JPH0698580A - Motor controller - Google Patents

Abstract

PURPOSE:To avoid a resonance and attenuate a shaking caused by an external disturbance and a torque ripple quickly by a method wherein torques and a revolution on both ends of an elastic coupling means are estimated from the revolution of a motor and a motor current to compensate a current reference value. CONSTITUTION:A system by which a motor is coupled with a load with an elastic coupling means is composed of a speed controller 1, a current controller 2, a torque conversion factor block 3, the transfer function block 4 of a rotation system, the transfer function block 5 of a mechanical shaft and the transfer function block 6 of a load. A monitor 10 is provided and the armature current ia of the motor and the motor speed nm are inputted to it. The monitor 10 estimates the output torque taus of the mechanical shaft, the load torque taul and nl as unknown parameters and outputs them. Those output signals are introduced into a compensation operating circuit 20 and the compensation operating circuit 20 generates a correction signal which corrects a current reference supplied from the speed controller 1 to the current controller 2 and outputs it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor for controlling the rotation speed of a motor to which a load is coupled via elastic coupling means, via a speed controller and a current controller so as to match a speed target value. The present invention relates to a control device.

[0002]

2. Description of the Related Art In speed control of an electric motor, for example, a DC electric motor, a current reference for matching a detected electric motor speed with a given speed target value, in other words, a difference between the speed target value and the detected speed. A current reference for making the (speed deviation) zero is created by a speed controller, and the current is controlled via the current controller so that the motor current conforms to the current reference.

FIG. 4 shows a drive circuit of a general electric motor. The electric motor M is represented by a DC machine. In this drive circuit, it is generally shown that the motor speed n _m is achieved by supplying the motor M with a current i _a from a power supply V _s via a DC reactor L _s . A mechanical load FW is coupled to the electric motor M. The electric motor M and the mechanical load FW may be coupled via elastic coupling means. Here, as the elastic coupling means,
A case where the machine shaft itself connecting the electric motor M and the machine load FW is flexible, a case where the joint connecting the mechanical shafts of the rigid bodies is flexible, and a case where both the machine shaft and the joint are flexible. There are three possible cases. Here, as an example, the description will proceed assuming that the mechanical axis S is flexible. When the electric motor M and the mechanical load FW are coupled via the flexible mechanical shaft S, on the other hand, the mechanical shaft S has an action of absorbing the pulsating torque and interrupting the pulsating torque thereat. On the other hand, since the electric motor M and the load FW are not integrated, the speed of the load FW cannot be directly controlled, and can be indirectly controlled via the mechanical axis S. In other words, there is the inconvenience that the desired control target cannot be directly controlled.
Further, when a disturbance on the load FW side is received, control for suppressing the disturbance or speeding up the damping can be performed only on the side of the electric motor, so that it is difficult to take effective measures.

One solution to this problem is the control circuit system shown in FIG. The control system shown in the figure includes a speed controller 1, a current controller 2, a torque conversion coefficient block 3, a transfer function block 4 of a rotary system, a transfer function block 5 of a machine axis S, and a transfer function of a mechanical system as a load. Blocks 6 are shown respectively. Reference numeral 10 is shown in detail in FIG.
And an armature current i _a
And the motor speed n _m are input, and the output torque τ _s of the machine shaft, the load torque τ _L , and the rotational speed n _{L of the} load are estimated as variables that are difficult to detect based on the given equation of state. In the figure, for the sake of convenience, the estimated value is shown with the symbol representing the variable in parentheses. The circuit of FIG.
In addition to the above blocks, a comparator 7, an adder 8 and transform coefficient blocks 11 to 15 are also provided.

The function of the observer 10 will be described first with reference to FIG. The left half of the figure is a state conversion display of the system to be controlled, which is blocked, where u is an input variable, x is a state variable, and y is a detected output variable. System matrix block A, input matrix block B,
And a block called output matrix block C is represented. This observer should be called the mathematical model, and it is made entirely by software. In the observer, a subsystem is created using a new variable z in the controlled object, and an input variable u and an output variable y are introduced into the observer, and unknown state variables x (output torque τ _{s of} the mechanical axis, load torque) τ _L , load rotation speed n _L ) is estimated. Blocks (A), (B), and (C) (The original block variables that represent these estimated values are originally represented by attaching a mountain-shaped hat symbol on top of the relevant symbols, but here, for convenience, parentheses are used. Represents a system matrix block, an input matrix block, and an output matrix block in the subsystem, and blocks (D) and (J) respectively represent a transformation matrix block. Note that x ^* and z ^*
(The symbol * is originally represented by a "dot" symbol, but is replaced by "*" for convenience here) represents an intermediate variable used inside the controlled object and the observer.

By using the observer of FIG. 6, the variables detected in the motor system (the armature current i _a and the motor speed n _{m of} FIG. 5) are variable-converted and introduced by the conversion matrix block D, and unknown variables are obtained. (X) (machine axis S
Estimated output torque (τ _s ), estimated load torque (τ _L ),
The estimated rotation speed (n _L ) of the load is obtained by converting the variable z into a variable by the output matrix block C. In this way, the observer can accurately grasp variables that are difficult to detect directly by mathematical means.

Returning now to FIG. 5, the main loop compares the target speed value n ^* and the motor speed n _m with the comparator 7 to find the deviation, and operates to make the deviation zero. It's a loop. In order to change the control characteristics of the motor, the five outputs of the observer 10, namely, the armature current i
_a , motor speed _nm , machine shaft output torque (τ _s ), load torque (τ _L ), and load rotation speed (n _L ),
Coefficients f ₁ , f ₂ , f ₃ , f ₄ and f ₅ are respectively multiplied in coefficient conversion blocks 11, 12, 13, 14 and 15 and added to the output of the speed controller 1 in an adder 8. This method is a so-called optimum control method, and achieves a desired purpose by adjusting the coefficients f ₁ , f ₂ , f ₃ , f ₄ , f ₅ according to the required control characteristics. However, the original purpose of the optimum control is to prevent the input amount (in this case, the “current command” given from the speed controller 1 to the current controller 2) from becoming excessive, and to control the output variable (in this case, the armature). Current i _a ,
Select an evaluation function such that the motor speed _nm , the output torque (τ _s ) of the machine shaft, and the rotation speed (n _L ) of the load do not become excessive, and determine the coefficients f _{1 to} f ₅ that realize it. That is. Therefore, it is a control method considering the overall balance, but it is insufficient for realizing a specific purpose in a specific application, for example, in a case where it is desired to suppress shaft vibration as much as possible.

[0008]

SUMMARY OF THE INVENTION The present invention provides a system in which an electric motor and a load are coupled by elastic coupling means,
An object of the present invention is to provide an electric motor control device capable of controlling the electric motor so as to damp the vibration when resonance occurs on the load side or vibration that has once occurred is not damped forever.

[0009]

In order to achieve the above object, an electric motor control device according to the present invention comprises an observer for estimating the torque and the rotational speed at both ends of an elastic coupling means by using the electric motor rotational speed and the electric motor current. Compensation calculation means is provided to correct the current reference supplied from the speed controller to the current controller so that the torque and rotation speed of the elastic coupling means estimated by this observer match at both ends of the elastic coupling means. It is characterized by that.

[0010]

In the motor controller of the present invention, the elastic coupling means can be operated as if it were a rigid body by manipulating the output signal of the observer, that is, the estimated value. Therefore, even when the electric motor and the load are coupled via the elastic coupling means, it is possible to rapidly damp system oscillation due to disturbance or torque ripple without causing resonance or the like in the mechanical system that is the load. .

The main purpose of the present invention is not control considering the overall balance such as referring to the evaluation function, but
This is a motor control technique for manipulating the output signal of the observer to operate the elastic coupling means as if it were a rigid body.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the embodiments shown in the drawings.

FIG. 1 shows the basic concept of the present invention. Also in the present invention, in the system in which the electric motor and the load are coupled via the elastic coupling means, the observer as described above is basically used. Then, basically, similar to that shown in FIG. 5, the main system includes the speed controller 1, the current controller 2, the torque conversion coefficient block 3, the transfer function block 4 of the rotary system, and the transfer function block of the mechanical axis S. 5 and the transfer function block 6 of the mechanical system of the load. The observer 10 receives variables detected in the electric motor system, that is, the armature current i _a and the electric motor speed n _m as input, and outputs unknown torque (τ _s ), load torque (τ _L ) and load of the mechanical axis. The rotation speed (n _L ) of is estimated and output. These output signals output from the observer 10 are introduced into the compensation calculation circuit 20, respectively, to create and output a correction signal for correcting the current reference supplied from the speed controller 1 to the current controller 2.

2 and 3 show a specific embodiment of the present invention. In order to suppress mechanical axis vibration, it is necessary to understand the mechanism of its generation. It can be thought of as follows.

The elastic coupling means, ie the flexible mechanical shaft or elastic coupling, can be regarded as a kind of spring. For example, in the case of a flexible mechanical shaft, when the shaft is twisted at both ends of the mechanical shaft, a deviation occurs in the phase (integrated value of speed) at both ends, and torque is generated to restore the deviation. The relationship between them can be expressed by (torque) = (constant) × (deviation of phase) (1). Now, it is assumed that the shaft output torque vibrates around the shaft input torque (motor torque). When vibration occurs, the vibration energy is attenuated by the mechanical system loss. At this time, if the shaft is a rigid body, the shaft will not twist, so that vibration does not occur, and the shaft output torque is the same as the shaft input torque (motor torque).
The torque is transmitted to the load. The following relationships exist between the torque deviation Δτ of the mechanical shaft input / output, the generated torque τ _m of the electric motor, the output torque (τ _s ) of the mechanical shaft, and the speed deviation Δn of the mechanical shaft input / output.

Δτ = τ _m − (τ _s ) = (integration) (Δn · dt) (2) From this equation, in order to prevent the shaft vibration from occurring, the following condition is satisfied. It will be good. (1) The motor side is controlled so that the shaft output torque (τ _s ) and the shaft input torque (motor torque) τ _m are equal. (2) The motor speed is controlled so that phase deviation does not occur at the input / output of the mechanical axis.

When the conditions (1) and (2) are realized, the electric motor M and the load FW behave as if they are connected by a rigid body. If there is no speed deviation at the input and output ends of the machine shaft S, the main loop is not the speed control loop of the electric motor, but the speed control of the load (not the electric motor) directly related to the quality of the steel plate or the like in the rolling mill, for example. Can be configured as

FIG. 2 shows a first embodiment of the present invention. The speed command n ^* and the load speed estimated value (n _L ) obtained by the observer 10 are compared by the comparator 7. The speed deviation Δn = n ^* -(n _L ) obtained as a result of the comparison is converted into a current reference through the speed controller 1 of the proportional-integral operation type,
It is introduced into the current controller 2 via the adder 8. The current controller 2 controls the current of the electric motor M by forming a current control signal so that the inputted current reference is achieved. Basically,
As a result, the speed n _L of the load FW is controlled so as to match the given speed reference n ^* . However, according to the present invention, the compensation arithmetic circuit 20 is provided in the latter stage of the observing device 10, and the output correction signal thereof causes the torque and the rotation speed of the mechanical axis S estimated by the observing device 10 to match at both ends thereof. From speed controller 1 to current controller 2
The current reference supplied to is corrected via the adder 8.

The compensation calculation circuit 20 includes a coefficient unit 21 and an integrator 2.
2, an adder 23, and comparators 24 and 25, and performs the following calculation to form a correction signal.

In order to realize the condition (1), the difference (torque difference) between the output torque (machine shaft input torque) τ _m of the electric motor and the estimated value (τ _L ) of the machine shaft output torque in the comparator 24. ε _τ = τ _m − (τ _L ) is calculated, and the coefficient unit 21
Multiplied by the appropriate coefficient K ₁ in. Similarly, the above (2)
So as to achieve the conditions, the difference between the output rotational speed of the electric motor (mechanical axis input rotation speed) n _m and the machine axis estimated value of the output rotational speed (n _L) (speed _{difference) ε n = n m - (} n _L ) is calculated in the comparator 25, the speed difference ε _n is integrated in the integrator 22, and further multiplied by an appropriate coefficient K ₂ .
By adding the outputs of the coefficient unit 21 and the integrator 22 in the adder 23, the output of the adder 23 is a current reference correction signal for "matching the input / output torque and the input / output rotation speed of the machine shaft as much as possible". Becomes Compensation calculation circuit 2
0 works effectively, the same be fed back to the speed n _L of if the torque and rotational speed are the same, respectively, be fed back to the motor speed n _m in the main loop load before and after ie input and output terminals of the machine axes You will get results. The functions of the torque conversion coefficient block 3, the transfer function block 4 of the rotary system, the transfer function block 5 of the mechanical axis, and the transfer function block 6 of the mechanical system of the load are the same as in the case of FIG.

FIG. 3 shows another embodiment of the present invention. In this embodiment, the fuzzy logic 26 is used instead of the control calculation by the mathematical formula of FIG. 2 to obtain the current reference correction signal. The outline of the fuzzy logic 26 is, as shown in the rule table in the same figure, the torque difference ε _τ = τ _m − (τ _L ) (corresponding to the integral value of the speed deviation) and the speed difference as input variables. ε _n = n _m − (n _L ) is used. The fuzzy logic 26 is described in the form of “IF˜, THEN˜” according to this rule table. The symbols in the rule table have the following meanings.

PB: Very large.

PS: Increase a little.

Z: Leave as it is.

NS: Make it a little smaller.

NB: Make it very small.

The rules are created as follows. Rule (1): When ε _τ > 0 and ε _n <0, the correction signal is left as it is.

(In this state, the output torque of the electric motor is excessive and the output phase of the machine shaft is delayed. However, if the speed difference ε _n is negative, the output rotation speed of the machine shaft becomes high, Since it is in a state of trying to regain the phase delay, it means waiting a little in the current state.) Rule (2): When ε _τ > 0 and ε _n = 0, the correction signal is slightly reduced.

(In this state, the output torque of the electric motor is too high, but the input and output rotational speeds of the machine shaft are almost the same. Therefore, it means that the torque of the electric motor should be reduced a little.) Rule (3) to rule (6) omitted) Rule (7): When ε _τ <0 and ε _n <0, the correction signal is made extremely large.

(In this state, the motor output torque is small,
The output phase of the mechanical axis is advanced. If the speed difference ε _n is negative in this state, the output phase of the machine shaft will advance further, so it is necessary to give a very large voltage to the motor to accelerate it and try to catch up with the output phase of the machine shaft. (Meaning) (Hereinafter, omitted) As described above, if all rules are described, control such that the mechanical axis always approaches a rigid body can be realized by control on the electric motor side.

[0031]

As described above, according to the present invention, in an electric motor system for driving a mechanical load through an elastic coupling means such as an elastic joint or a flexible mechanical shaft, the state quantity of the input / output of the mechanical shaft can be determined. By observing with an observer and adding the necessary current reference correction signal to match the torque and rotation speed before and after the elastic coupling means,
It is possible to suppress system vibration due to disturbance or torque ripple without causing mechanical system resonance or the like.

[Brief description of drawings]

FIG. 1 is a block diagram of a motor control device according to the present invention.

FIG. 2 is a block diagram showing a first specific example of a compensation calculation circuit in the control device of FIG.

3 is a block diagram showing a second specific example of a compensation calculation circuit in the control device of FIG.

FIG. 4 is a wiring diagram of a general electric motor drive control system that drives a load through elastic coupling means.

FIG. 5 is a block diagram of a conventional electric motor control device to which optimum control is applied.

6 is an explanatory diagram of an observer used in the control device of FIG.

[Explanation of symbols]

 1 Speed Controller 2 Current Controller 3 Torque Conversion Coefficient Block 4 Motor Rotor Transfer Function Block 5 Machine Axis Transfer Function Block 6 Load Transfer Function Block 7, 24, 25 Comparator 8, 10, 16, 23 Adder 20 Compensation arithmetic circuit 21 Coefficient unit 22 Integrator 23 Adder 26 Fuzzy logic

Claims (1)

[Claims] 1. A motor control device for controlling, via a speed controller and a current controller, a rotation speed of an electric motor, to which a load is coupled via elastic coupling means, so as to match a speed target value, wherein: An observer that estimates the torque and the rotation speed at both ends of the elastic coupling means using the speed and the electric motor current, and the torque and the rotation speed of the elastic coupling means estimated by the observation device match at both ends of the elastic coupling means, respectively. And a compensation calculation means for correcting the current reference supplied from the speed controller to the current controller.