CS216034B1 - Connection for regulation of the medium value of the motor speed - Google Patents

Description

The invention relates to a circuit for controlling the mean value of an engine speed to a defined mean value with a specified mean square deviation, wherein a numerically controlled control loop is used for this control. The invention further relates to circuits for this control.

The known devices used to control the mean value of the engine speed achieve a maximum control accuracy of the order of 0.1% of the rated speed. For industrial applications, this achieved control accuracy is sufficient, but for devices of fine mechanics and optics used for measuring purposes, due to high resolution requirements. Measurement requirements today are of the order of 0.01% and higher.

Engine parameters, motor speed sensors, load parameters and achievable signal processing accuracy play a major role in regulating the mean motor speed. The use of an analog engine speed measurement with a tachogenerator is suitable for a maximum accuracy of 0.3%. Incremental encoders, which are used extensively for position reading in numerically controlled machines, are used for greater accuracy in instantaneous motor speed measurement.

The accuracy of the controls is related to the load parameters, ie the moment of inertia of the load, the torque and the friction of the whole system. The engine speed changes as any of the system parameters changes. The most important is the choice of engine. Therefore, in order to achieve high accuracy in the regulation of the mean value of the motor speed, the correct motor type must be selected with a minimum time of electromechanical constant and sufficient power reserve.

On each control device according to the mentioned principles there is an evaluation part which:

216 034

216 034 transforms the measured quantity into a suitable electrical form and a control part, where by comparison with the setpoint a signal for regulating the motor speed is generated in a suitable sense.

Known motor speed control connections respond to the detected difference between the measured and desired velocity magnitude by increasing or decreasing the instantaneous motor velocity so that the resulting velocity difference approaches zero.

The shortcomings are eliminated by the average speed control circuit according to the invention, characterized in that the first input of the measurement block is connected to the j-measurement evaluation block and the second input of the measurement block is connected to the reference time interval source. The output of the measurement block is connected to the first input of the comparator, the second input of which is connected to the maximum deviation block. The comparator output is connected to the first input of the measurement block via series-connected blocks of the DAC, power module, motor, and j-th time evaluation blocks.

The exact frequency normal is used to digitally measure the instantaneous motor speed, the measured deviations from the reference speed sample are summed to give a total deviation from the set mean motor speed that defines the resulting control signal when compared to the entered mean square deviation value. After processing in the digital-to-analog converter, this signal determines the correction signal for the power Sien motor speed control loop. This ensures that the average speed of the motor is controlled with an accuracy of better than 0.01% over the measurement period.

The advantage of this circuit for the control of the mean value of the motor speed is that when extending the distance traveled, respectively. For the duration of the engine speed control, the accuracy of the engine speed control is constantly increasing.

The attached drawing shows a block diagram for controlling the mean value of an engine speed according to the invention.

The first input of measurement block 2 is connected to the j-th measurement evaluation block 2 ^{and the} second input of this measurement block 1 is connected to a reference source of time interval 9. The output of measurement block 2 is connected via summer 2 to the first input of comparator J whose second input is connected to maximum deviation block 2 · Comparator output J Ú® via series-connected blocks of digital-to-electronic converter 4, power element 6, motor 8 and j-th measurement time evaluation block 2 connected to the first input of measurement block 2 ·

The measurement block 2 determines the magnitude of the time deviation t ^ of the j-th measurement time ij and the reference measurement time t ^ specified by the reference time interval source 2 · the measured deviations / ^ t are added together ⁱⁿ the summator block 2. they are compared with the set value of the Maximum deviation block 2, thus a comparison is made and the resulting numerical series is controlled by a power-converter 6 of the speed control loop 8 through a digital-to-analog converter 4 which is connected to the j-measurement time evaluation block.

The following mathematical formulas apply to the connection according to the invention: ie - reference measurement time (setpoint speed)

Zs, t. - deviation of the j-th measurement from the reference time in

t _N j - time of j-th measurement

216,034 (1)

T _c - total control time

T - mean time of one measurement n - number of measurements <T - maximum error after n measurements

The deviation of the j-th measurement from the reference time is as follows:

For the total regulation time:

germany. T =

J '/

The mean time of one measurement can be expressed as follows:

* Nj (2) .'i (t '+ _T) <? JX (3) where the term P ^ j ^ředstavu A® standard deviation from the desired average.

Because the digital part of the control loop secures

At.Z 10 (3)

It follows that the mean time of one measurement with maximum error is given by:

T * t '+ i

10 '(5) ^U N n

For example:

To achieve the required accuracy of 0 = 10 ^{-U the} nominal motor speed will require at least n S * 100 measurements, resulting from (5).

10 ⁶ .in j ♦ 10 ⁴ . t '10 ⁶ . t _N

This wiring for controlling the average engine speed can be successfully used, for example, in an elliptometer and in all devices where the required engine speed control is better than 10 ” ² %.

The above-described means for controlling the mean value of the engine speed enables to achieve a high accuracy of controlling the mean value of the engine speed. This method is suitable where the highest demands are placed on the accuracy of motor speed control, such as an ellipsometer.

Claims (1)

Circuit for controlling the mean value of the motor speed, characterized in that the first input of the measurement block (1) is connected to the j-th measurement evaluation block (7), the second input of this measurement block (1) is connected to the reference time interval source (9) ), the output of the measurement block (1) being connected via a sump (2) to the first input of the coraperator (3), the second input of which is connected to the β block of maximum deviation (5), a transducer (4), a power member (6), a motor (8), and a block for - evaluation of the time of the j-th measurement (7) connected with β by the first input of the measurement block (1) _v