JPS62118783A - Controller for dc motor - Google Patents

Abstract

PURPOSE:To suppress a speed impact drop and a recovery time to small values at abrupt load change time by using a PI regulator as a speed regulator, and adding the output of a state observer to the output of the regulator. CONSTITUTION:A speed regulator 3 of a PI regulator outputs a current target value ia* responsive to a deviation between a speed target value omega* and an actual speed value omega. A current regulator 4 applies a control signal to a thyristor rectifier 5 in response to a deviation between the values ia* and an actual current value ia. A state observer 2 inputs the value ia and the value omega, calculates the estimated value of a load disturbance amount and its differentiated value, and adds the signal obtained by adding the estimated value and the differentiated value fed through an insensitive zone calculating element 16 to the value ia*.

Description

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

The present invention relates to a control device for an electric motor in which an automatic control loop for the motor torque or current is provided inside an automatic control loop for the motor speed.

[Conventional technology]

A Silyce Leonard direct current passive motor is used to drive the rolling mill for wire rods, steel bars, etc. The rolled material is spread over multiple stands, and it is desired that the rotational speed of each rolling mill be controlled to be constant regardless of the load. The moment the tip of the rolled material bites into the roll, the speed of the roll drops instantaneously and fluctuates transiently. As high-speed rolling is required to improve productivity and product quality, instantaneous drop in rolling roll speed (impact drop) due to steep load torque fluctuations when rolling material is bitten, It is necessary to control the speed recovery time as small as possible. Conventionally, for speed control of DC passive motors, a speed control device developed by Siris Leonard, which has a minor current control system as a minor loop, has been used to perform highly coordinated control, but the speed regulator operates in a proportional-integral manner. Therefore, there is a time delay in corrective action for speed fluctuations when the load suddenly changes, and there is a limit to reducing speed fluctuations. In order to eliminate such drawbacks, for example, according to Japanese Patent Application No. 54-5492 (Japanese Unexamined Patent Publication No. 54-109118), a pure P regulator is proposed as a regulator constituting an automatic control loop for the speed of an electric motor. and a state observation device that includes a circuit that simulates the starting time constant of the motor, receives detected values of the speed and current of the motor as input signals, and generates an estimated value equivalent to the load torque of the motor as an output signal, Control of the DC motor by adding the output signal of the condition observation device to the output signal of the regulator that makes up the automatic control loop for motor speed and gives it to the current regulator that makes up the automatic control loop for motor torque or current. Devices have already been proposed. FIG. 2 is a block diagram of the main parts of the DC motor control device according to this existing proposal. In FIG. 2, a broken line frame l indicates a speed control system, and a broken line frame 20 indicates a state observer. The master regulator for forming the automatic speed control loop, speed regulator 30, is a pure P regulator. An automatic torque or current control loop is provided as an inner loop (minor loop) of the automatic speed control loop. Here, the current regulator 4 constitutes an armature current control loop. Similarly, a pr regulator is used as the current regulator 4. The sirisk rectifier 5 controlled by the current regulator 4 is illustrated as a dead time element with a transfer function eXI)(-5rL). Voltage Ea is supplied from this sirisk rectifier to the armature circuit, and the speed ω
A DC motor rotating at a transfer function (1/Ra)/(1
+5Ta), a proportional element 7 having a magnetic flux φ as a coefficient, and a starting time constant circuit (mechanical system) 8 having a transfer function 1/(STJ). That is, by applying the difference voltage between the supply voltage Ea and the starting Eω=φ・ω to the primary lag element 6, the armature current ia is generated, and by multiplying this by φ, the motor torque τH−φ・ia is generated, It can be thought that the difference between the motor torque τ and the load torque τ is applied to an integral element 8 having an integral time T, + (starting time constant), and the output of this integral element 8 becomes the speed ω. . The actual speed of the direct current passive motor ω is led to the input side of the speed regulator 3o and is compared with the speed target value ω. The speed regulator 3o outputs the armature current target value ia'' according to the speed control deviation ω1-ω.The armature current actual value ia is led to the input side of the current regulator 4, and is outputted as the current target value ia''. be compared. The current regulator 4 generates a control signal for the thyrisk rectifier 5 in accordance with the current control deviation ia"-ia. In the existing proposal of FIG. 2, a state observation device ( Observers > 20 are combined to compensate for load disturbances.The state observer 20 inputs the actual current value ia and the actual speed value ω, and outputs the estimated value τL of the load disturbance amount τt. is added to the output signal of the speed regulator 30 consisting of a pure P regulator, that is, the current command value ia. It consists of amplifiers 13 and 14, an integrator 15, and an inverting amplifier 11 with a gain of 1.The operation of the state observation device is as follows.For example, when the load torque τL suddenly increases, the actual speed value changes. Therefore, a deviation signal of ε=ω−ω〈0 is produced.This deviation signal ε
The polarity of is inverted and compared with the actual current value ia via an amplifier 14 with a gain g2 and an integrator 15. The output of the integrator 15 is added to the speed regulator output signal, so that the current command value ia" increases and the actual current value ia increases. When the field φ is constant, the output of the integrator 15 is equal to the load torque. Equivalent value 1 child, i
As a increases, τ increases, and ω moves in the decreasing direction,
It becomes ω−ω. Eventually, the input to the integrator 12.15 becomes zero and balance occurs, resulting in τL=τL and ω=ω. The amplifying element g is added in order to suppress automatic oscillations caused by the two integral elements in the loop within the observer and to stabilize the system.

[Problems to be Solved by the Invention] By the way, the inventors of the present invention actually manufactured and conducted experiments on the conventional control device shown in FIG. 2, and found that the control device in FIG. It was found that τ2 = τ does not hold, and that an offset occurs between τL and τ. Therefore, the inventors of the present invention conducted various experiments and studies to find the cause of this problem, and found that the control device of the prior art configures the speed regulator 30 as a pure P regulator, that is, the speed regulator 30 By not performing an integral operation, it is possible to reduce the excessive speed adjustment control behavior when the speed target value changes stepwise, but the cause of this offset is due to the time constant in the condition observation device. The problem was found to be due to the calculation error caused by the speed regulator and the fact that the speed regulator was configured as a P regulator. That is, in the control device shown in FIG. 2, the relationship between the load disturbance τ and its estimated value τL is expressed by the following arithmetic expression % Formula % Here, the time constant T of the starting time constant circuit 8 of the electric motor. As for the time constant of the integrating circuit (starting time constant simulating circuit) 12, the first equation can be transformed into the second equation. gz gz If time is set to infinity in the second equation, the second equation becomes the third equation. τL: τL (3) However, as a practical matter, an integrating circuit (starting time constant simulating circuit) is used for the time constant T of the motor starting time constant circuit 8.
It is extremely difficult to completely match and simulate the 12 time constants T. Strictly speaking, it is often the case that TJ≠T. Therefore, considering the deviation between T and T, TJ-T, (
1+Δ). Substituting this relationship into the first equation, we get
The first equation is transformed into the fourth equation. to (1+Δ)τ, +(1-(1+Δ))τ4gz
gz gz gz Here, in the fourth equation, if time is assumed to be infinite as in the case described above, the fourth equation becomes the fifth equation. τ, ;τ, +Δ(τ, −τ, ) (5) In this way, in the control device shown in FIG. 2, an integrating circuit (starting time constant simulating circuit )12 time constants T, cannot be completely matched and simulated, for example, an offset of Δ(τ, −τH) in the second term on the right side of Equation 5 will occur. However, the principle of the control device shown in FIG. 2 is to use a pure P regulator as the speed control regulator 30.
Therefore, such an offset cannot be removed. Therefore, in the control device shown in FIG. 2, the influence of load disturbance cannot be completely eliminated. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and makes it possible to suppress the speed increase and recovery time during sudden load changes, and to reduce the time constant of the starting time constant circuit of the electric motor. Even if it is not possible to completely match the time constant T of the integrating circuit (starting time constant simulating circuit) 12 to TJ, there is a direct current that can match the load disturbance amount and its estimated value. The purpose of the present invention is to provide a control device for an electric motor. [Means for Solving the Problems] In order to achieve such an object, the present invention uses a PI regulator as a regulator constituting an automatic control loop for the speed of an electric motor, and also uses a PI regulator to control the starting time constant of the electric motor. A state observation device is provided that includes a starting time constant simulating circuit that simulates the motor, receives detected values of motor speed and current as input signals, and generates an estimated value equivalent to the motor load torque as an output signal, and the output of the state observation device is The present invention is characterized in that the signal is added to the output signal of a regulator that constitutes an automatic control loop for the speed of the electric motor, and is applied to a current regulator that constitutes an automatic control loop for the torque or current of the electric motor.

[Effect]

In the present invention, a PI regulator is used as the speed regulator. Therefore, in the present invention, it is not possible to completely match the time constant TJ of the motor starting time constant circuit with the time constant T of the integrating circuit (starting time constant simulating circuit), and the load disturbance amount τ, The deviation (offset) between and its estimated amount τ1
, the integral action (1) of the speed regulator eliminates such an offset.

【Example】

Next, embodiments of the present invention will be described in detail based on the drawings. FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a characteristic diagram for explaining one of the effects of the present invention. In FIG. 1, parts having the same functions as those in FIG. 3 are given the same reference numerals. The main difference between the embodiment of FIG. 1 and the prior art of FIG. 3 is that the speed regulator 3 is configured as a PI regulator. Below, the configuration of FIG. 1 will be explained in the same way as FIG. 2. A broken line frame 1 indicates a speed control system, and a broken line frame 2 indicates a state observer according to the present invention. The main regulator for forming the automatic speed control loop, namely the speed regulator 3, is a pr regulator according to the invention. An automatic torque or current control loop is provided as an inner loop (minor loop) of the automatic speed control loop. In this embodiment, the current regulator 4 constitutes an armature current control loop. Similarly, a PI regulator is used as the current regulator 4. The silice rectifier 5 controlled by the current regulator 4 is illustrated as a dead time element with a transfer function exp(5TL). A DC motor that is supplied with voltage Ea from this Sirisk rectifier to the armature circuit and rotates at a speed ω has a transfer function (]/Ra)/(1+5T
It is illustrated in principle with an armature circuit 6 having a), a proportional element 7 having a magnetic flux φ as a coefficient, and a starting time constant circuit (a mechanical system) 8 having a transfer function 1/(ST, ). . That is, by applying the difference voltage between the supply voltage Ea and the starting Eω-φ・ω to the first-order delay element 6, the armature current ia is generated, and by multiplying this by φ, the motor torque τH
= φ・ia is generated, and the difference between this motor torque τ4 and the load l - torque τL is applied to the integral element 8 having an integral time TJ (starting time constant), and the output of this integral element 8 becomes the speed ω. You can think like this. The actual speed value ω is led to the input end of the speed regulator 3 via the speed detection filter 10 illustrated as a −order lag element of 1/(1+STFω), and is compared with the speed target value ω4. The speed regulator 3 outputs an armature current target value ia'' according to the speed control deviation ω''-ω. The armature current actual value ia is transferred to the current regulator 4 via the current detection filter 9 shown as a second lag element, which has a transfer function of 1/(1+S TFC).
The current regulator 4 generates a control signal for the thyrisk rectifier 5 as a function of the current control deviation ia''-ia. In the present invention, two state observers are combined in the speed control system 1 described above to compensate for load disturbance. The state observation device inputs the actual current value ia and the actual speed value ω, and calculates the estimated value τ of the load disturbance amount τl and its value τL+τL,
It is added to the output signal of the conventional speed regulator, that is, the current command value ia''. The configuration of the state observation device includes a starting time constant equivalent model 12, amplifiers 13 and 14 with gains gr + g 2, Integrator 1
5. Dead band calculation element 16, inverting amplifier lJ with gain of 1 11
It is more established. The operation of the state observer is as follows. Now, for example, when the load torque .tau.l increases rapidly, the actual speed value decreases, and therefore a deviation signal of .epsilon.-.omega.-.omega.0 is produced. This deviation signal ε
The polarity of is inverted and compared with the actual current value ia via an amplifier 14 with a gain g2 and an integrator 15. The output of the integrator 15 is added to the speed regulator output signal, the current command ia" increases, and the actual current value ia increases. When the field φ is constant, the output of the integrator 15 is equivalent to the load torque. At the value τ, ia
As τ2 increases, ω moves in the decreasing direction, and ω
−ω. Eventually, the input to the integrator 12.15 becomes zero and balance occurs, resulting in τL=τ and ω=ω. The amplifying element g+ is added to suppress automatic oscillations caused by the two integral elements in the loop within the observer and to stabilize the system. Since the input signal of the integral element 15 is the differential value of the torque disturbance, this is added to τL to obtain τi+τL, which is the current command value r.
Since it is added to "a", it operates to push up ia when the load disturbance suddenly changes, and has the effect of further reducing the impact drop of speed. In this case, τ is made to pass through the dead band element 16, According to the present invention, the estimated value τ of the load disturbance τ and its differential value τL are added to the conventional speed control loop by using the current and the speed. Actual value i
Since we added a state observer that calculates data from a and ω and added τl+τt to the speed regulator output, the speed regulator output is almost always around zero and does not move, and when the load suddenly changes, the observer Compensation signal τ+
τt reduces speed impact drop and recovery time. Even if the estimated value τL by the observer cannot be obtained accurately, the actual speed value is precisely controlled to the set value by the integral action of the speed regulator.

【Effect of the invention】

As explained above, in the present invention, a PI regulator is used as the speed regulator. Therefore, according to the present invention, the time constant T of the motor starting time constant circuit and the time constant T of the integrating circuit (starting time constant simulating circuit)
Even if it is not possible to completely match J and simulate a deviation (offset) between the load disturbance amount τ and its estimated value 5, the integral action (1) of the speed regulator will compensate for this offset. can be removed. Therefore, the influence of load disturbance can be completely eliminated.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional DC motor control device. ■ - Automatic speed control system, 2 - Status observation device, 3 - Speed regulator, 4 - Current regulator, 5 - Cyrisk rectifier, 6 - Armature circuit, 8 - Starting time constant circuit, 9 -...
Current detection filter, io - = speed detection filter,
11--Inverting underground device, 12--Integrator (starting time constant simulation circuit), 13.14--Amplifier, 15--Integrator, 16- Dead band element.

Claims (1)

[Claims] 1) In a DC motor control device in which an automatic motor torque or current control loop is provided inside the motor speed automatic control loop, a PI controller is used as a regulator constituting the motor speed automatic control loop. ,and,
A state observation device is provided, which includes a starting time constant simulating circuit that simulates the starting time constant of the motor, receives detected values of the speed and current of the motor as input signals, and generates an estimated value equivalent to the load torque of the motor as an output signal. The output signal of the condition observation device is added to the output signal of a regulator that constitutes an automatic control loop for the speed of the electric motor, and the resultant signal is applied to a current regulator that constitutes an automatic control loop for the torque or current of the electric motor. DC motor control device.