JPS6035208A - Trouble detecting circuit of body-movement detector - Google Patents

Abstract

PURPOSE:To detect the trouble of a body-movement detector, by squaring two signals, which are proportional to the amount of the movement of a body and have different phases, respectivey, and adding the squared signals. CONSTITUTION:Encoder 10 generates two-phase pseudo sine wave signals S1= Vsinomegat and S2=Vcosomegat having the phase difference of 90 deg.. A deviation-amount measuring circuit 20 judges the rotating direction in the case of a rotary encoder, judges the moving direction in the case of a linear encoder, and supplies counting pulses to an up down counter in the next state. A trouble detecting circuit 30 comprises a first multiplier 31, a second multiplier 32, a signal generator 33, and a trouble judging device 34. The first multiplier 31 squares one output of the encoder 10 and outputs the result. The second multiplier 32 squares the other output of the encoder 10 and outputs the result.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to an object movement detector that outputs two signals having mutually different phases proportional to the amount of movement of the object as the object moves, particularly a rotary sensor; When measuring the amount of rotation or movement using a dowliner encoder, etc., the encoder may be malfunctioning.

The present invention relates to a failure detection circuit for an object movement detector that detects when the correct amount of rotation or movement cannot be measured.

[Technology background]

In servo mechanisms using DC servo motors, such as robots, the amount of rotation of the servo Tanabata is measured using an incremental four-tary encoder, and this is fed back to determine the target value position or Closed-loop control that compares speed is widely used. When performing position feedback control or speed feedback control using the output of such a rotary encoder, if the rotary encoder breaks down and the amount of rotation of the servo motor cannot be measured, there will be no feedback signal.

From the moment the servo motor expands, it will run out of control.

This situation is due to the fact that in the servo mechanism that converts the rotation of the servo motor into linear movement and controls the linear movement, the linear deviation is measured using a linear encoder, and this is fed back and compared with the target position or speed. The same applies to closed loop control.

Therefore, in rotary encoders and linear encoders, when a failure occurs in the encoder, it is always required to immediately detect the failure and take measures to prevent the servo motor from running out of control.

[Problems with conventional technology]

Conventionally, as a method for detecting runaway of a servo motor, a limit switch is provided to detect when the maximum movement range is exceeded. Alternatively, methods are used to detect when the absolute value of the deviation between the commanded position and the position measured by an encoder has become abnormally large. With these methods, for example, in the case of a robot, the machine has run quite a long time from the time it starts running out of control until it is detected, and even if the machine itself can be prevented from being destroyed, it can cause harm to people, such as a robot. This is not sufficient if there is a risk of damaging the object being worked on. In addition, in the latter case, it is possible to reduce the amount of servo motor rotation when the servo motor runs out of control, but this is only effective in the case of runaway due to causes other than encoder failure; However, the absolute value of the positional deviation remains zero and cannot be detected.

Another possible method is to determine a failure by detecting the amplitude or phase shift of the output signal from the encoder, but this method has the disadvantage that separate detection circuits must be provided for each, making the single circuit configuration complex.

[Purpose of the invention]

SUMMARY OF THE INVENTION In order to improve the above drawbacks, an object of the present invention is to provide a failure detection circuit that can detect the encoder itself at the moment of failure or before the failure occurs, in order to prevent the servo mechanism from running out of control due to encoder failure. It is to be.

[Structure of the invention]

In order to achieve the above object, the fault detection circuit for an object movement detector of the present invention detects a fault in an object movement detector, which outputs two signals with mutually different phases proportional to the amount of movement of the object as the object moves. The detector failure detection circuit is composed of a multiplier that squares the valley signal and an adder that adds each signal multiplied by 1, and detects a failure of the object movement detector using the output of the adder. It is characterized by detecting.

[Embodiments of the invention]

One embodiment of the present invention will be described in detail with reference to FIGS. 1 to 7.

FIG. 1 is a block diagram of one embodiment of the present invention.

Fig. 2 is an explanatory diagram of the configuration and operating waveforms of the enlarged rotary encoder/coder, Fig. 6 is a Lissajous waveform diagram of the two-phase pseudo sine wave signal S1 rS2 with a phase of 90'' obtained from the four-tary encoder, Fig. 4 is An explanatory diagram of the reference voltage sources of the first and second comparators, and FIGS. 5 to 7 show operation waveform diagrams when the encoder fails.

In Fig. 1, a two-phase pseudo sine wave signal S1-vamωt,1 with a phase difference of 90 degrees is generated by a 10-hiro encoder.
%5=Voosωt is generated. 20 surrounded by a dotted line is a deviation measuring circuit, which determines the rotation direction in the case of a C1-Tari encoder, and the movement direction in the case of a linear encoder, and sends counting pulses to the next stage Aggu-down kakunta (not shown). supply. 50, also surrounded by a dotted line, is a failure detection circuit that connects the first multiplier S1. The second multiplier 522 consists of a signal generator 33 and a fault discriminator 34 surrounded by a dotted line. Of the above configurations, the encoder 10 and the deviation measurement circuit 1
1 is the same as the known one, so first, the configuration and operation of both will be briefly explained.

909iC) Two-phase pseudo sine wave signal 51 (
The principle of the encoder 10 that generates -V-ωt) and s, (-v(2)ωt) is the same whether it is a rotary encoder or a linear encoder, so the following p-
This will be explained using the case of Talienkog as an example.

A rotary encoder that generates two-phase pseudo sine wave signals with a phase difference of 90 degrees is called an incremental rotary encoder. Incremental rotarien;-da is shown in Figure 2 (at, (bl),
A transparent glass code plate 12 that rotates around the shaft 11. A fixed mask plate 13° has a light emitting element 14 and first and second light receiving elements 15 and 16 (the light emitting element also often has two elements).

The code plate 12 has slits S, S, .
The mask plate 13 has a slit cord SC consisting of.

The code plate 12 has first and second mask codes MCI and MC consisting of one to several slits at positions corresponding to the slits (see FIG. 2 (cl)).

! - The mask plate 12 and the mask plate 15 are actually overlapped one above the other so that the slits of both correspond to each other, but for convenience of explanation, the two are shown separated. First mask code MC
, is the slit 811.8 of the corresponding slit code SC on the code plate 12 as shown in the figure. I! When there is a match, the second MC is selected to place Su,8u in a position shifted to the right by exactly % of its width, as shown in the diagram.

As a result, when the code plate 12 rotates, the first and second mask codes MCI, MC, and the slit code plate 12 (Z
) It is proportional to the product of the angular velocity and the number of slits, and the nine angular velocity is 2π.

Generates a triangular wave output that changes at degrees ω (-lower, T-Hiro synchronization). The first mask code MC1 receives light from the first mask code MC1.
The waveform output from the light receiving element 15 forms a triangular wave T1, as shown in FIG.
The triangular wave T: output from the second light receiving element 16 that receives the light from the i-nuku code MC has a phase difference of 90 degrees.

When the triangular waves T and T1 are passed through a filter (not shown) and only the fundamental waves are extracted, a two-phase pseudo sine wave signal 5l (
= V reflection ω')+'% ("■ (2) ωt)" is obtained.

Note that since the angular velocity ω changes from DC to about 100 KHz·2π, a filter is not possible.

The pseudo-sine wave signal appears to be due to light diffraction or leakage, and the peak of the triangular waveform becomes rounded.

The actual output will be a distorted waveform somewhere between a triangular waveform and a sine waveform.

The deviation measuring circuit 20 also includes first and second comparators 21, 221, a phase discriminator 26, and a zero volt reference voltage source S.
1 and 22 are inputs S, S, and a zero-volt reference voltage source S■. Compare input 81+s! Outputs rectangular waves iX, R, with the same phase relationship as . The phase discriminator 23 compares the phases of the rectangular waves R1 and R1.

When Rz (i.e., St relative to 81) is behind 90 m with respect to R work (for example, when a servo motor (not shown) is rotating clockwise), an up-count pulse is generated in the Ull child, and when it is ahead by 90 degrees ( counterclockwise rotation) generates a pulse for down counting at the D terminal and supplies it to an up/down counter (not shown) at the secondary stage.

Next, to explain the failure detection circuit 30, the first multiplier 51 outputs one output S1=w81 of the encoder 10.
Square nωt and get V! Output dωt. The second multiplier 52 outputs the other output of the encoder S! , -V(2)ωt to the power of 2 'V'ayt? Output w t.

Although the signal generator 35 includes an adder 65 and a square root circuit 36, the square root circuit 66 may not be used. Adder 35 Hiro first and second multipliers 31, 520
Add the outputs. Output S from encoder 10, S
, is the output during normal operation, that is, a two-phase pseudo sine wave signal 51 with an equal amplitude of V and a phase difference of 90 degrees, as shown in FIG.
When outputting ωt, the output of the adder 35 remains constant at ψ. The square root circuit 56 calculates the square root of the output (2) of the adder 35 and outputs an output signal TS (=V). As the output signal TI9, v3 can be used instead of V, but in that case.

Square root circuit 36 becomes unnecessary.

The fault discriminator 34 includes first and second comparators 37 and 38 and an OR circuit 39. The first comparator 37 has
As shown in FIG. 4, when the first reference voltage source SVl of a predetermined lower value is supplied with respect to the normal amplitude V of Sl, S, and the level of the output signal TS is lower than this SVl. generates output. The second comparator 38 includes a fourth
As shown in the figure, a second reference voltage @SV, which is a predetermined level higher than ■, is supplied, and an output is generated when the level of the output signal TS becomes lower than S■2. The OR circuit 59 outputs a fault signal F8 when an output is supplied from at least one of the first and second comparators 57, 38. The output signal T8 of the first and second reference voltage sources svl, sv is the signal S1. If the amplitude of S is ■ and ■
2, although it is set to different values depending on the case.

How to set this will be explained in the explanation of the operation of the failure detection circuit 5o in a failure state or an abnormal state of the primary encoder 10.

Due to the following causes, the encoder 10 may stop outputting or generate abnormal outputs, making it impossible to perform normal servo operation.

(2) When the gap between the code plate 12 and the mask plate 130 changes.

The gap between the code plate 12 and the mask plate 15 (see diagram @2) is approximately 100μm±20μ, although it varies depending on the number of patterns.
It changes at about m. When this gap changes due to, for example, an axial shift of the shaft 11, the phase difference between the two-phase signals 81+81 hardly changes, being 90 degrees, but the amplitude and offset amount of the signals change greatly. For example, when the gap narrows, the amplitude of S,, S, becomes large, and when it widens, the amplitude becomes small, and the degree of change in the amplitudes of Sl and 82 also differs.

Figures 5 and 6 show the output S, S, the surge waveform (figure a), and the waveform of the output signal TS (figure a) of the encoder 10 when the offset amount and amplitude ratio of the outputs S, S, change, respectively. Figure b) is shown in Figure 6. When the island is normal + PI when a 0.5 V offset occurs in S, + PR when a 0.5 V offset occurs in Sl and 82, P3 changes in amplitude by 0.5 V in s2 + P4 is the surge waveform (figure a) and the waveform of the output signal T8 (figure b) when a 2V amplitude change occurs in Sl.
shows. In the case of PR, the comparators 57 and 58 of Hiro 1st and 1g2 both generate outputs, and in the case of +PR, the 1st comparator
In the case of +P4 from the comparator 37, an output is generated from the second comparator 38, but in either case, the OR circuit 59 outputs the fault signal F8.

In FIGS. 5 and 6, 'O+ PI to P4 is expressed by the following formula.

An increase in the output amplitude means that the gap has become narrower, so before the gap between the code plate 12 and the mask plate 13 becomes narrower and the slit code SC and mask code MC, MC, formed thereon are damaged. It is possible to detect that an abnormality has occurred in the gap.

In the conventional failure detection method, a failure is detected only when the slit code SC or mask code MC, MC is damaged and the signal Sl+82 is no longer generated, which is an abnormal state, that is, a runaway state. According to the above, gap abnormalities can be detected before a runaway condition occurs.
It is possible to discover failures before they occur.

■ When there is a misalignment between the rotation centers of the shaft 11 and the cord board 20.

The eccentricity of the shaft 11 and the code plate 12 is Δ, and the code plate 12
When the middle diameter up to the slit is R, the angular error for one rotation of the code plate 12 appears in the form of a sine wave with an amplitude of ±Δ/R. At this time, since the optical path of the two-phase pseudo sine wave signal S1+1% is installed with a mechanical position shifted, the phase difference between the two signals is 901 times with one rotation of the code plate 12 as a period.
Changes from 1j.

However, the amplitude and offset amount of the two signals hardly change, but when the center of rotation of the code plate 12 shifts due to the bending of the shaft 11 (the gap also changes depending on the bending of the shaft), the amplitude It will also change.

In this case, the output signal TSiS1. Due to the phase difference fluctuation of S, it changes asymmetrically and complexly upward and downward centering on ■.
Since the voltage changes above and below the level of the second reference voltage source "I I S 7., the presence or absence of a failure can be easily discovered.

If the phase difference between the two-phase pseudo sine wave signals S, S, is 90 degrees, the direction of rotation can be determined accurately, but if the phase difference between the two signals approaches 0 degrees or 1801F, the direction of rotation cannot be determined. Unable to do so, he goes berserk.

In the conventional method, a failure could not be detected until a runaway actually occurred, but in the second embodiment, this abnormality can be detected before a runaway condition occurs, and a runaway can be prevented.

(2) When a relative positional shift occurs between the code plate 12 and the mask plate 13.

If the centers of the code patterns on the code plate 12 and mask plate 13 become non-concentric due to loose attachment of the mask plate 16 or wear of the shaft 110 bearing, the phase difference between the two-phase pseudo sine wave signals Sl, S, deviates from 90 degrees. The phase shift at this time is a constant amount regardless of the rotation period of the code plate 120. However, the amplitude and offset amount of both signals do not change. Figure 7 shows the surge waveform (figure a) when a phase shift occurs in the two-phase pseudo sine wave signal 81+'% and the state of the output signal TS (figure b), where Po is normal. + Pi is S, is 5o
When it deviates by 60'', + Pa is s, and when it deviates by 60'', P
? is the glue surge waveform when s2 deviates by 90' (Figure a)
and the waveforms of the output signal TS (Figure 1)). ”＋P
a, Pv, the first and second comparators 57.
Since 58 generates an output, the OR circuit 69 outputs the fault signal F.
Output S.

In this case as well, if the relative positional deviation between the code plate 12 and the mask plate 13 becomes large, a situation arises in which the direction of rotation cannot be determined as in the case (2) above, and a runaway situation occurs. Failures can be detected in

In FIG. 7, po, Pa, and "%r"7 are expressed by the following equations.

Various cases may be considered in addition to the above causes, but in any case, the amplitude change of the two-phase pseudo sine wave signal S1°S2 appears as a phase shift.

The failure detection circuit 30 allows the presence or absence of a failure to be easily discovered.

Further, the values of the first and second reference voltage sources SV, , S- are statistically selected from the mode of the abnormal state of the encoder that occurs due to these various causes and the waveform of the output signal TS at that time.

Note that the explanation up to now is for the case of a rotary encoder, but the same applies to the case of a linear encoder, so detailed explanation will be omitted.

〔Effect of the invention〕

According to the present invention, an encoder failure can be detected at the instant the failure occurs or just before the failure occurs, so the amount of deviation measured by the encoder can be fed back to the servo motor for closed loop control. In such cases, runaway behavior due to encoder failure can be prevented, which can be highly effective in ensuring the safety of robots and the like.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention. Fig. 2 is an explanatory diagram of the configuration and operating waveforms of the rotary encoder, Fig. 3 is a diagram of the two-phase pseudo sine wave signal 81+1% surge waveform during normal operation of the linear encoder, and Fig. 4 is a diagram of the waveform of the first and second comparators. Reference voltage power supply Sv1°S- and two-phase pseudo sine wave signal S1. An explanatory diagram of the relationship between the amplitude V of S, and Fig. 5~
FIG. 7 shows the two-phase pseudo sine wave signal S1+s! when an abnormal condition occurs in the encoder. FIG. 3 is a waveform explanatory diagram of a glue surge waveform and an output signal TS. +to in 11 is the encoder, 11 is the shaft. 12 is a code plate, 13 is a mask plate, 14 is a light emitting element, 1
5 is a first light receiving element, 16 is a second light receiving element, 20 is a deviation measurement circuit, 21 is a first comparator, and 22 is a second light receiving element.
23 is a phase discriminator, 50 is a failure detection circuit, 51 is a first multiplier, 32 is a second multiplier, and 33 is a signal generator. 54 is a fault discriminator, 35 is an adder, 37 is a first comparator, 58 is a second comparator, and 59 is an OR circuit. Patent Applicant: Fujitsu Ltd. Representative Patent Attorney Akira Yamatani Eisai 3 SV'+; I-4 5

Claims (1)

[Claims] 9. A failure detection circuit for an object movement detector that outputs two signals having mutually different phases proportional to the amount of movement of the object as the object moves, the circuit comprising: a multiplier for squaring each of the signals;
1. A failure detection circuit for an object movement detector, comprising an adder that adds each multiplied signal, and detecting a failure of the object movement detector based on the output of the adder.