JPS60250261A - Speed signal detector - Google Patents

Abstract

PURPOSE:To enable the outputting of a low ripple speed signal with a better response by converting a constant pulse width signal obtained from two-phase square wave outputs of an encoder into a pulse signal varied in the polarity in the direction of rotation to integrate the output thereof sequentially with first and second integration circuits. CONSTITUTION:Two-phase square waves (a) and (b) varying by 90 deg. in the phase of an encoder connected to a rotor are converted into constant pulse width signals (c) and (d) according to the direction of rotation with a pulse generation circuit 1 and the signals (c) and (d) are inputted into an OR circuit 2 and a direction of rotation deciding circuit 3 while both are inputted into a polarity conversion circuit 6 through power source conversion circuits 4 and 5 to obtain a pulse signal (i) different in the polarity in the direction of rotation. Then, the signal (i) is converted into a speed signal (j) with a first integration circuit 7 to be inputted into the second integration circuit 8, which inputs the signal (i) into a non-inversion terminal of an operational amplifier IC1 through a resistance R1, a capacitor C1 earthed and a resistance R2 and resistances R3 and R4 are connected between an inversion terminal and the earth and outputs to smooth the signal (i).

Description

DETAILED DESCRIPTION OF THE INVENTION 21\-, Industrial Application Field The present invention relates to a speed signal detection device used as a speed sensor for a power source that requires speed control, such as a machine tool or a robot.

Conventional Structures and Problems Generally, in a servo system that controls a mechanical system such as an industrial robot, a speed signal is required in order to stabilize the operation of the servo system and improve responsiveness. Therefore, conventionally, a DC tacho generator was installed as a speed signal detection device to detect the speed signal. However, since the DC tachogenerator has a rectifying brush, maintenance and inspection are required and the handling is complicated. Therefore, there is a speed signal detection device that detects a speed signal from the output signal of an encoder for position detection used in the servo system, which is shown in FIG. FIG. 3 shows the output waveform of the speed signal detection device shown in FIG. 1. A and b in FIG. 1 are two-phase rectangular waves having 900 different phases from the encoder coupled to the rotating body. Based on the pulse generation circuit 1 that receives two-phase rectangular waves a and b as input, first, the built-in one-shot multi-circuit generates a
The edges of inputs a and b are detected and converted into a constant pulse l] signal. Next, detect the rotation direction from the phases of inputs a and b,
Output pulses are output to C for unidirectional rotation and to d for reverse rotation. Here, the pulse width T of the output pulse. is the cycle T1 of the encoder outputs a and b at the maximum speed of the rotating body
against.

Satisfy To<T1/4. Next, an OR circuit 2 having inputs c and d converts them into a pulse signal e with a constant pulse width proportional to the rotation speed regardless of the rotation direction. Still c, d
In the rotation direction discrimination circuit 3 which receives as input, the output f is set to high level when an output pulse is output to C, and the output f is set to 0■ when an output pulse is output to d. Next, in the power supply conversion circuits 4 and 5, the high level of the inputs e and f is converted to the positive power supply voltage level, and the low level of the inputs f is converted to the level of the negative power supply voltage, and these are designated as g and h, respectively. In the polarity conversion circuit 6 configured with a three-stay IC, etc., which inputs q and h, q
By using the signal as a gate input and h as an input, it is converted into a pulse signal i whose polarity differs depending on the direction of rotation. Next, an integrating circuit 7 to which i is input detects a speed signal 1 whose average value is proportional to the rotational speed of the rotating body. Note that the power terminals of the polarity conversion circuit 6 and the integrating circuit element are connected to a positive power source and a negative power source.

In this case, the lower the minimum speed of the rotating body, the lower the period T and pulse width T of the output pulse of i. In order to reduce the ripple of the speed signal j, it is necessary to increase the discharge time constant of the integrating circuit 7, which has the drawback of impairing responsiveness. However, if the discharge time constant is made small in order to ensure responsiveness, the ripple in the speed signal i becomes large.

Purpose of the Invention The present invention has been made in view of the drawbacks of the above-mentioned conventional examples.
The present invention provides a speed signal detection device that outputs a speed signal with quick response and low ripple even at low speeds even when performing speed control with a large ratio between the maximum speed and the minimum speed of the rotating body.

Arrangement of the Invention Page 6' To achieve this object, the present invention provides a speed signal detection device that receives as input two-phase rectangular wave outputs having 90° different phases from an encoder coupled to a rotating body. a pulse generation circuit that converts the edge of a rectangular wave into a constant pulse 1 signal and switches its output terminal depending on the rotation direction; an OR circuit and a rotation direction determination circuit that receive the outputs of both terminals of the pulse generation circuit; a polarity conversion circuit that receives the outputs of the two circuits as input via a power conversion circuit and converts them into pulse signals with different polarities depending on the two rotational directions;
A first integrator circuit that integrates the obtained output and a second integrator circuit that further integrates the output are provided, and the polarity varies depending on the rotation direction from the output of the encoder and a low ripple speed that is proportional to the rotation speed. It detects signals.

Description of examples The following two embodiments of the present invention are shown in FIGS. 2 and 3 of the drawings.

This will be explained in detail with reference to FIGS. 4, 6, and 6. FIG. 2 is a block diagram of a speed signal detection device according to an embodiment of the present invention, FIGS. 3 and 4 are output waveform diagrams of various parts in FIG. 3 shows another circuit example of the second integrating circuit in FIG. In addition,
Components with the same reference numerals as those in the conventional example shown in FIGS. 1 and 3 indicate the same components, and a description thereof will be omitted. As shown in FIG. 3, in the second integrating circuit 8 which receives the output j of the first integrating circuit 7, the output j is connected to the operational amplifier ■ via a resistor R1.
A capacitor C1 and a resistor R2 are connected in parallel between the non-inverting terminal of IC1 and the ground. A resistor R3 is connected between the inverting terminal of the circuit C1 and the ground, and a resistor R4 is connected between the inverting terminal of the circuit C1 and the output terminal of the circuit C1, and the output signal is k.

In the integrating circuit 8 of FIG. 2, integration is performed by R1, R2, and C1, and non-inverting amplification is performed by the operational amplifier IC1.

In this way, by adding the second integrating circuit, the pulse width T is reduced in the first integrating circuit. By integrating the pulse signal i of , the pulse width is expanded, and by further smoothing it in the second integrating circuit, the integration time constant of the total 7 veils of the first and second integrating circuits can be increased by that amount. Great smoothness can be obtained without any problems. Therefore, the speed detection device shown in FIG. 2 can detect a speed signal with low ripple without impairing responsiveness.

Figure 5 shows another circuit example of the second integrating circuit 8 in Figure 2.
The figure and FIG. 6 will be explained. In FIG. 5, in a second integrating circuit 9 that receives the output j of the first integrating circuit, the output j is inputted to the inverting terminal of the operational amplifier IC2 via a resistor R5, and the inverting terminal of the IC2 and the IC2 are connected to each other. A capacitor C2 and a resistor R6 are connected in parallel between the output terminals of. A resistor R7 is still connected between the non-inverting terminal of IC2 and ground. The output t is directly integrated to obtain the output l, but in this case, the sign of the output t is inverted with respect to the output j. -1
In FIG. 6, the second integrating circuit 10 receives the output j of the first integrating circuit.

The output j is input to the non-inverting terminal of the operational amplifier IC3 via a resistor R8, a resistor R9 is connected between the non-inverting terminal of the IC3 and the ground, a resistor R1o is connected between the inverting terminal of the IC30 and the ground, and the IC3 and the inverted terminal of IC3
A capacitor C3 and a resistor R11 are connected in parallel between the output terminals of the . In this case as well, the output m is obtained by integrating 17.

Effects of the Invention According to the present invention, the two-phase output of an encoder connected to a rotating body is input and the polarity differs depending on the direction of rotation, and the speed has a low ripple proportional to the rotation speed. Signal can be detected.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional speed signal detection device, FIG. 2 is a block diagram of a speed signal detection device according to an embodiment of the present invention, and FIGS. 3 and 4 are respective parts of FIGS. 1 and 2. The output waveform diagrams of FIGS. 5 and 6 are circuit diagrams showing other embodiments of the second integrating circuit of FIG. 2. 1... Pulse generation circuit, 2... OR circuit, 3... Rotation direction discrimination circuit, 4, 5...
Power conversion circuit, 6...Polarity conversion circuit, 7, 8, 9
．． 10...Integrator circuit.

Claims (1)

[Claims] In a speed signal detection device that receives two-phase rectangular wave outputs with 90° different phases from an encoder coupled to a rotating body,
a pulse generating circuit that converts the edges of the two-phase rectangular wave into a signal of a constant pulse 1 and that switches the output terminal depending on the direction of rotation; an OR circuit that receives the outputs of both terminals of the pulse generating circuit; and the direction of rotation. a discrimination circuit; a polarity conversion circuit that inputs the outputs of the two circuits through power conversion circuits and converts them into pulse signals with different polarities depending on the two rotational directions; and a first integration circuit that integrates the obtained outputs. and a second integrating circuit for integrating the output thereof, the output of the encoder has a polarity that differs depending on the direction of rotation,
A speed signal detection device/device that detects a low ripple speed signal proportional to the rotation speed.