JPS6014110A - Detection for absolute position of servo control system - Google Patents

Abstract

PURPOSE:To improve the precision of position detection by detecting the deviation between an ideal position and an actual position of each division point based on a prescribed division point of an absolute encoder and storing this deviation in a memory preliminarily and correcting the detection output with the deviation. CONSTITUTION:A processor 102 of a numerical control device 102 reads out and executes successively working control programs in a program memory 102b. A servo motor 105 is subjected to servo control on a basis of a moving command Zc outputted from an input/output port 102g and a feedback pulse FP from an absolute pulse coder 106. The deviation between an ideal position and an actual position of each division point based on a prescribed division point of the pulse coder 106 is detected preliminarily and is stored in a memory 102c. When it is necessary to obtain the absolute position of the motor 105, the detection output of the pulse coder 106 is corrected with this deviation to obtain the absolute position.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to a servo control system that detects the absolute position of a servo motor using an absolute encoder, and is capable of correcting the deviation of the absolute encoder and detecting an accurate absolute position 1γt. Related to system absolute position detection method.

(Conventionally, servo motors have been widely used to position movable parts of wave industrial robots and the like with high precision, and such servo motors are servo-controlled.

For servo control, servo motor (i.e. 0■ moving part)
It is necessary to detect the position of For this reason, a pulse coder is installed on the shaft of the servo motor, and the position of the servo motor is detected by outputting a position 1a Hals every time the servo motor rotates by a predetermined angle, and by counting this position pulse with a counter. ing. This position detection by counting pulses is accurate when starting from the origin, but if the absolute position is lost for some reason, it is necessary to detect the absolute position 1a of the servo motor. In order to detect this absolute position Dot, an absolute encoder is provided on the shaft of the servo motor, either integrally with the pulse encoder or separately. The absolute encoder has a disk 1 as shown in Figure 1.
06a with four tracks T1°T2. T3. T4 is provided, and each track is provided with a slit so that a code corresponding to the rotation angle is output. The disc 106a is provided coaxially with the axis of the servo motor and rotates with the rotation of the servo motor, and the light emitting element 106b is provided at a fixed position as shown in FIG. 1 CB+.

The pattern of each track on the disk 106a is optically read by the light receiving element 106C. This absolute encoder divides 1/4 of the circumference into 1/16 (4 bits) and gives a different code to each divided position depending on the shape of the slit. That is, as in the second rotation, 1/4 of the circumference of the disk 106a is divided into 16 parts from 31 to all+, and each division position is divided by a slit, for example, al is 'oooo',
"+01'l: " 1101u, a8. is'JOO1
” is given a code.

(Problems with the Prior Art) On the other hand, since the slit pattern on the disk 106a is produced chemically or mechanically, such as by photoethoangulation, as shown in FIG. A certain amount of deviation Δa will occur between the points.

Furthermore, there are four light receiving windows for the light emitting element 106b and the light receiving element 106C, and the relative detection positions of each of them are, therefore, a deviation occurs between the ideal dividing point and the dividing point by the slit on the disk 106a. However, there was a drawback that accurate absolute position detection was not possible.

(Object of the Invention) An object of the present invention is to provide an absolute position detection method for a servo control system that is capable of accurate absolute position detection by correcting the deviation of the absolute encoder.

(Summary of the Invention) In the present invention, the deviation between the ideal position and the actual position of each division point based on a predetermined division point of the absolute encoder is detected and stored in a memory in advance, and the detected output of the absolute encoder is The deviation is corrected to obtain the absolute position.

That is, the ideal position of each dividing point is calculated based on a predetermined dividing point, and the actual position 1a of the dividing point is measured based on the detection output from the absolute encoder, and the deviation between the ideal position and the measured position is calculated. The error of the absolute encoder is corrected by using the deviation as a correction value for the subsequent detection output.

(Example) Fig. 3 is a general block diagram for explaining the servo control according to the present invention, and shows an example in which the position of one operating axis of an industrial robot, etc. is controlled by an NC (numerical control) device II. It is something.

In Fig. 3, numeral 101 is a paper tape with perforated numerical control (NC) command data, which stores NC command data such as positioning information for machining and M, 'S, and T function information, and 102 is a numerical value. A control (NC) device Kt is a data reader (to be described later) from the paper data 101 and N
At the same time as reading the C data, the read NC data is decoded, for example, M, S.

If it is a T function command or the like, it is sent to the machine side via a power panel (not shown), and if it is a movement command ZC, it is output to the subsequent pulse distributor. The NC equipment 102 includes a processor 102a that executes arithmetic processing according to a control program, a program memory 102b that stores a predetermined control program, a data memory 102c that stores data, and an operation panel 102d for operation. , data reader/puncher 102
e, display device 102f, Kapo Okawa) 102g, current position counter 102b, and absolute position detection circuit 10
2i and an address/data bus 102 that connects them.
It is composed of j.

Reference numeral 103 denotes a pulse distributor, which executes a known pulse distribution calculation based on the movement command Zc to generate a distribution pulse Ps of a frequency corresponding to the command speed. 104 is a known acceleration/deceleration circuit that linearly accelerates the pulse speed of the distributed pulse train Ps when the pulse train is generated and directly decelerates it at the end of the pulse train to generate the pulse train Pi; 105 drives the operating axis; The motor 106 is an absolute encoder that generates one feedback pulse FP every time the motor 105 rotates by a predetermined amount and detects the absolute position ai, and 107 is an error calculation storage unit, which is composed of, for example, a +tJ inverse counter. The number of input Hals PiO generated from the acceleration/deceleration circuit 104 and the feedback pulse FPO difference Er are stored. Note that this error calculation storage unit 107 includes a calculation circuit 107a that calculates the difference Er between Pi and FP as shown in the figure.
and an error register 107b that stores one row. That is, the error calculation storage unit 107 is instructed to rotate the motor 105 in the forward direction, and if the motor 105 is rotating accordingly, it counts up the input pulse Pi every time the input pulse Pi occurs, and also counts up the input pulse Pi. F.P.
Each time , the contents are counted down and the difference Er between the number of input pulses and the number of feedback pulses is stored in the error register 107I). 108 is an error register 107b
109 is a speed control circuit, which is a digital-to-analog (D A ) converter that generates a degree analog pressure proportional to the content of .・107 and 108 constitute the motor position control circuit.

Next, the operation of the embodiment 411 shown in FIG. 5 will be explained.

First, prior to processing, the chie reader puncher 102e reads the NC data of the paper tape 101 and transfers it to the data memory 102c via the bus 102.
Store C data. Next, a start command is sent to the processor 1 via the bus 102j by fψ operation on the operation panel 102d.
02a, the processor 102a sequentially reads out the processing control gummy grams from the program memory 102b,
Execute. That is, read out the NC data from the data memory 102C, read out necessary parameters (NC hallometer, feeding speed, machining voltage, etc.), and issue an X-axis movement command Xc for moving the table (not shown) in the X and Y directions.
, a Y-axis movement command Yc is created and sent to the Desol drive front section through an input/output port (not shown) to position the table. Although not shown in Figure 3, the input and output capo~)
The configuration that exists in the route from 102g to the servo motor 105 is also provided on the Y-axis and the Y-axis. Similarly, 2
An axis movement command ZC is created and sent to the machine via an input/output port (not shown) such as M, S, and T function commands. This movement command Zc is sent to the input/output port 10 via the bus 102J.
Output to 2g. Now, when the movement command pulse distributor 103 is given from the input/output capo 102g, the pulse distributor 105 executes a pulse distribution calculation based on the movement command ZclC and outputs a distribution pulse Ps. Acceleration/deceleration circuit 104
receives this distribution pulse Ps, accelerates or decelerates the pulse speed, and inputs a command pulse train Pi to the error calculation section 107. As a result, the contents of the error register 107b are no longer zero, so a voltage is output from the DA converter 108, the motor 105 is driven by the speed control circuit 109, and the operating axis is driven. When the motor 105 rotates at a predetermined rotation rate, a feedback pulse F#EQ is generated from the pulse distributor 106 and inputted to the error calculation storage section 107, and is input to the error register 107b.
The difference Er between the number of tri tW command pulses Pi and the number of feedback pulses FI) is stored.

Thereafter, the motor 105 is adjusted so that the errors E and r become zero.
is servo-controlled, and the operating axis is driven to the target position.

In this way, in servo positioning, Parnuhuda 1
The current position Iff is determined by counting the feedback pulses FP from 06 and is also used for position IW control.

On the other hand, the current position of the counter 102h is the servo motor 1
05, it is necessary to obtain the absolute position (actual current position) using the detected absolute position ai from the absolute pulse coder 106.

FIG. 4 is a detailed block diagram of the absolute position detection circuit 1021 configured in FIG. 1% EG is a register that stores the output prefecture number and old number according to the detection output EDS of the edge detection circuit EDC. SW is a switch, I) CC is a code discrimination circuit, which detects that the detection code stored in the register FLEG is 81, AI, U1 is a division point calculation circuit, and code discrimination circuit DCC. In response to the detection of , the ideal dividing position ai is determined based on the edge of al.

CUT is a counter that counts the feed pulse PLS given to the servo motor 105. ALU2 is a deviation calculation circuit, which calculates the deviation Δai from the value of the counter CUT and the output of the dividing point calculation circuit ALU 1. It is a calculation. Code discrimination circuit DCC.

The counter CUT and the arithmetic circuits ALU1 and ALU2 constitute a deviation detection circuit.

Next, the operation of the configuration shown in FIG. 4 will be explained using FIG. 2.

- First, connect the switch SW to the code discrimination circuit DCC side. Next, the processor 102a of NClO2
02j input/output capo) Pulse distributor 10 via 102g
A 1-pulse sending command is given to 3, and the servo motor 105 is sent 1-pulse in the same manner as described above. When the servo motor 105 rotates in this manner, the detection code at is output from the PALNU coder 106 and input to the detection circuit 1021. The edge (dividing point) of the detection code ai is detected by the circuit Ef)C to the edge side 11, and the detection code ai is detected by the register ratio EC)
The signal is then stored in the code discriminator circuit DCC.

When the servo motor 105 continues to rotate in this manner and the sign output ai changes to al, the sign discrimination circuit DCC
A counter C that determines this and counts the sending pulse PLS
(Reset JT.

At the same time, the dividing point detection circuit ALUI detects the ideal edge position aio(
i=2 to 16). That is, the edge of aH is used as the reference position.

At the same time, the servo motor 105 is fed one pulse, and the counter CUT counts this feed pulse PL8 from the time when the edge of al is detected.

When the °C1 servo motor 105 rotates in this manner, the detection sign of the pulse coder 106 changes from al to al. In response to this change, the edge detection circuit EDC issues a detection output and activates the arithmetic circuit ALU2. Computation amount 1ALU2
is the it & value c a of the counter CU'I' at this time.
1(Ca, ) is read out and the deviation Δai is calculated from the following formula.

Δa 1=ca i −a io (υIn this way,
Calculate equation (1) according to changes in detection codes a2 to al, al to a4°...al5 to al6, and calculate each Δai(
i22-16).

This deviation Δai is stored in the data memory 102C via the bus 102.

In this way, the absolute encoder 106
The deviation Δai is stored in the data memory 102C.

Next, in actual absolute position detection, the switch SW is connected to the F side in the figure, and the register FjEG is connected to the bus 102J. Then, the gummy processor 102a sends one pulse to the sweet motor 105 as described in DiJ, reads the detection code ai of the register ratio EG at 76 when the edge detection number 111 JiD8 occurs, and then reads the deviation Δai as described in +iiJ. Perform the following equation.

A-old'-Δa i (2) The current position [a
As set 4-ru.

+4+1 l'), in the present invention, based on the edge of l:am, the distance to the edge of each ai by the slit is calculated by the counter CtJ 'I' as (fl), and the difference between this and Rihong (position is determined as the Uni difference.Then, the square mark detected by the deviation thereafter is corrected by i11.

In addition, the above-mentioned deviation detection circuit 1) CC, AJJLJ 1.
AI, U2.

The cu'r can also be performed using a gram of the gummy processor 102a.

(Effects of the Invention) As explained above, according to the present invention, the deviation between the ideal position of the absolute dividing point and the actual position of each dividing point is detected and stored in the memory in advance, and the deviation is detected by the absolute encoder. Since the absolute position is obtained by correcting the output with the deviation, even if there is an error in the absolute encoder, it can be corrected, and the position detection accuracy is improved by +1J.

In addition, since the error deviation is obtained from the output of the absolute encoder, it is possible to measure without having to set up a special device ilt.
Another advantage is that it can be easily realized simply by adding a circuit. Another advantage is that even if there are variations in the error of the absolute encoder, the detected vcf degree can be made uniform.

Although the present invention has been described by way of one embodiment, various changes may be made within the scope of the gist of the present invention, and these are not excluded from the scope of the present invention.

[Brief explanation of drawings]

Figure 1 is a 47a diagram of the absolute encoder used in the present invention, Figure 2 is an error explanatory diagram of the absolute encoder, and Figure 3 is an implementation l/ll diagram of the present invention. In the figure, 102...N C)lIFC, 102,...
...Processor, 102c11. Data memo IJ, 10
2h-・Current position 11 count, 102I... Absolute position ttt 4; D output circuit, 105... Servo motor, 1
06...Absolute pulse coder. Special d' [Output: Iji person Fanuc Co., Ltd. Representative Patent Attorney Kangai Tsuji 7 Figures (A) (B)

Claims (1)

[Claims] Absolute position 1 of the servo control system that servo controls the servo motor
servo that detects u using an absolute encoder)
In the absolute position detection method of the υυ control system, the deviation between the ideal position of each division point and the actual position 1rt of each division point based on the predetermined division point of the absolute encoder is detected and stored in memory in advance. , a servo system (illI system) absolute position detection method, characterized in that the detected output of the absolute encoder is corrected by the deviation to obtain the absolute position.