JPH0830974B2 - Precision position control system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position control system for controlling the position of a machine by a numerical controller.

2. Description of the Related Art A position control method using a numerical control device interpolates a movement command instructed by a program according to a minimum setting unit in the program, distributes a pulse to a servo circuit of each axis, and It controls the position of the axis. That is, the minimum interpolation unit and the minimum movement unit of each axis of the machine are the minimum units set in the program.

Problems to be solved by the invention When interpolation is performed in the minimum setting unit of the movement amount instructed by the program and pulse distribution is performed for each axis of the machine, a command from -1/2 to +1/2 of the minimum setting unit is issued. There is an error. Therefore, even if the position control section of the servo circuit receives this distributed pulse and performs position control, the minimum setting unit of -1/2 to +1/2
Processing error occurs.

For example, as shown in FIG. 2, line segment L1 from point Q to point R
If a command to move along the line is given by the program, that is, the command X5Y7 to move along the line segment L1 at the point shifted by 5 units in the X-axis direction and 7 units in the Y-axis direction is read from the program. In this case, linear interpolation is performed, pulses are distributed to the X-axis and Y-axis servo circuits, and 5 pulses corresponding to the minimum setting unit are output in the X-axis direction, while 7 pulses are output in the Y-axis direction. As a result, the movable part of the machine moves in the X-axis and Y-axis directions as indicated by the locus shown by the broken line L2 in FIG. In the example of FIG. 2, first,
One pulse is output simultaneously to the X-axis and Y-axis servo circuits, then one pulse is output only to the Y-axis servo circuit, and then two pulses are output to both the X-axis and Y-axis servo circuits. Then, one pulse is output only to the Y-axis servo circuit, and finally two pulses are output to both the X-axis and Y-axis servo circuits, and the pulses are distributed to reach point R. As a result, the X-axis and Y-axis servomotors rotate according to the distributed pulses, the movable part of the machine moves along the locus L2, and the machine moves along the straight line L1 of the desired line segment QR. Since the part that should move moves along the locus L2, if it is a cutting process, as shown in Fig. 2, from -1/2 pulse to +1/2 pulse.
Pulse processing error, that is, the minimum setting unit of -1/2 to +1/2
Will result in a shape error.

Therefore, it is an object of the present invention to provide a position control method capable of reducing the above-mentioned processing error and processing a desired shape and corrugation as much as possible.

Means for Solving the Problems The present invention converts an interpolation unit smaller than the minimum setting unit of a movement command instructed by a program and interpolates, and calculates the movement amount per unit time of the interpolation result as data of the interpolation unit. The above problem is solved by inputting to the position control unit of the servo circuit and inputting to the control unit by using the position detection signal unit from the detector for detecting the position of the machine as the interpolation unit and inputting to the control unit.

Interpolation by a unit smaller than the minimum setting unit of the movement command instructed by the action program, the pulse interpolated by this small unit is distributed to each axis, and detection from the detector that detects the position of the moving part of the machine By making the signal unit the interpolation unit interpolated into the above-mentioned small unit, the position control is performed by this small unit, so that each axis that drives the movable part of the machine is smaller than the minimum setting unit of the program movement command. Since it is driven in units, the machining error in the cutting process by this precision position control method is -1 /
It goes from 2 to +1/2. That is, the value is changed from -1/2 to +1/2 which is a unit smaller than the minimum setting unit.

Embodiment FIG. 1 is a block diagram of a precise position control system according to an embodiment of the present invention, in which 1 is an NC tape on which a machining program is recorded, 2 is a decoding unit for reading and decoding the program from the NC tape, 3 Responds to the movement command of the decrypted program,
A unit conversion means for converting the minimum setting unit into a unit smaller than the minimum setting unit of the program movement command, and is composed of a multiplier. For example, if the minimum setting unit of the program is 1 μ, then It is converted into units. Reference numeral 4 is a pulse distributor for interpolating and distributing pulses to the movement command whose minimum unit is converted in this way, 5 is a position controller in the servo circuit, 6 is a speed controller, 7 is a servo motor, and the servo motor 7 The unit detector 8 is attached to the motor shaft of, and the rotational position of the servomotor 7, that is,
The position of the movable part of the machine driven by the servomotor 7 is detected. Reference numeral 9 is a unit of the pulse output from the pulse distributor 4 based on the detection output from the position detector 8, that is, an interpolation unit converted by the unit conversion means 3 (in the above example, 0.
If the unit conversion means for converting to 1μ unit) is composed of digital servo, it is composed of multiplication means.

In FIG. 1, only one servo motor 7 is shown, and only one position control unit 5, speed control unit 6, position detector 8 and unit conversion means 9 are shown. Each such means is provided for each axis of the moving part of the machine and is identical and only one is shown. Further, compared with the above-described position control method and the conventional unit control method of the semi-closed loop method, the difference is that the unit conversion means 3 and 9 are provided, and the other is the same as the conventional one. .

In the above configuration, the decoding unit 2 reads the program from the NC tape and decodes it, and if it is a movement command, the unit conversion means 3 makes the unit smaller than the unit of the movement command of the program, for example, the unit of the movement command of the program. Is 1μ
The unit is converted to a unit of 0.1 μ, the converted movement command is interpolated by a pulse distributor, and a distribution pulse (pulse in units of 0.1 μ) is output to each axis. Position controller 5
Then, the difference between the movement command value based on the distributed pulse amount and the position detection signal from the position detector 8 converted into the distributed pulse unit (0.1 μ) by the unit conversion means 9 is amplified and output. The difference is controlled so as to be "0" and output. The speed control unit 6 controls the speed of the servo motor 7 in accordance with the movement command output from the position control unit 5, and controls the position so as to be different from the position commanded by the program.

In this way, the position control method is the same as the conventional one,
The difference from the conventional position control method is that the interpolation pulse is output in units smaller than the program movement command unit,
Further, the signal from the position detector 8 is also converted by the unit conversion means 9 so as to be the same as this interpolation pulse unit, and the position control unit 5 determines the position in units smaller than the movement command unit 8 of this program. That is the point to be controlled. Then, the distribution pulse is output by being interpolated in units smaller than the movement command unit of this program, and the position control is performed in this unit, so that a machining error in cutting or the like is reduced.

FIG. 2 is a diagram explaining that the machining error is small,
When the distribution pulse output in the unit of the movement command of the program is P, the unit conversion means 3 converts the unit to 1/4, and the distribution pulse at this time is P ′ (4 × P ′ = P) When the movement command X5Y7 along the line segment L1 from the point Q to the point R is commanded by the program, linear interpolation is performed in the conventional method, and the locus is as described above.
The pulse distribution along L2 is performed, and the cutting shape is the locus L2.
It becomes the shape of. As a result, the shape error is the line segment L1 and the locus L2.
The difference is from -1 / 2P to + 1 / 2P, that is, from -1/2 to +1/2 which is the minimum setting unit of the program movement command. On the other hand, in the present example in which the minimum unit of the distribution pulse is 1/4 of the minimum unit of the movement command of the program, the pulse distribution is performed in the same pattern as the locus L2, and only the unit is different. It becomes the locus L3 shown by the solid line in the figure, and the shape error is -1 / 2P 'to + 1 /
2P '=-1 / 8P to + 1 / 8P, that is, -1/8 to +1/8 which is the minimum setting unit of the program movement command. In this way, the processing error becomes small.

For example, the minimum setting unit for program movement commands is 1μ.
If the minimum unit converted by the unit converting means 3 is 0.1 μ, a processing error of −0.5 μ to +0.5 μ occurs in the conventional method, but in the present embodiment, −0.05 to +0. 05
μ, and the processing error becomes small.

In the above-described embodiment, the unit of the signal from the position detector 8 is converted into the interpolation pulse unit by the unit conversion means 9, but recently, the resolution of the position detector is high, and the detection unit is the movement command of the program. Since it is often smaller than the minimum setting unit, if the interpolation unit, that is, the distribution pulse unit is set by the unit conversion unit 3 so as to be the same as the detection unit of this position detector, the unit conversion unit 9 is provided. No need.

EFFECTS OF THE INVENTION As described above, the present invention interpolates in a unit smaller than the minimum setting unit of the movement command of the program and distributes pulses, so that the command error in position control can be made small. When the cutting process is performed, the processing error is reduced and the processing accuracy is improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is
It is a figure explaining the difference of the linear interpolation by this invention and the conventional position control system. 1 ... NC tape, 3, 9 ... Unit conversion means, 7 ... Servo motor, 8 ... Position detector.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-54-132089 (JP, A) JP-A-58-3002 (JP, A) JP-A-55-66003 (JP, A)

Claims (1)

[Claims] 1. In a position control system for controlling a servo motor by a numerical controller to control a position of a machine, the interpolation result is converted into an interpolation unit smaller than a minimum set unit of a movement command instructed by a program, and an interpolation result is obtained. The movement amount per unit time of is input to the position control unit of the servo circuit by the data of the interpolation unit, and the position detection signal unit from the detector for detecting the position of the machine is input to the position control unit as the interpolation unit. A precision position control system characterized by performing position control.