JP2001061292A - Control device for drive mechanism having motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device that compensates for various fluctuation factors relating to a drive mechanism including a motor, and can satisfactorily control the drive mechanism. SOLUTION: A controller 10 for controlling drive of an electric motor 20 is equipped with a command voltage determination means 11, that generates a command voltage signal (r), a target response model means 12 that applies the command voltage signal (r) to a target response model M for generating a target current signal Mr, a subtraction means 13 that calculates the deviation between a current signal (y) of the electric motor 20 and the target current signal Mr, a model error correction means 14 that multiplies the deviation by a correction gain K, a feedforward means 16 that allows a signal Mr/P (P is a model of the electric motor in terms of design) corresponding to the target current signal, and an addition means 15 that adds the signal Mr/P to the output of the model error correction means 14 for generating a drive control signal. When the correction gain K is set to a sufficiently large value, y approaches Mr, thus achieving a nearly constant current response, without being affected by the amount of fluctuation ΔP of the actual electric motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for controlling a drive mechanism including a motor used as a drive source of a power steering device.

[0002]

2. Description of the Related Art Conventionally, there has been used an electric power steering device which transmits torque generated by an electric motor to a steering mechanism of a vehicle and thereby assists steering. The configuration of the motor control device for such an electric power steering device is shown in FIG. This motor control device performs feedback control of an electric motor 50 as a source of a steering assist force to be applied to a steering mechanism. That is, the motor current Imo, which is a current actually flowing through the electric motor 50, is fed back and input to the subtraction unit 51. A target current Ir set based on the torque applied to the steering wheel, the vehicle speed, and the like is input to the subtractor 51. Therefore, the difference between the motor current Imo and the target current Ir is output from the subtraction unit 51. Based on this deviation, a proportional-integral (PI) control unit 52 generates a control voltage to be applied to the electric motor 20. further,
The duty ratio corresponding to the control voltage is calculated by the duty calculator 53, and the electric motor 50 is driven and controlled by the PWM controller 54 based on the calculated duty ratio.

[0003] If necessary, instead of PI control, PID
(Proportional integral derivative) control may be applied.

[0004]

SUMMARY OF THE INVENTION PI control and PID
The control is a control method for controlling a control target using a constant control parameter. However, the electric motor to be controlled in the electric power steering device is:
The electric time constant τ (= L / R: L is the equivalent inductance of the electric motor, R is the electric time constant) due to various factors such as the ambient temperature and the length of the harness from the controller to the electric motor. Causes variations and fluctuations in the equivalent resistance of the electric motor. Therefore, in PI control or PID control using constant control parameters, a variation occurs in current response, and a stable steering feeling may not be obtained.

[0005] The problem of variation among the individual electric power steering devices is that the time constant of the electric motor is actually measured in each electric power steering device, and P
The problem can be solved by appropriately setting the control parameters of the I or PID control. However, this method requires the measurement of the time constant of each individual device and the process of inferring the optimal control parameters using a computer based on the measurement results. Not a suitable technique.

Further, since the time constant τ of the electric motor depends on the ambient temperature, it is necessary to consider the ambient temperature when the electric power steering device is used, and it is hoped that the ambient temperature is constant. Therefore, the above-mentioned method has a limitation in improving the control of the electric motor. SUMMARY OF THE INVENTION It is an object of the present invention to provide a control device capable of compensating for various fluctuation factors related to a drive mechanism including a motor and controlling the drive mechanism satisfactorily.

[0007]

According to a first aspect of the present invention, there is provided a control device for controlling a drive mechanism including a motor in accordance with a command signal. Target response model means for generating a target signal corresponding to a target operation state of the drive mechanism in response to a command signal; and determining a deviation between the target signal and an actual operation signal corresponding to an actual operation state of the drive mechanism. Deviation calculating means,
And a drive control signal generating means for generating a drive control signal to be given to the drive mechanism based on a signal generated by the model error correcting means. A control device for a drive mechanism having a motor, the control device comprising:

[0008] The drive control signal generating means may use the output of the model error correction means as the drive control signal. Also, as described in claim 2,
The control device may further include a feedforward unit that outputs a feedforward signal corresponding to the target signal. In this case, the drive control signal generation unit may include a feedforward signal output by the feedforward unit. The apparatus may further include an adding unit that creates the drive control signal by adding a forward signal to the signal generated by the model error correcting unit.

A command signal is represented by r, an actual operation signal is represented by y, a target response model is represented by M, a correction gain is represented by K, and a drive mechanism model is P + ΔP (P is a design drive mechanism model). , And ΔP represents a variation due to an actual drive mechanism variation or an effect of temperature, etc.). In the case of the configuration of claim 1, the actual operation signal y is expressed by the following equation (1) (transmission equation). ). (Mr-y) K (P + ΔP) = y (1) When this is solved for y, the following equation (2) is obtained.

[0010]

(Equation 1)

Therefore, by making the correction gain K sufficiently large, y → Mr. Therefore, a desired response corresponding to the command signal can be obtained irrespective of the actual variation ΔP of the drive mechanism. According to the second aspect of the present invention, since the signal corresponding to the target signal Mr is fed forward, the target signal is directly added to the control, so that the responsiveness can be further improved. it can.

For example, if the feedforward signal output from the feedforward means is represented by Mr / P, the actual operation signal y is represented by the following equation (3) (transmission equation). {(Mr−y) K + Mr / P} · (P + ΔP) = y (3) When this is solved for y, the following equation (4) is obtained.

[0013]

(Equation 2)

Therefore, by making the correction gain K sufficiently large, y → Mr. Therefore, a desired response corresponding to the command signal can be obtained irrespective of the actual variation ΔP of the drive mechanism.

[0015]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an electric configuration of an electric power steering apparatus according to one embodiment of the present invention. The steering torque applied to the steering wheel 1 as operating means is mechanically transmitted to a steering mechanism 3 via a steering shaft 2. A steering assist force is transmitted from the electric motor 20 to the steering mechanism 3.

The steering shaft 2 is divided into an input shaft 2A connected to the steering wheel 1 and an output shaft 2B connected to the steering mechanism 3;
The input shaft 2A and the output shaft 2B are connected to each other by a torsion bar 4. Torsion bar 4
Generates twist in accordance with the steering torque, and the direction and amount of the twist are detected by the torque sensor 5. The output signal of the torque sensor 5 is input to the controller 10 (ECU).

The controller 10 supplies a drive current corresponding to the steering torque detected by the torque sensor 5 to the electric motor 20, and controls the electric motor 20 so that a steering assisting force corresponding to the steering torque is supplied to the steering mechanism 3. Drive control. FIG. 2 is a functional block diagram for explaining a functional configuration of the controller 10. Controller 10
Has a microcomputer, and each functional means shown in FIG. 2 is realized by executing a predetermined program by the microcomputer.

More specifically, the controller 1
0 is an electric motor 2 based on signals from the torque sensor 5 and other sensors (for example, a vehicle speed sensor).
Command voltage determining means 1 for determining a command voltage to be applied to 0
1 is provided. A command voltage signal r representing the determined command voltage is input to the target response model means 12. The target response model means 12 outputs the command voltage signal r
Is applied to the target response model M to generate a target current signal Mr.

As the target response model M, for example, a model represented by the following equation (5) or (6) can be exemplified.

[0020]

(Equation 3)

The target current signal Mr is inputted to a subtracting means 13 (deviation calculating means). here,
A current signal y representing the current actually flowing through the electric motor 20
(Actual operation signal) is fed back. That is, the subtraction means 13 outputs a deviation u (= Mr−y) of the actual current signal y with respect to the target current signal Mr. The deviation u is input to the model error correction means 14 and multiplied by a correction gain K (u) (a linear or non-linear function of the deviation u). That is, the output signal of the model error correction means 14 is K
u.

The output signal Ku of the model error correction means 14
Is input to the adding means 15. A feedforward signal Mr / P (where P is a model corresponding to the design value of the electric motor 20) from the feedforward means 16 is input to the addition means 15. Then, the adding means 15 adds the output signal Ku of the model error correcting means 14 and the feedforward signal Mr / P, so that the electric motor 2
A motor drive control signal for drive control of 0 is created.
That is, the model error correcting means 14 and the adding means 15
Constitute a drive control signal generating means.

The feed-forward means 16 is for directly adding the target current signal Mr to the motor drive control signal, thereby improving the responsiveness. The electric motor 20 has individual variations in the time constant τ (= L / R), and the time constant τ varies due to a temperature change or the like. Therefore, if a model of the designed electric motor 20 is represented by P (for example, P = 1 / (Ls + R)), and a characteristic variation due to a variation or a temperature change of each electric motor is represented by ΔP, an actual electric motor The model of the motor 20 can be expressed as P + ΔP.

In this case, in the configuration of FIG. 2, the current signal y can be represented by the following equation (7). {(Mr−y) K + Mr / P} (P + ΔP) = y (7) By solving the equation (7) for y, the following equation (8) is obtained.

[0025]

(Equation 4)

Therefore, it can be seen that by making the correction gain K sufficiently large, y → Mr, and a desired response corresponding to the command voltage signal r can be obtained irrespective of the variation ΔP. FIG. 3 is a diagram showing a step response characteristic by control in this embodiment, and FIG. 4 is a diagram showing a step response characteristic by conventional PI control. FIGS. 3 and 4 show an equivalent DC resistance R0 (for example, R0 = 0.1Ω) of the electric motor in design.
And an equivalent inductance L0 (eg, L0 =
0.4 mH), the equivalent DC resistance R and equivalent inductance L of the actual electric motor 20 are
Equations (9) and (10) are assumed to fluctuate, respectively. When the equivalent DC resistance R and the equivalent inductance L take the values shown in Table 1 below, the curve C0
To C4 are depicted.

Rmin ≦ R ≦ Rmax (9) where Rmin = 0.5 · R0, Rmax = 1.5 · R0 Lmin ≦ L ≦ Lmax (10) Lmin = 0.5 · L0, Lmax = 1.5 · L0

[0028]

[Table 1]

3 and 4, the horizontal axis represents time, and the vertical axis represents the value of the current signal when a sufficient time has passed for the designed resistance R0 and inductance L0. As “1”, a value obtained by normalizing the current signal in each case is shown. From the comparison between FIGS. 3 and 4, in the conventional PI control, a remarkable variation occurs in the step response due to the variation and variation of the characteristics of the individual electric motors. It is understood that the variation in the response to the variation or variation in the characteristics is significantly suppressed.

FIGS. 5A to 5D show examples of the correction gain K (u). In the example of FIGS. 5A and 5B, the correction gain K is
When the deviation u is 0, it is set to 0. When the deviation u takes a value within a certain range centered on 0, the larger the absolute value of the deviation u, the larger the value.
Takes a value outside the certain range, it is a predetermined constant value. In the example of FIGS. 5C and 5D, the correction gain K
Takes a positive value even when the deviation u is 0, and when the deviation u takes a value within a certain range centered on 0, the larger the absolute value of the deviation u, the larger the value. Takes a value outside the certain range, it is a predetermined constant value.

In the examples of FIGS. 5A and 5C, when the deviation u takes a value within a certain range centered on 0, the correction gain K changes linearly with the deviation u. ing. In the example of FIGS. 5B and 5D, when the deviation u takes a value within a certain range centered on 0, the correction gain K changes nonlinearly with respect to the deviation u. . Command voltage signal r
In the case where the fluctuation frequency is high, the linear characteristic (Fig. 5 (a)
If (c)) is employed, the current signal y will be turbulent and difficult to converge. Therefore, it is preferable to employ the non-linear characteristics (FIGS. 5B and 5D).

Although one embodiment of the present invention has been described above, the present invention can be embodied in other forms. For example, as already described in the section of “Means for Solving the Problems and Effects of the Invention”, the responsiveness is slightly lowered, but the feedforward means 16 may be omitted. Also, the feedforward means includes:
Instead of giving the command voltage signal r, the target current signal Mr output by the target response model means 12 may be given. In this case, it is preferable that the feedforward means performs an operation based on the operator 1 / P on the target current signal Mr.

Further, in the above-described embodiment, a model representing a target response to the electric motor 20 is adopted as the target response model M. For example, the target response model of the entire drive mechanism including the electric motor 20 and the steering mechanism 3 is used. A model representing a response may be adopted to improve the responsiveness of the drive mechanism as a whole. Further, in the above-described embodiment, the case of the drive control of the electric power steering device for giving the drive force of the electric motor 20 to the steering mechanism 3 is taken as an example. However, the present invention provides steering by driving the pump by the electric motor. The present invention can also be applied to improve the responsiveness of an electric motor or an entire drive mechanism including the electric motor and the steering mechanism in the case of a hydraulic power steering device that generates hydraulic pressure for assistance.

Further, the present invention can be widely applied to a drive mechanism using an electric motor, and the use of the electric motor is not limited to the electric power steering device.
In addition, various design changes can be made within the scope of the matters described in the claims.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electric configuration of an electric power steering device to which an embodiment of the present invention is applied.

FIG. 2 is a functional block diagram for explaining a functional configuration of a controller for controlling the electric motor.

FIG. 3 is a diagram showing a step response characteristic by control in this embodiment.

FIG. 4 is a diagram showing a step response characteristic by conventional PI control.

FIG. 5 is a diagram illustrating a setting example of a correction gain.

FIG. 6 is a block diagram for explaining a configuration of a conventional motor control device.

[Explanation of symbols]

 Reference Signs List 3 Steering mechanism 10 Controller 20 Electric motor 12 Target response model means 13 Subtraction means 14 Model error correction means 15 Addition means 16 Feedforward means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) G05B 13/04 G05B 13/04 F-term (Reference) 3D033 CA03 CA16 CA20 CA21 EB02 5H004 GA14 GA15 GB12 HA10 HB10 HB14 JB09 KB13 KB32 KB39 KC34 KC35 LA01 LA02 LA13 5H570 AA21 BB11 DD01 GG01 JJ04 LL02 LL12 9A001 BB01 BB02 KK31 KK32 KK37 LL02

Claims (2)

[Claims] 1. A control device for controlling a drive mechanism including a motor in response to a command signal, wherein the target response model generates a target signal corresponding to a target operation state of the drive mechanism in response to the command signal. Means, a deviation calculating means for calculating a deviation between the target signal and an actual operation signal corresponding to an actual operation state of the drive mechanism, and a model error correction means for multiplying the deviation by a correction gain. And a drive control signal generating means for generating a drive control signal to be given to the drive mechanism based on the signal generated by the error correction means. 2. The apparatus according to claim 1, further comprising: a feedforward unit that outputs a feedforward signal corresponding to the target signal, wherein the drive control signal generation unit generates the feedforward signal output by the feedforward unit by the model error correction unit. 2. The control device for a drive mechanism having a motor according to claim 1, further comprising an adding unit that generates the drive control signal by adding the drive control signal to the signal.