JP2685962B2 - Encoder error detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention provides a pulse generator for generating three kinds of pulse signals of A phase, B phase, and Z phase according to the rotation of an input shaft as a sensor body. The present invention relates to a so-called pulse count type rotary encoder abnormality detecting device, and more particularly to a rotary encoder abnormality detecting device suitable for controlling an industrial robot.

[Conventional technology]

For example, an industrial robot or the like needs some rotary encoders for its control. At this time, these rotary encoders mainly use the pulse counting type rotary encoders described above in terms of cost and signal processing speed. Encoders are mainly used.

By the way, in such an industrial robot, if the position detection by the rotary encoder cannot be accurately obtained, the movement of the robot becomes abnormal, which may cause a dangerous situation.

Therefore, it is necessary to constantly monitor the encoder to prepare for the occurrence of an abnormality. As a conventional technique of such an encoder abnormality detection device, for example, as described in JP-A-1-197813, There is known a device that combines a pulse count type rotary encoder with a so-called absolute type rotary encoder that outputs the detected position as absolute position data, and constantly compares the detection results of these plural encoders to detect an abnormality. .

[Problems to be solved by the invention]

The above-mentioned conventional technique does not take into consideration the fact that a considerably expensive absolute type rotary encoder is required in addition to the original encoder, and there is a problem that the cost is significantly increased.

An object of the present invention is to provide an encoder abnormality detection device that can detect an abnormality reliably only with an original pulse count type encoder and has sufficient reliability, at low cost.

[Means for solving the problem]

To achieve the above object, the present invention compares the count data of an up-down counter incremented by the A-phase pulse signal and the B-phase pulse signal output from the pulse generator of the pulse count type encoder with predetermined constant data. , When the numerical value of the count data exceeds a first predetermined value determined by the number of the A-phase pulse signal and the B-phase pulse signal generated when the input shaft of the pulse generator makes one rotation, The count data value at the time when the phase pulse signal is generated is the A phase pulse signal and the B phase signal generated when the input shaft of the pulse generator makes one rotation.
Second predetermined value and numerical value 0 determined from the number of phase pulse signals
When any of the above does not match, an abnormality detection output is generated.

[Action]

A output from the pulse generator that constitutes the encoder
Looking at each phase, B phase, and Z phase pulse signal,
If the number of A-phase and B-phase pulse signals generated when the pulse generator makes one rotation is N, the count value of the A-phase and B-phase pulse signals between the two Z-phase pulse signals is It must be -N, O, or N.

Therefore, if the count value becomes smaller than -N or becomes larger than N, the pulse generator is set to 1
This means that the Z-phase pulse signal was not generated despite the rotation or more. On the other hand, when it did not match with any of -N, O, and N, it was related to the rotation of the pulse generator. Since it means that the pulse signal of at least one of the A phase and the B phase was not correctly generated, the abnormality can be detected by these determinations.

At this time, according to the present invention, 2 out of 3 kinds of signals of the A phase pulse signal and the B phase pulse signal and the Z phase pulse signal output from the pulse generator of the encoder are used.
Since the probability of abnormalities occurring simultaneously in the seed signals is extremely low, sufficient abnormality detection accuracy can be easily obtained.

〔Example〕

Hereinafter, an encoder abnormality detection device according to the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 is an embodiment of the present invention, in which the present invention is applied to control of a manipulator driving motor of an industrial robot, and a position command given from a robot controller is an adder.
The value is input to 10 and converted into a deviation from the position feedback value, and the motor control circuit 11 outputs a motor current according to the deviation and drives the motor 12. Then, the rotation of the motor 12 is detected by the pulse generator 13 as the A-phase pulse signal and the B-phase pulse signal, converted into the UP pulse signal and the DWUN pulse signal by the encoder signal processing circuit 14, and then input to the up-down counter 15. Then, the position feedback value is obtained, whereby the control of the motor 12 corresponding to the position command can be obtained.

Next, 16 is an encoder signal abnormality detection circuit, which detects the UP pulse signal and DW output from the encoder signal processing circuit 14.
The UN pulse signal and the Z-phase pulse signal generated directly from the pulse generator 13 are input, abnormality is detected by the arithmetic processing described later, and an encoder abnormality signal is output when the abnormality occurs.

Further, 17 is an abnormality processing circuit, which sends a predetermined signal to the control system of the motor 12 when the encoder abnormality signal is input from the encoder signal abnormality detection circuit 16 and
Perform predetermined error processing such as prohibiting driving of 12.

Next, the operation of this embodiment will be described in more detail.

The pulse generator 13 generates three types of pulse signals of A phase, B phase, and Z phase as the motor 12 rotates, and these signals have a relationship as shown in FIG.
That is, the A-phase and B-phase pulse signals have a phase difference of 90 degrees with each other, and the phase relationship between these signals is such that when the pulse generator 13 rotates in one direction (forward direction), the A-phase pulse signal The signal has a lead phase, and when in the opposite direction (negative direction), the B-phase pulse signal has a lead phase. Then, as described above, N number of these A-phase and B-phase pulse signals are generated during one rotation of the pulse generator 13.

On the other hand, one Z-phase pulse signal is generated each time the pulse generator 13 makes one revolution, but in this embodiment, Z pulse at this time is generated.
As shown in the figure, the phase pulse signal is generated in synchronization with the A phase pulse signal.

Next, FIG. 3 shows an embodiment of the encoder signal processing circuit 14, which comprises two D flip-flops 14a and 14b, one clock signal generator 14c and three D flip-flops 14a and 14b as shown. Inverters 14e, 14f, 14g and five AND circuits 14h, 14
i, 14j, 14k, 14l, 14m, and two OR circuits 14n, 14
It consists of p and. At this time, the frequencies of the clock signals generated by the clock signal generator 14c are A phase and B phase.
The frequency is chosen to be sufficiently high compared to the maximum possible frequency of the phase pulse signal.

First, the B-phase pulse signal is input to the D flip-flop 14a, and the output is further input to the next D flip-flop 14a.
By inputting to b, a signal synchronized with the clock signal of this B-phase pulse signal is produced. Then, the outputs of these D flip-flops 14a and 14b are converted into inverters 14f and 14g.
The AND circuit 14h, 14i outputs a rising pulse and a falling pulse which appear in synchronism with the clock signal at the rising and falling edges of the B-phase pulse signal, respectively. .

Next, the rising pulse and the falling pulse are processed together with the A-phase pulse signal including the output of the inverter 14e by a circuit composed of AND circuits 14j to 14m and OR circuits 14n and 14p, and these OR circuits 14n are processed. From the 14p output
The UP pulse signal and the DOWN pulse signal are obtained respectively.

Therefore, this encoder signal processing circuit 14 assumes that the encoder has rotated in the positive direction when the B-phase pulse signal rises when the A-phase pulse signal is at level "1".
One pulse of UP pulse signal is output, and conversely, when the phase A pulse signal is at level "0" and the phase B pulse signal rises, it is assumed that the encoder has rotated in the negative direction and one pulse of DOWN pulse signal is output. Will work like. As a result, when the encoder makes one rotation, the number of pulses of each of the UP pulse signal and the DONW pulse signal becomes 2N.

Next, FIG. 4 shows an embodiment of the encoder signal abnormality detection circuit 16, and as shown in the figure, the up / down counter 41 and S
-R flip-flop 42, data latch 43, and 4
Number of comparators 44, 45, 46, 47, constant setters 48, 49, 50, 5
1. Further, it is composed of OR circuits 48 and 50 and NOR circuit 49.

The up / down counter 41 is cleared to the count value 0 by the reset signal, and the count value capacity is from 2N or more to −2N.
The counter having the following functions to count up by UP pulse signal and count down by DOWN pulse signal.

The reset signal of the up / down counter 41 is Z
Both the phase pulse signal and the output signal of the SR flip-flop 42 which is reset by the system reset signal and reset by the Z phase pulse signal are supplied from the output of the OR circuit 52 to which the signals are input. Therefore, the up / down counter 41 is reset every time a Z-phase pulse signal is generated, and from the input of the system reset signal to the first generation of the Z-phase pulse signal. The reset state is also maintained for the period. This is because the state of the up-down counter 41 is indefinite during the period from the system reset to the time when the Z-phase pulse signal is first generated, and therefore erroneous detection may occur.

Count value D that is the output of the up / down counter 41
Is supplied to the four comparators 41 to 47. At this time, the count value D is directly supplied to the comparator 44 as it is, while the remaining comparators 45 to 47 are supplied. The data is latched in the data latch 43 once and becomes latched data D ', and is then input.

Therefore, first, regarding the comparator 44, since the count value D is directly input to the comparator 44, it is constantly compared with the constant 2N given from the constant setter 48.

As described above, the numerical value N is generated during one rotation of the pulse generator 13, that is, between the generation of a certain Z-phase pulse signal and the generation of the next Z-phase pulse signal. Is the number of pulses of the A-phase pulse signal and the B-phase pulse signal.

Therefore, if the count value D exceeds the constant 2N for some reason, the comparator 44 produces an output.

Here, regarding the point that this count value D exceeds the constant 2N, this means that the up / down counter 41 is reset even though the pulse generator 13 (encoder) has performed at least one revolution. It means that the reset signal was not output from the OR circuit 52, and the reason is that the Z-phase pulse signal is abnormal. Therefore, after all, the output of the comparator 44 operating under the condition of D> 2N , Z-phase pulse signal abnormality can be detected.

Next, regarding the data latch 43, since the data latch 43 uses the Z-phase pulse signal as a clock signal, the count value D of the up / down counter 41 is fetched at each generation timing of the Z-phase pulse signal, and the data is latched. The latched data D'is sequentially held as D '.
Is input to the comparators 45, 46 and 47, respectively.

Therefore, first of all, regarding the comparator 45,
Since 45 is given a constant from the constant setter 49, the comparator 45 eventually outputs the latch data D'as a constant (-
An output is generated only when it equals 2N + 1).

Similarly, the comparator 46 produces an output only when the latch data D'is equal to the constant (0), and the comparator 47 outputs the latch data D'to the constant (2N-
An output occurs only when it is equal to 1).

Then, since the outputs of these three comparators 45 to 47 are input to the NOR circuit 53, the NOR circuit 53, after all, with respect to the latch data D ′,
Output will be generated only when all the conditions of are not satisfied.

D ′ = (− 2N + 1) D ′ = (0) D ′ = (2N−1) First, considering the case where these conditions are satisfied, the latch data D ′ is the Z-phase pulse signal Since this data is fetched and updated each time it is generated, this data is stored in the next Z phase after a certain Z-phase pulse signal is generated.
It is the number of pulses of the A-phase pulse signal and the B-phase pulse signal that appear before the generation of the phase pulse signal, that is, the number of pulses of the UP pulse signal and the DOWN pulse signal.

On the other hand, regarding the behavior of the pulse generator 13 between the generation of a certain Z-phase pulse signal and the generation of the next Z-phase pulse signal, it is limited to the following three cases.

(1) When the position where the next Z-phase pulse signal is generated does not return to the original rotation start position after starting the rotation in the positive direction.

(2) After starting the rotation in the positive or negative direction, without reaching the position where the next Z-phase pulse signal is generated,
When returning to the original rotation start position.

(3) When the position where the next Z-phase pulse signal is generated does not return to the original rotation start position after starting the rotation in the negative direction.

Then, when the pulse generator 13 has no abnormality and only the A-phase pulse signal, the B-phase pulse signal, and the Z-phase pulse signal are correctly generated, either of the above conditions is satisfied. Eventually, the NOR circuit 53 produces an output when an abnormality occurs in the A-phase pulse signal and the B-phase pulse signal. Therefore, the output of the NOR circuit 53 causes the A-phase pulse signal and the B-phase pulse signal to be output. An abnormality can be detected.

Since the outputs of the comparator 44 and the NOR circuit 53 are respectively input to the OR circuit 54, by finally setting the output of the OR circuit 54 as an encoder abnormality signal, the A phase pulse signal, the B phase pulse signal, and the Z phase Even if an abnormality occurs in any of the pulse signals, the abnormality can be immediately detected.

Returning to FIG. 1, the encoder abnormality signal output from the encoder signal abnormality detection circuit 16 is input to the abnormality processing circuit 17, and as described above, the drive of the motor 12 is prohibited and the encoder signal The abnormal operation of the robot caused by the abnormality is suppressed and the dangerous state is prevented from occurring.

Therefore, according to this embodiment, the abnormality of the encoder signal can be surely detected without using the absolute type rotary encoder together, and the safety of the robot and the like can be easily ensured at low cost.

In the above embodiment, the encoder signal abnormality detection circuit
Although all functions including 16 are obtained by hardware configuration, this is only an example, and it goes without saying that the present invention can be implemented as software in any grade as required. .

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, since the abnormality of an encoder signal can always be detected reliably only by adding a simple signal processing function, without adding an extra encoder, a highly reliable encoder abnormality detection apparatus. Can be easily provided at low cost.

Further, according to the present invention, when an abnormality occurs in the encoder signal, the input shaft of this encoder has at most 1
Since the abnormality can be detected with certainty until the rotation of the robot, abnormality processing can be executed with high response in the servo control system of the motor drive mechanism, thus suppressing runaway accidents of the robot and ensuring sufficient safety. The effect is that it can be increased.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an encoder abnormality detecting device according to the present invention, FIG. 2 is a waveform diagram for explaining an encoder signal, and FIG. 3 is a block diagram showing an embodiment of an encoder signal processing circuit. FIG. 4 is a block diagram showing an embodiment of an encoder signal abnormality detection circuit. 10 …… Adder, 11 …… Motor control circuit, 12 …… Motor,
13 …… Pulse generator, 14 …… Encoder signal processing circuit,
15 …… Up / down counter, 16 …… Encoder signal error detection circuit unloader, 17 …… Abnormality processing circuit.

Claims (1)

(57) [Claims] Claims: 1. Two pulses whose phases are shifted for each predetermined rotation angle of the input shaft are generated as an A-phase pulse signal and a B-phase pulse signal, and the pulse is rotated at a predetermined rotation angle position during one rotation of the input shaft. A pulse generator that generates a single pulse as a Z-phase pulse signal, an UP pulse signal when the input shaft rotates in one direction and a DWUN pulse signal when the input shaft rotates in the other direction from the A-phase pulse signal and the B-phase pulse signal. In a rotary encoder having a signal processing circuit for generating, an up-down counter that counts up by the UP pulse signal, counts down by the DOWN pulse signal, and is reset by the Z-phase pulse signal, and a count of the up-down counter. An arithmetic means for comparing the data with a predetermined constant data is provided, and the count data value is
When the first predetermined value determined by the number of the A-phase pulse signal and the B-phase pulse signal generated when the input shaft of the pulse generator makes one revolution is exceeded, and when the Z-phase pulse signal is generated. The count data value does not match either the second predetermined value determined by the number of the A-phase pulse signal or the B-phase pulse signal generated when the input shaft of the pulse generator makes one revolution, or the numerical value 0. An encoder abnormality detection device characterized in that an abnormality detection output is generated from the arithmetic means when the above-mentioned operation is performed.