JPH04166718A - Linear type optical encoder - Google Patents

Abstract

PURPOSE:To obtain the detected commutation-angle signal directly from the detected signal of an encoder and to perform the commutation control of a motor by making the pitch of the slits of the encoder equal to the pitch of the gear teeth of the stator of the motor. CONSTITUTION:The pitch of the slits of an encoder 2 is made equal to the pitch of the gear teeth of a stator 11 of a motor 1. Therefore, the phase shift of the slits detected with the encoder 2 becomes the phase shift itself between the gear teeth of the stator of the motor and the gear teeth of a mover 12. Thus, the detected commutation-angle signal can be directly obtained from the detected signal of the encoder 2. The encoder 2 can be used for controlling the commutation of the motor 1. When the change of the phase shift is computed, the position of the mover of the motor 1 is detected. The speed of the mover of the motor 1 can be detected on the basis of the fluctuating period of the value of the phase shift. Thus, the controls for the commutation, position and speed of the motor 1 can be performed at the same time.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a linear optical encoder used in a linear servo motor.

- <Conventional Technology> In the field of FA (factory automation), pulse motors are often used as drive sources for industrial robots, processing machines, etc.

For example, in an apparatus for transporting semiconductor components, since the transport operation is linear motion, it is convenient to use a linear pulse motor because the power transmission mechanism becomes simple.

If a linear pulse motor is controlled by a linear servo motor, high positioning accuracy can be obtained. 'i, if you add commutation control and speed control functions to a linear servo motor,
Controllability can be improved.

<Problem to be solved by the invention> However, in order to provide the linear servo motor with the functions of position feedback control, 9-speed feedback control, and commutation control, a control system must be created for each function. The configuration becomes multiple.

As a sensor for detecting the movement of a moving element of a linear servo motor, there is a linear magnetic resolver that uses the stator of the motor as its own stator.

However, since this resolver uses the teeth of the stator of the motor as a scale, there is a problem in that detection accuracy deteriorates when the pitch of the teeth is large.

Other sensors include linear optical encoders.

However, in this encoder, since the pitch of the slits and the pitch of the fixed teeth of the motor are different, there is a problem that a signal for commutation control of the motor cannot be obtained from the detection signal of the encoder.

The present invention was made to solve these problems, and a signal for motor commutation control is directly obtained from the encoder detection signal itself, and the motor position control and speed control are performed from this detection signal. The purpose of this invention is to realize a linear optical encoder that can simultaneously obtain signals for commutation control and that can obtain high detection resolution regardless of the tooth pitch of the stator of the motor.

Means for Solving the Problems> The present invention is a linear optical encoder having the following configuration.

(1) A linear optical encoder for detecting movement of a moving element of a linear pulse motor, which is fixed to a stator of the linear pulse motor, and has slits arranged along the direction in which teeth of the stator are arranged; A slit plate whose slit pitch is equal to the tooth pitch of the stator of the linear pulse motor, a light emitting element and a light receiving element mounted on the mover of the linear pulse motor, and arranged facing each other across the slit; Based on the light detection signal of the element, the phase shift of the slit with respect to the light emitting element and the light receiving element due to the movement of the movable element is detected, and the detected phase shift itself is caused by the difference between the teeth of the stator of the linear pulse motor and the tooth of the movable element. A linear optical encoder characterized by being equipped with a signal processing circuit that causes a phase shift.

(2) The light receiving element is a photodiode array in which a plurality of photodiodes are arranged within one pitch of the slit, and the signal processing circuit includes a scanning circuit that scans photodetection signals of the plurality of photodiodes; A waveform shaping circuit that generates a phase modulation signal whose phase is modulated by 360 degrees when the linear pulse motor mover moves by one pitch of the stator teeth, based on the photodetection signal obtained by scanning, and the generated phase. Claim (2) characterized by comprising: a phase difference counter that measures a phase difference between a modulation signal and a reference signal whose phase is not modulated to determine a phase shift between teeth of a moving element and a stator of a linear pulse motor. encoder.

(3) Claim (2) further comprising a signal generation circuit that sends the phase shift determined by the phase difference counter to a commutation control section of the linear pulse motor as a commutation angle detection signal.
(4) The encoder 6 described above is provided with a signal generation circuit that generates a position detection signal for the moving element of the linear pulse motor by integrating the phase shift determined by the phase difference counter every scanning period of the scanning circuit. The encoder according to claim (2), characterized in that:

(5) The encoder according to claim (2), further comprising a signal generation circuit that generates a speed detection signal of a moving element of a linear pulse motor from a fluctuation frequency of the phase shift value determined by the phase difference counter. .

(6) Movement of a linear pulse motor In a linear optical encoder that detects the movement, the encoder is fixed to the stator of the linear pulse motor, and has slits at a pitch p1 along the direction in which the teeth of the stator are arranged. A slit row in which the slits are arranged is formed by the arranged slit row and the t chill 2, and p and ρ2 are the teeth of the stator of the linear pulse motor. /pm = 1/p+ -1/p2 PI<P2 A slit plate that satisfies the relationship: mounted on the mover of the linear pulse motor, provided in each of the two slit rows, and arranged facing each other with the slit in between. a light emitting element and a light receiving element, and a signal processing circuit that detects a phase shift between the teeth of the moving element and the tooth of the stator of the linear pulse motor from the light detection signals of the respective light receiving elements arranged opposite to each other in the two slit rows. A linear optical encoder that is characterized by:

(7) Each of the light receiving elements is a photodiode array in which a plurality of photodiodes are arranged within one pitch of the slit, and the signal processing circuit detects the light of each photodiode with respect to the two photodiode arrays. Based on the signal scanning circuit and the two photodetection signals obtained by scanning, when the linear pulse motor mover moves one pitch of the slits in each slit row, the phase is modulated 360°. 2
A waveform shaping circuit that generates two phase modulation signals, and a phase difference between the two generated phase modulation signals is measured, and the measured phase difference itself is the phase shift between the teeth of the moving element and the tooth of the stator of the linear pulse motor. 7. The encoder according to claim 6, further comprising: a phase difference counter.

(8) Claim (7) further comprising a signal generation circuit that sends the phase shift determined by the phase difference counter to a commutation control section of the linear pulse motor as a commutation angle detection signal.
Encoder listed.

(9) Measure one cycle of the phase modulation signal generated by the waveform shaping circuit every scanning cycle of the scanning circuit, and calculate the difference between this measurement value and the measurement value of the cycle of the reference signal whose phase is not modulated. The encoder according to claim 7, further comprising: a counter that integrates and detects the position of the moving element of the linear pulse motor.

00. The encoder according to claim 7, further comprising a signal generation circuit that generates a speed detection signal of a moving element of a linear pulse motor from a fluctuation frequency of the phase shift value determined by the phase difference counter.

In the present invention, since (pitch of slits of encoder) = (pitch of teeth of stator of motor), the encoder detects t: From the modulation phase of the phase modulation signal, the fixation of the motor is determined. The phase shift between the child teeth and the mover teeth is directly detected.

Then, a motor commutation angle detection signal is obtained from the detected phase shift. In addition, the phase shift is NXed to obtain a position detection signal of the movable element of the motor. Furthermore, the moving speed of the motor moving element is obtained from the fluctuation frequency of the phase shift value.

Furthermore, by forming two stages of slits with different pitches and making the pitch of these slits have a specific relationship with the tooth pitch of the motor stator, regardless of the tooth pitch of the motor stator, Guarantees high detection resolution.

<Example> Hereinafter, the present invention will be explained using the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, and (a
1 is a front view, and (b) is a side view.

In these figures, 1 is a motor and 2 is an encoder.

The motor 1 is a known linear pulse motor.

In the motor 1, 11 is a stator, 12 is a mover, and teeth are formed on these at a constant pitch. In the figure, a three-phase motor is shown, but a motor with a different number of phases may be used.

In the encoder 2, a slit plate 21 is fixed to the stator 11, and has slits 22 formed at a constant pitch in the direction in which the teeth 111 of the stator are arranged.

The arrangement pitch of the slits 22 is equal to the arrangement pitch of the teeth 111 of the stator. 23 and 24 are an LED and a photodiode array (hereinafter, the photodiode array will be referred to as PDA) which are arranged opposite to each other with the slit 22 in between, and these are both fixed to the movable member 12 side. 25 is a fixing member that fixes the LED 23 to the stator 12;
26 is a condensing lens that condenses the light emitted from the LED 23 and hits the PDA 24.

27 is a signal processing circuit that calculates the phase shift between the teeth of the linear pulse motor's mover and stator based on the photodetection signal of the PDA 24, and 28 is a signal that uses the determined phase shift to generate a signal used to control the linear pulse motor. It is a generation circuit.

The configurations of the signal processing circuit 27 and the signal generation circuit 28 will be explained.

FIG. 2 is a diagram showing the specific configuration of these circuits.

Components in FIG. 2 that are the same as those in FIG. 1 are given the same reference numerals.

The PDA 24 has eight photodiodes PDI to PD8 arranged in an array at one pitch P of the slits 22.

In the signal processing circuit 27, switches SWI to SW8 are sequentially closed at a fixed timing by an 8-phase clock supplied from the tarlock generator 271 to scan the photodetection signals of the photodiodes PDI to PD8.

272 is an OP amplifier, and each switch SW1 to SW8
amplify the signal given through the OP amplifier 272
The output is a stepped waveform, and the height of the waveform corresponds to the number of photodiodes that detected light. For example, at the first timing, the switch SW1. S
W2. SW3 and SW4 close, and at the second timing, switch SW2. SW3. SW4. SW5 is closed, and in the same manner, the switches to be closed are shifted four by four.

273 is a low-pass filter (hereinafter referred to as LPF) that extracts a low frequency component of the output of the OP amplifier 272; 274 is a comparator that shapes the waveform of the output of the LPF 273;

275 is a clock extraction circuit that extracts one phase of the eight-phase clock from the clock generator 271; 276;
The clock generator's 8 data clock is set to 1. With a frequency divider circuit that divides the frequency by '8! 〉. 277 is a phase difference counter that measures the phase difference between the phase modulation signal obtained from the comparator 274 and the reference signal, which is either the phase extracted by the clock extraction circuit 275 or is not modulated, at the timing of the frequency division clock of the frequency division circuit 276. The period of the divided clock is 8 switches S
This corresponds to the scanning period of WI to SW8.

In the signal generation circuit 28, 281 is a phase difference counter 2.
77 is an integration circuit that integrates the phase difference measured every scanning period to detect the position of the motor moving element, and 282 is a phase difference counter 277 that moves the motor moving element based on the fluctuation frequency of the measured phase difference. It is an F/'V converter that detects speed.

The operation of the encoder configured in this way will be explained.

The clock generator 271 opens and closes the switches SWI to SW8 at the timing of the 8-phase clock to turn on the photodiode P.
The photodetection signals from DI to PD8 are scanned. Since the photodiodes PDI to PD8 are image sensors that image the slit, when the PDA23 and LED24 (hereinafter referred to as optical sensors) move by one pitch of the slit, the phase of the step-like waveform signal obtained by scanning will change. 360°
Change. Therefore, the signal obtained by passing the stepped waveform signal through the LPF 273 and the comparator 274 becomes a phase modulation signal given by the following equation.

f (t) = As i n (ωt+2π(χ/P)
)...■ A: Signal amplitude 1 for 2 hours χ Relative movement amount of the Nislit p Pitch of the Nislit ω = 2πfS fs: Frequency of the 8-phase clock of the clock generator 271 Also extracted by the clock extraction circuit 27 The phase of the reference signal becomes ωt.

When the switches SWI to SW8 are switched eight times, the scan period III ends, so the period becomes the period of the divided clock by the frequency dividing circuit 276 or the scan period.

The phase difference counter 277 measures the phase difference between the phase modulation signal given from the cosciparator 274 and the reference signal given from the tallock extraction circuit 275 every scanning period at the timing of the frequency division clock. This phase difference is 2π(χ/p) from equation 0.

Here, (pitch of encoder slits) = (pitch of stator teeth of linear pulse motor), and the phase difference measured by the phase difference counter is the phase shift between the teeth of the motor stator and the tooth of the slider. Become that thing. Commutation control of the motor is performed based on this phase shift.

That is, the signal used for commutation control is directly detected by the phase difference counter.

In the signal generation circuit 28, the phase difference measured by the phase difference counter 277 is directly sent as a commutation angle detection signal to a commutation control section (not shown) of the motor.

Reference numeral 281 denotes an integration circuit, which integrates the change in the phase difference measured by the phase difference counter 277 at the timing of the frequency division clock of the frequency division circuit 276. This integration value becomes the position of the movable element of the motor.

Therefore, the oscillator xtii of the MX circuit 281 is applied as a position detection signal to a position feedback control section (not shown) of the motor.

282 is an F/V converter, which outputs a voltage signal proportional to the fluctuating frequency of the output of the comparator 274; This signal is given as a speed detection signal to a speed feedback control section (not shown) of the motor.

In this way, the signal generation circuit 28 simultaneously detects signals used for motor commutation control 9 position control and speed control.

FIG. 3 is a block diagram of another example of the actual rod of the present invention, in which <a) is a front view and (b) is a side view.

In FIG. 3, the slit plate 21 has two stages of slits 22. and 222 are formed.

The arrangement pitches p1 and p2 of the slits 221 and 222 have a distance expressed by the following formula with respect to the arrangement pitch ρ of the teeth 111 of the motor stator.

1/ρN ”” 1 y”’ P + 1 /”’
ρ2PI<92...■ LED is 23.according to the 2-stage slit. and 23
2, the PDA has 241 and 242, and the condenser lens has 26.
and 262 are provided.

2 is a signal processing circuit that calculates the phase shift between the moving element and stator teeth of the linear pulse motor based on the photodetection signals of PD A 24 + and 242, and 30 is a signal processing circuit that controls the linear pulse motor from the obtained phase shift. This is a signal generation circuit that generates signals used for.

The configurations of the signal processing circuit 29 and the signal generation circuit 30 will be explained.

FIG. 4 is a diagram showing a specific configuration example of the two signal processing circuits #1 and the signal generation circuit 30.6 In the signal processing circuit 29, eight photodiodes PDI to PD8 are provided for each of the PDAs 24+ and 242. , eight switches SWI to SW8 are also provided.

Also, corresponding to the two PD A 24 + and 242, the OP amplifier is 2721 and 2722, or the LPF is 27
3, and 2732, but the cossiparator is 274° and 2742
However, one was thrown each.

The phase difference counter 277 calculates the phase difference between the phase modulation signal from the comparator 274 and the phase modulation signal from the comparator 2742 at the timing of the frequency division clock of the frequency division circuit 276.

A counter 278 counts the period of the phase modulation signal from the comparator 274.

In the signal generation circuit 30, 301 is a comparator 27
4. An F/V converter 302 that outputs a voltage signal proportional to the fluctuating frequency of the output of the counter 278 is an integration circuit that Mx the count value of the counter 278.

The operation of the encoder configured in this way will be explained.

Slits 221 and 22 with arrangement pitches of ρ and ρ2
The phase modulation signals fl(t,) and f2(t) obtained from the comparators 2741 and 2742 based on the passing light of 2 are given by the following equations.

fl (j) = Asin iωtmo2π(χ/'pi
) f2 (shi)=As i n :ωt+2z (χz
'P2): The phase difference counter 277 calculates the
The phase difference between phase modulation signal f, (t) and f2 (t) is 2π(
χ/p,)-2π(χ/p2) =2πχ(1/p,-1,/ρ2)...■
Measure. Here, from the formula ■, 1/PM=1/PI
1. /P2, the phase difference is 2πχ/PM. This phase difference is the phase shift itself between the teeth of the stator of the motor and the teeth of the mover.

The signal generation circuit 30 sends the phase shift detected by the phase difference counter 277 to the commutation control section of the motor as a commutation angle detection signal. Further, the F/V converter 301 sends a voltage signal proportional to the fluctuation frequency of the detected phase shift value to the speed feedback control section of the motor as a speed detection signal.

The counter 278 and the integrating circuit 302 output the phase modulated signal f+
The position of the motor's moving element is determined by measuring the period of (t) for each scanning period! Detect.

For example, if the number of clocks required to count one period of the non-phase modulated signal As1nωt is 4096, then the counter 278 detects the position S of the moving element by performing integration given by the following equation.

S=Σ(Ci -4096) Ci: Number of clocks required to measure the first cycle The detected position is sent to the motor position feedback control section as a position detection signal via the signal generation circuit 30.

Here, for example, the tooth pitch of the stator of the motor is Pm=5
mm, the slit pitch is P+ = 1mm
, P2 = 1.25 mm, formula (2) is satisfied. From this, even if the pitch of the motor teeth is large, the encoder can obtain high detection resolution.

In this example, 1/2 of the area within 1 pitch of the slit is
When interpolating to 000, the resolution of position detection in the embodiment shown in FIG. 1 is 5 mm/'2000=2.5 μm.

On the other hand, in the embodiment shown in FIG. 3, the resolution of position detection using slits with a pitch of 1 mm is 1 mm/20
00=0.5 μm.

Effect〉 According to the present invention, the following effects can be obtained.

(1) In the example shown in Figure 1, (pitch of encoder slits) = (pitch of teeth of motor stator), so the phase shift of the slits detected by the encoder is due to the movement of the teeth of the motor stator. It becomes the phase shift of the child's teeth itself. Thereby, the commutation angle detection signal can be obtained directly from the detection signal of the encoder, and the encoder can be used for commutation control of the motor.

Further, by integrating the changes in the phase shift, the position of the movable element of the motor is detected, and the period of movement of the motor is detected from the period of variation of the value of the phase shift.

Based on these facts, the encoder detection signal ranks first in motor commutation control! Signals used for control and speed control can be obtained simultaneously.

(2) In the embodiment shown in FIG. 3, the slits are formed in two stages,
Since the pitch of these slits has a specific relationship with the pitch of the motor teeth, the pitch of the encoder slits can be made small regardless of the pitch of the motor teeth. This allows the encoder to obtain high detection resolution even if the pitch of the motor teeth is large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of the present invention, FIG. 2 is a block diagram of the main parts of FIG. 1, FIG. 3 is a block diagram showing another embodiment of the present invention, and FIG. FIG. 3 is a configuration diagram of the main parts of FIG. 3; DESCRIPTION OF SYMBOLS 1... Motor, 11... Stator, 12... Mover, 111... Teeth, 2... Encoder, 21... Slit plate, 22.22+, 222... Slit, 2
3.23+. 232...LED, 24.24+, 242...P
DA, 25...Fixing member, 27.29...Signal processing circuit, 28.30...Signal generation circuit, 271...Clock generator, 272.272+, 2722...O
P an 1.273.273+, 2732...LPF
, 274°274+, 2742... comparator,
275... Clock extraction circuit, 276... Frequency dividing circuit, 277... Phase difference counter, 278... Counter, 281° 302... Integrating circuit, 282,301...
...F/V conversion agent, patent attorney Shinsuke Tezawa 7゛.

Claims (10)

[Claims] (1) A linear optical encoder for detecting movement of a moving element of a linear pulse motor, which is fixed to a stator of the linear pulse motor, and has slits arranged along the direction in which teeth of the stator are arranged; A slit plate whose slit pitch is equal to the tooth pitch of the stator of the linear pulse motor, a light emitting element and a light receiving element mounted on the mover of the linear pulse motor, and arranged facing each other across the slit; Based on the light detection signal of the element, the phase shift of the slit with respect to the light emitting element and the light receiving element due to the movement of the movable element is detected, and the detected phase shift itself is caused by the difference between the teeth of the stator of the linear pulse motor and the tooth of the movable element. A linear optical encoder characterized by comprising a signal processing circuit that causes a phase shift. (2) The light receiving element is a photodiode array in which a plurality of photodiodes are arranged within one pitch of the slit, and the signal processing circuit includes a scanning circuit that scans photodetection signals of the plurality of photodiodes; A waveform shaping circuit that generates a phase modulation signal whose phase is modulated by 360 degrees when the linear pulse motor mover moves by one pitch of the stator teeth, based on the photodetection signal obtained by scanning, and the generated phase. Claim (2) characterized by comprising: a phase difference counter that measures a phase difference between a modulation signal and a reference signal whose phase is not modulated to determine a phase shift between teeth of a moving element and a stator of a linear pulse motor. encoder. (3) Claim (2) further comprising a signal generation circuit that sends the phase shift determined by the phase difference counter to a commutation control section of the linear pulse motor as a commutation angle detection signal.
Encoder listed. (4) A claim characterized by comprising a signal generation circuit that generates a position detection signal for a moving element of a linear pulse motor by integrating the phase shift determined by the phase difference counter for each scanning period of the scanning circuit. The encoder described in item (2). (5) The encoder according to claim (2), further comprising a signal generation circuit that generates a speed detection signal of a moving element of a linear pulse motor from a fluctuation frequency of the phase shift value determined by the phase difference counter. . (6) A linear optical encoder that detects the movement of a moving element of a linear pulse motor, which is fixed to the stator of the linear pulse motor, and has slits at a pitch of p_1 along the direction in which the teeth of the stator are arranged. A slit row in which slits are arranged and a slit row in which slits are arranged at pitch p_2 are formed, and p_1 and p_
2 is a slit plate that satisfies the relationship 1/p_M=1/p_1-1/p_2 p_1<p_2 with respect to the tooth pitch p_M of the stator of the linear pulse motor, and is mounted on the slider of the linear pulse motor, and A light-emitting element and a light-receiving element are provided in each of the two slit rows and are arranged facing each other across the slit, and the moving element of the linear pulse motor is detected from the light detection signals of the light-emitting element and the light-receiving element arranged facing each other across the two slit rows. A linear optical encoder characterized by being equipped with a signal processing circuit that detects a phase shift between teeth and stator teeth. (7) Each of the light receiving elements is a photodiode array in which a plurality of photodiodes are arranged within one pitch of the slit, and the signal processing circuit detects the light of each photodiode with respect to the two photodiode arrays. Based on the scanning circuit that scans the signal and the two photodetection signals obtained by scanning, when the moving element of the linear pulse motor moves one pitch of the slit in each slit row, the phase is modulated 360°2.
A waveform shaping circuit that generates two phase modulation signals, and a phase difference between the two generated phase modulation signals is measured, and the measured phase difference itself is the phase shift between the teeth of the moving element and the tooth of the stator of the linear pulse motor. The encoder according to claim 6, further comprising a phase difference counter. (8) Claim (7) further comprising a signal generation circuit that sends the phase shift determined by the phase difference counter to a commutation control section of the linear pulse motor as a commutation angle detection signal.
Encoder listed. (9) Measure one cycle of the phase modulation signal generated by the waveform shaping circuit for each scanning cycle of the scanning circuit, and integrate the difference between this measurement value and the measurement value of the cycle of the reference signal whose phase is not modulated. The encoder according to claim 7, further comprising: a counter that detects the position of the moving element of the linear pulse motor. (10) The encoder according to claim (7), further comprising a signal generation circuit that generates a speed detection signal of a moving element of a linear pulse motor from a fluctuation frequency of the phase shift value determined by the phase difference counter. .