JPH1169857A - Digital control of drive circuit for switched reluctance motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a speed control characteristic by introducing a digital circuit for SR(switched reluctance) motor operation control. SOLUTION: For the detection of a drive current, a digital current detecting circuit 15 is provided and an up- and down-counter 23 is also provided for calculating a speed command signal pulse and a speed detecting signal pulse as the up-signal and down-signal. An output signal from the digital current detecting circuit 15 and an output signal from the up-and down-counter 23 are input to a digital value comparison circuit 21 for the purpose of comparing and are then input to a one-shot 25, four gate signals from a position signal 31 for coil on and an output signal from the one shot 25 are calculated in a logic circuit consisting of OR circuits 28, 29 and AND circuits 26, 27 and a switch element 1 or 2 is on/off controlled by the gate signal from the AND circuit 26 or 27. As a result, a switch element 3 or 5 in the current output side and a switch element 1 in the current input side are on/off controlled with the same timing, and moreover switch element 4 or 6 and the switch element 2 are also on/off controlled with the same timing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital control method for a drive circuit for a switched reluctance motor (hereinafter referred to as an SR motor).

[0002]

2. Description of the Related Art An SR motor is a motor that sequentially excites respective stator poles, sequentially attracts a rotor pole by leakage magnetic flux, and rotates a rotor by the attraction torque. An excitation current to the stator pole is supplied to a drive circuit. It is supplied sequentially by controlling ON / OFF of the constituent switch elements.

FIG. 2 is a block diagram showing a configuration of an operation control circuit of a conventional SR motor. SR motor 1
07 is provided with four stator coils, and on the current inflow side of the stator coils, a drive circuit in which a switch element 101 and a commutation diode 108 are connected in series;
02 and a commutation diode 109 are connected in series to both ends of a DC power supply 114 in parallel. The commutation diode 110 and the switch element 103, the commutation diode 111 and the switch element 104, the commutation diode 112 and the switch element
5. Four driving circuits each including a commutation diode 113 and a switch element 106 are connected in parallel to both ends of a DC power supply 114. The drain terminals of the switch elements in the two drive circuits provided on the current inflow side of the stator coil are respectively connected in parallel to the current inflow sides of the two stator coils and provided on the current outflow side of the stator coil. 4
The source terminals of the switch elements in the two drive circuits are connected to the current outflow side of one stator coil, respectively.
A current detection resistor 115 is inserted between the anode terminal of the commutation diode 109 in the drive circuit on the current inflow side of the stator coil and the drain terminal of the switch element 103 in the drive circuit on the current outflow side.

A coil ON position signal 131 input through a rotation position detecting Hall sensor (not shown) or a decode logic circuit (not shown) provided on the rotor shaft of the SR motor 107 is provided by four switch elements. 103 ~
The on / off control 106 is sequentially performed in accordance with the timing of exciting the stator coil.

The drive current of the SR motor 107 is detected by a current detection resistor 115, input to a comparator 121, and compared with a control current command value input via a current limiter 122. An output signal from the comparator 121 is input to a PWM circuit 125 to generate a PWM signal. The PWM signal and the coil ON position signal 13
Are the OR gates 1 to 4
28 and 129 and AND circuits 126 and 127 perform logical operations. An output signal from the AND circuit 126 or 127 becomes a gate signal of the switch element 101 or 102 in the drive circuit on the current inflow side of the stator coil, and controls on / off of the switch elements 103 to 106 in the drive circuit on the current outflow side. On / off control is performed in accordance with the timing of the gate signal 〜, and a PWM chopper for driving current control is performed.

[0006] In the powering mode, the rotation speed of the SR motor 107 increases with an increase in the output torque, and decreases with a decrease in the output torque. Further, since the output torque of the SR motor 107 is almost proportional to the drive current, if the drive current is controlled to be controlled, the output torque and the number of revolutions can also be controlled. Therefore, the control current command value is generated by D / A converting the speed detection signal 130 detected via the coil ON position signal 131, inputting it to the comparator 123, and comparing it with the speed command 124. The current detection value detected from the current detection resistor 115 and the control current command value input to the comparator 121 via the current limiter 122 are compared in the comparator 121,
A PWM signal for controlling a drive current is generated via a PWM circuit 125.

[0007]

Since the SR motor is basically a torque current control motor like a DC motor, unlike a frequency control motor such as an induction motor, the rotation speed accuracy is not good. Also, at the time of no-load low-speed rotation, the control of the weak current is performed, so that the S / N ratio is poor and high-precision operation control characteristics cannot be expected. Therefore, in order to increase the speed accuracy to the same level as the induction motor, the entire control circuit must be digitized.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art SR motor, and is intended to improve the operation control characteristics by completely digitizing the control circuit. It is intended to be.

Although the PWM generation circuit is digitized in the prior art as well, since the current detection signal and the current command signal are analog signals, the entire circuit is constituted by an analog circuit. Although the speed detection signal from the rotational position sensor is originally a digital signal, it is converted into an analog signal by D / A conversion and compared with an analog speed command value. Therefore, the current detection signal is digitized by a commercially available current digital detection element,
Further, when the speed detection signal and the speed command value are also pulsed and processed by an up / down counter, a current command digital signal is obtained. Therefore, if a digital numerical comparison circuit for comparing the above-described current detection digital signal with the current command digital signal is provided, the entire control circuit is digitized.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a block diagram showing the configuration of an operation control circuit for an SR motor according to the present invention. Only the digitized circuit portion is different from the circuit according to the prior art shown in FIG. Therefore, in the following description, the emphasis is placed on the digitized circuit portion, and the drive circuit portion is completely the same, so that the description will be omitted.

The four gate signals output from the coil ON position signal 31 sequentially turn on and off the respective switch elements 3 to 6 in the four drive circuits provided on the current outflow side of the stator coil at a predetermined timing. Control off. Further, the speed detection signal 30 detected from the position signal 31 is pulsed to be a down signal, and the pulse signal of the speed command signal 24 and the up signal are input to the up / down counter 23 to perform the calculation.

A digital current detection circuit 15 using a commercially available current digital detection element is inserted between the anode terminal of the commutation diode 9 and the drain terminal of the switch element 3 to convert a digitized current detection signal. Output. The digital output signal from the up / down counter 23 becomes a current command digital signal via the current limiter 22 and is compared with the current detection digital signal from the digital current detection circuit 15 in the digital numerical value comparison circuit 21.

When the current command digital signal is larger than the current detection digital signal, the digital numerical comparison circuit 21 is turned on (H), and the pulse width is adjusted by the one-shot 25 before being input to the AND circuit 26 or 27 and The switch element 1 or 2 of the drive circuit provided on the inflow side is turned on. Conversely, when the current detection digital signal is larger than the current command digital signal, the digital numerical value comparison circuit 21 becomes L (off), and holds the off state for a predetermined period in the one-shot 25. Therefore, the switch element 1 or 2 of the drive circuit is also turned off for a predetermined time.

The AND circuit 26 is turned on when the gate signal of the coil ON position signal 31 or the ON signal from the one-shot 25 is input, and sends the gate signal to the switch element 1. Similarly, the AND circuit 27 turns on when the gate signal or the ON signal from the one-shot 25 is input, and sends the gate signal to the switch element 2. That is,
The switch element 3 or 5 on the current outflow side and the switch element 1 on the current inflow side are turned on / off at the same timing, and the switch element 4 or 6 and the switch element 2
Are turned on / off at the same timing. As is apparent from the above description, since the control signals are all digitized, high-precision speed control can be performed without being affected by the operation state of the SR motor.

[0015]

According to the present invention, since the current detection signal is converted into a digital signal using a current digital detection element, and the speed detection signal and the speed command signal are also digitized, speed control comparable to a general-purpose inverter can be realized at low cost. it can. Further, since the speed of the SR motor can be increased, the size of the motor is smaller than that of a general-purpose inverter, and the merit of replacement is increased.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an operation control circuit of an SR motor according to the present invention.

FIG. 2 is a block diagram showing a configuration of an operation control circuit according to a conventional technique.

[Explanation of symbols]

 1-6 Switch element 8-13 Commutation diode 7 SR motor 14 DC power supply 15 Digital current detection circuit 21 Digital numerical comparison circuit 22 Current limiter 23 Up / down counter 25 One shot 26,27 AND circuit 28,29 OR circuit

Claims (2)

[Claims] 1. Both ends of a plurality of drive circuits each comprising a series circuit of a switch element and a commutation diode provided in parallel with a current inflow side and a current outflow side of a stator coil, respectively, are connected in parallel to both ends of a DC power supply. A switching circuit for driving a switched reluctance motor by connecting the switching circuit is provided. The switching element of the driving circuit provided on the current outflow side is turned on / off by the timing of exciting the stator coil, and the driving circuit provided on the current inflow side is provided. In a driving control method for a switched reluctance motor, in which a switch element of a circuit is subjected to PWM control at the same timing as the above timing to control a motor drive current, an up signal in which a speed command signal is pulsed and a speed from a rotation position sensor A down signal obtained by pulsing the detection signal is input to an up / down counter, and the A digital output signal from the up / down counter is converted into a current command digital signal via a current limiter, and a current detection digital signal obtained by digitizing a detection signal from a current detection sensor is compared with the current command digital signal in a digital numerical comparison circuit. When the current command digital signal is larger than the current detection digital signal, the gate of the switch element of the drive circuit provided on the current inflow side to be controlled is turned on. Conversely, when the current detection digital signal is larger, A digital control method for a drive circuit for a switched reluctance motor, characterized in that a gate of a switch element to be controlled is controlled to be turned off for a predetermined period. 2. An anode side of a commutation diode (9) in a drive circuit provided on a current inflow side of a stator coil,
A digital detection signal from a current detection sensor provided between the drive circuit provided on the current outflow side and the drain side of the switch element (3), a digital detection signal from a rotation position sensor provided on the rotation shaft of the rotor, 2. The digital control method for a drive circuit for a switched reluctance motor according to claim 1, wherein the operation control of the switched reluctance motor is digitized.