JPH06258098A - Multiple rotation type absolute encoder - Google Patents

Abstract

PURPOSE:To reduce number of bits of an absolute signal and to reduce in size, simplify in a structure a circuit by detecting an absolute position within one rotation from a representative value of one rotation absolute value, an incremental signal and a reference signal. CONSTITUTION:Immediately after a main power source is turned ON, a decoder 12 judges a region of 1/24 of one rotation by 5 bit absolute signals 2<0>-2<4>, and outputs a representative value of the one rotation absolute responsive to the region to a one rotation absolute counter 14. This representative value becomes one rotation absolute data as it is, converted by a converter 18 to serial data together with a value of a multiple rotation counter 15 preset to a multiple rotation counter 16, and transferred to a driver system. Then, when a motor is driven, and an initial reference signal Zn is detected, the counter 14 outputs a value added with counted values of incremental signals A, B having resolution of 1/2048 to the representative value, and hence absolute signals 2<0>-2<4> within one rotation is small, but and an absolute position can be detected with high resolution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-rotational absolute encoder for detecting an absolute rotation angle of a rotating body, and more particularly to a rotary encoder incorporated in an AC servomotor.

[0002]

2. Description of the Related Art Servo motors used for driving various machines include a DC servo motor with a brush and an AC servo motor without a brush (DC brushless servo motor). In recent years, the AC servo motor is easy to maintain. Demand is increasing.

There are various types of position detectors for servo systems, but in recent years, rotary encoders used by incorporating them in servo motors have become widespread. Encoders incorporated in AC servomotors are roughly classified into incremental encoders and absolute encoders.

As shown in FIG. 8, the output signals of the incremental encoder are A and B two-phase signals having a phase difference of 90 degrees so that the rotation direction can be discriminated, a reference Z signal of one rotation and one pulse, and an AC servo. It is generally provided with commutation signals U, V, W for switching the energized phase of the motor.

The absolute encoder is an encoder that can recognize the absolute position within one rotation immediately after the power is turned on, and is a position alignment operation between the machine position and the controller, which is required immediately after the power is turned on, which is required in a control system using an incremental encoder. Since it does not require a home-return operation, it is becoming widespread in servo motors for large robots such as articulated robots, and many of them are multi-rotational absolute encoders with a motor rotation count function. Is.

A conventional multi-rotation absolute encoder will be described below. FIG. 9 shows functional blocks of a conventional multi-rotation absolute encoder.
In FIG. 9, reference numeral 91 is an incremental signal output unit, and 92
Is an absolute signal output section, 93 is a multi-rotation counter,
Reference numeral 94 is a backup circuit, and 95 is a conversion circuit.

The operation of the multi-rotational absolute encoder configured as described above will be described below. First, when the main power source is on, the incremental signal output unit 91 outputs the A and B signals having a 90-degree phase difference and the Z signal generated once per rotation in accordance with the rotational position of the encoder. Further, from the absolute signal output unit 92 outputs the 2 ⁰ 2 ^K-1 of the signal K bits corresponding to the resolution of 1 rotates one revolution absolute data. Further, the multi-rotation counter 93 counts the number of rotations by using the upper 2 bits 2 ^K-1 and 2 ^K-2 of the absolute signal output.

The conversion circuit 95 converts the one-turn absolute data and the multi-turn count data, which are parallel data, into serial data and sends the serial data to the driver or the NC system. On the other hand, when the main power is turned off, the backup circuit 9
Upper 2 bits of absolute signal output by 4 2 ^K-1
The detection of the 2 ^K-2 signal and the multi-rotation counter 93 are always operating. As a result, even when the main power is turned on again, the number of rotations can be held without being reset, and the number of rotations changed when the main power is turned off can be detected.

[0009]

However, in the above-mentioned conventional structure, a large number of absolute signals are required to determine the absolute position, and the number of signals increases as the resolution increases. Since it is necessary to increase the number of detection units corresponding to the number of signals, and the scale of the processing circuit also increases, there is a problem in that the circuit scale also increases in terms of structure.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a compact and compact multi-rotation absolute encoder.

[0011]

In order to achieve this object, a multi-rotational absolute encoder of the present invention comprises:
(1) A and B two-phase incremental signals having a 90-degree phase difference with each other, and at least N or more (N = (the number of motor poles PM of the motor to which the encoder is attached) × (the number of motor phase PH)) reference signals An original signal output section that outputs a total of three types of signals, Z _n and an M-bit absolute signal that determines the order of Z _n , and (2) a one-rotation absolute value corresponding to Z _n from the M-bit absolute signal. a decoder circuit for outputting a representative value of (3) from the output and Z _n signal of the decoder circuit, and Z ₀ signal generation circuit for selecting a Z ₀ signal corresponding to the zero value of 1 rotation absolute data,
(4) A one-rotation absolute counter that inputs the representative value and A, B, Z _n signals and outputs the absolute position within one rotation, and (5) the upper two of the M-bit absolute signals.
A multi-rotation counter 1 for counting the number of forward and reverse rotations of the motor using a bit, and (6) the output of the multi-rotation counter 1 and the carry borrow signal from the 1-rotation absolute counter are input, and 1 A multi-rotation counter 2 for detecting the upper data of the rotation absolute counter,
(7) A backup circuit that detects the absolute signal of the upper 2 bits of the M bits of the multi-rotation counter 1 and the original signal output section when the main power supply is turned off, for determining whether the number of rotations is normal or reverse, and (8) 1 A conversion circuit for converting parallel data from the rotation absolute counter and the multi-rotation counter 2 into serial data and outputting the serial data, (9) A, B, Z
The representative value of the 1-turn absolute value corresponding to the _n signal and Z _n is input, the count switching signal is detected from the up and down signals for counting the incremental signal and the first Z _n signal after the power is turned on, and the representative value is detected. 1-turn absolute counter that switches the preset operation and the up / down signal counter operation by the count switching signal, and the function of notifying the counter switching signal as an encoder signal processing status to the outside through the conversion circuit, and (10) Decoder circuit output The representative circuit and the output of the 1-turn absolute counter are compared with each other for each Z _n signal, and the comparison result is provided as an encoder signal processing status to the outside through the conversion circuit.

[0012]

With this configuration, the number of bits of the absolute signal within one rotation can be reduced as compared with the conventional multi-rotation type absolute encoder, so that the detection unit and the electric circuit unit can be downsized, and the small and compact multi-rotation can be achieved. A rotary absolute encoder can be obtained.

Further, by having the function of comparing the counter operations, it is possible to improve the reliability and safety of malfunctions due to external noise and the like.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a functional block diagram of an embodiment of the present invention. In FIG. 1, 11 is an original signal output unit, 12 is a decoder circuit, 13 is a Z ₀ signal generating circuit, 14 is a single-revolution absolute counter, 15 is a multi-revolution counter 1, 16 is a multi-revolution counter 2, 17 is a backup circuit, 18 Is a conversion circuit, and 19 is a comparison circuit.

FIG. 2 shows the configuration of the original signal output section 11. Here, 21 is a light emitting element, 22 is a rotary slit plate, 23 is a light receiving element, and 24 is a waveform shaping circuit. In this embodiment, the number of Z _n is set to 24 for a three-phase eight-pole AC servo motor, and one rotation absolute data is 2048 pulses.

FIG. 3 shows signals detected in accordance with the rotation of the rotary slit plate 22. Here, the A and B signals are 9
A signal having a phase difference of 0 degree, which is an incremental signal that generates 2048 pulses during one rotation, a Z _n signal is a signal that is generated 24 times during one rotation in synchronization with the A and B phases, and a 5-bit absolute signal.

FIG. 4 shows the movement of the one-turn absolute data output at the time of starting. The representative value is output from the 5-bit absolute signal and the decoder circuit 12.

FIG. 5 shows a one-turn absolute counter 14
FIG. 6 is a diagram showing the configuration of FIG. 2, in which an up pulse is output when the A phase is ahead of the B phase by the phase of the incremental signals A and B signals, and conversely when the A phase is behind the B phase. Direction discrimination circuit 51 for generating down pulse
A main power supply voltage monitoring circuit 52 for monitoring the on / off state of the main power supply voltage, an output of the main power supply voltage monitoring circuit 52 and A,
And operation switching circuit 53 detects the count switching signal from the first Z _n signal after the power-on by the Z _n signals, are constituted by a presettable up-down counter 54. The up / down counter 54 requires 11 bits because the resolution of one rotation of the incremental signal is 2048.

FIG. 6 shows an operation timing chart of the one-turn absolute counter when the power is turned on and off.

FIG. 7 is a diagram for explaining the operation of the comparison circuit 19 for comparing the representative value data of one rotation absolute and the one rotation absolute counter.

The Z ₀ signal generation circuit 13 is the decoder circuit 1
From the representative value data output from 2 and the N reference signals Z _n , the signal corresponding to the zero value of the one-turn absolute data is detected from Z _n .

The operation of the multi-turn absolute encoder having the above construction will be described below.

First, assuming that the encoder is located at point A in FIG. 4 immediately after the main power supply is turned on, the encoder circuit 12 outputs the 5-bit absolute signal output from the original signal output section 11 and the decoder circuit 12 to 24 times in one rotation. A one-third area is determined, and a representative value of one-revolution absolute corresponding to the area is output to the one-revolution absolute counter 14. At this time, the operation mode of the up / down counter 54 in the one-turn absolute counter 14 is a preset operation by the operation switching circuit 53, and the representative value is directly used as one-turn absolute data.

The value of the multi-revolution counter 1 detected and held by the backup circuit 17 is preset in the multi-revolution counter 2 by the operation switching circuit 53. The value of the multi-revolution counter 2, that is, the multi-revolution count data and the above Conversion circuit 18 combined with 1-turn absolute data
The data is transferred to the driver system that drives the AC servo motor after serial conversion.

In the driver system, a commutation signal for switching the energized phase of the AC servomotor is created from the one-turn absolute data by a sine wave ROM table, and the rotation of the motor is started. At this time, since the one-revolution absolute data is constant with only the representative value, the commutation signal on the driver system side does not change in a sine wave shape but has a constant value, and as a result, it is driven by the rectangular wave drive.

When the motor is driven to rotate in the CW direction from the point A and the position changes to the point B which is the position of Z _n , the operation switching circuit 53 detects Z _{n and} the operation mode of the up / down counter 54 is changed. The preset operation is changed to the count operation, and up / down pulses are counted by the up / down counter 54. As a result, the value of the one-rotation absolute counter becomes a value obtained by adding the value obtained by counting the incremental signal to the representative value from the representative value up to now.

Here, the direction discriminating circuit 5 is based on the phase relationship between the incremental signals A and B until Z _n is detected.
The up / down pulse detected in 1 is invalid because the up / down counter 54 performs a preset operation. FIG. 6 shows the operation timing.

Further, the multi-revolution counter 2 is detected by detecting Z _n.
Similarly, the operation mode of (1) is switched, and the operation of presetting the data of the multi-revolution counter 1 is switched to the operation of counting by the carry borrow signal of the one-revolution absolute counter.

Thereafter, the one-turn absolute data is updated by the change of the A and B phases. The detected 1-turn absolute data is the same as the above-mentioned multi-turn counter 2
Data is transferred to the driver system through the matching conversion circuit 18. At this time, since the one-turn absolute data changes with a resolution of 1/2048, the commutation signal can be changed in a sine wave shape on the driver system side, so that the motor is driven by a sine wave drive.

On the other hand, when the motor rotates in the CCW direction from the point A and passes through the point C which is the representative value switching point, 1
The representative value of the point A in the rotation absolute counter 14 is updated to the adjacent n-1th representative value, and the value of the multi-revolution counter 2 and the conversion circuit 18 are serially converted in the same manner as described above to convert the AC servo motor. Transfer data to the driving driver system. Further, when the position changes to point D, which is the position of Z _n−1 , after passing point C, the value counted by the incremental signal in addition to the one-turn absolute data as the representative value until now is changed to the value similar to point B. The addition mode is set, and thereafter, in this mode, the one-turn absolute data is updated by the change of the A and B phases. The detected 1-turn absolute data is processed in the same manner as above and transferred to the driver system.

As described above, the one-turn absolute counter and the multi-turn counter 2 of the present invention perform the data preset operation until the first Z _n is detected after the power is turned on, and the Z _{n is set.}
After the detection, the count operation is performed. In this operation switching, the count switching signal is used as the encoder signal processing status to transfer information to the external system via the conversion circuit 18.

Next, the operation of the comparison circuit 19 will be described with reference to FIG. The comparator circuit 19 compares the representative value obtained by processing the 5-bit absolute signal of the original signal output unit 11 by the decoder circuit 12 with the value of the one-revolution absolute counter 14 to detect a count malfunction of the one-revolution absolute counter 14. It is a thing.

In the present invention, the comparison result is detected for each Z _n as shown in FIG. 7, and the comparison result is transferred to the external system via the conversion circuit 18 as the encoder signal processing status.

As described above, the detected representative value of the Z phase is 2
By adopting a configuration in which the counting of the incremental signals having a resolution of 1/048 is added, it is possible to realize a compact multi-rotation absolute encoder which has a small number of absolute signals within one rotation but has high resolution in absolute position detection.

[0036]

As described above, according to the present invention, in the case of increasing the resolution of one-turn absolute, high resolution absolute detection can be performed only by increasing the resolution of the incremental signal. As a result, it is possible to realize a multi-rotation absolute encoder that can be made compact and in which a conventional absolute-compatible driver can be used.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a multi-turn absolute encoder according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an original signal output unit according to an embodiment of the present invention.

FIG. 3 is a timing diagram of detection signals of a multi-turn absolute encoder according to an embodiment of the present invention.

FIG. 4 is an operation explanatory diagram of the one-turn absolute encoder when the main power is turned on in the embodiment of the present invention.

FIG. 5 is a configuration diagram of a one-turn absolute counter according to an embodiment of the present invention.

FIG. 6 is a timing chart of the counting operation in the embodiment of the present invention.

FIG. 7 is an operation explanatory diagram of a comparison circuit according to an embodiment of the present invention.

FIG. 8 is an output timing chart of a conventional incremental encoder.

FIG. 9 is a block diagram of a conventional multi-rotation absolute encoder.

[Description of Reference Signs] 11 original signal output unit 12 decoder circuit 13 Z ₀ signal generation circuit 14 1-revolution absolute counter 15 multi-revolution counter 1 16 multi-revolution counter 2 17,94 backup circuit 18,95 conversion circuit 19 comparison circuit 21 light-emitting element 22 rotating slit plate 23 light receiving element 24 waveform shaping circuit 51 direction discriminating circuit 52 main power supply voltage monitoring circuit 53 operation switching circuit 54 up-down counter 91 incremental signal output unit 92 absolute signal output unit 93 multi-rotation counter

Claims (3)

[Claims] 1. An incremental signal of A and B phases having a 90-degree phase difference from each other and at least N or more (N
= (Number of poles P of the motor to which the encoder is attached P
M) × (motor phase number PH)) A reference signal Z _n and an original signal output section that outputs a total of three types of M-bit absolute signals that determine the order of Z _n , and an M-bit absolute signal, a decoder circuit for outputting a representative value of a corresponding one revolution absolute value Z _n, from the output and Z _n signal of the decoder circuit, Z ₀ signal generation circuit for selecting a Z ₀ signal corresponding to the zero value of 1 rotation absolute data If, enter the representative value and a, B, and Z _n signals, and a rotation absolute counter for outputting an absolute position within one revolution, one revolution or more motors with upper 2 bits of the absolute signal M bits The multi-revolution counter 1 which counts the number of revolutions in the forward and reverse directions, the input of the output of the multi-revolution counter 1 and the carry borrow signal from the one-revolution absolute counter, and the one-revolution absolute counter. A multi-revolution counter 2 for detecting upper data of the counter, and a multi-revolution counter 1 and an upper 2-bit absolute signal for determining whether the number of revolutions of the original signal output unit is normal or reverse when the main power is off. A multi-rotation absolute encoder having a backup circuit to be operated and a conversion circuit for converting parallel data from the one-rotation absolute counter and multi-rotation counter 2 into serial data and outputting the serial data. 2. An A, B, Z _n signal and a representative value of one revolution absolute value corresponding to Z _n are input, and an up and down signal for counting the incremental signal and a first Z _n signal after the power is turned on. A one-turn absolute counter that detects the count switching signal and switches the preset operation of the representative value and the counter operation of the up and down signals with the count switching signal, and the counter switching signal as the encoder signal processing status to the outside through the conversion circuit. The multi-rotational absolute encoder according to claim 1, further comprising a notification function. 3. A comparison circuit for comparing the representative value of the output of the decoder circuit and the output of the one-turn absolute counter for each Z _n signal, and a function of notifying the comparison result as an encoder signal processing status to the outside through the conversion circuit. The multi-rotation absolute encoder according to claim 1.