JP2903717B2 - Motor speed control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor speed control device for adjusting a control constant of a control device according to a change in a mechanical constant of the motor.

[0002]

2. Description of the Related Art Generally, in order to control the speed of a motor with high performance, the mechanical constant (moment of inertia) of the motor and its load must be known. However, since the mechanical constants are generally unknown or may fluctuate, it is necessary to identify them. Here, as a method for identifying this kind of mechanical constant, Japanese Patent Laid-Open No. 22828/1990
As disclosed in Japanese Patent Laid-Open Publication No. 5 (1993) -2005, a parameter identification circuit for identifying a mechanical constant by a signal proportional to the amount of change in the generated torque and speed of the motor is provided. There is known a method of identifying the mechanical constant by removing the influence of the disturbance torque by operating the.

FIG. 7 shows a basic configuration of the above-mentioned conventional technology, in which reference numeral 1 denotes an electric motor which is a control object to which a load is mechanically connected, and 2 denotes an encoder (rotary speed detector of the electric motor 1). Pulse encoder), 3 is an average speed calculation circuit for calculating the average speed n _AVE of the motor 1 from the encoder pulse, 4 is the speed command value n * and the average speed n of the motor 1
An adder to which _AVE is input with the reference numeral shown, a speed control circuit 5 including a speed controller, and a torque current command value I * (equivalent to a torque command value) output from the speed control circuit 5.
And an adder for inputting an actual torque current value I _IST of the motor 1 with reference numerals shown in the figure, a current control circuit 7 including a current regulator and the like, and a motor 8 which multiplies the torque current actual value I _IST by a magnetic flux φ multiplier for calculating a torque generated tau _M, 9 is a parameter identification circuit for identifying the machine constants to exclude disturbance torque based on the generated torque tau _M and the average speed n _AVE. In addition, actually, there is provided a means for changing the control constant by a relational expression between the mechanical constant and a control constant of the speed control device (for example, a proportional constant of the speed controller) based on the identified mechanical constant, Here, it is omitted for convenience.
Here, the motor 1, the adder 6, and the current control circuit 7 form a so-called current minor loop.

[0004]

In the conventional speed control device according to the above-described identification method, the average value n _AVE is detected as the speed of the electric motor 1 in identifying the mechanical constant. The actual speed may not coincide with the average value _nAVE . In particular, since the parameter identification circuit 9 performs an identification operation when the speed changes,
The error between the average speed n _AVE and the actual speed becomes a problem.
Further, since the generated torque τ _M of the electric motor 1 input to the parameter identification circuit 9 is not the average value of a certain period but always the current value, the accuracy of the mechanical constant identified based on these is low.

Further, in a conventional speed control device, various operations including multiplication and division are generally performed by a microprocessor when an average speed is detected or an identification operation is performed based on adaptive control theory. Extremely complex,
There is a problem that the execution time of the microprocessor becomes longer. In general, there is an error in a detection element that performs speed detection, current detection, and the like, and in addition to this, there is a rounding error at the time of calculation by a microprocessor.
On the other hand, since the parameter identification circuit 9 has an integrator inside, even if the various errors described above are individually small, they become considerably large due to the integration operation over a long period of time. This may cause a decrease in accuracy. In particular, in the related art, the identification operation is performed only during a transition in which the generated torque and the speed, which are the inputs of the parameter identification circuit 9, greatly change. It was a big problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a motor speed control device capable of improving the accuracy of identification of mechanical constants and shortening the calculation time required for identification. To provide.

[0007]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides an average speed calculating circuit for calculating an average speed of a motor during a certain period, and an average torque generated by the motor during the same period as the certain period. An average generated torque calculation circuit for calculating, and a mechanical constant is identified by a parameter identification circuit based on the average speed output from the average speed calculation circuit and the average torque output from the average generated torque calculation circuit. . Also, if necessary,
Means for stopping the operation of the parameter identification circuit when the average speed output from the average speed calculation circuit is within a certain value, and further, the rate of change of the torque command value or the speed command value of the motor is a certain value. Means for stopping the operation of the parameter identification circuit when the time is within the range.

[0008]

According to the present invention, by calculating the average torque during the same period as the period during which the average speed of the motor is calculated, the sampling points of the input variables of the discrete time system in the parameter identification circuit can be unified, and the accuracy can be improved. Can be identified. Further, by limiting the identification operation to the middle and high speeds of the motor, the period for detecting the average speed substantially coincides with the sampling interval, so that the calculation of the average torque becomes easy. Further, when the average torque or average speed, which is the input signal of the parameter identification circuit, is small, the error included in each signal becomes relatively large. In these cases, the error is stopped for a long time by stopping the identification operation. To be integrated over

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of the present invention. The same components as those in FIG. 7 are denoted by the same reference numerals, detailed description thereof will be omitted, and different portions will be mainly described below. That is, in this embodiment, the average generated torque calculation circuit 10 is added to the configuration of FIG. The arithmetic circuit 10 fetches the duration T _A to the average speed calculating circuit 3 is used for calculation of the average speed within the calculated generated torque tau _M and a magnetic flux φ which is not shown and the torque current actual value I _IST of the motor 1 as well as, to output the average torque tau _MAVE over the period T _a of the generated torque tau _M by calculating the parameter identification circuit 9.
Here, the arithmetic expression of the average torque τ _MAVE is as shown in the following Expression 1.

[0010]

(Equation 1)

With such a configuration, the input signals of the parameter identification circuit 9 are the average speed n _AVE and the average torque τ _MAVE during the same period T _A. For this reason, since the sampling points of the input variables (speed and generated torque) of the discrete time system equation in the parameter identification circuit 9 can be unified, the identification accuracy of the mechanical constant can be improved as compared with the conventional case.

FIG. 2 shows a second embodiment of the present invention. Here, the embodiments shown in FIGS. 2, 5, and 6 are intended to prevent accumulation of errors caused by the integration operation of the parameter identification circuit 9. First, the second embodiment shown in FIG. 2 is different from the embodiment shown in FIG. 1 in that a switch 11 is provided between the average generated torque calculation circuit 10 and the parameter identification circuit 9 and the area of the average speed n _AVE is determined. The identification operation by the parameter identification circuit 9 is stopped by providing the comparator 12 and turning off the switch 11 according to the output of the comparator 12. The comparator 12 turns off the switch 11 when the average speed is below a certain set value irrespective of the rotation direction of the motor 1, and does not input the average torque τ _MAVE to the parameter identification circuit 9 to perform parameter identification. The operation of the circuit 9 is stopped.

[0013] Figure 3, Figure 4, the rotational speed n, shows the relationship between the period T _A for the average velocity calculation which is determined by the torque current actual value I _IST and encoder pulses, Fig. 3 is speed n
When (average speed n _AVE ) is relatively low, FIG. In these figures, T _S is a sampling period of current and speed by the digital controller constituting the speed controller. First, as is apparent from FIG. 3, when the speed n is low, the interval between the encoder pulses is substantially equal to the sampling period T _S. In such a region, it is conceivable that no encoder pulse appears in the sampling period T _S , so the period T _A for calculating the average speed n _AVE based on the encoder pulse fluctuates and becomes longer. A large deviation also occurs from the sampling period T _S. On the other hand, the sampling of the actual current value I _IST is performed in synchronization with the sampling period T _S , and the current in that period can be linearly approximated, but the average current in the period T _A that fluctuates as described above is linearly approximated. Thus, the calculation required becomes considerably complicated, and this places a heavy burden on a calculation unit such as a microprocessor.

On the other hand, as shown in FIG. 4, when the encoder pulse is sufficiently input during the sampling period T _S at a medium or high speed, the period T _A can be made substantially the same as the period T _S. The start and cycle of T _A and the sampling timing can be regarded as substantially the same. In such a region, the calculation formula of the average torque τ _MAVE is as shown in the following formula 2, and the calculation is greatly simplified as compared with the above formula 1. In Equation 2, I _IST [i] indicates the i-th current sample value.

[0015]

(Equation 2)

Accordingly, as in this embodiment, the average speed n
_The comparator 12 turns off the switch 11 and stops the parameter identification circuit 9 at a low speed when the _AVE is equal to or less than a certain value. In other words, the switch 11 is turned on only when the average speed n _AVE is medium to high, and the parameter identification circuit 9 is identified. By performing the operation, the calculation in the average generated torque calculation circuit 10 is simplified, the calculation time is shortened, and the load on software can be reduced. Further, since the integration time in the parameter identification circuit 9 is shortened, the accumulated error is also reduced, and the identification accuracy can be improved.

FIG. 5 shows a third embodiment of the present invention. This embodiment differs from the embodiment of FIG. 2 in that a differentiation circuit 1 for differentiating a current command value I * output from the speed control circuit 5 is provided.
3 and a comparator 14 for judging the area of the output, and the switch 11 is turned off in accordance with the output of the comparator 14. Here, the parameter identification circuit 9 which differentiates and inputs the average torque τ _MAVE internally has a relatively large error in the average torque τ _MAVE in a region where the rate of change of the generated torque of the electric motor 1 is small. It is difficult to perform a simple identification operation. The present embodiment focuses on this point, and differentiates the region where the generated torque is small based on the torque current command value I * (equivalent to the torque command value).
3 and the comparator 14, the switch 1 is set in a region where the rate of change of the torque current command value I * is below a certain set value.
1 to turn off the average torque τ _MAVE to the parameter identification circuit 9
, The operation of the parameter identification circuit 9 is stopped.

According to the present embodiment, when the rate of change of the generated torque is equal to or less than a certain set value, and there is a possibility that an error caused by the integration operation of the parameter identification circuit 9 may increase, the operation of the parameter identification circuit 9 is performed. Is stopped, it is possible to prevent a decrease in identification accuracy. The switch 11 is also controlled by a comparator 12 for determining the area of the average speed n _AVE as in the embodiment of FIG. 2. However, the comparator 12 is omitted and the area of the change rate of the torque current command value I * is exclusively used. The switch 11 may be controlled only by the determination.

FIG. 6 shows a fourth embodiment of the present invention. In this embodiment, an area where the rate of change of the speed of the motor 1 is small is detected by the differentiator 13 and the comparator 14,
As in FIG. 5, the switch 11 is turned off to stop the identification operation of the parameter identification circuit 9. In this embodiment, the switch 11 is controlled by detecting the rate of change of the speed, which is one of the inputs of the parameter identification circuit 9. However, by using the speed command value n * as shown in FIG. The condition that the rate of change in speed is small can be detected before the speed changes, and the operation of the identification circuit 9 can be stopped early. When the change in the speed command value n * is large, the change in the torque current is also large. Therefore, by turning on the switch 11, the average torque τ _MAVE is _taken into the identification circuit 9, and an appropriate identification operation without error is performed. It is possible to make it. From this embodiment, it can be easily inferred that the rate of change of the second-order differential value of the position command value in the position control loop, which is a higher-order position of the speed control loop, is used for region determination. Further, as in the embodiment of FIG. 5, the comparator 12 can be omitted. Further, as shown in FIG. 5, a means for controlling the switch 11 by determining the area of the change rate of the current command value I * may be added to the configuration of FIG.

In each of the above embodiments, the actual line current value is input to the average generated torque calculation circuit 10 as the torque current, but the line current command value or the torque current command value in the control device is calculated by the average generated torque calculation circuit. Even if the average torque is input to the circuit 10 and calculated, it does not impair the present invention.
However, when these command values are used, it is necessary to consider the delay of the actual torque current.

Although not shown, the generated torque τ _M obtained by the method shown in FIG. 7 without providing the average generated torque calculation circuit 10 is input to the parameter identification circuit 9 via the switch 11. , FIGS. 2, 5 and 6
Even if the identification circuit 9 is stopped by the area determination of the average speed, the current command value, and the speed command value as shown in the respective embodiments, the error caused by the operation of the identification circuit 9 is reduced and the identification accuracy is improved. It is possible to achieve.

[0022]

As described above, according to the present invention, the average torque during the same period as the average speed of the motor is calculated, and the mechanical constants of the motor and the load are identified based on the calculated average torque. Therefore, high-accuracy identification can be performed by unifying sampling points of input variables in the parameter identification circuit. In addition, by operating the identification circuit only when the motor is at a medium or high speed as necessary,
The calculation time of the average generated torque can be greatly reduced. Further, when the rate of change of the torque command value or the rate of change of the speed command value is small, by stopping the identification operation,
Accurate identification can be performed with a relatively inexpensive system configuration without integrating the error more than necessary in the identification circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a current sampling period and an average speed calculation period at a low speed.

FIG. 4 is a diagram illustrating a relationship between a current sampling period and an average speed calculation period at the time of middle to high speed.

FIG. 5 is a block diagram showing a third embodiment of the present invention.

FIG. 6 is a block diagram showing a fourth embodiment of the present invention.

FIG. 7 is a block diagram showing a conventional technique.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 motor (and load) 2 encoder 3 average speed calculation circuit 4, 6 adder 5 speed control circuit 7 current control circuit 9 parameter identification circuit 10 average generated torque calculation circuit 11 switch 12, 14 comparator 13 differentiation circuit

Claims (4)

(57) [Claims] 1. A speed control device with a current minor loop for controlling a generated torque of an electric motor, wherein parameter identification for identifying mechanical constants of the motor and a load by excluding a disturbance torque of the motor based on the speed and the generated torque of the motor. A speed control device including a circuit, comprising: an average speed calculation circuit that calculates an average speed of the motor during a certain period; and an average generated torque calculation circuit that calculates an average generated torque of the motor during the same period as the certain period. A motor speed control device, wherein a mechanical constant is identified by the parameter identification circuit based on an average speed output from an average speed calculation circuit and an average torque output from the average generated torque calculation circuit. 2. The motor speed control device according to claim 1, further comprising means for stopping the operation of the parameter identification circuit when the average speed output from the average speed calculation circuit is within a certain value. 3. The motor speed control device according to claim 1, further comprising means for stopping the operation of the parameter identification circuit when the rate of change of the torque command value of the motor is within a certain value. 4. The motor speed control device according to claim 1, further comprising means for stopping the operation of the parameter identification circuit when the rate of change of the speed command value of the motor is within a certain value.