RU2342762C1 - Pulse frequency and phase control system of motor rotation speed - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention relates to electric engineering and may be used in fast-acting control systems with wide range of speed control, which require speed stabilisation at uniform rotation of the motor. Circuit switching device is implemented in pulse frequency and phase control system of motor rotation control. The circuit switching device allows for automatic measuring frequency capture moment and optimising control switching from automatic synchronisation circuit to phase self-tuning ensuring the technical result provided by the invention. Motor rotation range from super low speed (0.01 Hz) to high speed (10000 Hz) is also provided by the invention.

EFFECT: improvement of stability and running speed, reduction of correction requirements and wide range of motor rotation speed control.

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Description

The invention relates to electrical engineering and can find application in high-speed control systems with a wide range of speed control, in which speed stabilization is required with uniform rotation of the electric motor.

A device for controlling a non-contact direct current motor according to RU 2023343 C1, 1994.11.15, MKI Н02Р 6/02, comprising a bridge switch with transistors, a rotor position sensor, a rotational direction adjuster, a current limiting unit, a rotational speed control unit and a decoder, a decoder is made three inverters and six logic elements ZI - NOT or ZILI - NOT.

The disadvantages of this device are the limited frequency capture band and a narrow range of stabilized speeds.

Closest to the technical nature of the proposed one is a pulse-phase stabilization system for the speed of electric drives, described in the book "Control of Electric Drives", A. Basharin, V. A. Novikov, G. G. Sokolovsky, L .: Energoizdat, 1982, pp. .181-186, which includes a phase detector, a reference frequency generator, a code-frequency converter, a position controller, a frequency discriminator, a non-linear logic unit, a pulse speed sensor, rigidly connected to the shaft of the controlled motor.

This pulse-phase system for stabilizing the speed of the electric drive is selected as a prototype.

The objective of the present invention is to increase stability and speed, expand the range of regulation of the speed of rotation of the motor by automatically determining the moment of frequency capture and optimizing the moment of switching control from the automatic synchronization circuit to the phase loop.

To achieve this objective, a switching unit is introduced into the pulse-phase stabilization system of the electric drive speed, which contains serially connected master oscillator, frequency discriminator, pulse-phase discriminator, commutator, electric motor, the shaft of which is rigidly connected with a rotary transformer used as a rotational speed sensor of the electric motor loops, and the output of the master oscillator is connected to the first input of the frequency discriminator and the first input of the pulse-phase dis of the discriminator, the output of the frequency discriminator is connected to the first input of the circuit switching unit, and the output of the pulse-phase discriminator is connected to the second input of the circuit switching unit, the output of which is connected to the input of the switch, the output of which is connected to a motor rigidly connected to a rotating transformer, the output of which is connected to the second inputs of the pulse-phase and frequency discriminators.

The essence of the invention is illustrated by drawings, in which Fig. 1 shows a block diagram of a pulse frequency-phase system for controlling the rotation speed of an electric motor, Fig. 2 is a circuit diagram of a circuit switching unit, and Fig. 3 is a diagram of a voltage of a pulse-phase discriminator.

The pulse frequency-phase system for controlling the rotation speed of the electric motor contains a master oscillator 1, a pulse-phase discriminator 2, a frequency discriminator 3, a circuit switching unit 4, a switch 5, an electric motor 6, a rotating transformer 7, a quadrature voltage source 8.

To describe the system, we explain the operation of the frequency discriminator, the pulse-phase discriminator, and the circuit switching unit.

A sinusoidal voltage with a frequency F ₃ supplied from the master oscillator 1 is supplied to one input of the frequency discriminator 3. A feedback signal from the output of the rotating transformer 7 is supplied to the second input of the frequency discriminator 3 in the form of a sinusoidal voltage with a frequency of Foc. In the frequency comparison mode of the signals F ₃ and Foc, the characteristic of the frequency discriminator 3 is relay:

for F ₃ <Foc Uchd <0,

₃ when F> Foc Uchd> 0.

The operation of the pulse-phase discriminator is illustrated by the voltage plots presented in figure 3.

This system uses a low-inertia circuit of a pulse-phase discriminator, which has a low content of side harmonics and does not require bulky low-pass filters.

The pulse phase discriminator can have two states. In the case when the frequencies supplied to the inputs of the discriminator differ from each other by an amount greater than the capture band, the output signal of the pulse-phase discriminator is a step-shaped signal and a variable polarity Uifd, shown in Fig.3.

When the Foc frequency is captured, the discriminator output will have a constant voltage, the value of which is proportional to the phase difference of the input signals, and the sign depends on the sign of the phase difference.

Block switching circuits 4, presented in figure 2, operates as follows. When a step-shaped signal with a frequency of | F ₃ -Foc | arrives at the input of the circuit switching unit 4 from the output of the pulse-phase discriminator 2, a meander with the same frequency appears at the output of the comparator K, which arrives at the pulse shaper FI1. From the output of the pulse shaper FI1 short pulses with a duration of 4 μs and a frequency of | F ₃ -Fo | arrive at the zeroing input of the counter DD1 and at the input of FI2. From the output of FI2, the pulses shifted by an amount equal to the pulse duration of FI1 (4 μs) relative to the pulses from FI1 are fed to the input PE of the counter DD1. As a result, the counter is reset to zero by the pulse from FI1, and the pulses received at input C are enabled by the pulse from FI2. In the case when two logical units are not simultaneously present at the output of the DD1 counter in two high order bits, i.e. the counter does not have time to count up to 15 (1,1,1,1), at the output of the DD4-1 chip there is a logical unit arriving at one of the inputs of DD3-1. Another input DD3-1 receives pulses with a frequency of Fc. From the output DD3-1, pulses with a frequency of Fc are fed to the input C of the counter DD1. Subtracts the pulses Fc from the number N written on the parallel input DD1. In the high order of the counter DD1 there is a logical zero, which is fed to the control input A0 of the multiplexer DD2, prohibiting the passage of the signal Ufd from the output of the pulse-phase discriminator 2 and allowing the passage of the signal Uchd from the output of the pulse frequency-phase discriminator 3.

In the case of a decrease in the frequency difference | F ₃ -Foc |, i.e. increasing the period between pulses arriving at the inputs R and PE of the counter DD1, the time of one counting cycle increases, and at some point the counter counts up to 15 (1,1,1,1). In the two high-order bits of the counter DD1, two logical units will appear simultaneously, and a logical zero will appear at the output of DD4-1, which will prevent the passage of pulses of frequency Fc through DD3-1. The account will end. The number N and the frequency Fc are chosen so that at the time of termination of the count, i.e. by the time logical units appeared in the two high-order bits of DD1, a frequency capture occurred, and a constant voltage appeared at the output of the pulse-phase discriminator. The arrival of nulling pulses to the input R and recording pulses to the input PE of the counter DD1 will stop. The counter will be established in a steady state, and in its fourth category the logical unit will be constantly present. The logical unit in the fourth digit of the counter DD1, having entered the control input AO of the multiplexer DD2, will prohibit the passage of the signal Uchd and allow the passage of the signal Ufd.

The device operates as follows.

The pulse frequency-phase control system for the rotational speed of an electric motor consists of two control loops. This is an automatic synchronization circuit operating with a frequency discriminator 3, and a phase-locked loop operating with a pulse-phase discriminator 2. Switching from one control circuit to another is performed using the circuit switching unit 4.

Consider the case where the difference between the driving frequency and the feedback frequency | F ₃ -Foc | more capture band. In this case, an alternating step voltage is present at the output of the pulse-phase discriminator 2. In accordance with the logic of the circuit switching unit, the voltage Uchd will be output. The sign of this voltage depends on the sign of the frequency difference | F ₃ -Foc |. The voltage Uchd is supplied to the switch 5, which controls the engine 6. The system is in automatic synchronization mode. Acceleration or deceleration of the motor 6 and, consequently, an increase or decrease in the frequency Foc coming from the rotating transformer 7 occurs. As a result, the frequency Foc approaches the frequency F ₃ and the frequency difference | F ₃ -Foc | will begin to decrease. At some point, the circuit switching unit 4 prohibits the passage of the signal Uchd from the output of the frequency discriminator 3 and allows the passage of the signal Ufd coming from the output of the pulse-phase discriminator 2.

The system will switch to phase locked loop mode and the motor will rotate at the set speed.

This state will remain until the frequency difference | F ₃ -Foc | there will be no more capture band. As soon as a result of a change in the driving frequency F ₃ or the influence of disturbing factors on the motor shaft, the frequency difference | F ₃ -Foc | there will be more capture band, the process will repeat.

In the case when the reference frequency F ₃ is equal to the reference frequency Fo, the engine speed will be zero. This happens as follows. A rotary transformer 7 connected to the shaft of the electric motor 6 is supplied with a quadrature voltage generated by a quadrature voltage source 8 with a reference frequency Fo. Rotary transformer 7 operates in phase shifter mode. On its output winding there will be a frequency:

where Fo is the frequency of the quadrature voltage source;

ωвр - engine speed.

As can be seen from formula (1), when ωвр = 0, Foc = Fo, i.e. equal frequency frequencies F ₃ = Fo and Foc = Fo are applied to the input of the pulse-phase discriminator 2. In this case, at the output of the pulse-phase discriminator 2, there will be a voltage Uif = 0 supplied to the input of the circuit switching unit 4. Then, at the output of the circuit switching unit 4, the voltage Uif = 0 appears, which is supplied to the input of the switch 5 as the control voltage. Electric motor 6 will remain alone.

The frequency Fc and the number N are selected depending on the capture band and the dynamic properties of the system so that by the time of switching to the phase-locked loop, the system was in stable hold mode. The optimal choice of frequency Fc and number N allows you to adapt the control circuit to specific dynamic parameters of the system.

Switch 5 and a source of 8 quadrature voltages do not have fundamental features.

The stability and speed of the system is increased due to the optimal moment of switching control from the automatic synchronization circuit to the phase-locked loop, which occurs not at the moment when the frequency Foc is compared with the frequency F ₃ , as it happens in the prototype, but at the moment when the system is in mode sustainable retention. The range of motor control speeds is expanding due to the possibility of choosing the optimal system correction and the absence of inertial low-pass filters.

The introduction of the circuit switching unit into the system made it possible, by automatically determining the moment of frequency capture and optimizing the moment of switching the control from the automatic synchronization circuit to the phase-locked loop, to significantly increase the stability and speed of the system, reduce the requirements for correction of the system and expand the range of regulation of the motor rotation speed from ultra-low speeds (0.01 Hz) to high (10000 Hz).

Of the patent information materials known to the applicant, no signs were found that are similar to the totality of the features of the claimed object.

This device has been tested on a prototype. The test results indicate the achievement of the task. FSUE NPOPM proposes to use this technical solution on standard products.

Claims (1)

A pulse frequency-phase system for controlling the rotational speed of an electric motor, comprising a serially connected master oscillator, a frequency discriminator, a pulse-phase discriminator, a commutator, a motor whose shaft is rigidly connected to a rotary transformer used as a motor rotational speed sensor, characterized in that a circuit switching unit is introduced, and the output of the master oscillator is connected to the first input of the frequency discriminator and the first input of the pulse-phase discrete minator, the output of the frequency discriminator is connected to the first input of the circuit switching unit, and the output of the pulse-phase discriminator is connected to the second input of the circuit switching unit, the output of which is connected to the input of the switch, the output of which is connected to a motor rigidly connected to a rotating transformer, the output of which is connected to the second inputs of the pulse-phase and frequency discriminators.

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