system of a vehicle.

[Prior art]

A motor control device for an electric power steering device as described above generates an assist signal having a characteristic that the absolute value increases with an increase in the torsion torque, based on the output of a torsion torque sensor that detects the torsion torque of the steering system. Is provided, and a phase compensation command unit that immediately generates an assist assist signal in accordance with the rate of change of the torsion torque. The addition signal of these signals is used as a command signal to determine the rotation direction of the electric motor.
A controllable rotating torque has already been proposed by the present applicant (see Japanese Patent Laid-Open No. 61-98675).

[Problems to be Solved by the Invention]

The phase compensation command unit immediately outputs an assist assist signal corresponding to a large change rate even if the torsion torque is small, so that the inertial force of the electric motor is immediately absorbed when the steering wheel is repeatedly turned left and right. The steering feeling is improved. However, there is a problem that the assist assist signal is output even when the road surface vibration during traveling of the vehicle is twisted and picked up and output by the torque sensor, which easily causes disturbance. Although it is possible to remove the disturbance by giving a hysteresis to the input of the torsional torque, if the width of the hysteresis is large, the response of the control system deteriorates. The present invention has been made to solve the above problems, and provides a motor control device for an electric power steering device capable of effectively removing control disturbance due to road surface vibration while ensuring control responsiveness. The purpose is to do.

[Means for Solving the Problems]

For this purpose, the motor control device of the electric power steering device according to the present invention is configured such that the drive control unit causes the drive controller to rotate and rotate the electric motor in response to a command signal based on the output signal of the torsion torque sensor that detects the torsion torque of the steering system. In an electric power steering apparatus that controls torque, a hysteresis that inputs an output signal of the torsion torque sensor and converts the characteristics of the output signal into a characteristic having hysteresis that makes the torsion torque change to zero in a range of a predetermined value or less. And a phase compensation command section for outputting an assisting auxiliary signal as a command signal according to the rate of change of the torsion torque based on the differential value of the output signal of the torsion torque sensor input via the hysteresis means, The hysteresis means is a hysteresis band which is a dead band width based on the output signal of the vehicle speed sensor for detecting the vehicle speed. Cis width is the means by being configured so as to increase to a predetermined value with an increase in vehicle speed.

[Work]

With such a means, when the torsion torque increases above a predetermined value passing through the hysteresis means, an assist assist signal corresponding to the rate of change is generated and an electric motor control command signal is immediately generated. When the torsional torque is equal to or less than a predetermined value as in the case of the disturbance, the hysteresis means cuts off the output of the assisting auxiliary signal. The hysteresis width of the hysteresis means is small when the vehicle vibration is small and the road surface vibration is small, and is large when the vehicle speed is high when the road surface vibration is large.

【Example】

An embodiment of the present invention will be specifically described below with reference to the drawings. In FIG. 1, reference numeral 1 is an electric motor for power assist, which is connected to a pinion shaft of a rack and pinion mechanism of a steering system (not shown) via a speed reducer, a joint, etc., and can provide an assist force to the steering system. It is like this. Such an electric motor 1 includes a positive / negative determination unit 21, an absolute value conversion unit 22, a duty control unit 23, an armature current detection unit 24,
With the drive control unit 2 including the electric motor drive unit 25,
The rotation direction and the rotation torque are controlled based on a command signal described later. That is, the command signal is input to the positive / negative determination unit 21 and the absolute value conversion unit 22, and the determination signal of the positive / negative determination unit 21 is input to the electric motor drive unit 25, whereby the direction of the motor current is switched according to the command signal. Controlled and absolute value converter
The output signal of 22 is input to the duty control unit 23 to determine the duty ratio, and by inputting this to the electric motor drive unit 25, the rotation torque according to the magnitude of the command signal is set. The rotation torque of the electric motor 1 is converged to a constant instruction value by the armature current detection unit 24 detecting the armature current of the electric motor 1 and feeding back the detected value to the duty control unit 23. Controlled by. Here, in order to output a command signal to the drive control unit 2, in this embodiment, an assist command unit 3, a return command unit 4, a phase compensation command unit 5, and a steering angle phase compensation command unit 6 are provided. . The assist command unit 3 basically generates an assist signal according to the magnitude and direction of the torsion torque of the steering system, and is installed in, for example, a pinion of the steering system (steering system), and the direction of the torsion torque and Based on a torsion torque sensor 31 for detecting the magnitude and an output voltage signal (see FIG. 2) of the torsion torque sensor 31, basically, an assist signal having a characteristic as shown by the solid line in the graph of FIG. That is, if the magnitude of the torsion torque is below a predetermined value, it is not output, and if it exceeds the predetermined value, an assist torque value instruction function unit that outputs an assist signal that increases or decreases according to the value of the torsion torque with a polarity according to the direction of the torsion torque. 32 and. Further, the assist command section 3 is provided with a vehicle speed sensor 33 for detecting the speed of the vehicle, and based on the output voltage signal of the vehicle speed sensor 33, the assist command section 3 decreases as the vehicle speed increases as shown in the graph of FIG. The addition constant function unit 34 for generating the addition constant signal Sv having the characteristics described above, and the addition calculation unit 35 for inputting the addition constant signal Sv and the output signal of the torsion torque sensor 31 and outputting the same to the assist torque value instruction function unit 32. Is provided. The addition calculation unit 35 adds and subtracts the addition constant signal Sv according to the polarity of the output signal of the torsion torque sensor 31, so that the characteristic shown in the graph of FIG. 3 has the vehicle speed as a parameter in the X-axis direction. It is designed to be translated. That is, to show an example of the characteristics in the case of right-turning, as shown by the solid line in FIG.
For the same output, the absolute value of the output decreases as the vehicle speed increases, and for the same vehicle speed, the absolute value of the output increases as the absolute value of the torsion torque increases. A multiplication constant function unit 36 and a multiplication calculation unit 37 are provided to correct such output characteristics as shown by the broken line in FIG. 5 according to the vehicle speed. This multiplication constant function unit 36 is a multiplication constant signal having the characteristic shown in FIG. 6 based on the output voltage signal of the vehicle speed sensor 33, that is, the multiplication constant is 1 when the vehicle speed is 0, and the constant gradually increases as the vehicle speed increases. Generates a multiplication constant signal having a characteristic of decreasing as 0 approaches 0. The multiplication calculation unit 37 multiplies the output of the assist torque value instruction function unit 32 by the multiplication constant, and the assist signal it from the multiplication calculation unit 37 corresponds to the vehicle speed as shown in FIG. As shown by the broken line. Next, the return command unit 4 generates a return signal in the direction of returning the steering angle to the neutral (straight) position according to the turning angle of the steering system. For example, a rack in a rack and pinion mechanism of the steering system. Steering angle sensor 41 for detecting a steering angle based on the amount of movement of the steering wheel, and a return torque value indicating function for outputting a return signal iθ having the characteristic shown in the graph of FIG. 7 based on the output voltage signal of the steering angle sensor 41. The unit 42 is provided. Here, the phase compensation command unit 5 generates an assist auxiliary signal ia corresponding to the change rate of the torsion torque as a command signal, and has a hysteresis width instruction function unit 51 for inputting the output signal of the vehicle speed sensor 33. 52, a phase compensator 53 for inputting the output signal of the torsion torque sensor 31 via the hysteresis means 52, and the phase compensator 53
And a phase compensation indicator function unit 54 for inputting a signal from the output signal of the phase compensation unit 53. The output signal of the phase compensation unit 53 is added to the output signal of the torsion torque sensor 31 and input to the addition calculation unit 35 of the assist command unit 3. As shown in the graph of FIG. 10, the hysteresis width instruction function unit 51 outputs a hysteresis width signal H having a characteristic that it increases proportionally to a predetermined value as the vehicle speed increases and then becomes a constant value. There is. Further, the phase compensator 53 differentiates the output signal of the torsion torque sensor 31 input via the hysteresis means 52, and generates a signal proportional to the differentiated value. And the phase compensation indicator function unit 54
As shown in FIG. 8, when the degree of change in the torsion torque is proportionally increased / decreased within a predetermined value and exceeds the predetermined value, an assist auxiliary signal ia having a constant value is output. Further, the steering angle phase compensation command unit 6 generates an attenuation signal in a direction opposite to the direction in which the rudder moves in accordance with the speed of the steering operation. The output signal of the rudder angle sensor 41 is input and the differential value thereof is input. Based on the output signal of the steering angle phase compensating unit 61, a steering angle phase compensating instruction function that outputs a damping signal i having the characteristic shown in the graph of FIG. And a section 62. Further, in this embodiment, the return signal iθ from the return command unit 4 and the attenuation signal i from the steering angle phase compensation command unit 6 are used.
A vehicle speed determination unit 7 that regulates the output of the vehicle is provided. The vehicle speed discriminating unit 7 inputs the addition signal of the return signal iθ and the attenuation signal i, and outputs the addition signal as it is when the vehicle speed is 5 km / h or more based on the output signal of the vehicle speed sensor 33. When the vehicle speed is 5 km / h or less, the output of the addition signal is regulated. Then, under the regulation of the vehicle speed determination unit 7, the assist signal it from the assist command unit 3, the return signal iθ from the return command unit 4, the assist auxiliary signal ia from the phase compensation command unit 5, Damping signal i from the steering angle phase compensation command unit 6
The addition signal of and is output to the drive control unit 2 as a command signal. In the above configuration, when a twisting torque is generated in the steering system due to the steering operation, the twisting torque sensor 31 detects this and generates an output signal, but at this time, the vehicle speed sensor 33 and the steering angle sensor 41 Correction is added to the assist signal it based on the above output signal by each of the above information. Then, the rotation direction and the rotation torque of the electric motor 1 are controlled through the positive / negative determination of the assist signal it and the duty ratio control according to the absolute value. Here, the relationship between the torsion torque and the assist signal it is basically as shown in the graph of FIG. 3. For example, a positive assist signal corresponds to the torsion torque when turning right. The output is increased so that Therefore, the electric motor 1 is rotationally driven by the output torque according to the magnitude of the torsion torque in the rotation direction that assists the right turning, and the steering force at the time of the right turning is reduced. In addition,
Electric motor 1 based on a negative assist signal when turning left
Is controlled in a rotation direction that assists left cutting, and thus operates in the same manner as in right cutting. Here, the functional characteristics of the torsion torque and the assist signal change based on the output signal of the vehicle speed sensor 33 in this embodiment.
For example, in FIG. 5 showing a characteristic graph of an assist signal with respect to right-turning torsion torque, when the state of the vehicle speed O is shown by Mo, as the vehicle speed increases to V ₁ and V ₂ , the addition constant function unit 3
On the basis of the addition processing of the addition constant signal Sv from 4, the characteristic graph changes in parallel with M ₁ and M _{2 in} the X-axis direction of FIG. Then, the characteristic graph M _{1 is obtained} by the multiplication processing of the multiplication constant signal.
Changes to m ₁ and M ₂ decreases to m ₂ . Therefore, when the magnitudes of the torsion torques are the same, the magnitude of the assist signal decreases as the vehicle speed increases. This is
This means that the output torque of the electric motor 1 with respect to the same torsional torque decreases as the vehicle speed increases. While the vehicle is traveling at low speed, sufficient power assist can be obtained, but the steering force becomes excessive during traveling at high speed. Therefore, there is no fear that the steering wheel is too light when steering. On the other hand, the steering angle sensor 41 detects the steering angle in accordance with the steering operation, and based on this, the characteristic shown in FIG. 7, that is, the steering angle O is not output in the vicinity of the neutral position and exceeds this range. The ratio increases proportionally in the range of the left and right steering angles ± θ ₀ , and becomes a constant value when it exceeds ± θ _{0. A} negative value (left turning direction) in the right steering area, a positive value in the left steering area. A return signal i.theta. That is in the (right cutting direction) is output. Further, when the turning speed is fast, such as when the vehicle travels on a curve with a small radius with a sharp steering wheel, the turning angle θ changes abruptly, which is detected by the steering angle phase compensator 61.
A damping signal i is output from the steering angle phase compensation indicator function unit 62 based on the detection signal. This is the characteristic shown in FIG. Here, when the vehicle is traveling, the return signal iθ and the attenuation signal i are added by the action of the vehicle speed determination unit 7 so as to decrease the assist signal it. Therefore, there is no fear that the steering wheel will be too light when turning suddenly. Further, for example, when the steering is held at the right turning angle θ ₁ , a positive assist signal based on the output signal of the torsion torque sensor 31 described above.
It and a negative return signal i based on the output signal of the steering angle sensor 41
The electric motor 1 is controlled by the addition signal with θ ₁ . If the graph of the assist signal it is shown by the solid line in FIG. 3, the addition signal is shown by the broken line. Therefore, when the steering holding state of the right turning angle θ ₁ is released, the torsional torque T is drastically reduced and the addition signal immediately becomes a negative value (left turning direction) along the broken line in FIG. 3. As a result, torque in the left-turn direction is generated in the electric motor 1 to cancel the frictional force of the speed reducer and the like, the moment of inertia of the motor, etc. Therefore, when the vehicle is running, the steering system is in a straight traveling state due to the caster effect. The steering wheel return operation is good, such as smooth restoration to. Then, as the turning angle θ decreases, the magnitude of the return signal iθ gradually decreases to approach 0, and when the turning angle returns to the neutral position, the torque of the electric motor disappears. On the other hand, when the steering wheel is returned from the quick turn (high G turn),
The handle may exceed neutral due to the inertia of the motor.
However, when the damping signal i is output from the steering angle phase compensation command unit 6, the damping signal commands an output torque opposite to the rotation direction of the steering wheel, so that the steering wheel does not return too much, and the steering wheel is released when the vehicle is traveling at high speed. The convergence property from is also improved. Next, the steering operation in the stopped state of the vehicle, that is, the stationary steering will be described. In this case, since the ground resistance is large, the torsion torque sharply increases with the steering operation, and the output voltage of the torsion torque sensor 31 also increases. Increase rapidly in proportion. At this time, since the hysteresis width is zero, the output voltage of the torsion torque sensor 31 remains unchanged as the hysteresis means 52.
Pass through. Then, the tendency of the torsional torque to increase rapidly is detected by the phase compensator 53 of the phase compensation commander 5, and an output signal corresponding to the degree of increase of the torsional torque is added to the output signal of the torsional torque sensor 31. Therefore, even when the torsion torque T is small and the assist signal it associated therewith is not yet generated, the assist signal it is immediately output if the degree of change in the torsion torque is large, and the electric motor 1 is operated during the stationary steering. Will start immediately without a delay in response, and the occurrence of self-excited vibration will be prevented. Then, at the time of stationary steering, the return signal iθ of the return command unit 4
Since the damping signal i from the steering angle phase compensation command unit 6 is regulated by the vehicle speed determination unit 7, light steering can be realized without energy labor. Here, when the vehicle is in the middle or low speed, the hysteresis width of the hysteresis means 52 takes a relatively small value according to the vehicle speed. Therefore, when the left and right steering is repeated, the output signal of the torsion torque sensor 31 that exceeds the hysteresis width is input to the phase compensation unit 53. Therefore, the assisting signal ia is immediately output from the phase compensation instruction function unit 54 in accordance with the direction of change of the torsion torque.
The control response is good, such as improving the steering feeling by absorbing the inertial force when starting and stopping. Further, since the road surface vibration when the vehicle is traveling straight ahead is relatively small at medium and low speeds, the torsion torque due to such disturbance is cut by the hysteresis means 52. Road surface vibration also increases at high speeds of the vehicle, but since the hysteresis width of the hysteresis means 52 increases accordingly, disturbances due to road surface vibration can be effectively removed, and a useless signal from the phase compensator 53 is generated. Do not output.

【The invention's effect】

As described above, according to the present invention, the phase compensating unit that outputs the assisting auxiliary signal cuts the output based on the minute input via the hysteresis means, and the hysteresis width is large at high speed according to the vehicle speed, Since it changes so as to become smaller at low speeds, it is possible to effectively remove the disturbance due to road surface vibrations even at high speeds, and at the same time, to secure the necessary control responsiveness at low speeds.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of the present invention, and FIG.
The figure shows the characteristic graph of the output signal of the torsion torque sensor, FIG. 3 shows the basic characteristic graph of the assist signal, FIG. 4 shows the characteristic graph of the addition constant signal, FIG. 5 shows the characteristic change of the assist signal, and FIG. Is a characteristic graph of a multiplication constant signal, FIG. 7 is a characteristic graph of a return signal, FIG. 8 is a characteristic graph of an assist assist signal, FIG. 9 is a characteristic graph of an attenuation signal, and FIG. 10 is a characteristic graph of hysteresis width. . 1 ... Electric motor 2 ... Drive control unit 21 ... Positive / negative discrimination unit, 22 ... Absolute value conversion unit 23 ... Duty control unit, 24 ... Armature current detection unit 25 ... Electric motor drive unit 3 ... Assist command unit 31 …… Torsion torque sensor, 32 …… Assist torque value instruction function unit, 33 …… Vehicle speed sensor, 34 …… Addition constant function unit, 35
…… Addition calculation unit, 36 …… Multiplication constant function unit, 37 …… Multiplication calculation unit 4 …… Return command unit 41 …… Steering angle sensor, 42 …… Return torque value instruction function unit 5 …… Phase compensation command unit 51 ...... Hysteresis width instruction function unit, 52 ...... Hysteresis means, 53 ...... Phase compensation unit, 54 ...... Phase compensation instruction function unit 6 ...... Steering angle phase compensation command unit 61 ...... Steering angle phase compensation unit, 62 ...... Steering angle phase compensation instruction function section 7 ... Vehicle speed determination section

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP 62-6867 (JP, A) JP 60-161255 (JP, A) JP 60-193765 (JP, A) JP 61- 81866 (JP, A) JP 61-215166 (JP, A)

Claims (1)

[Claims] 1. An electric power steering apparatus in which a drive control unit controls a rotation direction and a rotation torque of an electric motor according to a command signal based on an output signal of a torsion torque sensor for detecting a torsion torque of a steering system. The output signal of the torque sensor is input, and a hysteresis means for converting the characteristic of this output signal into a characteristic having hysteresis such that the change of the torsional torque becomes zero within a range of a predetermined value or less is provided, and the hysteresis signal is inputted through this hysteresis means. The phase compensation command unit outputs as a command signal an assist auxiliary signal corresponding to the rate of change of the torsion torque based on the differential value of the output signal of the torsion torque sensor. The hysteresis means outputs a vehicle speed sensor that detects the vehicle speed. The hysteresis width, which is the dead band width, is configured to increase to a predetermined value as the vehicle speed increases. The motor control apparatus for an electric power steering apparatus characterized.