JP3041752B2 - Absolute position encoder for industrial robots - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absolute position encoder used for an industrial robot.

[0002]

2. Description of the Related Art A conventional absolute position encoder will be described below with reference to FIG. FIG. 2 shows a block diagram of a conventional absolute position encoder. As shown in FIG. 2, the absolute position data register 7 contains signals such as absolute position data and motor magnetic pole position indicating the position of the armature of the servomotor, and the output is transmitted to the robot controller via a parallel signal line. Instead, the data is held by the data holding circuit 8a during transmission, converted into serial data by the all-frame serial converter 11 of long data bits, and transmitted to the robot controller by the S-phase driver 12. Further, two-phase signals obtained from the rotating disk 1 and the light receiving elements 2a and 2b are transmitted to the robot controller by the A-phase driver 13 and the B-phase driver 14. The A-phase and the B-phase have the same configuration as that of the incremental encoder, and are for preventing delay due to serial transmission of long data bits in all frames. The robot controller adds the subsequent relative rotation amount, that is, data obtained by counting the two-phase pulses A and B to the initial absolute position data sent at the start of the operation, so that absolute position data without any delay is always obtained. Has become. Reference numeral 3 denotes a backup battery for the absolute position data register 7.

[0003]

A problem with the absolute position encoder according to the prior art is that the encoder wiring is a signal line for transmitting absolute position data in series in addition to the power supply line, and a two-phase signal indicating a relative rotation amount. That is, a total of three sets of signal lines are required. The wiring between the encoder and the control device of the industrial robot needs to be routed inside the robot machine main body, and it is inevitable to involve a movable part. For this reason, a large number of wirings from the encoder not only increases a wiring routing area, but also causes wiring damage and lowers reliability.

An absolute position encoder for temporally switching between an absolute position data signal line and a two-phase pulse signal line in order to further reduce the number of signal lines is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-26.
No. 3600. However, this absolute position encoder requires two sets of signal lines.

[0005] As a method of reducing the number of signal lines to one set, 2
It is conceivable that the phase pulses A and B are abolished and the absolute position data is repeatedly transmitted by serial communication. However, since the data length of the absolute position data is larger than the communication speed, a transmission delay occurs, and the smoothness of the industrial robot is reduced. Operation is impaired.
For example, if the communication speed is 1 M pulse / sec and the absolute position data length is 52 bits, the transmission of the absolute position data requires 52 μsec, and this delay is as large as the general servo control cycle of an industrial robot. It is inevitable that the operating performance will deteriorate.

An object of the present invention is to solve the above-mentioned problems, and to reduce the number of wires between an absolute position encoder and a control device without deteriorating the control performance of an industrial robot.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention holds absolute position data from an absolute position data register in a data holding circuit during transmission, and then uses a signal dividing circuit to set the absolute position data for each fixed bit length. A transmitted data holding circuit that divides a frame into a plurality of frames, sequentially selects one frame by a signal selection circuit, converts the frame into a serial signal by a serial converter, and then holds the transmitted data by an absolute position encoder that transmits the signal to a signal line. And a difference determination circuit for taking a difference between the absolute position data and the absolute position data. When the difference determination circuit determines that there is a difference, a difference data frame is added between frames sequentially selected by the signal selection circuit. Is transmitted.

[0008]

According to the present invention, in the above-described configuration, the difference between the absolute position data can be set to one frame time, for example, 10 μs when the communication speed is 1 M pulse / second and one frame is 10 bits. It is short and does not degrade control performance.

The maximum amount of change of the absolute position data within 10 μs, that is, the maximum of the difference data can be obtained from the number of pulses and the maximum number of rotations of the absolute position encoder. Can be represented by one frame.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An absolute position encoder for an industrial robot according to one embodiment of the present invention will be described below with reference to FIG. The same components as those described in the conventional example are denoted by the same reference numerals, and description thereof is omitted.

FIG. 1 is a block diagram of an absolute position encoder of an industrial robot according to the present invention. As shown in the figure, the output of the absolute position data register 7 is held by a data holding circuit during transmission 8a in order to avoid a change in the middle of transmission, and then divided by a signal dividing circuit 9 into data for each fixed frame, and a signal is selected. The signal is sent to the chronological serial converter 10 by the circuit 6, converted into a serial data string, and transmitted to the robot controller by the S-phase driver 12. If the absolute position data changes during transmission, difference data is generated by the difference circuit 4 from the output of the absolute position data register 7 and the transmitted data holding circuit 8b. This difference data is checked by the difference determination circuit 5, and if it is not zero, it is additionally transmitted before the next transmission frame.

Therefore, according to the present invention, the data mainly sent changes depending on the degree of change of the absolute position data.
That is, if the change is severe, the difference data is sent at short time intervals, and if the change is small, the absolute position data is sent at long time intervals.

[0013]

As is apparent from the above description, according to the present invention, after the absolute position data from the absolute position data register is held in the data holding circuit during transmission, a plurality of data are stored for each fixed bit length by the signal dividing circuit. Divided into frames
One frame is sequentially selected by a signal selection circuit, converted to a serial signal by a serial converter, and then transmitted to a signal line by an absolute position encoder. The difference between the transmitted data holding circuit that holds transmitted data and the absolute position data is calculated. A differential data frame and a differential determining circuit, wherein when the differential determining circuit determines that there is a difference, a differential data frame is added and transmitted between frames sequentially selected by the signal selecting circuit. Accordingly, the number of wires between the absolute position encoder and the control device can be reduced without lowering the control performance of the industrial robot.

[Brief description of the drawings]

FIG. 1 is a block diagram of an absolute position encoder of an industrial robot according to one embodiment of the present invention.

FIG. 2 is a block diagram of a conventional absolute position encoder of an industrial robot.

[Explanation of symbols]

 Reference Signs List 4 Difference circuit 5 Difference judgment circuit 6 Signal selection circuit 7 Absolute position data register 8a Data holding circuit during transmission 8b Transmitted data holding circuit 9 Signal dividing circuit 10 Serial converter

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01D 5/00-5/252 G01D 5/39-5/62

Claims (2)

(57) [Claims] After holding the absolute position data from the absolute position data register in a data holding circuit during transmission, the signal is divided into a plurality of frames for each fixed bit length by a signal dividing circuit, and one frame is sequentially processed by a signal selecting circuit. And select
After being converted to a serial signal by the serial converter, the absolute position encoder transmitting to the signal line, a transmitted data holding circuit for holding transmitted data and a difference circuit and a difference determination circuit for taking the difference between the absolute position data, An absolute position encoder for an industrial robot, wherein when the difference determination circuit determines that there is a difference, a difference data frame is added and transmitted between frames sequentially selected by the signal selection circuit. 2. The absolute position encoder for an industrial robot according to claim 1, wherein the frame is constituted by 7-, 8-, or 9-bit information as a fixed bit length.