JPS631839B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed control device for an electric motor that drives a load directly connected to the shaft of an elastic body. Rather, the present invention relates to a motor speed control device for suppressing torsional vibration of a shaft connecting a motor and a load, as well as speed impact drop when a sudden load change occurs.

A motor and a load that are directly connected by a shaft made of an elastic body may form a resonant system in relation to the elastic coefficient of the shaft and the moments of inertia of the motor and load, and torsional torque is generated on the shaft. If the torsional torque increases, the life of the shaft will be shortened, and in the worst case scenario, the shaft may break. In controlling the rotational speed of an electric motor, it is desirable to take into account the suppression of torsional vibration of the shaft. Furthermore, even if the speed of the motor is controlled, the speed may suddenly change and drop depending on the load condition (this is called speed impact drop), and it is desirable to reduce the amount of speed drop as much as possible. There are also demands. A conventional motor speed control device developed to meet such demands will be explained with reference to FIG.

FIG. 1 is a block diagram showing an example of a circuit configuration of a conventional motor speed control device.

Refer to the same figure. The DC motor 1 is connected to a load 3 by an elastic shaft 2, which is symbolized by a torsion spring. A load torque τ _L acts on the load 3, a shaft torque τ _S acts on the elastic shaft 2, and a motor torque τ _M proportional to the armature current i _M acts on the DC motor 1. Further, n _L indicates the rotation speed of the load 3, and n _M indicates the rotation speed of the electric motor 1. The armature current i _M of the DC motor 1 is supplied from a converter 4 connected to three-phase AC power sources R, S, and T.
The output of the current regulator 5 is added to the control circuit. The armature current i _M of the DC motor 1 is the current transformer 11
, and is introduced to the comparator circuit 7 as an actual value. current regulator 5, converter 4, current transformer 11,
The current regulation loop consisting of the comparison circuit 7 is placed below the speed regulator 10, and the output amount of the speed regulator 10 is the current command value i _M ^* for the current regulator 5. On the input side of the speed regulator 10, a command value n _M ^* of the rotational speed and an output signal of the tacho dynamo 6a coupled to the electric motor 1, that is, the actual value of the rotational speed are input.
The output quantity of the comparator circuit 9 from which _nM is derived is added. Further, the output signal of the tacho dynamo 6b coupled to the load 3, that is, the actual value n _L of the rotational speed of the load 3 and the actual value n _M of the rotational speed of the electric motor 1, is led to a comparator circuit 8, and its output is The command value is sent to the comparator circuit 7 as a command value, thereby suppressing torsional vibration of the elastic shaft 2.

The conventional electric motor speed control device as schematically explained with reference to FIG. If it is physically difficult to install a tacho dynamo on the load side, this means that the speed control described above cannot be performed. Furthermore, even if it is possible to install a tacho dynamo on the load side, special processing may be required for installation, which increases the cost, or the cost of the tacho dynamo itself. The device had the disadvantage of being expensive.

The present invention has been made to eliminate the drawbacks of the prior art as described above, and an object of the present invention is to eliminate torsional vibration of an elastic shaft without requiring a tacho dynamo on the load side. It is an object of the present invention to provide a speed control device for an electric motor that can suppress speed change impact drop, etc.

The main point of the configuration of this invention is to simulate the load torque, the difference between the load torque and the shaft torque, and the difference between the motor rotation speed and the load rotation speed, given the actual values of the armature current and rotation speed of the motor. The present invention is characterized in that a load condition observation device capable of outputting a load condition is provided, and the current command value for the current regulator is compensated using these various quantities outputted from the observation device.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram showing one embodiment of the present invention. In the figure, 12 is a load condition observation device, and other components that are the same as in FIG. 1 are given the same reference numerals.

See Figure 2. An electric motor 1 with a moment of inertia J _M is connected to an elastic shaft 2 having a torsion spring constant,
It is connected to load 3 with moment of inertia J _L. It is assumed that a load torque τ _L is generated in the load 3, a shaft torque τ _S is generated in the shaft 2, and a motor torque τ _M is generated in the electric motor 1, and the motor rotation speed and load rotation speed are n _M and n _L.

The main control system of the electric motor 1 is a speed control system with a current minor control loop, and includes a speed regulator 10,
Current regulator 5, ignition pulse generator (not shown),
Thyristor conversion device 4, current transformer 1 for current detection
It consists of 1.

For this main control system, the state observation device 12 calculates the load torque _{τ L} , shaft torque τ _S , motor speed n M , and load speed n _L from the actual speed value n _M and the actual current value i _M
Create simulated values τ^ _L , τ^ _S , n^ _M , n^ _L and τ^ _L
，
K ₁ (n^ _M - n^ _L ) and _K2 ([tau]^ _L - [tau]^ _S ) are added to the command value _iM ^* of the current regulator 5 in the comparator circuit 7 for compensation. Note that K ₁ and K ₂ are proportionality constants. The feedback of the simulated value τ _L of the load torque is for performing feed-forward compensation of the load disturbance torque τ _L , and is expressed as K ₁ (n^ _M − n^ _L ),
K ₂ (τ^ _L −τ^ _S ) is a feedback and feedback compensation signal for suppressing the torsional vibration torque of the elastic shaft 2 and stabilizing the main control loop.

FIG. 3 is a block diagram showing details of the load condition observation device in FIG. 2.

See Figure 3. The observation device 12 shown in the figure is
By including integrators 121 to 123 that act as memory circuits, it includes a linear model of the mechanical parts to be controlled (electric motor 1, elastic shaft 2, load 3) shown with reference numerals 1 to 3 in FIG. . Integrator 121~
Each of the 123 blocks is filled with its respective transfer function, where S is the Laplace operator and T _M
is the integration time of the integrator 121 corresponding to the moment of inertia J _M of the electric motor 1, T _C is the integration time of the integrator 122 corresponding to the torsion spring constant or rigidity of the elastic shaft 2, and T _L is the moment of inertia of the load 3. It represents the integration time of the integrator 123 corresponding to _JL .
This model is driven by the actual armature current i _M of the motor. At the output of the integrator 121, a simulated value n^ _M is obtained which corresponds to the actual value _nM of the motor rotational speed. This is true when a simulated value τ^ _L corresponding to the load torque τ _L acting on the load 3 is introduced to the input side of the integrator 123 that simulates the load 3 as a model. An integrator 124 is used to simulate the load torque τ _L , and this integrator receives the actually measured motor rotational speed actual value n _M via a proportional circuit 128 with an amplification factor g ₄ . and the simulated value n^ _M of the motor rotation speed obtained by simulation by the integrator 121 is derived. Therefore,
The output amount of the integrator 124 is the actual motor rotation speed.
Until n _M and the simulated motor rotation speed value n^ _M exactly match,
Therefore, the controlled object model included in the state observer continues to change until it completely matches the actual controlled object in terms of functionality. In this way, in particular, the simulated value τ^ _L of the load torque that is simulated and used for feedforward during disturbances and the simulated value (n^ _M − n^ _L ) of the rotational speed difference obtained by simulation are actually This corresponds to each amount occurring in the controlled object.

In order for the model of the controlled object included in the condition observer to always be in a state that adapts to changes in the operating conditions of the controlled object, and for the “observed” simulated value n^ _M to match the actual value, this is necessary. It is important that adaptation occurs as quickly as possible. In the example shown here, the state observer 12 is composed of a regulating loop having four memory circuits (integrator circuits), that is, a fourth-order regulating loop, so that the stability and dynamic characteristics of the state observer are affected. Particular attention should be paid to Therefore, the feedback circuit 128 with an amplification factor g ₄
In addition to the above, three proportional feedback circuits 125 to 127 having amplification factors g ₁ to _{g 3} are provided, and on the input side of these feedback circuits, the motor rotation speed obtained by simulating the actual motor rotation speed is provided. A voltage corresponding to the difference between the rotational speed and the simulated value is introduced, and the output quantities of these feedback circuits are applied to the input terminals of integrating circuits 121 to 123, respectively. The amplification factors of these feedback circuits therefore influence the coefficients of the transfer function of the state observer or the coefficients of the characteristic differential equation describing its dynamic characteristics. By appropriately selecting the amplification factors g ₁ to _{g 4} through well-known optimization adjustments, the state observer can be given characteristics optimally adapted to the current state. Note that 129 and 130 are proportional circuits having amplification factors K ₁ and K ₂ respectively.

As explained above, according to the present invention, in order to stably control the motor speed in the controlled object consisting of the motor, shaft, and load, the state observation device measures the armature current i _M and the motor speed n. From the simulated values τ^ _L , τ^ _S , n^ M , n^ _L obtained by simulating the load torque τ _L , shaft torque τ _S , motor speed n _M , and load speed n _L using _M as input _. , (n^ _M −
n^ _L ), (τ^ _L −τ^ _C ), and τ^, K ₁ (n^ _M −n
^ _L ),
Feedback of K ₂ (τ^ _L −τ^ _C ) to the current command value has the advantage that stable speed control can be achieved and transient decreases in speed can be suppressed when the load suddenly changes. Further, since the speed regulator is a PI (proportional, integral action) regulator, even if there is an error in the simulation value, this error is compensated by the operation of regulator I, so no offset occurs.

In addition to the speed control device for a controlled object consisting of a DC motor, shaft, and load as described above, this invention also provides the following features:
It can also be applied to position control devices.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a configuration example of a conventional motor speed control device, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a block diagram showing an example of the configuration of a conventional motor speed control device. FIG. 3 is a block diagram showing details. Description of symbols, 1...DC motor, 2...Elastic shaft,
3... Load, 4... Conversion device, 5... Current regulator, 6a, 6b... Tacho dynamo, 7, 8, 9...
... Comparison circuit, 10 ... Speed regulator, 11 ... Current transformer, 12 ... Load condition observation device.

Claims (1)

[Claims] 1. A speed regulator that receives the difference between a command value and an actual value of the rotational speed of a motor that drives a load directly connected to the shaft of an elastic body and outputs a current command value; A speed control device for a motor, comprising a current regulator that receives the difference between the actual current value supplied to the motor and the current command value output from the speed regulator and generates a control output of the motor supply current, as follows: Elements of, a) Integral time corresponding to the moment of inertia of the motor
_TM , and outputs a simulated value of the motor rotation speed by integrating the difference between the actual current supplied to the motor and the simulated value of the shaft torque of the elastic body obtained in the condition observation device. Integral element 121, (b) has an integration time T _C corresponding to the axial torsional spring constant or rigidity of the elastic body, and combines the simulated value of the motor rotation speed from the first integral element and the load rotation obtained in the state observation device. a second integral element 122 that outputs the simulated value of the shaft torque by integrating the difference with the simulated value of the speed; C. an integration time corresponding to the moment of inertia of the load;
T _L , and outputs the simulated value of the load rotational speed by integrating the difference between the simulated value of the shaft torque from the second integral element and the simulated value of the load torque obtained within the state observation device. a third integral element 123; (d) a value obtained by multiplying the difference between the actual value of the rotational speed of the electric motor and the simulated value of the rotational speed of the electric motor from the first integral element by a predetermined gain;
a first gain element 125 that feeds back to the integral element of; Second
a second gain element 126 that feeds back to the integral element 126; Third
a third gain element 127 that feeds back to the integral element; g) outputs a value obtained by multiplying the difference between the actual value of the motor rotation speed and the simulated value of the motor rotation speed from the first integral element by a predetermined gain; A fourth gain element 128 that performs, H. A value obtained by integrating the output of the fourth gain element, to the third integral element,
a fourth integral element 124 which is provided as a simulated value of the load torque used in the integral calculation; The difference between the simulated value of the load torque output from the element and the simulated value of the shaft torque output from the second integral element, and the simulated value of the motor rotation speed output from the first integral element and the A speed control device for an electric motor, characterized in that a difference between a simulated value of the load rotation speed outputted from a third integral element is extracted and added to or subtracted from the current command value.