JP2009284644A - Apparatus for preventing malfunction in determining clockwise/counterclockwise rotation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that when a detection signal from an encoder is input to a clockwise/counterclockwise rotation determining unit and clockwise/counterclockwise rotation of a rotor is carried out based on a determination signal from the clockwise/counterclockwise rotation determining unit, an abrupt polarity change may be caused by a missing encoder output pulse or by noise to negatively affect a controlled object. <P>SOLUTION: A malfunction preventing unit having a speed limiting interlock and a signal holding circuit is connected to the output end of a clockwise/counterclockwise rotation determining unit. A switching unit and a comparing unit that switch clockwise/counterclockwise rotation indicated by a speed detecting signal for control is connected the output end of a speed detecting unit. The comparing unit has a preset unit and a comparator, makes a determination based on a signal indicative of a difference between a preset value from the preset unit and the speed detecting signal, outputs a signal to the speed limiting interlock when the speed of the rotor drops to a given value or lower, and outputs a switching signal to the switching unit via the signal holding circuit. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a malfunction preventing apparatus for forward / reverse rotation determination in a rotating body such as a dynamometer or an electric motor.

When forward / reverse control is performed using a rotating machine such as a dynamometer or an electric motor, generally a detector such as an encoder is attached to the rotating part, and the forward / reverse direction is determined using the speed detection signal. Yes. In other words, judgment is performed using a pulse signal with a phase difference output from the encoder, and the result is output as a forward or reverse bit signal, speed detection polarity switching, speed control at zero speed and continuous forward / reverse rotation Speed control is performed. As described above, Patent Document 1 is well known as a forward / reverse operation of a motor using an encoder. This Patent Document 1 describes that a driving circuit is turned off by detecting the timing of reverse rotation in a rotational direction by a program without requiring a conventional logic circuit.
7-60606

  When the speed pulse detected by the encoder is lost for some reason and the number of pulses increases due to the influence of noise, the phase relationship between the A-phase and B-phase pulses having a phase difference changes. As a result, there is a case where reverse rotation is detected even when forward rotation is being performed, and a reverse rotation detection signal is output although reverse rotation is being performed. When such a phenomenon occurs, for example, when the speed detection is +10 rpm, the speed is instantaneously −10 rpm, and the difference is 20 rpm. Even if there is a change of about 20 rpm instantaneously in a relatively low speed range, in this case, a control disturbance occurs, and although it is related to the control gain, there is no large current change, and the actual speed is a little. Fits in change.

  However, when the polarity detection phenomenon occurs at a high speed, for example, +4000 rpm, and the speed detection becomes −4000 rpm, the difference becomes 8000 rpm, and if the speed detection changes instantaneously, the speed is greatly controlled. It becomes a disturbance and causes a large current change in relation to the control gain, and the actual speed also suddenly generates a large speed change. When such a sudden change phenomenon occurs in a production facility, the product is destroyed and the quality is deteriorated, and in the test machine, there is a possibility that a great damage such as destruction of a specimen occurs. Note that Patent Document 1 does not describe such prevention of malfunction.

  Accordingly, it is an object of the present invention to provide a malfunction prevention apparatus for forward / reverse rotation determination of an apparatus for controlling forward / reverse rotation of a rotating body.

According to the first aspect of the present invention, the speed of the rotating body is detected by the encoder, the forward / reverse determination unit determines the forward / reverse rotation, and the motor is operated by using the determination signal and the speed detection signal from the speed detection unit. In what to do,
A switching unit configured to connect a malfunction prevention unit having a speed limit interlock and a signal holding circuit to an output side of the forward / reverse rotation determination unit, and to perform forward / reverse switching of a speed detection signal for control on an output side of the speed detection unit; In addition to connecting the comparison unit, the comparison unit has a preset unit and a comparator, and the determination is made based on a difference signal between the setting value of the preset unit and the speed detection signal, and the speed of the rotating body becomes a predetermined value or less. Sometimes, a signal is output to the speed limit interlock, and a switching signal is output to the switching unit via a signal holding circuit.

  A second aspect of the present invention is characterized in that a preset value of the preset unit is approximately ± 1% of the maximum control speed of the rotating body.

  As described above, according to the present invention, when the determination output by the forward / reverse determination unit changes at a certain speed or more set by the preset unit, the change signal is determined to be a malfunction and the change signal is ignored. On the other hand, since it is possible to switch between forward and reverse rotation when the value is less than the preset value, the speed fluctuation level is small below the preset value even if the forward / reverse determination unit malfunctions. There is little influence on the control body. Further, since the output value does not change above the preset value, the speed detection polarity does not change, and therefore there is no influence on the controlled object.

  FIG. 1 is a block diagram showing an embodiment of the present invention. Reference numeral 1 denotes an encoder, and reference numeral 2 denotes a forward / reverse determination unit. The speed detection signal of the encoder 1 is input to determine forward rotation or reverse rotation. For example, a commercially available product is used in which an A-phase pulse and a B-phase pulse are input, and whether forward rotation or reverse rotation is determined depending on whether the leading edge or the trailing edge of both pulses is forward or backward. Reference numeral 3 denotes a speed detection unit which performs frequency-voltage conversion on the A-phase or B-phase signal from the encoder 1 and outputs the speed detection signal as a control speed detection signal and also outputs it to the comparison unit 4. . The comparison unit 4 includes a preset unit 41, a comparator 42, and a subtraction unit 43. The set value in the preset unit 41 is set to about ± 1% of the maximum control speed of the controlled body, and the set value is subtracted from the detected speed signal in the subtractor 43.

  Reference numeral 5 denotes a malfunction prevention unit, which includes a speed limit interlock unit 51 composed of AND1 and AND2 and a signal holding circuit 52 composed of an RS flip-flop. A forward rotation determination signal from the forward / reverse rotation determination unit 2 is input to one input terminal of AND1, and a reverse rotation determination signal from the forward / reverse rotation determination unit 2 is input to one input terminal of AND2. Further, the output signal of the comparison unit 4 is input to the other input terminals of AND1 and AND2, respectively. A forward / reverse switching unit 6 outputs a normal rotation signal in the state shown in the figure during normal rotation, and switches to the output side of the polarity inversion unit 7 during reverse rotation.

The malfunction prevention device of the present invention configured as described above is based on the fact that a rotating body such as a motor has a limited speed change rate.
That is, when the forward / reverse motor is operated in forward / reverse direction, the speed is reduced by the forward / reverse determination function, the motor deceleration torque, and the external finite braking torque, and the motor rotating at a certain speed is instantaneously zero. There is a physical characteristic that it does not become speed or reverse. In other words, when shifting from forward rotation to reverse rotation, or vice versa, it temporarily stops and then rotates in reverse or forward rotation, and a certain time is required. The present invention has been made paying attention to this point.

  Since the electric motor rotating at a certain speed or more does not reverse (or forward) the sequence circuit or detection circuit within the operable time, the value corresponding to this speed is ± 1% FS in the present invention. Set in the preset section 41. When the forward / reverse rotation determination signal changes at a preset speed or higher, it is determined as a malfunction, and the forward / reverse determination signal is ignored. Specifically, the subtraction unit 43 performs a difference calculation between the speed detection signal converted by the speed detection unit 3 and the signal set by the preset unit 41, and the comparator 42 makes a comparison determination. When the speed detection value> the preset value, the comparator 42 is in an inoperative state and there is no output from the speed limit interlock 51. In this state, even if the forward / reverse rotation determination unit 2 inputs, for example, it is determined that the rotation is reverse due to a missing A-phase pulse, the speed limit interlock 51 does not satisfy the operation condition, and the forward rotation determination signal is output via the signal holding circuit 52. The speed detection signal is output to the control circuit (not shown) through the switching unit 6.

  Next, when a reverse rotation command is issued to the motor in the normal rotation state by a control command from the control circuit, the motor is gradually decelerated. Along with the deceleration, the speed detection signal also decreases. When the speed detection value ≦ preset value, the comparator 42 operates to close the contact 42a and output a signal to one input terminal of the speed limit interlock 51. Thereby, the operating condition of AND1 is established, and the signal holding circuit 52 is maintained in the set state while the determination of the forward / reverse rotation determination unit 2 is forward rotation, and continues to output the forward rotation determination signal. If the forward / reverse rotation determination unit 2 determines reverse rotation due to noise or the like when the operating condition of the speed limit interlock 51 is established, AND2 is turned on, AND1 is turned off, the signal holding circuit 52 is reset, and the reverse rotation signal is switched. 6 is switched to the output side of the polarity inversion unit 7. Therefore, in this case, a reverse rotation command is output even though forward rotation is in progress, but since the rotation speed is ± 1% FS or less, the control disturbance is suppressed and the current does not change greatly. The actual speed change is small.

The block diagram which shows embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Encoder 2 ... Forward / reverse determination part 3 ... Speed detection part 4 ... Comparison part 5 ... Malfunction prevention part 6 ... Switching part 7 ... Polarity inversion part

Claims (2)

In what detects the speed of the rotating body with an encoder, determines forward / reverse in the forward / reverse determination unit, and performs forward / reverse operation of the electric motor using this determination signal and the speed detection signal from the speed detection unit,
A switching unit configured to connect a malfunction prevention unit having a speed limit interlock and a signal holding circuit to an output side of the forward / reverse rotation determination unit, and to perform forward / reverse switching of a speed detection signal for control on an output side of the speed detection unit; In addition to connecting the comparison unit, the comparison unit has a preset unit and a comparator, and the determination is made based on a difference signal between the setting value of the preset unit and the speed detection signal, and the speed of the rotating body becomes a predetermined value or less. A malfunction prevention device for forward / reverse rotation determination, characterized in that a signal is output to the speed limit interlock and a switching signal is output to the switching unit via a signal holding circuit. 2. The malfunction prevention device for forward / reverse rotation determination according to claim 1, wherein the preset value of the preset unit is approximately ± 1% of the maximum control speed of the rotating body.

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