JPS6333389B2 - - Google Patents

Description

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

The present invention provides a rotational speed regulator that receives a difference between a commanded value and an actual value of the rotational speed of an electric motor that drives a machine that is directly connected via an elastic shaft, and outputs a current command value, and The present invention relates to a rotational speed regulating device having a current regulator which receives a difference between an actual current value and a current command value outputted from the rotational speed regulator and generates a control output of a motor supply current.

[Conventional technology]

Such a rotational speed regulating device is known from German Patent Application No. 23 37 722. In order to adjust the rotational speed of a machine driven by an electric motor and with load fluctuations, this known device includes a rotational speed regulation loop and a current regulation loop placed below it, the amount being proportional to the load torque. is fed forward to the current regulator as an additional setpoint value. In this known device, in order to obtain an additional setpoint value for the current regulator, a shaft torque detection device is provided on the shaft connecting the drive motor to the machine for directly detecting the shaft torque.

[Problems to be solved by the invention]

However, in this known device, it is impossible in principle to obtain a pure load torque using the shaft torque detection device, and a relatively complicated correction circuit including a multiplier is used to eliminate the acceleration moment. There is a problem in that it must be added to the torque detection device. This multiplier becomes a source of error. Furthermore, since devices for direct measurement of shaft torque are always accompanied by errors, known devices require a rotational speed regulator to compensate for this error or to ensure sufficient accuracy of the rotational speed adjustment. is PI
shall be configured as a regulator. This has the problem that, in the event of a sudden change in the setpoint value, the adjustment process is likely to be overdone. SUMMARY OF THE INVENTION The present invention has been made in view of these points, and first, an object of the present invention is to provide a rotational speed adjusting device that can obtain load torque by simple means without using a torque detection device. shall be. Another object of the invention is then to be able to obtain the load torque in a simple manner, without the use of torque detection devices, and with good dynamic characteristics, in particular a high adjustment course with few overshoots. The goal is to be able to obtain precision.

[Means to solve the problem]

In order to achieve such an objective, the present invention
In the rotational speed adjusting device mentioned at the beginning, (a) an input amount, an elastic axis, and an axis having an integral time corresponding to the moment of inertia of the electric motor and representing the torque generated by the electric motor obtained from the actual current supplied to the electric motor; a first integral element that outputs a simulated value of the motor rotation speed by integrating the difference between the torque and the simulated value; a second integral element that outputs a simulated value of the shaft torque of the elastic shaft by integrating the difference between the simulated value of the motor rotation speed and the simulated value of the machine rotation speed from the first integral element; It has an integration time corresponding to the moment of inertia of the machine, and simulates the machine rotation 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 acting on the machine. 3rd to output the value
and (d) a value obtained by integrating 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 as the simulated value of the load torque. , the third
a fourth integral element input to the integral element; and a state observer consisting of
The simulated value of the load torque created by the integral element is extracted and added to the current command value output from the rotational speed regulator. Furthermore, in order to achieve the other objects of the present invention mentioned above, the present invention provides the rotational speed regulating device described at the beginning, in which the rotational speed regulator is composed of a pure proportional regulator, and (a) It has an integration time corresponding to the moment of inertia, and the motor rotation speed can be determined by integrating the difference between the input amount representing the motor generated torque obtained from the actual current supplied to the motor and the simulated value of the shaft torque of the elastic shaft. (b) having an integration time corresponding to the torsion spring constant or rigidity of the elastic shaft, the simulated value of the motor rotation speed from the first integral element and the machine; (c) a second integral element that outputs a simulated value of the shaft torque of the elastic shaft by integrating the difference between the rotation speed and the simulated value; A third unit that outputs a simulated value of the machine rotation 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 acting on the machine.
and (d) a value obtained by integrating 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 as the simulated value of the load torque. , the third
A fourth integral element that is input to the integral element of
The simulated value of the load torque created by the integral element is extracted and added to the current command value output from the rotational speed regulator.

【Example】

Next, embodiments of the present invention will be described in detail based on the drawings. FIG. 1 shows, as an example of the application of the invention, a speed regulation loop of a drive motor which is elastically coupled to a machine (load). A DC motor 1 with a moment of inertia θ _M is connected by an elastic shaft 2 , symbolized by a torsion spring, to a machine 3 with a moment of inertia θ _L . Machine 3 has load torque
m _L acts on the elastic shaft 2, a shaft torque m _W acts on the elastic shaft 2, and a motor torque m _M proportional to the armature current i _M acts on the DC motor 1 in the directions of the arrows.
The arrows labeled n _M and n _L indicate the direction of the motor rotation speed or machine rotation speed. The armature current i _M of the DC motor 1 is a three-phase AC power supply R,
supplied by a converter 4 connected to S, T;
The output of a current regulator 5 configured as a PI regulator is added to the control circuit of this converter. The armature current of the DC motor 1 is measured by a current transformer 8 and fed as an actual value to a comparison circuit 7 of a current regulator 5. The current regulation loop described so far is placed below the rotational speed regulator 10, and the output amount of the rotational speed regulator 10 is the target value for the current regulator 5. On the input side of the rotational speed regulator 10, which is configured as a proportional regulator, the rotational speed setpoint value n _M ^*
and the output variable of a comparator circuit 9, from which the output signal of the tachometer dynamo 6 connected to the drive motor 1, ie the actual rotational speed value _nM , is added. A quantity m^ _L proportional to the load torque is also introduced into the comparator circuit 7 as an additional target value. The disturbance feedforward amount proportional to this load is the actual rotational speed value.
n _M and the actual armature current value i _M of the DC motor 1 by the state observer 12 with high precision. Providing these input quantities to the state observer does not imply any additional costs. This is because these input variables must be detected in any case for adjusting the rotational speed or the current. By means of this disturbance feedforward, the current regulator 5 is provided precisely with the required setpoint value in steady state to compensate for the loads acting on the machine 3. Therefore, the rotational speed regulator 10 does not need to be involved in the setpoint value of the current regulator 5 in the steady state. That is, even though the rotational speed regulator 10 is configured as a pure proportional regulator,
A state in which the control deviation is zero (n _M ^* = n _M can be accurately obtained).On the other hand, by configuring the rotational speed regulator 10 as a proportional regulator, that is, by not allowing the rotational speed regulator to perform an integral operation. This results in the advantage that the control behavior of the rotational speed adjustment is less likely to be overdone during stepwise changes of the rotational speed setpoint value.The actual values n _M and i _M supplied by the tacho dynamo 6 and the current transformer 8 are: In order to reduce ripples in the output quantity of the state observer 12, it is guided to the state observer 12 via a smoothing circuit 11 of the same design as possible.The time constants of these smoothing circuits are selected to be as small as possible. If there is a significant difference between the moment of inertia θ _M and the moment of inertia _{θ L of} the machine 3, the simulated motor rotational speed is It is advantageous to also feed forward a quantity proportional to the quantity generated by the state observer as the difference between n^ _M and the simulated rotational speed n^ _L of the machine 3 to the current regulator 5 as a setpoint value. In this case, the proportional coefficient is determined by the amplification factor K5 of the proportional circuit 13. By the way, the electric motor 1-elastic shaft 2 in FIG.
-The machine 3 system can be represented by the block diagram shown in FIG. Here, θ _M is the moment of inertia of the electric motor 1, K is the torsional spring constant or rigidity of the elastic shaft 2, θ _L is the moment of inertia of the machine 3, and S is the Laplace operator. Shaft torque m _W acting on elastic shaft 2
is fed back to the input side of the electric motor 1, and the rotation speed _nL of the machine 3 is fed back to the input side of the elastic shaft 2. Then, a load torque m _L acts on the machine 3. The actual rotational speed _nM of the electric motor 1, indicated by the dotted arrow, is measured by the tacho dynamo 6 as explained in FIG. Then, the state observation device 12 shown in FIG.
includes the model of the electric motor 1 - elastic shaft 2 - machine 3 system shown in Fig. 3, and based on these,
Load torque without using a torque detection device
It is configured to obtain a simulated value m^ _L that simulates m _L. Next, the specific configuration and operation of the state observation device 12 will be explained with reference to FIG. This state observation device, together with integrators 14 to 17 acting as memory circuits, is a linear model of the mechanical parts of the controlled object (electric motor 1,
elastic shaft 2, machine 3). Integrator 14~
Each transfer function is written above the 16 blocks, where S is the Laplace operator and T _M
is the integration time of the integrator 14 corresponding to the moment of inertia θ _M of the drive motor 1, T _C is the integration time of the integrator 15 corresponding to the torsion spring constant or rigidity K of the elastic shaft 2, and T _L is the integration time of the integrator 15 corresponding to the moment of inertia θ M of the drive motor 1. It means the integration time of the integrator 16 corresponding to the moment of inertia θ _L. This model is measured by current transformer 8 and has a time constant T _I
is driven by the armature current actual value i _M which is led to the input of an integrator 14 via a smoothing or first-order lag circuit 11 with . At the output of the integrator 14, a quantity n^ _M is obtained ("observed") which should correspond to the actual rotational speed value _nM actually generated by the tacho dynamo 6. This can only be true if at the input of the integrator 16, which simulates the machine 3 in a model manner, a quantity m^ _L is introduced which exactly corresponds to the load torque m _L acting on the machine 3. Load torque m _L
An integrator 17 is used to simulate this, and this integrator includes a time constant circuit 11 that is actually measured through a proportional circuit having an amplification factor K4.
The actual motor rotational speed n M derived through n _M and the motor rotational speed simulated by the integrator 14
The difference between n^ _M is derived. Therefore, the integrator 17
The output quantity of is increased until the actual motor rotational speed n _M and the simulated motor rotational speed n^ _M exactly match, so that the controlled object model contained in the condition observer also matches the actual controlled object and the machine. will continue to change until they match perfectly. Thus, in particular, the value of the simulated load torque m^ _L used for the disturbance feedforward and the simulated rotational speed difference n^ _M −n^ _L correspond to the respective quantities actually occurring in the controlled object. I will do it. Here, it will be briefly explained that the simulated value m^ _L of the load torque m _L becomes equal to the load torque m _L. For ease of understanding, we will now refer to Machine 3
It is assumed that the rotation speed n _L and the motor rotation speed n _M are constant. It is also assumed that the simulated value n^ _L of the machine rotational speed and the simulated value n^ _M of the motor rotational speed are also constant. Therefore, in order for n^ _L to be constant, the input amount to the integrator 16 must be zero, and therefore it can be assumed that m^ _W = m^ _L . Similarly, in Figure 3, since n _M = constant, i _M = m _W , and since n _L = constant,
It is also m _W = m _L. On the other hand, the output amount n^ _M of the integrator 14
In order for M to be constant, the input quantity of the integrator 14 must also be zero, and therefore it can be assumed that i _M = m^ _W.
In this case, as mentioned above, since m^ _W = m^ _L , i _M
= m^ _L . Also, in FIG. 3, i _M = m _W ,
Since m _W = m _L , i _M = m _L. After all, m^ _L = m _L
becomes. The model of the controlled object contained in the state observer is always in a state that is adapted to the fluctuations in the operating conditions of the controlled object, and this adaptation is necessary for the “observed” value n^ _M to match the actual value. It is important that this is done as fast as possible. Since in the example shown here the state observer 12 is a regulating loop with four memory circuits, ie a fourth-order regulating loop, special attention should be paid to the stability and dynamics of the state observer. Therefore, in addition to the feedback circuit with an amplification factor of K4, three proportional feedback circuits with amplification factors of K1 to K3 are provided, and on the input side of these feedback circuits, the actual motor rotational speed n _M is simulated. A voltage corresponding to the difference (n _M −n^ _M ) between the motor rotational speed n^ _M There is. Therefore, the amplification factors of these feedback circuits influence the coefficients of the transfer function of the state observer or the coefficients of the characteristic differential equation describing its dynamic characteristics or the coefficients of the characteristic differential equation describing its dynamic characteristics. Amplification factor K1 ~ by well-known optimization adjustment
By appropriately selecting K4, the state observer can be given characteristics optimally adapted to the current state. It has been found to be particularly expedient to determine the amplification factors K1 to K4 such that the "double ratio" of the coefficients of the polynomial representing the characteristic differential equation of the state observer is constant and equals 0.5. . Here, the double ratio means the ratio between the ratios of adjacent coefficients in the polynomials of the denominators of the transfer functions arranged in order of increasing order of the Laplace operator or the characteristic equations arranged in the same way. The condition observer adjustment loop in our example is similar to the constant double ratio method described above (by Ernst and Strole).
Industrieelektronik (industrial electronics)”
1973, pp. 62-68), the ratio of adjacent coefficients is a geometric series term (a, aq, aq ² , aq ³ ); Here, the first term a corresponds to the so-called equivalent time constant of the state observer, and q has a value of 0.5. The time constant T ₁ of the smoothing circuit 11 and the equivalent time constant of the state observer should be chosen as small as possible. The lower limit is determined by the ripple size that can be tolerated in the output signals m^ _L and n^ _M -n^ _L of the state observer. In order to keep this ripple small, it is expedient not to include any proportional or differential elements in the circuit 17 for simulating the load torque, but to construct this circuit as a purely integral regulator.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a speed control loop to which the present invention is applied, FIG. 2 is a block diagram showing the configuration of its state observation device, and FIG. 3 is a block diagram showing its motor-shaft-mechanical system. DESCRIPTION OF SYMBOLS 1... DC motor, 2... Elastic shaft, 3... Machine, 4... Conversion device, 5... Current regulator, 6...
Tacho dynamo, 7...comparison circuit, 8...current transformer,
9... Comparison circuit, 10... Rotation speed regulator, 11
... Smoothing circuit, 12 ... State observer, 13 ... Proportional circuit, 14-17 ... Integrator.

Claims (1)

[Scope of Claims] 1. A rotational speed regulator 10 that receives the difference between the command value and actual value of the rotational speed of the electric motor 1 that drives the machine 3 directly connected via the elastic shaft 2 and outputs a current command value. and a current regulator 5 which receives the difference between the actual current value supplied to the motor and the current command value output from the rotation speed regulator and produces a control output of the motor supply current. In the regulating device, (a) an input quantity and an elastic shaft having an integral time (T _M ) corresponding to the moment of inertia of the motor and representing the motor generated torque obtained from the actual current (i _M ) supplied to the motor; The first output unit outputs the simulated value of motor rotation speed (n^ _M ) by integrating the difference between the simulated value of shaft torque (m^ W) and the simulated value of shaft torque (m^ _W ).
(b) has an integral time (T _C ) corresponding to the torsional spring constant or rigidity of the elastic shaft, and has a simulated value (n^ _M ) of the motor rotation speed from the first integral element; and the simulated value of machine rotation speed (n^ _L )
A second output unit outputs a simulated value (m^ _W ) of the shaft torque of the elastic shaft by integrating the difference between
(c) has an integral time (T _L ) corresponding to the moment of inertia of the machine, and has a simulated value (m^ _W ) of the shaft torque from the second integral element and the load acting on the machine. a third integral element 1 that outputs the simulated value (n^ _L ) of the machine rotational speed by integrating the difference with the simulated value (m^ _L ) of torque;
6, and (d) the actual value of the motor rotational speed (n _M ) and the first
A value obtained by integrating the difference between the integral element and the simulated value (n^ _M ) of the motor rotation speed is input to the third integral element as the simulated value (m^ _L ) of the load torque. and a state observation device 12 consisting of a fourth integral element 17, which extracts the simulated value of load torque (m^ _L ) created by the fourth integral element 17 of the state observation device, and obtains the current instruction. A rotation speed adjusting device characterized by adding to a value. 2. A rotation speed regulator 10 that receives the difference between the command value and actual value of the rotation speed of the electric motor 1 that drives the machine 3 directly connected via the elastic shaft 2 and outputs a current command value; a current regulator 5 which receives a difference between an actual current value and a current command value output from the rotation speed regulator and generates a control output of the motor supply current; The speed regulator 10 is constructed from a pure proportional regulator, and (a) has an integral time (T _M ) corresponding to the moment of inertia of the motor, which is obtained from the actual current (i _M ) supplied to the motor; The first step outputs the simulated value of the motor rotation speed (n^ _M ) by integrating the difference between the input amount representing the torque generated by the motor and the simulated value of the shaft torque of the elastic shaft (m^ _W ).
(b) has an integral time (T _C ) corresponding to the torsional spring constant or rigidity of the elastic shaft, and has a simulated value (n^ _M ) of the motor rotation speed from the first integral element; and the simulated value of machine rotation speed (n^ _L )
A second output unit outputs a simulated value (m^ _W ) of the shaft torque of the elastic shaft by integrating the difference between
(c) has an integral time (T _L ) corresponding to the moment of inertia of the machine, and has a simulated value (m^ _W ) of the shaft torque from the second integral element and the load acting on the machine. a third integral element 1 that outputs the simulated value (n^ _L ) of the machine rotational speed by integrating the difference with the simulated value (m^ _L ) of torque;
6, and (d) the actual value of the motor rotational speed (n^ _M ) and the first
A value obtained by integrating the difference between the integral element and the simulated value (n^ _M ) of the motor rotation speed is input to the third integral element as the simulated value (m^ _L ) of the load torque. and a state observation device 12 consisting of a fourth integral element 17, which extracts the simulated value (m^ _L ) of the load torque created by the fourth integral element 17 of the state observation device, and extracts the simulated value (m^L) of the load torque and calculates the current command. A rotation speed adjusting device characterized by adding to a value.