JPS6295984A - Speed controller for motor - Google Patents

Abstract

PURPOSE:To improve speed-control characteristics at low speed by using the inverse number of a pulse period detected by a rotational-speed detecting means as a speed signal. CONSTITUTION:A pulse encoder 2 generates pulses in number proportional to the angular velocity of rotation. A period detecting means 5 counts the number of clock pulses CL generated at one pulse interval of the pulse encoder 2, and D/A converts the number of CL and generates a voltage signal E representing the inverse number (a period) of the rotational speed of the pulse encoder 2. A period inverse detecting means 6 changes a period detected by the period detecting means 5 into an inverse number, and outputs it as a speed signal B. A speed control circuit 4 amplifies a deviation signal C between a speed command signal A and the speed signal B, and outputs a motor control signal D.

Description

[Detailed description of the invention] [Fields of application of I-I] The present invention relates to improvements in speed control devices for electric motors.

In particular, the present invention relates to an improvement in the speed control characteristics at low speeds of a speed control device for an electric motor using a rotational speed detection means such as a pulse encoder that emits a number of pulses proportional to the rotational angular speed.

[Conventional technology]

In the prior art, a speed control device for an electric motor is known, the block diagram of which is shown in FIG.
1 is an electric motor, and 2 is a pulse encoder, which generates a number of pulses proportional to the rotational angular velocity. Reference numeral 3 denotes a D/A converter that converts the pulse train frequency CtrL generated by the pulse encoder 2 (the number of pulses generated during the open time, that is, the same wave number of the pulse train) into a voltage signal, and outputs a speed signal B. 4 is a speed control circuit which receives the speed command signal '7A and the speed signal B and calculates the deviation value C (11,
This is amplified and a motor control signal is output.

[Problem that the invention seeks to solve]

The number of pulses generated by the rotational speed detection means, which generates a number of pulses proportional to the rotational angular velocity, becomes extremely low when the speed of the motor is low, and the number of pulses generated by the rotational speed detection means is extremely low when the speed of the motor is low. The signal J contains pulsations and cannot be controlled in good speed.

An object of the present invention is to eliminate this drawback, and is an improvement that improves the speed control characteristics at low speeds of a speed control device for an electric motor using a rotation speed detection means that emits a number of pulses proportional to the rotation angular speed. Our goal is to provide the following.

[Means for solving problems]

[The F stage adopted by the present invention in order to achieve the first goal of the two legs is: (a) As a speed signal, the pulse frequency of the rotational speed detection means 2 which emits a number of pulses proportional to the rotational angular velocity is 5 rotations. The period of the pulse train of the rotational speed detection stage 1 and 2, which emits a number of pulses proportional to the angular velocity (for example, the number of clock pulses generated in the interval between the 1 signal and the J pulse) is used as the original signal.

(b) A period detection means 5 for detecting the period of the signal pulse train detected by the rotation speed detection stage 1 2 (for example, the number of clock pulses generated in l signal pulse intervals), and the reciprocal of the period detected by the period detection means 5. Period reciprocal detection means 6 that outputs
and (c) use the J, 14 period reciprocal (frequency) outputted by the period reciprocal detection means 6 as a speed signal.

[Effect]

The disadvantage of item 1-- (at low speeds the speed 1 one-sided reliability pulsates and speed control becomes difficult) is that the number of pulse encoder pulses input to the clock pulse interval becomes extremely small at low speeds. Conversely, if the pulse train period of the pulse encoder (for example, the number of clock pulses occurring at 14A'j pulse intervals) is used as the source signal, this source signal will be a signal with an extremely large number of pulses at low speed, and this will be used as the D/A signal. The voltage signal obtained by conversion does not include pulsations.

Therefore, we decided to use this signal that does not include pulsation as the original speed signal, find a signal (frequency signal) having a value corresponding to the reciprocal of this signal, and use this frequency signal as the original speed signal. It is used as a speed signal.

〔Example〕

Hereinafter, the speed control device for an electric motor according to the present invention will be further explained with reference to the drawings.

In the diagram of FIG. 1, ``■'' is an electric motor, and 2 is a pulse encoder, which generates a number of pulses proportional to the rotational angular velocity.

5 is a period detection means according to the gist of the present invention.

The pulse train and clock pulses CL output by the pulse encoder 2 are input, the pulse encoder 2 counts the number of clock pulses CL generated at one pulse interval, converts it from D/A, and outputs the clock pulse CL to the pulse encoder 2. A -L pressure signal E representing the inverse a (period) of the rotational speed is generated.

6 is a period reciprocal number detection means according to the gist of the present invention, which converts the period detected by the period detection means 5 into a reciprocal number and outputs the same.

An example of this period reciprocal detection means 6 will be explained with reference to FIG.

In the diagram of FIG. 2, 61 is a multiplier, which combines the voltage signal E representing the period and the speed signal -'jB output from the seven period reciprocal detection stages 6.
The deviation G between the output signal F of the 0 multiplier 61 and the reference voltage R is amplified by the amplifier 62 and used as the speed signal B. This speed signal B is also fed back to the multiplier 61.

The operation of this period reciprocal detection means 6 will be further explained. At the output end of this circuit, B=K (R-EXB) However, is the amplification factor of the amplifier 82 and is generally a large value.

holds true. If this equation is transformed, B(upper+E)=R, and if K is omitted since it is generally small, B=dan, and B represents the reciprocal of the period E, that is, the frequency.

:iS1 See FIG. 11 The deviation C between the speed signal B and the speed command signal A is input to the speed 11J control circuit 4, where it is amplified and used as a motor control signal to control the motor I.

〔Effect of the invention〕

As explained below, the motor speed control according to the present invention amplifies the deviation between the speed signal detected by the seven rotational speed detection stages that emit a number of pulses proportional to the rotational angular velocity and the speed command signal and uses it as a motor control signal. The device includes a period detection means for detecting the pulse interval (period 1) detected by the rotational speed detection means, and a period reciprocal detection stage for outputting the reciprocal (frequency) of the period detected by the first period detection stage. The period reciprocal number (frequency) output from this period reciprocal detection stage F is at a speed of 4.
Since it is considered to be No. 11, it is the primitive signal (period) of the speed signal.
is a smooth signal without pulsation even at low speeds,
Excellent speed control can be achieved regardless of the speed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a speed control device for an engine according to an embodiment of the present invention. FIG. 2 is a block diagram of period reciprocal detection means according to the gist of the present invention. FIG. 3 is a block diagram of a speed control device for an electric motor according to the prior art. 106. Electric motor, 200. Pulse encoder (rotational speed detection stage F that emits a number of pulses proportional to the rotational angular speed)
, 3...D/A converter, 4◆...speed control circuit,
5... Period detection means, 6... Period reciprocal detection means, 61... Multiplier, 6211・φ amplifier, A
...Speed command signal, B...Speed signal, C...
・Deviation signal, D...'111 control signal, E・
・ ・Representative signal t), F... Multiplier output signal, G... Deviation between multiplier output and reference, CL...
...Cronk signal, R...Reference voltage.

Claims (1)

[Claims] A speed signal (B) and a speed command signal (
A speed control device for an electric motor that amplifies the deviation (C) from the rotational speed detecting means (2) to generate a motor control signal (D). period detection means (5) for detecting the period detection means (5);
) is provided, and the period reciprocal number detection means (6) outputs the reciprocal number (frequency) of the period detected by the period reciprocal number detection means (6), and the period reciprocal number (frequency) outputted by the period reciprocal number detection means (6) is used as the speed signal (B). A speed control device for an electric motor, characterized by: