JPH03182881A - Electrically driven power steering device - Google Patents

Abstract

PURPOSE:To secure and enhance stable steering feeling by estimating disturbing torque with the revolution and current of an assist motor detected, and thereby compensating the assist command in such a way as to cancel the aforesaid disturbing torque. CONSTITUTION:The current of an assist motor 10 is detected by the armature current detecting section 66 of a current control section 60 so as to be inputted into the disturbing torque estimating section 52 of a disturbing torque compensating section 50. The disturbing torque estimating section 52 inputs the revolution of the assist motor 10 which is detected by a steering angular velocity detecting section 51, so that disturbing torque is estimated based on the current and revolution of the motor. The estimated value is added to the assist command outputted from an assist command section 20 so as to be compensated. The compensated assist command is added to and/or subtracted from the outputs from a viscosity compensating section 30 and an inertia compensating section 40 so as to be outputted to the current control section 60. The assist motor 10 is controlled in such a way that the disturbing torque is compensated. By this constitution, stable steering feeling can thereby be secured and enhanced.

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;
Some devices perform inertia compensation, viscosity compensation, etc. in consideration of viscosity, friction, etc.

However, such inertia compensation and viscous compensation cannot compensate for changes in frictional force or self-lining torque caused by changes in road surface conditions. Therefore, in conventional electric power steering devices, changes in the road surface cause problems such as deterioration of the feeling during steering, that is, the steering wheel turns too much or not enough.

Summary of the Invention Purpose of the Invention The purpose of this invention is to provide an electric power steering wheel that can provide a constant and favorable steering feeling regardless of road surface conditions.
An object of the present invention is to provide a steering device.

Structure 2 of the Invention Functions and Effects This invention provides an electric power motor that creates an assist command based on detected steering torque, detected vehicle speed, etc., and controls a steering assist motor that generates steering assist torque using this assist command. The steering device includes means for detecting the rotational speed of the assist motor, means for detecting the current flowing through the assist motor, means for estimating the disturbance torque based on the detected rotational speed and the detected current, and means for detecting the estimated disturbance torque. The present invention is characterized by comprising means for correcting the assist command so as to erase the assist command.

According to this invention, the armature current of the assist motor and the rotational angular velocity (steering angular velocity) of the rotor of the assist motor are detected, and based on this, the torque applied to the motor shaft of the assist motor, that is, the frictional force that is positioned as a disturbance. Disturbance torque compensation is performed by estimating the total torque value of self-lining torque and self-lining torque, and correcting the assist command value given to the assist motor so as to cancel out the estimated disturbance torque. Therefore, even under variously changing road surface conditions, it is possible to provide constant power assist to the steering wheel, and it is possible to prevent the steering wheel from being turned too sharply or not sharply enough. In this way, according to the present invention, a consistently favorable steering feeling can be obtained regardless of changes in road surface conditions, and safety on rough roads is also improved.

DESCRIPTION OF EMBODIMENTS FIG. 1 is a block diagram functionally showing an entire embodiment of an electric power steering device according to the present 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 Figure 2 is Let me explain.

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. Further, the rotational force of a steering assist (auxiliary) motor (DC motor) 10 controlled and driven by the control device 11 is transmitted to the rack shaft 74 through 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 7I. The nozzle 71 and the rotating shaft of the motor 10 are mechanically connected by gears 72, 73 and a rack shaft 74. Steering torque
The sensor 21 detects steering torque (torsion torque).

Further, the vehicle speed is 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 described later. The control device 11 and the motor 10 are equipped with a battery 1 mounted on the vehicle.
Its operating power is supplied from 2.

As will be described later, the control device 11 includes a current detector, a steering angular velocity detection section, a drive circuit that drives the motor 10, and a computer (CP) that controls the overall control of the motor 10.
It consists of an interface circuit between the computer, the above-mentioned person, and output equipment, etc. FIG. 1 shows the control device 11
Various functions of the computer built into the block,
It can be positioned as a drawing along with blocks showing other people, output devices, and various circuits.

In the first prisoner, the assist command unit 20 has the detected torque VT of the torque sensor 21 and the detected vehicle speed v of the 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 unit 25 is a value determined by the detected torque V 1 and the detected vehicle speed Vs. Figure 3 shows that in response to the steering torque VT, a motor current approximately proportional to the steering torque V within a certain range (another curve may be used) flows (assist torque is generated). , so that when the above range is exceeded, a certain constant motor current flows (assist torque is generated), and according to the vehicle speed Vs, when the vehicle speed Vs is high, the motor current (assist torque) is reduced,
This indicates that when the vehicle speed Vs is slow, an assist command is generated to control the motor 0 so as to increase the motor current (assist torque). Detection torque V
T is also given to the phase compensation section 26, and this phase compensation section 2B
By adding the differential value of the detected torque vT to the output of the multiplication calculation unit 25, the assist command unit 2
The output is 0 (reference current command value).

Compensation values generated from a viscosity compensator 30, an inertia compensator 40, and a disturbance torque compensator 50, which will be described later, are added to (or subtracted from) this reference current command value, and then given to the current control unit 60 as a target current command value. It will be done. The current control section 60 may be entirely constructed from a node/ware circuit, or
Part of it can also be realized by computer software.

The current control unit 60 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 6I. 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 duty ratio generated by the duty generation unit 65 and the determined polarity are given to the motor drive unit 63, and based on these, the motor drive unit 63 turns on and off the four switching elements wired in an H-bridge shape. to drive the motor 10.

The viscosity compensator 30 calculates a viscosity compensation value based on the detected steering angular velocity (rotational speed of the assist motor IO) θ and, if necessary, the vehicle speed V8. This viscosity compensation value is added to (or subtracted from) the assist command value of the assist command unit 20. This suppresses the instability that tends to occur when the vehicle is released and returns at high speeds, and compensates to reduce viscosity at low vehicle speeds, reducing the sense of activation of the steering wheel and providing a good feeling. It becomes like this.

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 adjusts the return speed when the hand is released. It acts to speed up the process. The steering angle acceleration (rotational acceleration of the motor 10) θ is detected in the inertia compensator 40, and an inertia compensation value is calculated based on this detected acceleration. The calculated inertia compensation value is added to the assist command value of the assist command unit 20.

The disturbance torque compensation unit 50 includes a steering angular velocity detection unit 51 and a disturbance torque estimation unit 52. The steering angular speed detection unit 51 detects the rotational speed θ of the assist motor 0, and may include a sensor such as a tacho generator or an encoder, or may include an observer that estimates the steering angular speed instead of the sensor. You can. This observer estimates the steering angular velocity based on the applied voltage of the motor 0 and the armature current, or based on the command current value to the motor 0 and the measured armature current.

The disturbance torque estimation section 52 is given the steering angular velocity θ detected or estimated by the steering angular velocity detection section 51 and the armature current (motor current) ia detected by the armature current detection section 66. The disturbance torque estimation unit 52 estimates the disturbance torque T applied through the wheels 75 due to changes in the road surface condition based on these values θ,i. This disturbance torque T or the value converted into a current command value is the assist command unit 20.
is added to the assist command value. As a result, disturbance torque compensation is performed that corrects the assist command to cancel the disturbance torque. 1. It is possible to provide stable steering power assist even under variously changing road surface conditions, and prevents the steering wheel from turning too sharply or not sharply enough. You will be able to do this.

FIG. 4 shows a block diagram based on the control theory of the assist motor (DC motor) 10 and a functional block diagram of the disturbance torque estimation section 52. It goes without saying that the command value ref given here as a voltage command value E can also be applied to a current command value through voltage/current conversion. A block designated by the reference numeral 10A shows the contents of the motor O.

Here, E: Motor applied voltage T: Disturbance torque (including torque due to viscosity) θ: Motor angular velocity (steering angular velocity) R: Motor armature resistance L: Self-inductance KT: Torque constant J: Motor rotor inertia Ko = speed The transfer function P from the electromotive force constant applied voltage E to the steering angular velocity is given by the following equation.

P-/(Ts+1) = (1/K)/[(JR/KTK8)S+1]...
(1> In equation (1), L is considered to be sufficiently small compared to J, and L
ignored.

Reference numeral 52A indicates the functional configuration of the disturbance torque estimating section 52, which includes a block 53 that calculates the first estimated applied voltage when the steering angular velocity θ and the armature current i are manually input and a disturbance factor is taken into account. , a block 54 that calculates a second estimated applied voltage when the steering angular velocity θ is human power and no disturbance factor is considered, and a subtraction unit 55 that subtracts the second estimated voltage from the first estimated voltage. . Then, the output of this subtraction unit (corresponding to the output of the disturbance torque estimation unit 52) is the voltage command value E
is given to motor OA by adding rer to .

The influence of disturbance torque T is canceled.

The relationship between disturbance torque T (s) and steering angular velocity θ(s) is given by the following equation.

1 θ(s) /T(s) −f (R” /KT)[1,/(τ2s+1)−(
Ls+R)/R"]/(δ (s)0-(δ(S)/
δ (s) ) (1/ (τ2 s + 1) )]+
1) 1 2 1 (K ''/ (T's+1))
-(2) 111m where δ1(s) - (KJ/TIS thousand 1)) ([(RJ/KT) (R" J '/
KT")] s thousand Ko- to 8"+(JLs/KT))・
...(3) δ2 (s) −(K,”/ (K,”s
+ 1) 1((R”J/Ni, ) −(R”J”/K
T”) s) −(4) TI, l*= R* J
*/KT*Ko* ,,,
(5) K”-1/K”
...〈6〉Ile In Fig. 4 and above, * is a nominal value (roughly set value).

From the above, it can be seen that the deviation due to the torque disturbance can be canceled if the torque is ``R-R''. Also, τ2 may be set earlier than the electrical time constant of the motor.

In the above embodiment, the output of the disturbance torque estimating section 52 is added to the output of the assist command section 20, but the gain of the assist command section 20 (for example, the gain of the detected torque VT) is determined by the output of the disturbance torque estimating section 52. You may change it.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing an embodiment of the present 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 an example of the configuration of the disturbance torque estimation section. 10... Steering assist motor. 20...Assist command unit. 21... Torque conflict sensor. 22...Vehicle speed sensor. 30...Viscosity command section. 40...Inertia compensation section. 50...Disturbance torque compensation section. 51... Rudder angular speed detection section. 52...Disturbance torque estimation unit. 60... Current control unit. 66... Armature current detection section.

Claims (1)

[Scope of Claims] An electric power steering device that creates an assist command based on detected steering torque, detected vehicle speed, etc., and controls a steering assist motor that generates steering assist torque using this assist command.・Means for detecting the rotational speed of the motor, means for detecting the current flowing through the assist motor, means for estimating disturbance torque based on the detected rotational speed and detected current, and means for detecting the disturbance torque by canceling the estimated disturbance torque. An electric power steering device comprising: means for correcting a command.