JPH03176272A - Motor-driven power steering device - Google Patents

Abstract

PURPOSE:To determine the angular position, revolving speed, and acceleration of a steering assist motor without using a rotational position sensor or speed sensor by calculating at least one of the angular position, speed, and acceleration of the motor through the use of the sensed voltage and current. CONSTITUTION:Voltage and current of a steering assist motor 10 are sensed by sensors 51, 66, and using these values sensed, at least one of the rotational angular position, speed, and acceleration of the steering assist motor 10 is calculated by calculating parts 53, 54. This permits accomplishment of cost-down and lessening of the number of wirings to lead to preclusion of trouble generation originating from wire severance etc.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering device that assists steering force with the rotational output of a motor.

Prior Art and Its Problems In a conventional electric power steering device, a steering assist (auxiliary) motor is controlled based on a detected steering torque value and a detected vehicle speed value to generate steering assist torque. inertia of the motor and steering mechanical system;
When controlling the rotational position, speed, or acceleration of a steering assist motor to perform inertia compensation, viscosity compensation, etc. that take into account viscosity, friction, etc., conventionally, the angular position or rotation was determined from a detector such as an encoder or tachogenerator. I was getting a signal that represented my speed. This has made conventional electric power steering devices expensive.

Summary of the Invention Purpose of the Invention The object of the invention is to make it possible to obtain the angular position, rotational speed, and acceleration of a steering assist motor without using an encoder, tachogenerator, etc. rotational position or speed detector. .

Structure 1 of the invention Operation and effect The first invention provides an electric power steering device that controls a steering assist motor based on a detected steering torque value, a detected vehicle speed value, etc. and generates a steering assist torque. A means for detecting a voltage applied to the assist motor, a means for detecting a current flowing through the steering assist motor, and at least one of the angular position, speed, and acceleration of the motor using the detected voltage and detected current. The method is characterized by comprising means for calculating one.

According to this invention, the voltage and current of the steering assist motor are detected, and the detected voltage value and the detected current value are used to determine at least one of the rotational angular position, speed, and acceleration of the steering assist motor. Since these values are calculated, there is no need for conventional detectors such as encoders and tacho generators to obtain these values. therefore.

Since it is possible to reduce costs and reduce the number of wiring lines, it is possible to prevent failures due to disconnection or the like.

A second invention is an electric power steering device that controls a steering assist motor based on a detected steering torque value, a detected vehicle speed value, etc. and generates a steering assist torque, in which a current command value is applied to the steering assist motor. means for detecting the current flowing through the steering assist motor, and the current command value and the detected current value.

The present invention is characterized by comprising means for calculating at least one of the angular position, speed, and acceleration of the motor.

According to the second invention, what is actually detected is only the motor current, and since the detection of the motor current is also necessary for the feedback control of the steering assist motor, it is possible to detect the angular position, velocity, and acceleration. It is no longer necessary to newly provide a detector in the second layer, and the cost and wiring of the - layer can be reduced.

In the first and second inventions, the calculation process of the angular position, velocity, and acceleration in the calculation means calculates the armature resistance, self-inductance, torque constant, speed electromotive force constant, and rotor inertia of the motor.

Parameters calculated based on motor internal parameters such as viscosity coefficient are used. Since the internal parameters of the motor described above change due to changes in the ambient temperature inside the motor, errors occur between the calculated values and the actual values of the angular position, velocity, and acceleration.

A third invention is to prevent the occurrence of calculation errors due to temperature changes in the motor, and in the electric power steering device according to the first or second invention, the temperature of the steering assist motor is further measured. and means for correcting parameters for calculation processing in the calculation means based on the measured temperature.

According to the third invention, when calculating the position, speed, and acceleration of the motor/rotor using the applied voltage value and current value of the motor, the temperature of the motor is measured, and the internal parameters of the motor to be used are determined based on the measured temperature. is corrected according to its temperature characteristics, so errors in calculated values due to temperature changes can be minimized. Therefore, the position, speed, and acceleration of the motor can be accurately controlled using the calculated values, and a desirable steering feeling can be obtained.

Description of examples First, the first invention will be explained.

FIG. 1 is a block diagram functionally showing the entire embodiment of an electric power steering device according to the first invention.

FIG. 2 is a configuration diagram showing an example of a steering mechanical system to which this power steering device is applied.

First, the power steering mechanical system shown in FIG. 2 will be explained.

The rotational force of the steering handle 71 is transmitted through the handle shaft to a steering gear 72 including a pinion gear, and further transmitted to the rack shaft 74 by the pinion gear.
The wheel 75 is turned through the knuckle arm and the like. In addition, the 1G rotational force of a steering assist (auxiliary) motor (DC motor) controlled and driven by the control device 11 is transmitted to the rack shaft 74 through the engagement between the steering gear 73 including a pinion gear and the rack shaft 74, and is transmitted to the steering wheel. This will assist the steering by 71. Handle 7
The rotating shafts of the motor 1 and the motor 10 are mechanically connected by gears 72, 73 and a rack shaft 74. A steering torque sensor 21 detects steering torque (torsion torque).

The vehicle speed is also detected by the vehicle speed sensor 22, and the control device 11 controls the motor 10 based on the detected torque, vehicle speed, etc., as will be described later. Operating power is supplied to the control device 11 and the motor 10 from a battery 12 mounted on the vehicle.

The control device 11 is a drive circuit that drives the motor 10 and detectors such as a current detector and a voltage detector.

A computer (C
It consists of a PU (for example, a microprocessor), memory, and an interface circuit between the computer and the above-mentioned people and output devices. Figure 1 shows the control device 1.
It can be positioned as a block diagram of the various functions of the computer built in 1, along with blocks representing other people, output devices, and various circuits.

In FIG. 1, an assist command unit 20 has a torque vT detected by a torque sensor 21 and a vehicle speed vT detected by a vehicle speed sensor 22.
8 is given. Assist in the assist command unit 20
The torque value instruction function unit 23 outputs a command value representing the assist torque to be generated by the motor 10 in accordance with the detected torque VT. Further, the multiplication constant function unit 24 has a detected vehicle speed v
8, and this constant is multiplied by the above-mentioned assist torque command value in the multiplication calculation section 25. As a result.

As shown in FIG. 3, the assist torque value (or motor current command value) output from the multiplication calculation unit 25 is a value determined by the detected torque V 1 and the detected vehicle speed Vs. Figure 3 shows that depending on the steering torque vT, a motor current approximately proportional to the steering torque VT within a certain range flows (assist reference torque is generated), and when the above range is exceeded, a certain motor current flows. (assist torque is generated), and the vehicle speed V is adjusted according to the vehicle speed Vs.
When s is fast, the motor current (assist torque) is decreased, and when the vehicle speed Vs is slow, the motor current (assist torque) is increased.

This indicates that an assist command for controlling motor O is generated. The detected torque VT is also given to the phase compensation section 2B, and the detected torque VT is
By adding the differential value of T to the output of the multiplication calculation section 25, it finally becomes the output (reference current command value) of the assist command section 20.

After adding (or subtracting) command values for angular position, velocity, and acceleration control (at least one of them), which will be described later, to this reference current command value, the command value is sent to the current control unit 60 as a target current command value. Given. Current control section 60
may be composed entirely of hardware circuits, or
Part of this can also be realized using computer software.

The current control unit 80 is, for example, a PWM (Pulse
The motor 0 is driven and controlled by a chopper operation using Width Modulation (width modulation) pulses, and current feedback control is performed. The armature current i 2 of the motor 0 is detected by the armature current detection unit 6B, and the deviation between the given target current command value and the detected current i 2 is calculated in the current deviation calculation unit 61. The absolute value of this deviation is obtained by the absolute value converter 64, and the duty ratio of the PWM pulse is determined based on this absolute value. on the other hand,
The polarity (positive or negative) of the deviation is determined by the positive/negative determining section 62. The generated duty ratio and the determined polarity are given to the motor drive unit B3, and the motor drive unit 63 controls the on/off of four switching elements wired in an H-bridge type based on these to drive the motor 0. drive

The applied voltage V of the motor 0 is detected by the applied voltage detection section 51. The detected applied voltage V and the above-mentioned armature current i are provided to the steering angular velocity estimating means 52. This steering angular speed estimating means 52 is an observer that estimates the rotational speed of the motor 0 from the given motor voltage V and motor current i. The estimated value is marked with eight and is expressed, for example, as θ.

An example of the functional configuration of the steering angular velocity estimating means 52 is shown in FIG. The block diagram in FIG. 4 realizes the calculation of the following arithmetic expression.

z(t)−Fz(t)+Gi(t)+LOv(t)
Determine F so that Nio+ε(t) −0.

where z(t), z(t), F, G, LO, H and J
O is a parameter in the observer.

Further, in FIG. 4, 1/S represents an integral element.

The above observer parameters are internal parameters in the motor O, such as armature resistance R1 self-inductance L,) torque constant K, speed induced voltage constant K, and viscous resistance coefficient of the motor shaft.

Calculated using rotor inertia J, etc.

The estimated speed θ obtained from the steering angular velocity estimating means 52 in this way is differentiated by the differential calculation unit 53 and converted into an estimated acceleration θ, and is also integrated by the integral calculation unit 54 and converted into an estimated angular position θ. be done. In this way, the acceleration, speed, and position of the motor O will be estimated. It is also possible to directly estimate the acceleration 1 position using the observer without using the differential calculation section 53 and the integral calculation section 54.

The estimated acceleration θ is sent to the viscosity command unit 30 that performs negative feedback.
are respectively given to the inertia compensator 40 that performs positive feedback of the steering angle acceleration, and are used to control the position, speed, and acceleration of the motor 10. Any one or two of these controls may be performed, or all of them may be performed.

The viscosity command unit 30 basically generates a force that returns the steering angle to the neutral position.
In other words, it generates restoring force.

The estimated speed θ is given to a viscosity compensation value instruction function unit 31, and this function unit 31 outputs a command value that has a larger absolute value and generates a torque in the opposite direction as the speed θ increases.

On the other hand, vehicle v8 detected by vehicle speed sensor 22 is given to vehicle speed calculation constant function section 34, and this function section 34 outputs a larger constant as vehicle v8 becomes larger. This vehicle speed calculation constant is multiplied by the command value output from the function part 31 in the multiplication calculation part 32 via the multiplication calculation part 35 (described later). This multiplication result passes through the viscosity command output command section 33 and is subtracted from the reference current command value output from the assist command section 20. In this way, the output of the viscosity command section 30 works to reduce the output of the assist command section 20 more as the steering angular velocity θ increases.

Furthermore, as the vehicle speed v8 increases, a larger constant is applied, so the effect of viscous braking increases.

This suppresses the instability that tends to occur at high vehicle speeds when you release the wheel and return it, giving you a good steering feel. Also, at low vehicle speeds, compensation works to reduce viscosity, which reduces the sense of activation of the steering wheel and provides a good feeling.

Further, the estimated steering angle position θ is given to the multiplication constant function section 36. This function section 36 outputs a constant that becomes smaller as the absolute value of the steering angle position increases, and this constant is multiplied by the constant outputted from the function section 34 in the multiplication operation section 35, and this result is given to the multiplication operation section 32. It will be done. On the other hand, the viscosity command output command section 33.

Only in this case, the output of the multiplication calculation unit 32 is subtracted from the output of the assist command unit 20, and in other cases, the output of the viscosity command unit 30 is set to zero. In this way, the output of the viscosity command unit 30 is output only in the hands-off state, and its magnitude increases as the absolute value of the steering angle θ decreases.

Therefore, viscous braking can prevent the steering wheel from becoming unstable near neutral when the user releases the grip. Furthermore, since the braking starts to take effect at a relatively large steering angle, the braking force is small at this time, and as the vehicle approaches neutrality, a greater braking force is obtained, which makes convergence to the neutral position more natural.

Only the viscosity compensation by the above-mentioned functional blocks 31, 32, 33, and 34 may be performed.
Only the viscosity compensation according to (35) and 33.36 may be performed, or all of these viscosity compensations may be performed.

The inertia compensator 40 controls the rotor inertia of the motor 10 as if it had become smaller, and it eliminates the weight caused by the motor 10 not following the rotation of the steering wheel when the steering wheel is suddenly turned, and improves the locking speed when the handle is released. It acts to speed up the process. The estimated steering angle acceleration θ is given to the inertia compensation value instruction function section 41, and this function section 41
The command value obtained by multiplying the command value outputted from the assist command unit 42 by an appropriate constant in the multiplication calculation unit 42 is added to the reference current command value of the assist command unit 20.

FIG. 5 shows an embodiment of the second invention. Components that are the same as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

In comparison with FIG. 2, the applied voltage detection section 51 is not provided in FIG. The above-mentioned detected armature current l 1 and the current command value i outputted from the assist command section 20 are given to the steering angular velocity estimating means 52A. The current command value i is determined by the assist command unit 20 as shown in FIG.
In addition to the value obtained by adding the command value of the viscosity command unit 30 to the reference current command value of , the reference current command value or the current control unit 6
A target current command value given to 0 may also be used.

A functional block diagram of the steering angular velocity estimating means 52A is shown in FIG. The block configuration is the same as that shown in FIG. 4, but the input and parameter values of each block are different. In the block diagram of FIG. 6, the parameters are determined according to the internal parameters of motor 0 described above so as to perform the following calculations.

z(t) −F z(t) +c t(t) +
F so that LOia (t)fll-ε(t)-0
decide.

FIG. 7 shows an embodiment of the third invention. In Fig. 7, the same parts as shown in Fig. 1 are given the same reference numerals.
The explanation will be omitted.

Since the above-mentioned internal parameters of the motor 10 change depending on the temperature, the parameters of each element in the functional block diagram of FIG. 4 or FIG. 6 calculated based on these also change depending on the temperature. The third invention corrects the internal parameters of the motor according to the detected temperature of the motor so that the degree θ can be estimated based on the temperature change. This allows accurate position, velocity and acceleration control to be achieved.

FIG. 8 shows an example of a configuration for detecting the temperature of the motor IO. In this figure, a thermistor 101 for temperature detection is attached to the inner surface of a case 110 of a motor 10. Since the resistance value of the thermistor changes depending on the temperature, the internal temperature of the motor 10 can be measured thereby. The thermistor 01 is connected to a temperature detection circuit of a motor temperature detection section 55 (FIG. 7) via a lead wire 102.

It goes without saying that the thermistor 01 can be installed at other locations. The other components in FIG. 8 are as follows. 103 is a permanent magnet, 104 is an armature core, and 105 is an armature coil.

106 is a commutator, 107 is a brush, 108 is a motor drive lead wire, and 109 is a rotating shaft of the motor.

In FIG. 7, the temperature detected by the motor temperature detection section 55 is given to the motor internal parameter table (memory) 5B. This table 56 includes armature resistance R9 self-inductance L, an example of which is shown in FIG.
Data representing temperature characteristics of torque constant K, speed induced voltage constant K, viscous resistance coefficient of the motor shaft, and rotor inertia J are stored in advance. The table 56 outputs the value of each motor internal parameter corresponding to a given temperature or its temperature correction value and supplies it to the steering angular velocity estimating means 52. In this way.

Detects the internal temperature of the motor in real time.

Since the steering angular velocity is estimated by the estimating means 52 using the internal parameters corrected according to the detected temperature, an accurate estimated value can be obtained.

It goes without saying that the third invention is also applicable to the second invention shown in FIG.

[Brief explanation of drawings]

FIG. 1 is an AL function block diagram showing an embodiment of the first invention. FIG. 2 is a configuration diagram showing an example of a power steering mechanical system. FIG. 3 is a graph for determining the reference current command value based on the steering torque and vehicle speed. FIG. 4 is a functional block diagram showing the configuration of the steering angular velocity estimating means shown in FIG. 1. FIG. 5 is a functional block diagram showing an embodiment of the second invention, and FIG. 6 is a functional block diagram showing the configuration of the steering angular velocity estimating means in FIG. Fig. 7 is a functional block diagram showing an embodiment of the third invention, Fig. 8 is a sectional view showing the internal temperature detection position of the motor, and Figs. 9 (A) to (P) show the temperature characteristics of various internal parameters. This is a graph showing. 10... Steering assist motor. 20...Assist command unit. 21...Torque sensor. 22...Vehicle speed sensor. 30...Viscosity command section. 40...Inertia compensation section. 51... Applied voltage detection section. 52, 52A: Rudder angular speed estimating means. 53...Differential calculation section. 54... Integral calculation section. 55...Motor temperature detection section. 56...Motor internal parameters 60...Current control section. 66... Armature current detection section. table. More than meter

Claims (4)

[Claims] (1) In an electric power steering device that controls a steering assist motor and generates steering assist torque based on a detected steering torque value, a detected vehicle speed value, etc., means for detecting the voltage applied to the steering assist motor. , means for detecting a current flowing through the steering assist motor, and means for calculating at least one of the angular position, speed, and acceleration of the motor using the detected voltage and detected current. An electric power steering device characterized by: (2) In an electric power steering device that controls a steering assist motor based on a detected steering torque value, a detected vehicle speed value, etc. and generates a steering assist torque, means for giving a current command value to the steering assist motor. , means for detecting a current flowing through the steering assist motor, and means for calculating at least one of the angular position, velocity, and acceleration of the motor using the current command value and the detected current value. An electric power steering device characterized by: (3) Claim (1) or (2) further comprising means for measuring the temperature of the steering assist motor, and means for correcting parameters for calculation processing in the calculation means based on the measured temperature. The electric power steering device described in . (4) Based on the value calculated by the above calculation means,
The electric power steering device according to claim 1, further comprising a control means for performing at least one of position control, speed control, and acceleration control of the steering assist motor.