JPH01293274A - Motor control device for electric power steering device - Google Patents

Abstract

PURPOSE:To secure safety at the time of a re-start by outputting an instruction signal from a neutral position reset instruction part for resetting steering to a neutral position upon parking and stopping of a vehicle and resetting steering to the neutral position via the driving of an electric motor. CONSTITUTION:A neutral position reset instruction part 7 generates a reset signal for automatically resetting steering to a neutral position as an instruction signal upon parking and stopping a vehicle. The neutral position reset instruction part 7 is equipped with a deviation amount operation part 74 and a reset target value setting part 75 for being inputted with output voltage from a steering angle sensor 41 via a vehicle speed judgement part 71, a torsional torque judgement part 72 and a time limiting part 73, and a reset torque value instruction function part 76 for being inputted with a signal from the aforesaid deviation amount operation part 74. A reset target value setting part 75 saves an initial steering angle theta0 on the basis of a steering angle signal initially inputted from the time limiting part 73, and sets a reset target thetac, multiplying the initial steering angle theta0 by the predetermined multiplier constant. This constant has characteristics of gradual decrease with the passage of time and, therefore, the reset target value shifts gradually nearing zero with the passage of time.

Description

[Detailed description of the invention] [Industrial application field]

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

[Conventional technology]

The motor control device for the electric power steering device described above includes a torsional torque sensor that detects the torsional torque of the steering system, a vehicle speed sensor that detects heavy speed, and a steering angle sensor that detects the steering angle. and corrects the command signal based on the output of the torsional torque sensor so that it decreases as the vehicle speed increases based on the output of the vehicle speed sensor, and increases the command signal based on the output of the steering angle sensor as the steering angle increases. The applicant has already proposed a method in which the return signal is added to control the torque per rotation in the rotational direction of the electric motor (see Japanese Patent Laid-Open No. 61-98675).

[Problem to be solved by the invention]

However, in the conventional motor control device of the electric power steering device as described above, the automatic return of the steering wheel to the neutral position is limited to when the vehicle is running, and only a light steering operation can be performed when the vehicle is parked or stopped. For this reason, it was difficult to tell whether the steering wheel was misaligned from the neutral position or not, and if the vehicle was parked with the steering misaligned, the driver would start without noticing the misalignment and then hastily re-steering the vehicle, resulting in poor operability. The present invention was made in order to solve the above-mentioned problems, and is an electric power steering device that can automatically return the steering wheel to a neutral position when parking or stopping, and protect the drive motor at that time. The purpose of the present invention is to provide a motor control device.

[Means to resolve issues]

For this purpose, the present invention includes a torsional torque sensor that detects torsional torque of a steering system, a vehicle speed sensor that detects vehicle speed,
In an electric power steering device comprising a steering angle sensor that detects a steering angle, the drive control unit controls one rotational torque in the rotational direction of an electric motor for power assist in accordance with a command signal based on the output signal of each of the above-mentioned sensors. , a neutral position return command unit that generates a command signal to return the steering wheel to the neutral position based on the output signal of the steering angle sensor when the absolute value of the output signals from the torsional torque sensor and the vehicle speed sensor is less than a predetermined value when the vehicle is parked or stopped; The neutral position return command section is configured so that the return target value gradually approaches zero. The neutral position fi return command unit is configured to generate a command signal for a predetermined period of time.

[For production]

With such means, when the vehicle is parked or stopped, the absolute value of the output signals from the torsion torque sensor and the vehicle speed sensor becomes less than a predetermined value, and the neutral position return command unit sends the steering to the return target based on the output signal of the steering angle sensor. A command signal is output that follows the value and gradually returns to the neutral position. The output of this command signal is then stopped after a predetermined period of time has elapsed.

【Example】

Hereinafter, one embodiment of the present invention will be specifically described based on the drawings. In FIG. 1, reference numeral 1 is an electric motor for power assist, and 1! is not shown. It is connected to the binion shaft of the rack and binion mechanism of the rudder system via a reduction gear, a joint, etc., and can apply assist force to the above-mentioned steering system. Such an electric motor 1 has a positive/negative determining section 21 .
Absolute value converter 22. Duty control unit 23. Armature current detection section 24. A drive control unit 2 including an electric motor drive unit 25 and the like controls nine rotational torques in the rotation direction based on a command signal to be described later. That is, the command signal is input to the positive/negative determining section 21 and the absolute value converting section 22.
1 discrimination signal is input to the electric motor drive section 25, the direction of the motor current is switched and controlled according to the command signal, and the output signal of the absolute value conversion section 22 is input to the duty control section 23 to change the duty. A ratio is determined, and by inputting this ratio to the electric motor drive section 25, a rotational torque is set according to the magnitude of the command signal. The rotational torque of the electric motor 1 is converged to a certain specified value by the armature current detection section 24 detecting the armature current of the electric motor 1 and feeding back the detected value to the duty control section 23. controlled by. Here, in this embodiment, the assist command section 3 and the return command section 4 are used to output command signals to the drive control section 2.
1 phase compensation command section 5. Rudder angle phase compensation command section 6. A neutral position return command section 7 is provided. The assist command unit 3 basically controls the torsional torque of the steering system,
It generates an assist signal according to the magnitude and direction of the torsional torque, and is based on the torsional torque sensor 31 that detects the direction and magnitude of the torsional torque, and the output voltage signal of this torsional torque sensor 31 (see Fig. 2). Basically, the assist signal has the characteristics as shown by the solid line in the graph in Figure 3, that is, it is not output when the magnitude of the torsional torque is less than a predetermined value, and when it exceeds a predetermined value, the polarity changes depending on the direction of the torsional torque. and an assist torque value indicating function unit 32 that outputs an assist signal that increases or decreases depending on the value of the torsional torque. The assist command unit 3 is also provided with a vehicle speed sensor 33 that detects the speed of the vehicle.
An addition constant function section 34 generates an addition constant signal Sv having a characteristic that decreases as the vehicle speed increases, as shown in the graph of FIG. 4, based on the output voltage signal of the addition constant signal S.
A control unit that inputs v and the output signal of the torsional torque sensor 31 and outputs it to the assist torque value instruction function unit 32.
An x section 35 is provided. Then, the addition calculation unit 35 adds and subtracts the addition constant signal Sv to the output signal of the torsion torque sensor 31 in accordance with the polarity of the output signal, so that the characteristics shown in the graph of FIG. It is designed to be translated in parallel. That is, to give an example of the characteristics in the case of a right turn, as shown by the solid line in FIG. In this case, the absolute value of the output increases as the absolute value of the torsional torque increases. Then, such output characteristics are adjusted according to the vehicle speed.
The multiplication constant function unit 36
A squaring and arithmetic operation section 37 is provided. This multiplication constant function unit 36 generates a multiplication constant signal having the characteristics shown in FIG. This generates a multiplication constant signal with a characteristic that approaches 0 and decreases. Further, 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 i from the multiplication calculation unit 37 is

[ is shown by the broken line in FIG. 5 depending on the vehicle speed. Further, the assist and torque it may be map instructions using torque and vehicle speed as input values. Next, the return command unit 4 generates a return signal in the direction of returning the steering angle to the neutral (straight ahead) position according to the turning angle of the steering system, and for example, the return command unit 4 generates a return signal in the direction of returning the steering angle to the neutral (straight ahead) position according to the turning angle of the steering system. A steering angle sensor 41 that detects the steering angle based on the amount of movement of the steering angle sensor 41. A return torque value indicating function unit 42 is provided which outputs a return signal 1θ having characteristics shown in the graph of FIG. 7 based on the output voltage signal of the steering angle sensor 41. The phase compensation command unit 5 includes a phase compensation unit 51. which receives the output signal of the torsional torque sensor 31 and generates a signal proportional to its differential value. and a phase compensation instruction function section 52 that outputs an assist auxiliary signal ia having characteristics as shown in the graph of FIG. 8 based on the output signal of the phase compensation section 51. The output signal is further added to the output signal of the torsional torque sensor 31 and inputted to the addition calculation section 35, thereby influencing the input signal to the assist torque value indicating function section 32. Further, the steering angle phase compensation command section 6 generates a damping signal in the direction opposite to the direction in which the rudder advances in accordance with the speed of the steering operation, and inputs the output signal of the steering angle sensor 41 and calculates the differential value thereof. and a steering angle phase compensation instruction function that outputs an attenuation signal 1υ with the characteristics shown in the graph of FIG. 9, for example, based on the output signal of the steering angle phase compensation unit 61. 62. Here, the neutral position return command unit 7 generates a return signal in to automatically return the steering wheel to the neutral position when the vehicle is parked. 71° twisting torque determination section 72
A deviation amount calculation section 74 and a return target value setting section 75 each receive an input via the one-hour limiter 73, and a return torque value instruction function section 76 receives a signal from the deviation amount calculation section 74.
It will be equipped with. The vehicle speed determination unit 71 detects the steering angle sensor 4 only when the vehicle speed is approximately zero based on the output signal of the vehicle speed sensor 33.
The output voltage signal from No. 1 is output as is, and the output is regulated at other times. Further, the torsional torque determination section 72 includes the torsional torque sensor 3
Based on the output signal of 1, the signal from the vehicle speed determination section 71 is output as is only when the torsional torque is approximately zero (for example, 063 to 9" or less at the end of the steering wheel), and the output is regulated otherwise. Furthermore, the time limiter 73
After inputting the signal from the torsional torque determining section 72, the signal is output for only 5 seconds, for example. On the other hand, the return target value setting section 75 is the time limit section 73! −
) Fi stores an initial steering angle θ0 based on the first input steering angle signal, and calculates this and a predetermined multiplication constant f(t) which is a function of time.
The return target value θC'@- is set by multiplying by . Here, the multiplication constant f(t) has a characteristic that gradually decreases from 1 to O as time (1) passes, as shown in Figure 10, and is therefore expressed as θC = θ0・f(t). The return target value θC is
As time passes (in this embodiment, a predetermined time within 5 seconds corresponding to the time limiter 73), it gradually approaches zero and moves. Next, the deviation amount calculation unit 74 converts the actual steering angle θ based on the steering angle signal from the time limiter 73 into the return target value setting unit 75.
The deviation amount (θC - θ
) is output as a signal to the return torque value instruction function section 76. In this case, θC1θ both take a positive value in the right steering region and a negative value in the left steering region. The return torque value indicating function section 76 calculates the deviation amount (θC-θ).
In response to this, a return signal in having the characteristics shown in the graph of FIG. 11 is output. In other words, in the left steering region where the deviation amount (θC - θ) is a positive value, it is a positive value (rightward steering direction), and in the rightward steering region where the deviation amount (θC - θ) is a negative value, it is a negative value (leftward direction). When the absolute value of the deviation amount (θC-θ) is within a predetermined value, the absolute value increases proportionally, and when the absolute value exceeds the predetermined value, the absolute value becomes constant.A return signal in is output. Further, in this embodiment, the return signal iθ from the return command section 4 and the attenuation signal i from the steering angle phase compensation command section 6 are
A single series determination unit 8 is provided that regulates the output of υ. This single-unit discrimination section 8 inputs the addition signal of the return signal iθ and the attenuation signal iθ, and outputs the addition signal as is when the vehicle speed is, for example, 5 kn/h or more based on the output signal of the vehicle speed sensor 33. 1, and the output of the addition signal is regulated when the vehicle speed is below 5 kn/h. Then, under the regulation of the single-unit discriminating section 8, the assist signal it from the assist command section 3, the assist auxiliary signal ia from the phase compensation command section 5, and the return signal iθ from the return command section 4 are output. , the addition signal of the attenuation signal iυ from the steering angle phase compensation command section 6 and the return signal in from the neutral position return command section 7 is output to the drive control section 2 as a command signal. In the above configuration, when torsional torque is generated in the steering system due to a steering operation, the torsional torque sensor 31 detects this and generates an output signal. The assist signal it based on the output signal is corrected using each piece of information. The one-rotation torque of the electric motor 1 in the rotational direction is controlled by determining whether the assist signal it is positive or negative and controlling the duty ratio according to the absolute value. If we look at the relationship between the torsional torque and the assist signal it, it is basically as shown in the graph in Figure 3. For example, for the torsional torque when turning right, a positive assist signal indicates the torsional torque. The output increases as the value increases. Therefore, the electric motor 1 is rotationally driven in the rotational direction that assists the right turn with an output torque corresponding to the magnitude of the torsion torque, and the steering force during the right turn is reduced. Note that when turning to the left, the electric motor 1 is controlled in a rotational direction that assists the turning to the left based on the negative assist signal, so that the same effect as in the case of turning to the right occurs. Here, the functional characteristics of the torsional torque and the assist signal are shown in FIG. , the state of vehicle speed 0 is M
, if the vehicle speed is ■1.・As it increases to V2,
Based on the addition process of the addition constant signal Sv from the addition constant function unit 34, the characteristic graph changes by moving in parallel to Ml and M2 in the X-axis direction in FIG. Then, by the multiplication process of the multiplication constant signal, the characteristic graph M1 changes to ml and M2 changes to m2 so as to reduce the slope. Therefore, when the magnitude of the torsional torque is the same, the magnitude of the assist signal decreases as the vehicle speed increases. This means that the output torque of the electric motor 1 with respect to the same torsional torque decreases as the vehicle speed increases, and when the vehicle is running at low speed, there is sufficient power assistance! Despite this, the steering force does not become excessive when driving at high speeds, and therefore, there is no need to feel uneasy because the steering wheel is too light when turning the steering wheel. On the other hand, along with the steering operation, the steering angle sensor 41 detects the steering angle, and based on this, the steering angle sensor 41 detects the steering angle as shown in FIG. The left and right steering angle increases proportionally in the range of ±θO, and becomes a constant value when exceeding ±θ0. In the right steering area, the value is negative (left steering direction), and in the left steering area, it is a positive value (right A return signal Iθ is output that corresponds to the cutting direction). Furthermore, when the steering speed is high, such as when the vehicle is driving around a curve with a small radius with a sharp steering wheel, the steering angle θ changes rapidly, and this is detected by the steering angle phase compensator 61. Based on the signal, an attenuation signal iυ is output from the steering angle phase compensation instruction function section 62. This results in the characteristics shown in FIG. Here, when the vehicle speed is 5 kn/h or more, the return signal iθ and the attenuation signal iθ are set so that the assist signal 1t is decreased by the action of the vehicle speed discrimination unit 8 when the steering is turned in a direction in which the absolute value of the steering angle increases. Added. This eliminates the feeling of anxiety due to the steering wheel being too light before making a sudden turn. For example, when the steering is held at the right steering angle θ1, a positive assist signal it based on the output signal of the torsional torque sensor 31 described above and a negative return signal based on the output signal of the steering angle sensor 41 are generated. The electric motor 1 is controlled by the addition signal of 1θ1. If the graph of the assist signal 1t is shown as a solid line in FIG. 3, the added X signal will be shown as a broken line. Therefore, when the steering holding state of the right steering angle θ1 is released, the torsional torque T is drastically reduced and the torque is increased! The signal immediately goes negative (to the left) along the dashed line in FIG. This generates torque in the left-turning direction in the electric motor 1, which offsets the drag force of the reducer and the moment of inertia of the motor.
/h or more), the steering system can be smoothly restored to a straight-line position in combination with the caster effect, resulting in good steering wheel return operation. As the steering angle θ decreases, the magnitude of the return signal iθ gradually decreases to approach O, and when the steering angle returns to the neutral position, the torque of the electric motor disappears. On the other hand, when returning the steering wheel from a sharp turn (high G turn),
The steering wheel may go beyond neutral due to motor inertia. However, when the attenuation signal 1t is output from the steering angle phase compensation command section 6, this attenuation signal commands the output torque opposite to the rotating direction of the steering wheel.This prevents the steering wheel from returning too much, and when driving at high speed, etc. It also improves convergence when the steering wheel is released. Next, we will explain the steering operation when the vehicle is stopped, that is, stationary steering. In this case, since the ground resistance is large, the torsional torque rapidly increases with the steering operation, and the output voltage of the torsional torque sensor 31 also increases accordingly. increase proportionately. Then, this rapid increase tendency of the torsional torque is detected by the phase compensation section 51 of the phase compensation command section 5, and an output signal corresponding to the degree of increase in the torsional torque is added to the output signal of the torsional torque sensor 31. Therefore, even if the torsional torque T is small and the associated assist signal it has not yet been generated, if the degree of change in the torsional torque is large, the assist signal 11 will be immediately output, and the electric The motor 1 starts immediately without response delay, and self-excited vibrations are prevented from occurring. During stationary steering, the vehicle speed is 5kll/h or less, and the return signal iθ from the return command unit 4 and the attenuation signal iυ from the steering angle phase compensation command unit 6 are regulated by the vehicle speed determination unit 8, so that the energy Light steering is achieved without the labor costs of Further, when the output signal is issued from the phase compensator 51, the assist auxiliary signal ia having the characteristics shown in FIG. 8 is output from the phase compensation instruction function section 52. That is, the degree of change in torsional torque increases or decreases proportionally within a predetermined value, and when it exceeds a predetermined value, the assist signal 1a, which becomes a constant value, is immediately output in accordance with the direction of change in torsional torque. Therefore, when left and right steering is repeated, the assist assist signal 1a is immediately output to absorb the inertial force when starting and stopping the electric motor 1. Now, control when the vehicle is parked or stopped will be explained with reference to the flowchart of FIG. 12. The vehicle speed determining unit 71 then determines whether the vehicle speed has become approximately zero (the set value has hysteresis) (Sl), and if YES, the torsional torque determining unit 72 then determines whether the torsional torque has become approximately zero. It is determined whether or not (S2). If YES here, it is determined that the driver has no intention to steer and the vehicle is parked, and the next step (S3)
Proceed to step +31), ! 32), the neutral position return command unit 7 is reset (S4). In step (S3), the time limiter 73 controls the predetermined time (
5 seconds), and after a predetermined period of time has elapsed, the No.
In this case, the end is reached. When a predetermined period of time has elapsed, the neutral position return command section 7 does not restart unless either the vehicle speed or the torque exceeds a predetermined value. If YES here, the following control will be performed only during that time. That is, the actual steering angle θ is inputted to the deviation amount calculation unit 74 and the return target value setting unit 75 (S5), and the return target value θC is set by the return target value setting unit 75 (se). The deviation amount (θC-θ) is calculated (87), and based on this, the return torque value instruction function section 76 outputs the return signal i.
n is output (S8). With this kind of control, if you park or stop with the steering wheel turned,
The electric motor 1 is driven for a predetermined time (5 seconds) by a return signal in based on the output signal of the steering angle sensor 41, and the steering automatically returns to the neutral position. In this case, even if the initial steering angle is large, the return target value θC is not zero from the beginning but gradually approaches zero, and the actual steering angle θ follows this, so the deviation amount (θC - θ) has a relatively small absolute value. Therefore, the return signal in also takes a relatively small absolute value, and the steering wheel rotates slowly from start to finish and returns automatically, providing a good feeling and safety. In addition, when automatically returning to the neutral position when parking or stopping, even if the tires hit an obstacle and the vehicle cannot be steered,
After a predetermined period of time has elapsed, the return signal disappears and the driving of the electric motor 1 is stopped, so that the electric motor 1 is not damaged by overload. [Effects of the Invention] As explained above, according to the present invention, when the vehicle is parked or stopped, a command signal for returning the steering wheel to the neutral position is output from the neutral position return command unit, and the steering wheel is returned to the neutral position by the driving force of the electric motor. Automatically return. Therefore, steering when restarting can be performed safely and reliably. In this case, the steering wheel gradually returns to the neutral position following the movement of the return target value, so the steering wheel feels good and is safe. The output of the above command signal will stop after a predetermined time has elapsed, so
Even if the electric motor is overloaded in a situation where the tires hit an obstacle and steering cannot be performed, the overload will be resolved after a predetermined period of time has elapsed, and the electric motor will be protected.

[Brief explanation of the drawing]

FIG. 1 is a configuration block diagram showing one embodiment of the present invention, and FIG.
The figure is a characteristic graph of the output signal of the torsional torque sensor, Figure 3 is a basic characteristic graph of the assist signal, Figure 4 is a characteristic graph of the addition constant signal, Figure 5 is a graph showing characteristic changes of the assist signal, and Figure 6 is a graph showing the characteristics change of the assist signal. is a characteristic graph of the multiplication constant signal, FIG. 7 is a characteristic graph of the return signal, FIG. 8 is a characteristic graph of the assist assist signal, FIG. 9 is a characteristic graph of the attenuation signal, FIG. 10 is a characteristic graph of the multiplication constant, and FIG. FIG. 11 is a characteristic graph of the return signal, and FIG. 12 is a flowchart showing the operation of the neutral position return command section. 1... Electric motor 2... Drive control section 21... Positive/negative discrimination section, 22... Absolute value conversion section 23.
...Duty control section, 24... Armature current detection section 2
5... Electric motor drive unit 3... Assist command unit 31... Torsional torque sensor, 32... Assist torque value instruction function unit, 33... Vehicle speed sensor, 34... Between addition constants, Part, 35... Addition calculation part, 36... Multiplication constant function part, 37... Multiplication calculation part 4... Return command part 41... Rudder angle sensor, 42... Return torque value instruction function Section 5... Phase compensation command section 51... Phase compensation section, 52... Phase compensation instruction function section 6... Rudder angle phase compensation command section 61... Rudder angle phase compensation section, 62... Rudder angle phase compensation@indication function unit 7...neutral position return command unit 71...vehicle speed discrimination unit, 72...torsion torque discrimination unit,
73... Time limit section, 74... Deviation amount calculation section, 75
. . . Return target value setting section 76 . . . Return torque value instruction function section 8 . . . Vehicle speed determination section. Patent Applicant Fuji Heavy Industries Co., Ltd. Agent Patent Attorney Nobu Kobashi Ukasa Patent Attorney Susumu Murai Figure 5 Figure 6 Book, a, (V) Figure 4 Figure 2 Figure 3 Round Cutting Method Akatsuki , 拮水儂 7th - Figure S, Section 9, Figure 10, Figure 11

Claims (1)

[Claims] 1. A torsional torque sensor for detecting torsional torque of a steering system, a vehicle speed sensor for detecting vehicle speed, and a steering angle sensor for detecting a steering angle, and commands based on output signals of the above-mentioned sensors. In an electric power steering device in which the rotational direction and rotational torque of an electric motor for power assist are controlled by a drive control unit in accordance with a signal, parking is performed when the absolute value of the output signal from the torsional torque sensor and the vehicle speed sensor is less than or equal to a predetermined value. A neutral position return command section is provided that generates a command signal to return the steering wheel to the neutral position based on the output signal of the steering angle sensor when the vehicle is stopped, and the neutral position return command section is configured to move so that the return target value gradually approaches zero. A motor control device for an electric power steering device, characterized in that: 2. The motor control device for an electric power steering device according to claim 1, wherein the neutral position return command section is configured to generate a command signal for a predetermined period of time.