JP5163963B2 - Abnormality monitoring device - Google Patents

Description

  The present invention relates to an abnormality monitoring device for detecting an abnormality in a pulse encoder (hereinafter also simply referred to as an encoder) or a wiring system and realizing a safety function in a power converter that drives an electric motor such as an inverter or a servo system. .

  Inverters and servo systems that calculate the motor speed and rotor position from the output signal of a pulse encoder attached to the output shaft of the motor and feed back the calculated values to drive the motor at a variable speed have become widespread. In these devices, if there is an abnormality in the output signal of the encoder, normal operation becomes difficult. Therefore, various methods for stopping operation by detecting an abnormality in the encoder or an abnormality in the wiring system have been proposed. .

For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2008-232978) uses the internal functions of a microprocessor for abnormality monitoring, thereby minimizing the number of parts and minimizing circuits, thereby reducing costs. A wiring abnormality detection device is disclosed.
In this conventional technique (referred to as the first conventional technique for convenience), first, an encoder output signal is input as an analog signal to the wiring abnormality detection device. Then, when the analog signal is A / D (analog / digital) converted, and the converted voltage level is a predetermined intermediate voltage level except for a transient state, incomplete contact or short circuit is caused in the signal system. An abnormality is detected by judging that it has occurred.
The circuit configuration and operation of this prior art will be described below with reference to FIG.

In FIG. 8, the wiring abnormality detection device 100 includes a microprocessor 120, a program memory 121, an AD converter 123, a constant voltage power supply circuit 130, a buffer amplifier 135, series resistors 131a and 131b, a filter capacitor 132a, 132b and pull-down resistors 134a and 134b. Reference numeral 122 denotes a memory in the microprocessor 120.
Reference numeral 110 denotes a rotary encoder for detecting a rotation angle of an electric motor (not shown). The encoder 110 outputs a rotation angle detection signal that outputs a two-phase (A phase, B phase) signal as a rotation angle detection signal. The circuit 115 includes sensor switches 111a and 111b as A-phase and B-phase signal output transistors, dropper diodes 112a, 112b, 113a, and 113b, and bleeder resistors 114a and 114b.

Furthermore, 101 is a DC power source, 102 is a power switch, 103 is a ground line, 104 is a power line, and 105 and 106 are signal lines.
A and B in the encoder 110 are output terminals for the A phase signal and the B phase signal, A1 and A2 in the wiring abnormality detection device 100 are analog input signals, and D1 and D2 in the microprocessor 120 are open / close logics of the sensor switches 111a and 111b. A signal, V _m , indicates a monitoring voltage.

  As an operation of the encoder 110, when the sensor switches 111a and 111b are turned on or off by an output signal of the rotation angle detection circuit 115, a voltage drop is generated by the action of the dropper diodes 112a, 112b, 113a and 113b and the bleeder resistors 114a and 114b. To do. By detecting the voltage due to this voltage drop from the output terminals A and B as the A-phase signal and the B-phase signal and inputting them to the wiring abnormality detection device 100 via the signal lines 105 and 106, the abnormality detection operation as described below is performed. I do.

FIG. 9 shows the characteristics of the A-phase and B-phase analog input signals A 1 and A 2 input to the wiring abnormality detection device 100. Hereinafter, the characteristics of the A-phase analog input signal A1 will be described, but the same operation is performed for the B-phase analog input signal A2.
When the sensor switch 111a is turned on, the voltage level V _{L in} FIG. 9 is detected due to the on-voltage drop of the dropper diode 112a. On the other hand, when the sensor switch 111a is turned off, the voltage level _VH is detected by the voltage drop of the bleeder resistor 114a and the dropper diode 113a. Actually, in consideration of variations in the characteristics of the dropper diodes 112a and 113a, the normal “L (Low)” level and the normal “H (High) are within a certain range centered on the voltage levels V _L and V _H , respectively. ) ”Level.
As described above, the presence or absence of a pulse for detecting the rotation angle is detected by determining whether the voltage level of the analog input signal is “L” level or “H” level.
At this time, for example, if the signal line 105 has a disconnection or a ground fault with the ground, the voltage drop component described above is not detected, and the analog input signal is fixed to the ground level. Can do.

Further, when the output terminal A of the encoder 110 is short-circuited with the positive power source _Vcc , the analog input signal is fixed at a voltage level higher than _VH, so that it can be detected that an abnormality has occurred in the same manner. Further, when incomplete contact between the positive power supply _Vcc and the ground or contact with another signal line occurs, the analog input signal is detected as the intermediate voltage level (logic determination level) V _s1 or V _{s2 in} FIG. Even if these intermediate voltage levels V _s1 or V _s2 continue for a certain period, it is also determined as abnormal.

When the sensor switch 111a is turned on / off, the voltage waveform of the A-phase analog input signal A1 is filtered by the low-pass filter including the series resistor 131a and the filter capacitor 132a. For this reason, depending on the sample timing, the intermediate voltage levels V _s1 and V _s2 are transiently detected even at the normal time, and as a result, there is a possibility that the abnormality is erroneously detected.
In order to prevent the above-described erroneous detection, in this prior art, detailed determination is executed when the intermediate voltage levels V _s1 and V _s2 are detected, and the intermediate voltage levels V _s1 and V _s2 are generated transiently. If it has continued for a certain period of time, it is determined that there is an abnormality due to the incomplete contact between the positive power source _Vcc and the ground or the contact with another signal line. doing.

As another prior art (referred to as the second prior art for convenience), two-phase signals (A-phase signal and B-phase signal having different phases) output from the encoder are A / D converted and then input to individual counters. There is a known method of counting the number of pulses for a certain period and detecting an abnormality based on the number of pulses.
For example, when the motor is rotating, the number of pulses corresponding to the rotation speed is measured as an A-phase signal and a B-phase signal, but the signal line of one phase is disconnected or is in contact with the power line or ground line. If this occurs, an error occurs in the number of pulses in each phase. Therefore, an abnormality can be detected by comparing the number of pulses of each phase. Further, by comparing the speed detection value corresponding to the number of pulses of each phase with the current speed command value or the like, it is possible to detect not only one phase but also simultaneous abnormality in two phases.

According to the first conventional technique, even when the motor is stopped, a wiring abnormality can be detected according to the voltage level of the analog signal input to the wiring abnormality detection device 100. However, during operation of the electric motor, it is difficult to determine the wiring abnormality, and even if the wiring is normal, it may be erroneously determined to be abnormal. The reason is as follows.
In general, an encoder determines the number of output signals per machine cycle (one rotation in the case of a rotary motor) of a rotating body such as an electric motor, and the interval between output signals becomes shorter at higher speeds. On the other hand, since an arithmetic processing unit such as a microprocessor normally performs arithmetic processing at a constant cycle, the interval between output signals from the encoder is often significantly shorter than the arithmetic cycle of the arithmetic processing unit.
At this time, if the sample timing by the AD converter on the arithmetic processing unit side coincides when the encoder output signal changes, the intermediate voltage level as described above is continuously detected, and the wiring system is normal. Nevertheless, it may be erroneously determined to be abnormal.

FIG. 10 is a timing chart showing the encoder output signal, the AD conversion sample timing, the power supply voltage V _c , the detected value of the voltage level of the analog input signal, and the ground level at the time of the erroneous determination described above.
As shown in the figure, when the AD conversion sample timing period is a specific multiple of the encoder output signal period, the detected value at each sample timing becomes equal, and the voltage level of the analog input signal is at the intermediate voltage level. There is a possibility of misidentifying that it is fixed (ie abnormal).
In order to prevent such misjudgment and increase the reliability of the apparatus, it is effective to use a high-speed AD converter with a short sample timing period, but a high-speed AD converter is generally expensive, There is a problem that the cost of the apparatus increases.

  On the other hand, in the second prior art, it is impossible to detect an abnormality when the motor is stopped because of the principle of detecting an abnormality based on the number of two-phase pulses. Accordingly, it is necessary to separately prepare an abnormality detection means when the motor is stopped, which causes an increase in cost.

In addition, by combining the first conventional technique and the second conventional technique, it is possible to configure an abnormality detection device that can handle both when the motor is operating and when it is stopped. On the other hand, abnormality detection is impossible.
(1) Case where the phase of the two-phase output signal of the encoder is abnormal.
For example, when the interval between two-phase output signals changes temporarily due to a partial short circuit of the signal line.
In this case, the abnormality can be detected only when the output signal of the encoder is generated by the operation of the electric motor, and it cannot be detected simply by comparing the number of pulses as in the second prior art. .
(2) The output signal oscillates due to noise or the like even though the number of two-phase pulses should be different due to abnormality, and happens to coincide with the number of two-phase pulses.
In addition to the above, since there may be no difference in the number of pulses due to other causes at the time of abnormality, in such a case, abnormality cannot be detected.

In view of the above points, the present applicant has already applied for the following abnormality monitoring apparatus as Japanese Patent Application No. 2009-49375.
The abnormality monitoring apparatus according to this prior application inputs an output signal of an encoder that detects the position of a rotating body such as an output shaft of an electric motor to the control apparatus as an analog signal, and detects an abnormality that occurs when the rotating body is stopped as a voltage level of the analog input signal. Detect based on. Further, when the rotating body rotates, a digital signal obtained by converting at least two-phase analog input signals is used to compare the difference in the number of pulses in each phase with a predetermined threshold value. Further, the abnormality is detected by monitoring the pulse width of the combined signal obtained by combining two or more digital signals having different phases or the pulse width of the digital signal of each phase.

The outline of the prior invention will be described below.
In FIG. 11, 10 is an encoder that outputs a two-phase analog signal that is 90 degrees out of phase, 20 is a cable composed of a power line, a signal line, and a ground line, and 310 is an encoder 10 error by processing the output signal of the encoder 10. And a control device that detects an abnormality in the wiring system including the cable 20.

The encoder 10 includes an optical sensor that generates two relative position detection signals (A-phase signal and B-phase signal) whose phases are different by 90 degrees due to rotation of a rotating body such as an electric motor output shaft. The phase signal is input to the bases of the complementary transistors Tr ₁ and Tr ₂ , respectively.
The collector of _one transistor Tr ₁ is connected to the power supply terminal V _c (the power supply voltage is also expressed as V _c ), and the collector of the other transistor Tr ₂ is connected to the ground terminal M. The connection point between the transistors Tr ₁ and Tr ₂ is connected to the A-phase signal terminal A and the B-phase signal terminal B via the limiting resistor R ₁ , respectively.

The power supply voltage V _c is supplied to the encoder 10 from the control device 310 via the cable 20, and the electric signal of each part of the encoder 10 is based on the potential common to the control device 310. The power supply circuit in the control device 310 is not shown.
Usually, in order to prevent the influence of noise, the encoder 10 and the control device 310 may be electrically insulated by a photocoupler or an insulation amplifier at the A phase signal terminal A, the B phase signal terminal B, etc. in FIG. Here, in order to simplify the description, the encoder 10 and the control device 310 are at the same potential.

Next, in the control device 310, a bias is generated between the power supply terminal V _c , the A-phase signal terminal A, and the ground terminal M, and between the power supply terminal V _c , the B-phase signal terminal B, and the ground terminal M. Voltage dividing resistors R _x and R _y are connected as means.
When the A-phase signal output from the encoder 10 is at “H” level (a state where the transistor Tr ₁ is on and the transistor Tr ₂ is off), the analog voltage of the A-phase signal terminal A detected by the control device 310 V _adet (corresponding to the voltage of the analog signal SigAana in FIG. 11) is expressed by Equation 1 when the on-voltage drop of the transistor Tr ₁ is ignored.

On the other hand, when the A-phase signal is at the “L” level (the transistor Tr ₁ is turned off and the transistor Tr ₂ is turned on), the analog voltage V _{adet at} the A-phase signal terminal A is the on-voltage drop of the transistor Tr _2. Is ignored, it is expressed by Equation 2.

That is, the failure to the encoder 10 is disconnected or short circuit in the cable 20 without the normal no land絡等, as shown in FIG. 12, as an analog voltage V _ADET, when the A-phase signal is "H" level, the power supply voltage V An analog high level (R _y · V _c / (R ₁ + R _y ) obtained by subtracting the bias from _c is detected, and when the A-phase signal is at the “L” level, an analog obtained by adding the bias to the ground voltage A low level (R ₁ · V _c / (R ₁ + R _x )) is detected.
Equations 1 and 2 are similarly established for the analog voltage at the B-phase signal terminal B.

In FIG. 11 again, the analog signal SigAana of the A phase signal terminal A and the analog signal SigBana of the B phase signal terminal B are input to the analog input units 331A and 331B in the microcomputer 311 which is an arithmetic processing unit in the control device 310, respectively. Is done. The output signals of the analog input units 331A and 331B are converted into digital signals by the AD conversion units 332A and 332B. Then, in the subsequent level abnormality detection units 333A and 333B to which these digital signals are input, an abnormality is detected by determining whether the analog high level or the analog low level is detected as an analog voltage. The
That is, in this prior application invention, the level abnormality detectors 333A and 333B detect the voltage level of the analog input signal, thereby detecting an abnormality when the rotating body is stopped (disconnection of the cable 20, the signal line and the power line). Short circuit, ground fault, etc.) can be detected, and even when the rotating body is rotating, it is possible to detect a short circuit between the signal line and the power supply line and a ground fault.

On the other hand, the digital signal processing means 31A and 31B in FIG. 11 are a kind of AD conversion means, and the A-phase and B-phase digital signals SigA and SigB input to the microcomputer 311 are generated by comparing the analog signal with a threshold value by a comparator or the like. To do.
These digital signals SigA and SigB are input to the pulse number comparison abnormality detection unit 336 via the digital input units 334A and 334B and the counters 335A and 335B in the microcomputer 311 to compare the number of pulses of the digital signals SigA and SigB. Thus, an abnormality is detected.

The digital signals SigA and SigB are input to digital input units 337A and 337B in the microcomputer 311, respectively. Timers 338A and 338B for measuring the width of the “H” level of the A-phase and B-phase digital signals SigA and SigB are connected to the output sides of the digital input units 337A and 337B, respectively, and the pulses are connected to the output sides of the timers 338A and 338B. A width comparison abnormality detection unit 340 is connected.
The pulse width comparison abnormality detection unit 340 compares the previous value of the timer value (the “H” level width of the digital signals SigA and SigB) with the current value for each of the A phase and the B phase, The timer value is compared with the B-phase timer value, and an abnormality is detected when the difference exceeds a predetermined threshold value.

Next, the abnormality detection operation during rotation of the rotating body, which is executed by the pulse number comparison abnormality detection unit 336 and the pulse width comparison abnormality detection unit 340, will be described in detail.
FIG. 13 is a timing chart showing the output signals of the digital signal processing means 31A and 31B and the output signals of the counters 335A and 335B and the timers 338A and 338B at the normal time.

Counter 335A of the A-phase counts the number rising edge of the digital signal SigA detected between the control cycle T _s, stores the count value in the internal memory in each control cycle T _s. FIG. 13 shows the previous count value CountA ₀ and the count value CountA ₁ measured during the current control period T _s . In this example, since the rising edge of the digital signal SigA is detected four times during the control period T _s , the count value is 4.
The counter 335B of B phase also counts the number of rising edges of the digital signal SigB detected between the control cycle T _s, stores the count value in the internal memory in each control cycle T _s. FIG. 13 shows the previous count value CountB ₀ and the count value CountB ₁ measured during the current control cycle T _s . In this example, the rising edge of the digital signal SigB is shown during the control cycle T _s. Since it was detected five times, the count value is 5.

The A-phase timer 338A starts the operation at the rising edge of the A-phase digital signal SigA and stores the timer value at the falling edge, thereby measuring the “H” level width of the A-phase digital signal SigA from this timer value. .
Similarly, the B-phase timer 338B starts the operation at the rising edge of the B-phase digital signal SigB and stores the timer value at the falling edge, so that the “H” level width of the B-phase digital signal SigB from this timer value. Measure. 13, T _A0 , T _A1 ,..., T _B0 , T _B1 ,... Indicate timer values (widths of the “H” level of the digital signals SigA and SigB).
The pulse width comparison abnormality detection unit 340 compares the previous value and the current value of the timer values of the A phase and the B phase, respectively, and determines that the previous value and the current value are normal in the example of FIG.

FIG. 14 is a timing chart when an abnormality occurs in the A-phase digital signal SigA. When the A-phase digital signal SigA is fixed at the “H” level because the A-phase signal line is short-circuited with the power supply line or the like, the difference between the count values CountA ₁ and CountB ₁ by the counters 335A and 335B is a predetermined threshold value. When it becomes larger than (for example, 2), it is judged as abnormal. Even when the A-phase digital signal SigA is fixed at the “L” level due to a cable break or ground fault, or when an abnormality occurs in the B-phase digital signal SigB, the abnormality can be detected by the same principle.

FIG. 15 is a timing chart when abnormality occurs in both the A-phase and B-phase digital signals SigA and SigB.
In this case, since the count values CountA ₁ and CountB ₁ are both 2, the pulse number comparison abnormality detection unit 336 cannot detect the abnormality. Therefore, in this case, the previous value and the current value of the timer values of the A phase and the B phase are respectively compared.
That is, in FIG. 15, the “H” level widths (ie, timer values) T _A1 and T _B1 of the digital signals SigA and SigB immediately before the occurrence of an abnormality are measured for both the A phase and the B phase. Since the falling edges of the digital signals SigA and SigB for storing the values do not appear, the timer values are added to both the A phase and the B phase after the abnormality occurs. Therefore, if the timer values T _A1 and T _B1 that are currently being added for the A phase and the B phase at a predetermined timing are compared with the previous timer values T _A0 and T _B0 , respectively, between T _A1 and T _A0 , T _B1 Since there is a large difference between T _B0 and T _B0 , it is detected that an abnormality has occurred in both the A-phase and B-phase digital signals SigA and SigB when these differences exceed a predetermined threshold.

FIG. 16 is a timing chart when an abnormality occurs in the phase of the A-phase digital signal SigA. Such a phase abnormality is caused by a partial short circuit with the B phase side, a failure of the transistors Tr ₁ and Tr ₂ in the encoder 10, or the like.
In this case, the number of pulses of the A-phase and B-phase digital signals SigA and SigB does not differ by more than a threshold value (for example, 2), but between the abnormal A-phase timer value and the normal B-phase timer value, That is, there are differences between T _Aerr1 and T _B1 and between T _Aerr2 and T _B2 . Further, for example, a difference also occurs between the current timer value T _Aerr1 of the A-phase digital signal SigA and the previous timer value T _A1 .
Therefore, in the pulse width comparison abnormality detection unit 340, the difference between the timer values T _Aerr1 and T _B1 , the difference between the timer values T _Aerr2 and T _B2 , or the difference between the timer values T _Aerr1 and T _A1 is less than a predetermined threshold value. By detecting the large value, the abnormality of the A-phase digital signal SigA is detected.

JP 2008-232978 A (paragraphs [0010] to [0017], FIG. 1, FIG. 2, etc.)

In the prior application invention shown in FIG. 11, it is assumed that the encoder 10 is a complementary type composed of transistors Tr ₁ and Tr ₂ , and is compatible with a differential output type (line driver type) encoder. Absent. Here, the line driver format, per phase, signal A and the inverted signal A ^- outputting a set of differential signal formed from the differential signal A at these received receiver side, A ^- the reference potential By converting to a logic level adapted to the above, there is an advantage that it is possible to construct a system that is not easily affected by fluctuations in the common mode potential and is resistant to noise.

However, if a line driver type encoder is applied as it is to the control device 310 of the prior invention, the following problems occur.
(1) Since the encoder output signal is a differential signal, double AD conversion units are required per phase, and if the number of channels such as a microcomputer is insufficient, additional AD conversion units must be added. Equipment space and cost increase.
(2) As a countermeasure of the above (1), when the number of AD conversion units is reduced by AD converting the output signal of the line receiver after conversion to a logic level that matches the reference potential, two per phase. An abnormality cannot be detected when only one of the two differential signal lines is disconnected. As described above, the intermediate voltage level is detected at the time of disconnection, but is fixed to either the high level or the low level according to the threshold level of the differential signal of the line receiver. It is because it will do.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an abnormality monitoring apparatus that can detect an abnormality with high accuracy without causing an increase in space and cost even when a line driver type encoder is used.

In order to achieve the above object, an abnormality monitoring device according to claim 1 is an output signal of an encoder that detects the position of a rotating body, and a plurality of signals having different phases are arranged in a wiring system including a power supply line and a signal line. Each of which is input to the control device as a set of differential signals, and the control device processes the differential signals to detect an abnormality in the encoder or the wiring system.
The controller is
A first abnormality for converting a plurality of sets of the differential signals into digital signals based on the ground potential of the control device and detecting an abnormality in the encoder or the wiring system based on the number of pulses of these digital signals Detection means;
Second anomaly detection means for detecting an anomaly in the encoder or wiring system based on a plurality of pulse widths of the digital signals;
At least one set of differential signals is converted into an analog signal of a predetermined level by a level measuring means, and the voltage level of the analog signal is detected from a digital signal obtained by converting the analog signal to detect an abnormality in the encoder or the wiring system. A third abnormality detecting means for detecting ,
The third abnormality detection means includes
As the level measuring means, a dual power supply type analog calculation means to which the differential signal is input, or an analog calculation means to which the differential signal is input and which is a single power supply method, and an offset voltage is superimposed. Prepared,
An abnormality of the encoder or the wiring system is detected when the voltage level of the analog signal output from these analog calculation means is outside the normal range on the positive side or outside the normal range on the negative side .

The abnormality monitoring device according to claim 2 is the abnormality monitoring device according to claim 1, wherein when the rotating body rotates, the abnormality is detected by the first or second abnormality detecting means, and when the rotating body is stopped, An abnormality is detected by the third abnormality detection means .

According to the present invention, even when a line driver type encoder is used, the third abnormality detection means converts a set of differential signals into analog signals of a predetermined level by the level measurement means, and based on the voltage level. Thus, it is possible to detect an abnormality in the encoder itself or the wiring system when the rotating body is stopped. Further, when the rotating body rotates, the first or second abnormality detecting means can detect an abnormality based on the digital signal obtained by converting the analog signal.
In particular, according to the present invention, since an AD conversion unit is not required to be added, there is no possibility of increasing the space and cost of the apparatus, and it is possible to detect only one of the two differential signal signal lines, thereby detecting abnormality. Can be improved.

It is a circuit diagram showing an embodiment of the present invention. It is the circuit diagram and operation | movement explanatory drawing which show the modification of the level measurement means in FIG. It is operation | movement explanatory drawing at the time of normal of embodiment. It is operation | movement explanatory drawing at the time of abnormality of embodiment. It is operation | movement explanatory drawing at the time of abnormality of embodiment. It is operation | movement explanatory drawing at the time of abnormality of embodiment. It is a flowchart which shows the abnormality detection operation | movement of embodiment. It is a circuit diagram of a wiring abnormality detection device according to the first prior art. FIG. 9 is a characteristic diagram of an analog input signal of the wiring abnormality detection device in FIG. 8. It is a timing chart for demonstrating the problem of a 1st prior art. It is a block diagram which shows the structure of prior invention. It is explanatory drawing of the analog voltage level at the time of normal of prior invention. It is a timing chart which shows the operation | movement at the time of normal of prior invention. It is a timing chart which shows the operation | movement at the time of abnormality of prior invention. It is a timing chart which shows the operation | movement at the time of abnormality of prior invention. It is a timing chart which shows the operation | movement at the time of abnormality of prior invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit diagram showing an embodiment of the present invention. In this embodiment, the configuration of the microcomputer 311 in the control device 350 is the same as that of the prior application invention of FIG. 11, and the difference is that the A-phase and B-phase digital signals SigA and SigB and the A-phase and B-phase input to the microcomputer 311 are different. Since this is a means for generating the phase analog signals SigAana and SigBana, this point will be mainly described below.

In FIG. 1, reference numeral 11 denotes a line driver type encoder, which outputs an A-phase input signal and a B-phase input signal that are 90 degrees out of phase from an optical encoder 12 provided on an output shaft of a motor or the like. These signals A phase, B phase line drivers 13A, for input to 13B, a pair of differential signals A, respectively, A ^- and B, B ^- are produced. In FIG. 1, the inverted signals A ⁻ and B ⁻ are indicated by adding “−” on the symbols A and B, respectively.
The differential signals A, A ⁻ and B, B ⁻ are input to the control device 350 via the cable 21.

In the control device 350, the differential signals A, A ⁻ and B, B ⁻ are divided by the voltage dividing resistors R _x , respectively connected between the power supply terminal V _c (the power supply voltage is also expressed as V _c ) and the ground M. The signal is input to the A-phase line receiver 351A and the B-phase line receiver 351B via a connection point between _Ry .
The line receivers 351A and 351B convert the A-phase and B-phase input signals into A-phase and B-phase digital signals SigA and SigB, and these digital signals are input to the digital input units 334A, 337A, 334B, and 337B in the microcomputer 311. Is done. The processing after these digital input units 334A, 337A, 334B, and 337B is the same as that of the prior application invention of FIG. 11, and the abnormality in rotation of the rotating body is detected by the pulse number comparison abnormality detection unit 336 and the pulse width comparison abnormality detection unit 340. Is detected.

On the other hand, differential signals A, A ^- and B, B ^- are positive and negative power supply (power supply voltage _V c, and -V _c) positive A-phase operational amplifier 352A and the B-phase operational amplifier 352B as an analog operation means for system Input to the input terminal and negative input terminal respectively. Note that the operational amplifiers 352A and 352B have an amplification resistor and a feedback resistor, and the amplification ratio is determined by these, but for simplicity of explanation, the illustration of the resistor is omitted here, and the operational amplifiers 352A and 352B are This will be described as a differential amplifier circuit with a gain of 1.

The analog output signals of the operational amplifiers 352A and 352B are input to the voltage level conversion means 353A and 353B, respectively. Voltage level conversion unit 353A, 353B includes an operational amplifier 352A, while adding about 1/2 of the voltage of the pre-supply voltage _{V c} to the analog output signal 352B, converts the amplified ratio so as not to exceed the power supply voltage _{V c} It has a function of adjusting the input voltage level to the AD conversion units 332A and 332B in the microcomputer 311. This is because the AD conversion units 332A and 332B built in the microcomputer 311 cannot handle voltages having positive and negative polarities.
Here, the operational amplifier 352A and the voltage level conversion means 353A constitute an A phase level measurement means 341A, and the operational amplifier 352B and the voltage level conversion means 353B constitute a B phase level measurement means 341B.

In FIG. 1, line receivers 351A and 351B, digital input units 334A and 334B, counters 335A and 335B, and pulse number comparison abnormality detection unit 336 constitute first abnormality detection means in the claims.
The line receivers 351A and 351B, the digital input units 337A and 337B, the timers 338A and 338B, and the pulse width comparison abnormality detection unit 340 constitute second abnormality detection means in the claims.
Further, the level measuring means 341A, 341B, the analog input units 331A, 331B, the AD conversion units 332A, 332B, and the level abnormality detection units 333A, 333B constitute third abnormality detection means in the claims.

The level measuring means 341A and 341B including the operational amplifiers 352A and 352B and the voltage level converting means 353A and 353B can be configured by a circuit as shown in FIG.
That is, for example, will be described A phase, (the _{V d} the power supply voltage) op amp single power supply method 352A1 and the may be used in combination the offset voltage _{V off.} This case, omission high positive supply voltage _{V d} than _{V c,} the negative power supply by using two voltage levels: (about 1/2 of example _{V d)} an offset voltage _{V off V} lower than _d It is possible to perform the same operation as the level measuring means 341A of FIG.
Figure 2 (b) ~ (e), the differential signals A, A ^- Logical shows the A-phase analogue signal SigAana corresponding to a predetermined voltage level as in the case of using an operational amplifier dual supply system It can be detected.
Although not shown, the analog signal SigBana can be obtained for the B phase using a single power supply type operational amplifier and an offset voltage similar to those shown in FIG.

Next, an abnormality detection operation when the rotating body is stopped using the A-phase and B-phase analog signals SigAana and SigBana will be described. Hereinafter, the A phase will be described, but the operation is the same for the B phase.
First, FIG. 3 is a diagram for describing the operation of the normal, 3 (a) shows the circuit from the line driver 13A to the operational amplifier 352A, FIG. 3 (b) shows the level of the output signal _{Y A} of the operational amplifier 352A Yes. Incidentally, the A-phase input signal input from the optical encoder 12 in FIG. 1 the line driver 13A and X _A.

Line driver 13A is constituted by a combination of semiconductor devices such as FET, the level of the differential signal A power supply voltage V _c when the A phase input signal X _A is at "H" level, the differential signal A ^- is ground level of the terminal M (ground potential) and, a phase input signal X _a is "L" level differential signal a is level ground terminal M in the case of the differential signal a ^- the level of the supply voltage V _c Become. Further, due to the on-voltage drop and wiring resistance of the cable of the semiconductor device, the output voltage decreases when the A phase input signal X _A is at "H" level, the A-phase input signal X _A is "L" level In this case, the output voltage increases.

Now, assuming that the error voltage due to the on-voltage drop of the semiconductor element and the wiring resistance of the cable is V ₀ and this error voltage is generated in both the differential signals A and A ⁻ , the A-phase input signal X _A is “H”. The input signals V _A and V _A ⁻ of the operational amplifier 352A at the “level” are as shown in Equation 3.
In the in the specification text, the inverted signal of the V _A V _A ^- is expressed as, in the FIG. 3 below, on the code V _A - it is represented the inverted signal denoted by "."
[Equation 3]
V _A = V _c −V ₀
V _A ⁻ = M + V ₀
(M represents ground potential)
Therefore, the output signal _{Y A} of the operational amplifier 352A becomes Equation 4.
[Equation 4]
Y _A = V _A −V _A ⁻ = V _c −2V ₀

Further, the input signals V _A and V _A ⁻ of the operational amplifier 352A when the A-phase input signal X _A is at the “L” level is expressed by Equation 5.
[Equation 5]
V _A = M + V ₀
V _A ⁻ = V _c −V ₀
Therefore, the output signal _{Y A} of the operational amplifier 352A becomes Equation 6.
[Equation 6]
Y _A = V _A −V _A ⁻ = −V _c + 2V ₀

Then, Figure 4, the differential signal A, A ^- in the circuit diagram in the case where both of the cable 21 is disconnected in (FIG. 4 (a)) and a diagram of the levels of the output signal _{Y A} (FIG. 4 (b)) is there. At this time, regardless of the logic of the A phase input signal X _A, the input signal V _A of the operational amplifier _352A, V _A ^- is a divided value by both dividing resistor power supply voltage V _c as in Equation 7 Become.
[Equation 7]
V _A = V _A ⁻ = V _c · R _y / (R _x + R _y )
_Thus, V _A -V A ^- = 0, and the output signal _{Y A} of the operational amplifier 352A becomes ground potential M as shown in Figure 4 (b).
Therefore, since the level of the output signal Y _A is different from the normal of Fig. 3, it detects an abnormal level abnormality detection unit 333A of FIG. 1, and outputs an abnormality detection signal to the outside.
Since the case where the power supply line and a ground line connected to the encoder 11 is broken is not supplied power to the encoder 11, the output signal Y _A is also ground potential M next to the operational amplifier 352A, level abnormality detection unit 333A is abnormal Can be detected.

Next, FIG. 5 is a circuit diagram of a case where the cable 21 of the differential signal A-side is broken (FIG. 5 (a)) and a diagram of the levels of the output signal Y _A (Figure 5 (b)). In this case, the output signal Y _A of the operational amplifier 352A according to the logic level of the A phase input signal X _A are different levels.
That is, when the A phase input signal _{X A} is at the "H" level, the input signal _V A of the operational amplifier 352A, _{V A} ^- becomes Equation 8.
[Equation 8]
V _A = V _c · R _y / (R _x + R _y )
V _A ⁻ = M + V ₀
Therefore, the output signal _{Y A} of the operational amplifier 352A becomes Equation 9.
[Equation 9]
^{_{Y A = V A -V A -}} = V c · R y / (R x + R y) -V 0
In the case of R _x = R _y , Equation 9 becomes (V _c / 2) −V ₀ , and as shown in FIG. 5 (b), V ₀ is _calculated from the level of the broken line between M and V _c. Reduced voltage.

Also, when the A phase input signal X _A is at "L" level becomes the reverse, an output signal Y _A of the operational amplifier 352A becomes Equation 10.
[Equation 10]
^{_{Y A = V A -V A -}} = V 0 -V c · R y / (R x + R y)
In the case of R _x = R _y , Equation 10 becomes − (V _c / 2) + V ₀ , and as shown in FIG. 5B, the level of the broken line V is between V and M and −V _{c. The} voltage is _zero .

Therefore, A-phase input signal X _A is "H" level, if any of the "L" level, the output signal Y _A of the operational amplifier 352A is to become a different level than the normal of Fig. 3, detects an abnormality be able to.
Incidentally, the differential signals A ^- the case where the side of the cable 21 is disconnected, and only between the logical and formulas 9 and 10 of the A phase input signal X _A is reversed, can be similarly detected abnormal is there.

Figure 6 is a circuit diagram of a case where the cable 21 of the differential signal A-side is short-circuited to the power supply line (FIG. 6 (a)) and a diagram of the levels of the output signal Y _A (Figure 6 (b)).
In this case, when the A phase input signal _{X A} is at the "H" level, the input signal _V A of the operational amplifier 352A, _{V A} ^- it becomes Equation 11.
[Equation 11]
V _A = V _c
V _A ⁻ = M + V ₀
Therefore, the output signal _{Y A} of the operational amplifier 352A becomes Equation 12.
[Equation 12]
Y _A = V _A −V _A ⁻ = V _c −V ₀
In this case, as is apparent from a comparison of FIG. 6 (b) and FIG. 3 (b), the level of the output signal Y _A than that in the normal differ by V _0. Thus, if taking steps, such that V ₀ is a resistor on the output side of the line driver 13A such that a sufficiently large value, reliably distinguish between abnormal and normal by short-circuiting between the power supply line be able to. Further, when it is difficult to distinguish between normal and abnormal when V ₀ is small, it is supplemented by the detection results by the pulse number comparison abnormality detection unit 336 and the pulse width comparison abnormality detection unit 340 that detect abnormality during rotation. Also good.

On the other hand, when the A phase input signal _{X A} is at "L" level, the input signal _V A of the operational amplifier 352A, _{V A} ^- it is the formula 13.
[Equation 13]
V _A = V _c
V _A ⁻ = V _c −V ₀
Therefore, the output signal _{Y A} of the operational amplifier 352A becomes Equation 14.
[Formula 14]
Y _A = V _A −V _A ⁻ = V ₀
Therefore, as with the A phase input signal X _A is at "H" level, it is possible to distinguish between normal.
Incidentally, the differential signals A ^- If end of the cable 21 is short-circuited to the power line, between the logical and formulas 12 and 14 of the A phase input signal X _A is reversed, also, the differential signal A-side of the cable 21 Is short-circuited to the ground line, _VA in Equations 11 and 13 only becomes the ground potential, and thus an abnormality can be similarly detected.

FIG. 7 is a flowchart showing an abnormality detection operation in the present embodiment.
First, it is determined whether the rotating body is rotating or stopped. If the rotating body is rotating, the pulse number comparison abnormality detection unit 336 and the pulse width comparison are performed using the digital SigA and SigB output from the line receivers 351A and 351B of FIG. An abnormality is detected by the abnormality detection unit 340 (step S1 No, step S7).

If the operation is stopped, an abnormality is determined using the A-phase and B-phase analog signals SigAana and SigBana based on the output signal Y _A of the operational amplifier 352A (and the output signal Y _{B of the} operational amplifier 352B) (step S1Yes, step S2). ).
That is, for example, the output signal _{Y A} based on the A-phase analogue signal SigAana the scope of the value obtained by adding a margin of detection error in FIG. 3 (b) to the normal shown positive voltage level _(V c -2V _{0) (} If it is determined that it is out of the range (step S3 Yes), the range of the value obtained by adding a detection error margin to the normal negative voltage level (−V _c + 2V ₀ ) (Negative normal range) is compared (step S4). Here, the margin value may be determined in consideration of an AD conversion error, an offset voltage of the operational amplifiers 352A and 352B, and the like.
If the negative side is also outside the normal range (step S4 Yes), it is determined that there is an abnormality and an abnormality detection signal (alarm) is generated (step S5). If the positive side or the negative side is within the normal range (step S3 No, step S4 No), it is sufficient to drive the rotating body such as an electric motor by determining that there is no abnormality in the normal mode processing, that is, the encoder and the wiring system.

  As described above in detail, according to the present embodiment, even in a system using the line driver type encoder 11, disconnection, short circuit, ground fault in the encoder or in the wiring system can be detected without adding an AD converter. can do.

  INDUSTRIAL APPLICABILITY The present invention can be used not only for an electric motor but also for monitoring an abnormality of an encoder for detecting the rotational speed and position (angle) of various rotating bodies and its wiring system.

11: Line driver type encoder 12: Optical encoder 13A, 13B: Line driver 21: Cable 311: Microcomputer 331A, 331B: Analog input unit 332A, 332B: AD conversion unit 333A, 333B: Level abnormality detection unit 334A, 334B, 337A , 337B: Digital input unit 335A, 335B: Counter 336: Pulse number comparison abnormality detection unit 338A, 338B: Timer 340: Pulse width comparison abnormality detection unit 341A, 341B: Level measurement means 350: Controller 351A, 351B: Line receiver 352A , 352B, 352A1: operational amplifiers 353A, 353B: voltage level conversion means R _x , R _y : voltage dividing resistors

Claims (2)

A plurality of signals with different phases, which are output signals of an encoder that detects the position of the rotating body, are input to the control device as a pair of differential signals via a wiring system including a power supply line and a signal line, and this control is performed. In the abnormality monitoring apparatus, in which the apparatus detects the abnormality of the encoder or the wiring system by processing the differential signal,
The controller is
A first abnormality for converting a plurality of sets of the differential signals into digital signals based on the ground potential of the control device and detecting an abnormality in the encoder or the wiring system based on the number of pulses of these digital signals Detection means;
Second anomaly detection means for detecting an anomaly in the encoder or wiring system based on a plurality of pulse widths of the digital signals;
At least one set of differential signals is converted into an analog signal of a predetermined level by a level measuring means, and the voltage level of the analog signal is detected from a digital signal obtained by converting the analog signal to detect an abnormality in the encoder or the wiring system. Third abnormality detecting means for detecting;
Equipped with a,
The third abnormality detection means includes
As the level measuring means, a dual power supply type analog calculation means to which the differential signal is input, or an analog calculation means to which the differential signal is input and which is a single power supply method, and an offset voltage is superimposed. Prepared,
An abnormality monitoring device for detecting an abnormality in the encoder or the wiring system when the voltage level of the analog signal output from these analog operation means is outside the normal range on the positive side or outside the normal range on the negative side . In the abnormality monitoring device according to claim 1,
An abnormality monitoring apparatus , wherein an abnormality is detected by the first or second abnormality detecting means when the rotating body is rotating, and an abnormality is detected by a third abnormality detecting means when the rotating body is stopped .

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