JP2007064858A - Disconnection detecting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a disconnection detecting system for detecting the disconnection of a cable transmitting a measuring signal of a position sensor cyclically changing a signal level at a real time in response to the movement of a measuring object. <P>SOLUTION: The disconnection detecting system for detecting disconnection of the cable transmitting the measuring signal of the position sensor cyclically changing the signal level in response to the movement of the measuring object comprises: a phase shift means for generating a reference signal shifting the phase of the measuring signal; an addition means for generating an addition signal adding the measuring signal and the reference signal; and a disconnection detecting means for detecting the disconnection in response to a comparison result by comparing the addition signal with a threshold of a prescribed level. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a disconnection detection device that detects disconnection of a cable that transmits a measurement signal of a position sensor whose signal level periodically changes according to the movement of a measurement object.

  FIG. 8 is a functional block diagram illustrating a configuration example of a conventional position measuring apparatus that receives a measurement signal of a position sensor whose signal level periodically changes according to movement of a measurement target. Reference numeral 1 denotes a receiving device, and 2 denotes a moving position sensor. Reference numeral 3 denotes a flexible cable connecting the receiving device 1 and the position sensor 2. Reference numeral 4 denotes a host device that communicates with the receiving device 2.

  FIG. 9 is an image diagram illustrating details of the position sensor 2. In the figure, reference numeral 21 denotes a scale plate arranged in parallel with the measurement direction, and a plurality of slits 22 (one representative is shown in the figure) are formed at a predetermined pitch in the longitudinal direction. Light from the light source 23 is transmitted from above the slit plate 21 perpendicular to the scale plate 21.

  The slit 22 is shaped so that the amount of transmitted light changes in a sine wave shape in the longitudinal direction. Reference numeral 24 denotes a sensor substrate for measuring the movement distance, and moves in the direction of arrow Q in parallel with the scale plate 21. Reference numerals 250 to 25n denote a plurality of light receiving elements arranged at a predetermined interval in the Q direction on the sensor substrate 24, and receive light transmitted through the slit 22.

  e0 to en are detection signals of transmitted light by these light receiving elements, and change in a sine wave shape according to the shape of the slit 22. A0 to An are buffer amplifiers that buffer these detection signals and output them to a plurality of lead lines L0 to Ln. When the sensor substrate 24 moves, the detection signal focused on one light receiving element that receives the transmitted light from the slit formed in the scale plate periodically changes in a sine wave shape.

  A flexible cable 3 that connects the receiving device 1 and the position sensor 2 is formed by bundling a plurality of lead wires L0 to Ln, a power supply (+ V) line, a ground (GND) line, a clock signal line, and the like given from the host device 4. It is. When the number of light receiving elements 25 is eight (n = 0 to 7), there are eight lead wires L0 to L7, and the detection signals of the lead wires are stepped from e0 to e7. It becomes a voltage distribution signal.

  Returning to FIG. 8, the configuration of the receiving apparatus 1 will be described. A clock generation circuit 11 generates a clock signal CLK having a predetermined period based on a command signal from the host device 4. Reference numeral 12 denotes a counter that counts the clock signal CLK. Reference numeral 13 denotes an 8-bit shift register, which receives the count-up signal P1 of the counter 12 and is transmitted through the lead wires L0 to L7 of the cable 3 described with reference to FIG. Are sequentially switched in a time-sharing manner, and this is transferred to the filter circuit 14 as a measurement signal E0.

  The filter circuit 14 to which the measurement signal E0 is input smooths the stepped voltage distribution signals e0 to e7, converts the stepped voltage distribution signals e0 to e7 into a sine wave output signal S0, and passes it to the host device 4. Reference signal generation circuit 15 receives a clock signal CLK, generates a reference signal S1 synchronized with switching by the 8-bit shift register 13, and passes it to the host device 4.

  The host device 4 measures the moving distance and moving direction of the sensor substrate 24 based on the phase difference of the output signal S0 and the polarity of the phase difference with respect to the reference signal S1. Reference numeral 16 denotes a reset circuit provided in the receiving device 1, which generates a reset signal RS in response to a command from the host device 4 at the measurement start timing, and resets the counter 12 and the reference signal generating circuit 15.

  Patent Document 1 discloses an encoder signal transmission circuit that detects the presence or absence of a disconnection of a signal line of an encoder that generates a two-phase signal with a 90 ° phase shift.

No. 6-50080 gazette

The conventional position measuring apparatus having such a configuration has the following problems.
(1) Since the cable 3 composed of a plurality of lead wires moves as the position sensor 2 moves, there is a risk of disconnection due to stress such as wear. If even one of the wires is disconnected, correct position measurement is impaired. Therefore, it is desired to generate a disconnection alarm in real time but there is no appropriate alarm means.

(2) Although a simple method for monitoring a change in the DC potential of a lead wire and alarming a disconnection is well known, this method cannot be adopted because the voltage of each lead wire changes periodically.

  Therefore, the problem to be solved by the present invention is to realize a disconnection detecting device capable of detecting in real time a disconnection of a cable that transmits a measurement signal of a position sensor whose signal level periodically changes according to the movement of a measurement object. It is in.

In order to achieve such an object, the configuration of the present invention is as follows.
(1) In a disconnection detecting device for detecting disconnection with respect to a cable that transmits a measurement signal of a position sensor whose signal level periodically changes in accordance with movement of a measurement object,
Phase shift means for generating a reference signal by shifting the phase of the measurement signal;
Adding means for generating an addition signal obtained by adding the measurement signal and the reference signal;
A disconnection detecting means for comparing the sum signal with a threshold of a predetermined level and detecting disconnection according to a comparison result;
A disconnection detecting device comprising:

(2) The disconnection detecting device according to (1), wherein the phase shift means generates a reference signal obtained by shifting the phase of the measurement signal by 180 °.

(3) The disconnection detecting device according to (2), wherein the cable is normal when the addition signal becomes a predetermined constant level within the range of the threshold value. .

(4) The disconnection detecting means according to (2), wherein, when the addition signal periodically exceeds the threshold value range, at least one of the cables is disconnected. Detection device.

(5) Any one of (1) to (4), wherein the disconnection detection means generates a disconnection alarm signal of the cable when the addition signal first exceeds the threshold range. Disconnection detection apparatus as described in 2.

As is apparent from the above description, the present invention has the following effects.
(1) If even one cable consisting of multiple lead wires is disconnected, a disconnection alarm can be generated immediately, and measurement can be stopped and maintenance performed, contributing to improved device reliability. Can do.

(2) A disconnection alarm can be issued with a simple configuration in which a periodically changing measurement signal is phase-shifted and added to the original signal, and a disconnection detection device can be realized at low cost.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram showing an embodiment of a position measuring device incorporating a disconnection detecting device to which the present invention is applied. The same elements as those of the conventional apparatus described with reference to FIG. Hereinafter, the characteristic part of the present invention will be described.

  In FIG. 1, a dotted line block 100 is a break detection device to which the present invention is applied. In this disconnection detecting device, 101 is an 8-bit shift register similar to the shift register 13, which receives the count-up signal P2 of the counter 12 and transmits it via the leads L1 to L8 of the cable 3 described in FIG. The stepped voltage distribution signals e1 to e8 are sequentially switched in a time-division manner and output as reference signals Er.

  The count-up signal P2 is shifted in phase by 180 ° with respect to the count-up signal P1, and therefore the phase of the measurement signal E0 that is the output of the shift register 13 and the reference signal Er that is the output of the shift register 101 is 180. ° Shifted.

  Reference numeral 102 denotes an adding means that adds the measurement signal E0 output from the shift register 13 and the reference signal Er output from the shift register 101 to generate an addition signal Es. Reference numeral 103 denotes disconnection detecting means, and specifically, realized by window comparator means for setting a predetermined range of threshold values.

  The disconnection detection means 3 generates an alarm signal AL when the addition signal Es deviates from a predetermined threshold value Eh, and superimposes the alarm signal AL on the reference signal S1 by the multiplication means 104. Pass to 4.

  Hereinafter, an operation example of the disconnection detecting device of the present invention will be described with reference to FIGS. FIG. 2 is a comparison diagram between a normal waveform and a single broken waveform. FIG. 2A is a waveform diagram of the measurement signal E0 in a normal state. When the number of light receiving elements 25 is eight (n = 0 to 7), eight lead wires L0 to L7 are used. The detection signal obtained by the above becomes stepwise voltage distribution signals e0 to e7 corresponding to the scan numbers 0 to 8. FIG. 2B is a waveform diagram showing the voltage distribution signal of E0 when one lead wire L4 is disconnected, and the voltage e4 periodically becomes zero level (circuit reference potential).

  FIG. 3 is a waveform diagram of the reference signal and the addition signal when the measurement signal has a normal waveform without disconnection. As shown in FIG. 3A, if the measurement signal E0 is a normal waveform, the reference signal Er shown in FIG. 3B obtained by shifting the scan by 180 ° has a symmetrical waveform with E0.

  Therefore, as shown in FIG. 3C, the addition signal Es of E0 and Er has a constant DC level (4V in the drawing). Therefore, the alarm signal AL is not generated by setting the range of the threshold value Eh set in the disconnection detecting means 103 to 3.5V to 4.5V.

  FIG. 4 is a diagram for explaining the operation of the window comparator function of the disconnection detecting means 103. The range of the threshold value Eh is set to 3.5V to 4.5V in the power supply voltage range of 0V to 10V. The addition signal Es is normally designed to be 4V. An area where the addition signal Es is 3.5V or less and an area where the addition signal Es is 4.5V or more are determined to be errors, and a disconnection alarm is generated.

  FIG. 5 is a waveform diagram of the reference signal Er and the addition signal Es in the case of an abnormal waveform in which at least one disconnection exists in the measurement signal E0. In the measurement signal E0 shown in FIG. 5A, if e4 of the scan number 4 is an abnormal waveform having a zero level (circuit standard level 5V), the reference signal in FIG. Er has an asymmetric waveform with E0.

  Therefore, as shown in FIG. 5C, the addition signal Es of E0 and Er periodically becomes zero level (5V) for every scan number 4, and becomes constant DC level (4V) for other scan numbers. Become. Therefore, by setting the range of the threshold value Eh set in the disconnection detecting means 103 to 3.5 V to 4.5 V, the alarm signal AL can be generated at a timing that deviates from this threshold value range first. Real-time disconnection alarm can be realized.

  FIG. 6 is a waveform diagram of the reference signal and the addition signal when the lead wire of the power supply voltage + V (eg, +10 V) is disconnected. In the measurement signal E0 in FIG. 5A, the power supply voltage + V is clamped from the normal value 5V to 8V in the scan numbers 0 to 7 in each cycle. The same applies to the reference signal Er in FIG. 5B obtained by shifting the scan by 180 °.

  As shown in FIG. 5C, the addition signal Es of E0 and Er changes from the normal value 4V to 0V and deviates from the range of the threshold value Eh, so that the alarm signal AL can be generated.

  FIG. 7 is a waveform diagram of the reference signal and the addition signal when the ground (GND) lead wire is disconnected. In the measurement signal E0 of FIG. 7A, the ground level is clamped from the normal value 5V to 1.64V at the scan numbers 0 to 7 in each cycle. The same applies to the reference signal Er in FIG. 7B obtained by shifting the scan by 180 °.

  As shown in FIG. 7C, the addition signal Es of E0 and Er changes from the normal value 4V to 0V and deviates from the range of the threshold value Eh, so that the alarm signal AL can be generated.

  FIGS. 6 and 7 show examples of the lead wire disconnection alarm and the ground (GND) lead wire disconnection alarm of the power supply voltage + V (for example, +10 V) according to the method of the present invention. Since the level is a direct current and is not a periodically changing voltage, it is also possible to employ a conventionally known technique of disconnection alarm by simple level comparison.

It is a functional block diagram showing one embodiment of a position measuring device incorporating a disconnection detecting device to which the present invention is applied. It is a comparison figure of a normal waveform and a single disconnection waveform. It is a waveform diagram of a reference signal and an addition signal when the measurement signal is a normal waveform without disconnection. It is operation | movement explanatory drawing of the window comparator function of a disconnection detection means. It is a waveform diagram of a reference signal and an addition signal in the case of an abnormal waveform in which at least one disconnection occurs in a measurement signal. FIG. 6 is a waveform diagram of a reference signal and an addition signal when a power supply voltage lead wire is disconnected. FIG. 6 is a waveform diagram of a reference signal and an addition signal when a ground lead wire is disconnected. It is a functional block diagram which shows the structural example of the conventional position measuring apparatus. It is an image figure explaining the detail of a position sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Receiving device 11 Clock generation circuit 12 Counter 13 Shift register 14 Filter circuit 15 Reference signal generation circuit 16 Reset circuit 2 Position sensor 3 Cable 4 Host device 100 Disconnection detection device 101 Shift register 102 Addition means 103 Disconnection detection means 104 Multiplication means

Claims (5)

In a disconnection detecting device for detecting disconnection with respect to a cable for transmitting a measurement signal of a position sensor whose signal level periodically changes according to movement of a measurement object,
Phase shift means for generating a reference signal by shifting the phase of the measurement signal;
Adding means for generating an addition signal obtained by adding the measurement signal and the reference signal;
A disconnection detecting means for comparing the sum signal with a threshold of a predetermined level and detecting disconnection according to a comparison result;
A disconnection detecting device comprising:   The disconnection detection apparatus according to claim 1, wherein the phase shift unit generates a reference signal obtained by shifting the phase of the measurement signal by 180 °.   3. The disconnection detecting device according to claim 2, wherein the disconnection detecting means makes the cable normal when the addition signal becomes a predetermined constant level within the range of the threshold value.   The disconnection detection device according to claim 2, wherein the disconnection detection unit assumes that at least one of the cables is disconnected when the addition signal periodically exceeds the threshold range. The disconnection detection means according to any one of claims 1 to 4, wherein the disconnection detection means generates a disconnection alarm signal of the cable when the addition signal first exceeds the threshold range. apparatus.

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