JPH05280997A - One-rotation positional-signal detection system - Google Patents

Abstract

PURPOSE:To accurately detect a reference position for a rotation body even when the output of pseudo-sinusoidal waves from a sensor is drifted by a temperature change and their amplitude is changed by a method wherein the pseudo-sinusoidal wave part from the sensor is input, via a capacitor, to an amplifier having an extreme amplification factor, the output of the amplifier is compared with a set value by means of a comparator and a position detection signal is output at a stage where the amplified output reaches the set value. CONSTITUTION:A waveform drift voltage Va which is input to a pseudo-sinusoidal wave input terminal ZO is cut by means of a capacitor C; the change portion of an AC voltage, i.e., pseudo-sinusoidal waves from which an irregularity due to a temperature change has been excluded, are output from said capacitor C. The neutral position of the pseudo-sinusoidal waves is stabilized at a stage prior to their amplification; the pseudo-sinusoidal waves are amplified extremely by means of an operational amplifier OP. Thereby, irrespective of whether the amplitude of the pseudo-sinusoidal waves input from the input terminal ZO is large or small, a comparator COMP shortens the time required from detecting the arrival of the set value of an amplified waveform, and it outputs a position detection signal surely in synchronization with a change in the output of the pseudo-sinusoidal waves from a position detector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is directed to an improvement of a detection method of a single rotation position signal which is a reference position signal in a position detector for detecting the rotation position of a servo motor or a position coder for detecting the rotation position of a spindle of a machine tool. Regarding

[0002]

2. Description of the Related Art In a position detector having a one-rotation signal for knowing one rotation position of a rotating body such as a position coder for knowing a rotation position of a main shaft of a machine tool, a sine or cosine of n waves per rotation is used. The pseudo sine wave signal signal of is detected by a sensor, and this pseudo sine wave signal signal is interpolated to generate a rotational position signal. For example, in a position coder that generates 256 sine wave signals per rotation, quadruple interpolation is performed. Also, one rotation signal is
Shape a pseudo sine wave signal of one wave per revolution into a rectangular wave,
One that detects the one rotation position (reference position) of the rotating body at the time of forward rotation by the rising (or falling), and detects the reference position at the time of reverse rotation by the falling (rise). Are known.

[0003]

Conventionally, in the case of detecting one rotation signal and converting the pseudo sine wave output from the sensor into a rectangular wave, the pseudo sine wave output is amplified by an amplifier as it is, and then the amplifier. A comparator compares the output from the above with a set value, and when the amplified output reaches the set value, a rectangular wave serving as a position detection signal is output. However, the pseudo sine wave output from the photoelectric converter or the like that constitutes the output part of the sensor includes drift and amplitude fluctuation due to temperature change,
Further, there is a problem that the output timing of the rectangular wave is deviated due to the phase delay due to the number of rotations of the rotating body such as the main shaft, and the generation timing of the one-rotation position detection signal is likely to vary.

Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to accurately determine the reference position of the rotating body even if the pseudo sine wave output from the sensor has a drift or an amplitude change due to a temperature change. The object is to provide a one-rotation position signal detection method capable of detecting a single rotation position signal.

[0005]

According to the present invention, a pseudo sine wave output from a sensor is input to an amplifier having an extreme amplification factor via a capacitor, and the output of the amplifier and a set value are compared by a comparator. The object is achieved by outputting a position detection signal when the amplified output reaches a set value.

[0006]

Since the drift due to the temperature change is absorbed by the capacitor, the error due to the amplification of the drift is prevented and the neutral point position of the amplified waveform is stabilized. Also, since the pseudo sine wave output is extremely amplified, the amplitude of the amplified waveform input to the comparator is uniformly increased, and the time required for the comparator to detect the arrival of the amplified waveform set value is the pseudo sine wave. The wave output becomes uniform regardless of the amplitude of the wave output, and the amount of deviation is small. In combination with the stable neutral point position, the output timing of the position detection signal is reliably synchronized with the change of the pseudo sine wave output, and the one-rotation position can be accurately detected.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing an essential part of a one-rotation position detection circuit according to one embodiment. Z0 is an input terminal of a pseudo sine wave signal from a sensor such as a light receiving element, and the pseudo sine wave signal is an amplifier (an operational amplifier) whose gain is specified by the values of the resistors R3 and R4 via the capacitor C from the input terminal Z0. )
Input to inverting input terminal Z1 of OP. The inverting amplified output from the amplifier OP is connected to the comparison input terminal Z2 of the comparator COMP (comparator) having hysteresis (dead band width) with the resistors R5 and R6. Gain of amplifier OP (R4 / R3)
Is set to be extremely larger than the gain α of the amplifier used in the conventional one-rotation position detection circuit. R1 and R2 are resistors having the same resistance value, and the neutral point voltage Vcc / 2 is connected to the capacitor C.
It is to be superimposed on the pseudo sine wave signal output from.
The neutral point voltage Vcc / 2 is input to the non-inverting input terminal of the operational amplifier OP, which is an amplifier.
The difference between cc / 2 and the pseudo sine wave signal output from the capacitor is amplified and output.

The comparator COMP compares the output of the amplifier OP with the neutral point voltage Vcc / 2 and outputs a square wave signal ZP of one rotation signal.
Is output.

First, since the pseudo sine wave output input to the pseudo sine wave input terminal Z0 has a drift due to the temperature characteristics of the light emitting element of the detector, the photoelectric converter, etc., that is, the variation of the DC voltage, the pseudo sine wave is generated. A drift voltage Va as shown in FIG. 2 is generated in the waveform input to the wave input terminal Z0, and the drift voltage Va fluctuates. In the present invention, the drift voltage Va is cut by the capacitor C, and the capacitor C outputs a pseudo sine wave in which variations in the AC voltage, that is, variations due to temperature changes are eliminated.

Then, the neutral point voltage is added to the pseudo sine wave output from the capacitor C by the resistors R1 and R2. The waveform input to the inverting input terminal Z1 of the operational amplifier OP is shown in FIG.
As shown in (a), it stabilizes as a pseudo sine wave based on the neutral point voltage Vcc. In the case of the conventional one-rotation position detection circuit, since a capacitor for drift cut corresponding to the capacitor C is not provided,
As shown in (b), the neutral point voltage fluctuates due to the temperature characteristics of the light emitting element, the photoelectric converter, etc., and the waveform of the fluctuation of the neutral point voltage is directly input to the amplifier.

The difference between the pseudo sine wave signal input to the inverting input terminal Z1 of the amplifier OP and the neutral point voltage Vcc / 2 by adding the neutral point voltage is extremely large by the amplifier OP (R4 / Although it is amplified by R3), the gain (R4 / R3) is extremely larger than the gain α of the amplifier used in the conventional one-turn position detection circuit, so the amplitude of the amplified waveform output from the amplifier OP is very large. It becomes large, and the rising and falling edges of the pseudo sine wave signal become steep. Further, when the absolute value voltage of the pseudo sine wave output exceeds the amplification limit of the operational amplifier OP, a saturation state occurs, so that the waveform is substantially rectangular as shown in FIG. 4 (a).

In the comparator COMP, the amplified waveform input from the amplifier OP to the comparison input terminal Z2 is the upper limit of hysteresis + V.
At a stage beyond ref (see FIG. 4A), a constant voltage position detection signal as shown in FIG. 5A is raised and output to the position detection signal output terminal Z3. When the amplified waveform falls below the lower limit of hysteresis −Vref, it returns to the initial state of zero output. However, as shown in FIG. 4A, the amplitude of the amplified output from the amplifier OP is extremely large. 4b and FIG. 4 where the gain of the amplifier is α is the time until the voltage of reaches the upper limit of hysteresis + Vref, that is, the time T until the comparator COMP detects the arrival of the set value of the amplified waveform. 5 (b) is much shorter than the detection time T'of the conventional example, and the position detector irrespective of the magnitude of the amplitude of the pseudo sine wave at the time of being input to the pseudo sine wave input terminal Z0. Position detection signal according to the change of pseudo sine wave output from It can be quickly output, the rising edge of this signal can be accurately detected a rotational position.

Further, unlike the conventional amplified waveform shown in FIG. 4B, the fluctuation of the drift Va is not amplified as it is and does not affect the neutral point position of the waveform. Even if it is set to a large value, the position detection signal can be output accurately and quickly in synchronism with the change in the pseudo sine wave output from the position detector without being affected by disturbance factors such as temperature changes. ..

In the above example, the case where the reference position of the rotating body is detected during the forward rotation by the rise of the position detection signal has been described, but the reference position during the reverse rotation is also detected by the fall of the detection signal. Only the polarity of the waveform is reversed, and the phenomenon as a whole is similar to the above-mentioned example.

[0015]

According to the one-rotation position detecting method of the present invention, since the pseudo sine wave output from the detector is input to the amplifier through the capacitor, the DC component drift caused by the temperature change is absorbed in the capacitor, The error due to the amplification of the drift element is prevented, and the neutral point position of the amplified waveform of the pseudo sine wave is stabilized. Moreover, since this pseudo sine wave is extremely amplified and input to the comparator, the rise and fall of the pseudo sine wave signal input to the comparator become sharp, and the comparator reaches the set value of the amplified waveform. The position to detect is accurate. Also, even if the temperature environment of the position detector changes and the amplitude of the pseudo sine wave output fluctuates, the pseudo sine wave signal input to the comparator rises and falls sharply, resulting in amplitude fluctuations. Exactly 1 without being affected
It is possible to output one rotation position signal capable of detecting the rotation position.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of a one-rotation position detection circuit of an embodiment to which the present invention is applied.

FIG. 2 is a schematic diagram showing an example of a pseudo sine wave output from a position detector.

FIG. 3 is a schematic diagram showing an example of a pseudo sine wave output input to an amplifier, FIG. 3 (a) is a diagram showing an embodiment, and FIG. 3 (b).
FIG. 6 is a diagram showing a conventional example.

FIG. 4 is a schematic diagram showing an example of an amplified output waveform from an amplifier, FIG. 4 (a) is a diagram showing an embodiment, and FIG. 4 (b) is a diagram showing a conventional example.

5A and 5B are schematic diagrams showing an example of a position detection signal output from a comparator, FIG. 5A is a diagram showing an embodiment, and FIG.
FIG. 6 is a diagram showing a conventional example.

[Explanation of symbols]

 Z0 Pseudo-sine wave input terminal Z3 Position detection signal output terminal C capacitor OP operational amplifier COMP Comparator Comparator R3, R4 resistance R5, R6 resistance

Claims (2)

[Claims] 1. An extreme amplification factor in a one-rotation position signal detection system for converting a pseudo sine wave output from a sensor into a rectangular wave and detecting one rotation position indicating a reference position of a rotating body at the rising or falling thereof. The pseudo sine wave output is input to the amplifier having a capacitor through a capacitor, the output of the amplifier is compared with a set value by a comparator, and when the amplified output reaches the set value, a position detection signal composed of a rectangular wave is generated. One rotation position signal detection method to output. 2. The one-rotation position signal detection system according to claim 1, wherein the comparator output having a constant hysteresis is used to compare the output of the amplifier with the set value.