JPS63284414A - Servo device with encoder open-phase detecting circuit - Google Patents

Abstract

PURPOSE:To take a corresponding countermeasure speedily by detecting the open phase of a pair of signals in an incremental two-phase encoder when the signals are in the open-phase state and deciding abnormality. CONSTITUTION:The 90 deg. out-of-phase A-phase and B-phase outputs 2 and 3 of the incremental two-phase encoder 1 are supplied to a processing circuit 4, which generates pulses by a part 5 at the leading-edge and trailing-edge parts of the A-phase and B-phase pulses 2 and 3, multiply the pulses by two, and send the signals to an open-phase detecting circuit 20. When the pulse 2 enters the open-phase state and is held at a high potential, a clear pulse input for the counter of the A-phase monitor circuit 21 misses, B-phase doubled pulses are counted successively, and an output appears at a terminal 26, so that the output 34 of the circuit 20 becomes an 'H' signal indicating the open- phase state. Further, when the B-phase is open, the output 34 rises to 'H' by the similar function of a B-phase monitor circuit 27.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a servo device with an encoder open-phase detection circuit used, for example, for controlling a servo motor for FA, and more specifically, for rotational and linear motion, Velocity in two directions of forward and reverse movement
This invention relates to a servo device with an encoder open-phase detection circuit that can detect open-phase in one direction when using a two-phase encoder for position detection and improve operational safety of the device.

[Conventional technology]

Traditionally, encoders have been used for both forward and reverse motion, such as rotation and linear motion.
It is often used as a speed and position detector in the direction of motion.

Based on optical or magnetic principles, these encoders are configured to generate electrical pulses in response to angles and positions.In particular, incremental encoders are 2-bit encoders. A phase to generate two-phase pulses.

B phase is formed, and in addition to detecting forward and reverse rotation, the number of pulses is 2.
It is generally widely used because it can double or quadruple it and improve the resolution of the detector. An example of its application is a digitally controlled servo motor using a microcomputer. The rotational position of the motor is detected by forming four times the number of clock pulses from the two-phase output pulses of the encoder (hereinafter referred to as fine counting). ), this is counted by an 8-bit counter, and the direction of one rotation is determined from the phase relationship (lead phase, slow phase) of the two-phase outputs that are electrically 90 degrees apart, and in the case of forward rotation, a fine count is used. A frequently used method is to constantly detect the current position using an up/down counter that adds up and subtracts in the case of reversal. The specific control circuit is 4 bits, 8 bits, or 1 bit.
It is mainly composed of a 6-bit microcomputer, etc.
Many parts are covered by software, but peripheral parts that require processing speed are covered by various TTL digital ICs.
There are many examples where it is constructed by

Note that prior art related to motor control includes, for example, (1) “
Mechatronics 1: Cutting-edge control motors” No. 154
Pages - No. 157, February 27, 1984, Published by Gijutsu Kenkyukai Co., Ltd. (2) "The driving force of mechatronics" 83
"Small Motor Technology Symposium" (Date: February 1982)
Monthly 22nd to February 25th) Document cylinder pages 6-3-1 to 6-3
-8 pages, published by the Japan Management Association (3) "Continued: Utilization of control motors", pages 66 to 74, March 1, 1938, published by Taiga Publishing Co., Ltd. (4) rDC motors "Control Circuit Design", pages 141 to 160, May 20, 1985, published by CQ Publishing Co., Ltd.

[Problem that the invention seeks to solve]

By the way, conventionally, when the entire pulse signal from the encoder is abnormally lost (for example, due to abnormal axis locking or disconnection of the circuit), this is detected as a lack of response to the command.
Activating the protection circuit has already been done.

However, one of the two phase pulses is missing, so-called "
Regarding "open phase", it is difficult to distinguish it from normal operation.
No inexpensive and effective detection method has been found, and in the case of an open phase, erroneous signals are generated for the entire speed, position, and direction of rotation, which adversely affects the reliability and safety of the system.

The present invention was made as a result of various studies in order to solve the problems of the prior art described above, and its purpose is to solve the problems of the prior art described above. It is an object of the present invention to provide a servo device with an encoder open-phase detection circuit that can quickly detect this open-phase, determine an abnormality, and take immediate measures such as an emergency stop. [Means for solving the problem] In order to achieve the above object, a servo device with an encoder open phase detection circuit according to the present invention has an incremental two-phase encoder for detecting two forward and reverse motion directions, and The present invention is characterized by having means for mutually monitoring and detecting open phase by using corresponding signals created from the generated signals of each phase, with one input being used as a clear input and the other input being used as a count input.

[Effect]

In the above configuration, when the device is in normal operation, pulses corresponding to each phase are generated alternately, and only when the movement direction is switched, two pulses of the same phase are generated consecutively.

If any phase is open, pulses of this phase will not be generated, and only pulses of the remaining normal phases will be generated. That is, in the event of an abnormality due to one phase loss, a clear pulse is not input, so three or more pulses of the same phase continue. Therefore, this time is detected as the time when an abnormality occurs, and which phase is open is also detected.

〔Example〕

Hereinafter, the present invention will be explained based on an embodiment shown in Figs. 1 to 4. Fig. 1 is an electric circuit diagram of a servo device with an encoder open phase detection circuit, and Figs. 2 to 4 are all electrical circuit diagrams. 2 is a diagram of various signal waveforms of the servo device shown in FIG. 1. FIG.

In Figure 1, 1 is an incremental two-phase encoder, and the A-phase and B-phase outputs of 2 and 3 each output digital pulses with an electrical phase difference of 90 degrees, as shown in Figure 2. . Reference numeral 4 designates a conventional processing circuit that processes the outputs 2 and 3 of the encoder 1 to determine the creation of a fine count and the rotation direction.

In the processing circuit 4, the doubling circuit 5 for each phase pulse is D
It is composed of a type flip-flop 6 and exclusive ORs 7 and 8, and as shown by reference numeral 9.10 in FIG. Double the amount.

Reference numeral 11 denotes a pulse quadrupling circuit, which uses a data selector/multiplexer 12 to output pulse signals 9 and 10 from an exclusive OR 13.

Selectively invert output to outputs 14 and 15. The waveform is
As shown in Fig. 2 with reference numerals 16, 14, and 15, when the rotation is reversed from normal rotation, the electrical phase relationship between the A phase and B phase becomes second.
It is determined by the output 16 that the rotation is reversed after time t1 in the figure, and this is reflected in the outputs 14 and 15.
As shown at 8, it is output as a rotation direction display signal.

Further, the outputs 14 and 15 operate the up/down counter 19, grasp the current position, and implement various controls in collaboration with related circuits (not shown). and.

The gist of the present invention is to perform open phase detection by adding an open phase detection circuit shown by the reference numeral 20 in FIG. 1 to the conventional processing circuit 4 as described above.

In the open phase detection circuit 20, 21 is an A phase monitoring circuit;
2 is a 4-bit binary counter.

The B-phase doubled pulse 10 is input as a count pulse via the logical sum 23. And A phase 2 to be monitored
Doubling pulse 9 is input as a clear pulse. During normal operation of the device, the output states of the QA, Qa, and Qc terminals 24, 25, and 26, which are the 2° 21.2z outputs of the counter 22, are as shown by the same symbols in FIG. It does not appear.

27 is a B-phase monitoring circuit configured similarly to the A-phase monitoring circuit 21, and the B-phase monitoring circuit 27 includes a counter 28, a logical sum 2
9. It has terminals 30, 31, and 32. However, in contrast to the counter 22 of the A-phase monitoring circuit 21, the inputs of the counter 28 of the B-phase monitoring circuit 27 are exchanged. When the device is operating normally, the counter 28 is 2o and 2t.
, 2z outputs QA , Qa , Qc terminals 30,3
The output state of 1.32 is as shown by the same reference numerals in FIG.

FIG. 3 shows the operating waveforms of each part of the device when the A-phase output 2 has an open phase at time tz and continues to be at a high potential.

At time tz in FIG. 3, the A-phase output 2 has an open phase and if the high potential continues, the output of the A-phase doubled pulse 9 is absent and the other outputs 16°14.15.18 It can be seen that an abnormality has also occurred. Then, the A phase monitoring circuit 2
Since the pulse 9 which is the clear pulse input to the counter 22 of No. 1, that is, the output of the A-phase doubling pulse 9, is missing, the B-phase doubling pulse 10 is sequentially counted.

Finally, one terminal 22, Q terminal 2, which is the output terminal.
The output appears at 6. That is, the pulse count reaches 4, and as a result, the count pulse input of the counter 22 is held at a high potential via the logical sum 23, and subsequent pulse counts are not performed.

Output 34 is held at a high level indicating an open phase.

Incidentally, in the B-phase monitoring i-path 27, there is no count pulse failure due to the A-phase open phase, and all signals are at a low level.

Even if the phase A is not kept at a high level but continues to be at a low level resulting in a phase failure, basically the counter 22 of the monitoring circuit 21 exceeds the normal count limit of 2 and reaches 3, as described above. , 4, and the output 34 is set to a high level to detect an open phase.

Further, FIG. 4 shows the operating waveforms of each part of the device when the B phase is out of phase.

However, at time t8 in FIG. 4, if the B-phase output 3 has an open phase and continues to be at a high level.

The counter 28 of the B-phase monitoring circuit 27 counts 3 and 4, exceeding the normal limit count number 2, and sets the output 34 to a high level to detect an open phase. Even when the phase continues to be at a low level, resulting in an open phase, open phase detection is performed in the same manner as described above.

In the embodiment shown in FIG. 1, each counter 22 and 28 of the detection circuit 20 outputs a 22-bit Qc terminal 26 . Alternatively, the case where open phase detection is performed using count number 4 of 32 has been exemplified;
Count number 3 when both Q@terminals 24 and 25 are at high level. Alternatively, an open phase can be detected when both terminals 30 and 31 are at a high level at a count of 3.

In addition, if we consider the condition discrimination between forward and reverse commands, and exclude the transient period, phase loss can be detected using the output of the 21-bit qa terminal 25 or terminal 31 one count earlier. You can also do that.

On the other hand, if the count amount of the counters 22 and 28 is expanded without using the logical sum 23.29 at the count pulse input section of the counters 22 and 28, it is possible to calculate how much period (time) the phase is lost. It can also be counted and used effectively as various control information.

On the other hand, a shift register may be used instead of the counters 22 and 28.

Furthermore, in the present invention, as shown in FIG. 1, the use is not limited to the case where a fine count quadrupled pulse is used, but simply the rise of a pulse of one phase among two phases.

Alternatively, you can use the falling edge.
Explaining based on FIGS. 5 and 6, FIG. 5 is an electric circuit diagram showing another embodiment of the servo device according to the present invention, and FIG. 6 is a diagram of various signal waveforms of the servo device shown in FIG. It is.

In FIG. 5, 40 is a forward rotation pulse 41° and a reverse rotation pulse 4 using the A phase output 2 and B phase output 3 of the encoder 1.
This is an up/down pulse generation circuit that generates 2. The up/down pulse generation circuit 40 is composed of monostable multivibrators 43 and 44 and an inverter 45.
The monostable multivibrators 43 and 44 each generate a pulse output 46.47 at the rise and fall of the A-phase pulse. These outputs 46 and 47 output reverse and forward pulses 42 and 41 as up pulses and down pulses by a logical product 48°49 with the B-phase output 3.

The relationship is shown in FIG.

Further, in FIG. 5, outputs 41 and 42 are input to the up/down counter 19 as in FIG. 1, and are used to display the current position, calculate the deviation from the target position, and perform other controls.

Note that FIG. 6 shows an example in which the rotation is reversed from normal rotation at time t4. In the embodiment shown in FIG. 5, in order to perform open-phase monitoring and detection, a fifth
An additional circuit indicated by reference numeral 50 in the figure is added.

The additional circuit 50 also provides A for the encoder B phase output 3.
Similarly to the phase, the rising pulse 51. To obtain the falling pulse 52, monostable multivibrators 54, 55 . It has a pulse generation circuit 53 consisting of an inverter 56,
Both phase B has a logical sum of 58.59 to obtain a logical sum of rising and falling pulses for pulse doubling. 1 and 2, it outputs a human phase doubling pulse 9 and a B phase doubling pulse 10, respectively, and has the same open phase detection circuit 20 as in FIG. In the above configuration, the detection of phase loss of phase A or phase B is the same as in the case of FIG. 1, and its explanation will be omitted.

〔Effect of the invention〕

The present invention is as described above, and as is clear from the explanation of the illustrated embodiments, according to the present invention, when one phase signal in an incremental two-phase encoder has a phase loss, the phase loss can be promptly detected. It is possible to obtain a servo device with an encoder open-phase detection circuit that can detect abnormality and immediately take measures such as emergency stop.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing an embodiment of a servo device with an encoder open-phase detection circuit according to the present invention, and FIGS. 2 to 4 are various signal waveform diagrams of the servo device shown in FIG. 5
The figure is an electric circuit diagram showing another embodiment of the servo device according to the present invention, and FIG. 6 is a diagram of various signal waveforms of the servo device shown in FIG. 5. 1... Incremental two-phase encoder, 4...
Fine count creation and rotation direction determination processing circuit 20
...Open phase detection circuit, 21...A phase monitoring circuit, 22.
... 4-bit binary counter, 27... B phase monitoring circuit, 28... 4-bit binary counter.

Claims (1)

[Claims] 1. It has an incremental two-phase encoder for detecting two forward and reverse motion directions, and uses corresponding signals created from the generated signals of each phase so that one of them is used as a clear input and the other is used as a count input. A servo device with an encoder open phase detection circuit, characterized in that it is equipped with means for mutually monitoring and detecting open phase. 2. In the invention described in claim 1, there is provided a servo with an encoder open-phase detection circuit, which has a pulse doubling circuit for each phase between the encoder and the open-phase monitoring/detection means as a corresponding signal generation circuit. Device. 3. A servo device with an encoder open phase detection circuit having a D-type flip-flop and an exclusive OR circuit in each phase as a pulse doubling circuit according to the invention as set forth in claim 2. 4. A servo device with an encoder open-phase detection circuit that discriminates when the count pulse has a set value of 3 or more in the invention as set forth in claim 2. 5. The invention as set forth in claim 2, further comprising a pulse quadrupling circuit, a current position counter, and a rotation direction display circuit located at a subsequent stage of the pulse doubling circuit, and A servo device with an encoder open-phase detection circuit that has an open-phase detection circuit that receives the pulse doubling circuit output in parallel. 6. A servo device with an encoder open phase detection circuit having a monostable multivibrator and an OR circuit as the pulse doubling circuit according to the invention as set forth in claim 2.