JPH04303709A - Displacement sensor and fault judging method thereof - Google Patents

Abstract

PURPOSE:To obtain a displacement sensor which is suitable for multiplex systems by realizing a method for juding the fault of the displacement sensor itself or its sensor system based on the output signal of the displacement sensor. CONSTITUTION:A displacement sensor is provided with a plurality of detecting element parts which output the detected signals for every unit displacement of an object to be measured 31. The displacement detecting positions of a plurality of the detecting element parts are deviated by the specified phase difference. At least three detecting element parts 36 are provided. The displacement detecting positions of the detecting element parts 36A-36C are set so that the phase differences of the output signals of the detecting elements parts 36A-36C become the values obtaiend by equally dividing an electric angle of 360 degrees by the number of the elements. The detected signal is always outputted from any of the detecting element parts.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an incremental displacement sensor and a displacement sensor failure determination method suitable for a multiplex system using the same.

0002

2. Description of the Related Art Generally, displacement sensors such as incremental encoders or scales are used to measure rotational displacement or linear displacement. For example, a photodiode or a magnetic head) outputs a displacement detection signal for each unit displacement of the object to be measured with a predetermined phase difference, thereby detecting the direction of displacement and the length of the displacement of the object to be measured.

As a conventional displacement sensor of this type, there is an optical rotary encoder as shown in FIG. 6, for example. In the figure, 1 is an encoder plate that rotates integrally with a rotating shaft (not shown), and 2 is the encoder plate 1.
A plurality of slits are formed at predetermined radial positions at predetermined pitch intervals. Reference numeral 3 denotes a sensor head holding member disposed on one side of the encoder plate 1 to face the slit 2, and the sensor head holding member 3 allows one end of the light emitting side optical fibers 5A, 5B to extend in the circumferential direction of the encoder plate 1. are kept apart. Further, one end of each of the light receiving side optical fibers 6A, 6B is held by the sensor head holding member 4 so as to face one end of each of the light emitting side optical fibers 5A, 5B. Further, the light emitting side optical fibers 5A, 5B are connected to light emitting circuits 7A, 7B including light emitting elements, and the light emitted from the light emitting circuits 7A, 7B passes through the slit 2 according to the rotation of the encoder plate 1. From the light receiving side optical fibers 6A, 6B to the light receiving circuits 8A, 8
B, or blocked by the encoder plate 1. The light receiving circuits 8A and 8B convert the output signals of the internal light receiving elements according to the respective amounts of received light into rectangular wave output signals (signals generated when a predetermined amount of light or more is received, which is "H" in FIG. 7). Therefore, the phase difference (
A and B phase output signals having a phase difference of 90 degrees electrical angle are output.

Incidentally, such displacement sensors are used in a multiplex system as shown in FIG. 8 in aircraft and the like that require a high degree of reliability. In this case, the same command corresponding to the target position of the hydraulic cylinder 11 (actuator) is input to channels CH1 and CH2, respectively, and position detection signals are fed back from displacement sensors 12 and 13 via processing circuits 14 and 15, respectively. , the deviation is input to the servo amplifiers 16 and 17. The servo amplifiers 16 and 17 send currents I1 and I2 corresponding to the respective input signals to the electromagnetic coils 18a and 18b of the electric/hydraulic servo valve 18, and the electric/hydraulic servo valve 18 receives currents generated by both the electromagnetic coils 18a and 18b. A valve body (not shown) is displaced by electromagnetic force, and the state of oil pressure supplied to the hydraulic cylinder 11 is changed. In a system in which control loops are multiplexed in this way, for example, if a failure occurs in one feedback loop (sensor system), this failed system is isolated from the others and
Servo control can be performed using the system's feedback loop.

[0005] Such a displacement sensor is also used for the purpose of detecting the valve speed of the hydraulic servo valve 18, as shown in FIG. 9, and is fed back by a sensor 21 and its signal processing circuit 22.

[0006]

[Problems to be Solved by the Invention] However, in such a conventional displacement sensor, both the A and B phase output signals output from the light receiving circuits 8A and 8B are "L" even during normal operation. (see t1 in Figure 7) occurs, for example, one sensor system fails and
Even if the outputs of both phases become “L”, the sensor output signal indicates that the light is blocked by the encoder plate 1 (
normal state), that is, the electrical angle 90 including t1 in FIG.
It was not possible to easily determine whether the object to be measured was positioned within the range of 30° or a failure had occurred.

Furthermore, when applied to a dual system as shown in FIG. 8, if an abnormality occurs in CH2, for example, the current I2 flowing to the electric/hydraulic servo valve 18 becomes an abnormal value. Therefore, the valve body driving force as in the normal state is not generated, and even the feedback signal (position detection signal) of the normal channel CH1 has a value different from the command input, making it impossible to perform normal servo control as it is. Therefore, when such an abnormality occurs, it is necessary to identify the faulty system, isolate it from others, and perform servo control using a normal feedback loop, but as mentioned above, the abnormality cannot be determined from the sensor output signal. Therefore, if an abnormality occurred in one system, the entire system (both systems) had to be shut down.

The present invention has been made in view of such conventional problems, and provides a failure determination method that can determine failure of the displacement sensor itself or its sensor system from the output signal of the displacement sensor. The object of the present invention is to provide a displacement sensor that allows easy failure determination and is suitable for multiple systems.

[0009]

[Means for Solving the Problems] To achieve the above object, the invention according to claim 1 is provided with a plurality of detection element sections that output a detection signal for each unit displacement of an object to be measured, and a plurality of detection element sections. In the displacement sensor in which the displacement detection position of is shifted by a predetermined phase difference of the detection signal, at least three of the detection element parts are provided, and the phase difference of the output signals of these detection element parts is equal to the number of the elements such that the phase difference between the output signals of these detection element parts is 360 degrees in electrical angle. The displacement detection position of each detection element section is set so as to be equally divided by , and the detection signal is always outputted from one of the detection sections.

In order to achieve the above object, the invention according to claim 2 is a method for determining failure of the displacement sensor, wherein when the detection signals of the detection element portions of the displacement sensor are all at the same level, the displacement sensor Otherwise, it is determined that a failure has occurred in the sensor system.

[0011]

[Operation] In the invention as claimed in claim 1, the phase difference between the detection signals of at least three detection element sections is a value obtained by equally dividing 360 electrical degrees by the number of the elements, and the phase difference is always measured from at least one detection element section. A detection signal for each unit displacement of the object is output. Therefore, the presence or absence of a failure can be determined based on the presence or absence of this detection signal.

In the invention as claimed in claim 2, if the detection signals of the detection element section of the displacement sensor are not all at the same level, it is determined that there is no failure in the displacement sensor and the sensor system, and all the detection signals of the detection element section are determined to be at the same level. If they become the same level, it is determined that a failure has occurred in that displacement sensor or its sensor system. Therefore, a failure of the displacement sensor itself or its sensor system can be easily determined from the output signal of the displacement sensor.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on the drawings. 1 to 4 are diagrams showing an embodiment of a displacement sensor and a sensor system using the same according to the invention as claimed in claims 1 and 2, and show an example in which the invention is applied to an optical fiber type rotary encoder. ing.

In FIGS. 1 and 2, 31 is a disk-shaped encoder plate (object to be measured) that rotates integrally with a rotating shaft (not shown), and 32 is formed at a predetermined radius position of the encoder plate 31 at equal pitch intervals. Multiple slits. 33 is a sensor head holding member disposed on one side of the encoder plate 31 so as to face the slit 32;
(at least three) light emitting side optical fibers 35A, 35
One ends of B and 35C are held so as to be spaced apart from each other by a predetermined distance in the circumferential direction of the encoder plate 31. Further, one end of each of the light receiving side optical fibers 36A, 36B, and 36C is held at a predetermined interval by a sensor head holding member 34 so as to face one end of each of the light emitting side optical fibers 35A to 35C. On the other hand, the light emitting side optical fibers 35A to 35C
are connected to light emitting circuits 37A, 37B, and 37C including light emitting elements such as LDs (laser diodes), and the light emitted from the light emitting circuits 37A to 37C and propagated through the light emitting side optical fibers 35A to 35C. is radiated from the light emitting side optical fibers 35A to 35C to the encoder plate 31 side. Depending on the rotation of the encoder plate 31, this emitted light enters one of the light-receiving optical fibers 36A to 36C through one of the slits 32, or is blocked by the encoder plate 31. When light enters any one of the light receiving side optical fibers 36A to 36C (hereinafter also simply referred to as the light receiving side optical fiber 36), the light receiving circuit 3
Any one of 8A to 38C (hereinafter also simply referred to as the light receiving circuit 38) receives the light from the light receiving side optical fiber 36 by an internal light receiving element (not shown), and converts the output signal of the light receiving element into a detection signal which is a rectangular wave output. (a "H" level signal generated when a predetermined amount of light or more is received) and output. In addition, 39A to 39C are light receiving circuits 38A to 38C.
This is the output terminal of

Further, the mutual spacing between the light-receiving side optical fibers 36A to 36C in the rotating direction of the encoder plate 31 (equal to the mutual spacing between the light-emitting side optical fibers 35A to 35C) is such that when the encoder plate 31 is rotated, the slit 3
In order to make the timing of receiving a predetermined amount of light through 2 (or blocking the light amount to less than a predetermined value by the encoder plate 31) by a predetermined phase difference (120 electrical degrees) for each of the receiving side optical fibers 36A to 36C. The positions of the light-receiving optical fibers 36A to 36C with respect to the same slit 32 may be slightly shifted by the phase difference, or may be shifted by an interval corresponding to several slits. Therefore, three-phase output signals of A phase, B phase, and C phase are output, which have a phase difference corresponding to the separation of the light receiving side optical fibers 36A to 36C in the rotational direction of the encoder plate 31. That is, in this embodiment, the light receiving side optical fiber 3 which is the detection element section
At least three optical fibers 6A to 36C are provided, and each optical fiber 3 is connected so that the phase difference of the photodetection signals of these detection element parts becomes 120 degrees, which is the value obtained by equally dividing 360 degrees of electrical angle by the number of the elements 3.
Light receiving positions (detection positions) of 6A to 36C are set.

FIGS. 2A to 2C show the positional relationship between the slit pattern of the slits 32 of the encoder plate 31 and the light receiving positions of the light receiving side optical fibers 36A to 36C, and in this case, the light receiving circuit 38A The output signal waveform from ~38C is shown in FIG. As is clear from both figures, the photodetection signal is always output from at least one of the three channels A-phase to C-phase. Furthermore, since the phase difference between the three-phase output signals is 120 degrees, displacement (position) detection with a resolution of 60 degrees is possible by providing an appropriate comparison circuit or the like.

FIG. 4 shows an example of a circuit implementing the failure determination method in this embodiment. In the same figure, 51
is an OR circuit that inputs three-phase output signals from the light receiving circuits 38A to 38C, and the OR circuit 51 is an OR circuit that inputs three-phase output signals from the light receiving circuits 38A to 38C.
Only when the outputs of ~38C are all “L” (low), that is, at the same level, an “L” level signal is output,
The occurrence of a failure can be notified to a control circuit (not shown). That is, the failure determination method of this embodiment determines that a failure has occurred in the displacement sensor or its sensor system when the output signals of the light receiving circuits 38A to 38C, which are the detection element portions, are all at the same level.

In the displacement sensor of this embodiment, the phase difference of the photodetection signals output from the light receiving circuits 38A to 38C (detection element section) is equal to 120 degrees, which is obtained by equally dividing 360 degrees of electrical angle by the number of the elements. Connect the receiving side optical fibers 36A to 3 so that
6C (detection element section), there is always at least one light receiving circuit 38 connected to the encoder plate 3.
A detection signal for each unit displacement is output. therefore,
Depending on the presence or absence of this photodetection signal (output signal at H level), the presence or absence of a failure can be easily determined, making the displacement sensor suitable for a multiplex system with easy failure determination.

Furthermore, in the displacement sensor failure determination method of this embodiment, if all the output signals of the light receiving circuits 38A to 38C are at the "L" level, it is determined that a failure has occurred in the displacement sensor of this embodiment or its sensor system. It is determined that the light receiving circuit 38
If any of the output signals from A to 38C is not at the same level as the others, it is determined that there is no failure in that displacement sensor and sensor system. Therefore, the failure determination circuit can be realized as a simple failure determination circuit including only the OR circuit 51, and a failure of the displacement sensor itself or its sensor system can be easily determined from the output signal of the displacement sensor. for example,
If a failure occurs in one of the feedback loops (sensor systems) in the multiplex system as shown in FIG. 8, the occurrence of the failure can be easily detected by the output signal of the OR circuit 51, and The system can be identified very easily.

In this embodiment, the light receiving side optical fibers 36A to 36C, which are the detection element portions, are spaced apart in the rotational direction (circumferential direction) of the encoder plate 31 to obtain the predetermined phase difference. The receiving side optical fibers 36A to 36C may be arranged across the slit 32 so as to have a predetermined phase difference, or the slit 32 may be lengthened in the radial direction of the plate and the receiving side optical fibers 36A to 36C may be arranged in a radial direction. For example, the sensor head can be easily assembled even when the resolution is high and the slit interval is small. moreover,
Encoder plate 31 and light receiving side optical fibers 36A to 3
It is also possible to provide a known fixed slit member between the fixed slit member 6C and obtain a predetermined phase difference of the output signal depending on the slit position of the fixed slit member. In this case, for example, three fixed slits formed side by side in the radial direction of the encoder plate 31 are shifted in the circumferential direction so that the three light receiving elements are lined up in a row in the radial direction without being shifted in the rotational direction of the encoder plate 31. It can also be done. Furthermore, it is also possible to use one light emitting element that emits a large amount of light, or to configure one detection element section by combining a plurality of light receiving elements into one group.

Furthermore, although this embodiment is a rotary type displacement sensor that detects rotational displacement using an optical fiber, it is possible to use general devices such as LEDs (light emitting diodes) and phototransistors as the light emitting and receiving elements. The present invention can be applied in the same way even to linear type devices (for example, linear encoders and scales). Furthermore, although the present embodiment is of a light transmission type sensor, it can also be applied to a reflection type sensor in which a light reflection film portion of a predetermined pattern is provided by, for example, chromium vapor deposition or gold plating. Although not mentioned individually, it goes without saying that various conventional light emitting/receiving methods can be applied.

FIG. 5 is a diagram showing another embodiment of the displacement sensor according to the invention as claimed in claims 1 and 2, and shows an example in which the invention is applied to a magnetic digital scale. In the figure, 61 has a plurality of magnetic elements 61a on one side.
are magnetic scales provided at regular intervals, 62A,
62B and 62C are a plurality of magnetic heads arranged close to one side of the magnetic scale 61. magnetic head 6
2A to 62C are known excitation circuits 63A and 63, respectively.
B, 63C and the signal processing circuits 64A, 64B, 64C, and transmits a signal obtained by multiplying the magnetic flux by the excitation from the excitation circuits 63A to 63C and the magnetic flux by the magnetic scale 61 to the signal processing circuits 64A, 64B, 64C. Output. That is, in this embodiment, the magnetic head 62A
62C constitute three detection element sections, and although details are not shown, the magnetic heads 62A to 62C are positioned relative to the magnetic element 61a so that the phase difference of their output signals is 120 degrees, as in the above example. The magnetic scale 61 is shifted in the longitudinal direction (movement direction). The signal processing circuits 64A to 64C are connected to a failure determination circuit similar to the OR circuit 51 in the above example. Note that the magnetic heads 62A~
The interval 62C can be appropriately set depending on the pitch of the magnetic elements 61a.

Also in this embodiment, the signal processing circuit 64A
The phase difference of the detection signal output from ~64C is 36 electrical degrees.
0 degrees divided equally by the number of magnetic heads 62A to 62C
Since the angle is set to 20 degrees, the signal processing circuit 6 is always
A detection signal for each unit displacement of encoder plate 31 (displacement corresponding to the pitch of magnetic element 61a) is output from at least one of 4A to 64C. Therefore, the presence or absence of a failure can be easily determined based on the presence or absence of this detection signal (output signal at H level), making the displacement sensor suitable for multiplexed systems, with easy failure determination.

[0024]

According to the invention as set forth in claim 1, the phase difference between the output signals of at least three detection element sections is 360 electrical degrees.
The displacement detection position by the detection element section is set so that the degree is equally divided by the number of elements, so that at least one detection element section always outputs a detection signal for each unit displacement of the object to be measured. Therefore, the presence or absence of a failure can be easily determined based on the presence or absence of this detection signal, and it is possible to provide a displacement sensor that is easy to determine a failure and is suitable for a multiplex system.

According to the second aspect of the invention, when the detection signals of the detection element section all become the same level, it is determined that a failure has occurred in the displacement sensor or its sensor system, so that the output signal of the displacement sensor It is possible to easily determine a failure in the displacement sensor itself or the sensor system from only this, and at the same time, the failure determination circuit can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of a displacement sensor according to the present invention.

FIG. 2 is a diagram showing the relationship between the slit pattern of the encoder plate and the position of the optical fiber in one embodiment.

FIG. 3 is a diagram showing signal waveforms of three-phase outputs in one embodiment.

FIG. 4 is a configuration diagram of a failure determination circuit for explaining an embodiment of the displacement sensor failure determination method according to the present invention.

FIG. 5 is a schematic configuration diagram showing another embodiment of the displacement sensor according to the present invention.

FIG. 6 is a schematic configuration diagram of an example of a conventional displacement sensor.

FIG. 7 is a diagram showing an output signal waveform of the conventional example.

FIG. 8 is a configuration diagram of a multiplex system using conventional displacement sensors.

FIG. 9 is a configuration diagram when the system includes speed detection.

[Explanation of symbols]

31 Encoder plate (measurement object) 32
Slits 35A to 35C Emitter side optical fibers 36A to 36
C Light receiving side optical fiber (detection element part) 37A~3
7C Light projecting circuit 38A to 38C Light receiving circuit 51 OR circuit (failure determination circuit) 61 Magnetic scale (measurement object) 61a Magnetic element 62A to 62C Magnetic head (detection element section) 63
A~63C Excitation circuit 64A~64C Signal processing circuit

Claims (2)

[Claims] 1. A displacement sensor comprising a plurality of detection element sections that output a detection signal for each unit displacement of a measuring object, and in which displacement detection positions of the plurality of detection element sections are shifted by a predetermined phase difference of the detection signals. , at least three of the detection element sections are provided, and the displacement detection position of each detection element section is set such that the phase difference between the output signals of these detection element sections is a value obtained by equally dividing 360 degrees of electrical angle by the number of the detection element sections. A displacement sensor characterized in that the detection signal is always output from one of the detection sections. 2. The displacement sensor failure determination method according to claim 1, wherein when all the detection signals of the detection element portion of the displacement sensor are at the same level, it is determined that a failure has occurred in the displacement sensor or its sensor system. A method for determining a failure of a displacement sensor, the method comprising: determining a failure of a displacement sensor.