JPS6380310A - Servo positioning device - Google Patents

Abstract

PURPOSE:To attain accurate positioning by arranging a scale of an aperiodic pattern to one member along with driving and arranging a detector reading the displacement from the scale to the other member to use a detected value as a position signal. CONSTITUTION:Biphase sinusoidal wave signals a1, b1 with prescribed pitch are obtained from aperiodic and periodic scales attended with the movement of a base converted 64, 66 respectively into binary signals a2, b2, FFs 70, 72 and AND gates 74, 76 apply direction discrimination 68 to obtain signals a3, b3. Moreover, they are converted into pulses a4, b4 having equal level by converters 78, 80 respectively, rectified 82, subject to differential amplification 88 to obtain a speed output (q). When the base is moved quickly in a direction, the frequency of the pulse a4 or b4 is increased and the polarity of the output (q) depends on the moving direction. Through such constitution above, the servo positioning device not limited by the response speed and accumulated with no error due to noise is obtained.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a servo positioning device, and in particular, the relative positioning of two members that move relatively along a drive shaft involving a servo motor, suitable for use in NC machine tools, measuring machines, setting tools, etc. This paper focuses on improving a servo positioning device that automatically controls speed and position i by feeding back feed to a servo motor control circuit.

[Prior art] Servo AM, which automatically controls processes by feeding back position and speed information using a servo motor, has become popular in the fields of NC machining tools, measuring machines, and setting tool caps. I'm doing it. These servo P4m are also required to be faster and more efficient in response to demands for more efficient machining and measurement. This figure shows a servo system that positions a moving table 10 in a closed loop using a linear servo motor 12. In this servo system, the moving table 10 is restrained by a guide mechanism (not shown). However, in the X direction, the rod (secondary conductor) 14 and stator 1
It is driven by a linear servo motor 12 consisting of 6. In this servo system, the feedback of ['+27t is obtained by using a grating 19 formed on the main scale 18'-, which is made up of periodic scales in the form of vertical stripes of light and dark, and a scale corresponding to the periodic scale. A detector 20 including an index scale (not shown) outputs two-phase sine wave signals with different 90' phases, which are pulsed by a counting circuit 22 and counted in an incremental manner. In, 2.1 is a latch circuit, 2.
6 is a comparison circuit, 28 is a setting circuit, 30 is a CPU, 32 is a pass line, and 34 is a motor drive circuit. On the other hand, speed feedback is performed by inputting a signal from a linear speed sensor 36 connected to the stator 16 to a speed detection circuit 38, converting it into a speed signal, and then inputting it to the motor drive circuit 34. be exposed. The linear speed sensor 36 is an AC tachometer developed in a straight line. In order to increase the speed of sound, development is progressing not only in servo systems using linear servo motors, but also in cases where spindle-type servo motors are used. [Problems to be Solved by the Invention] However, in the conventional device, since the position feedback element is an incremental type length measurement, the counting may not be able to follow up when performing a high-speed suction. In addition, the current power supply environment in the factory is poor, and noise is likely to mix in during the process, so in the case of an incremental type, there are problems such as errors are reduced to Wtn and positioning errors occur. The above problem can be alleviated somewhat by using a rotary potentiometer, which is an absolute type within a narrow range within one rotation of a ball screw, as a position feedback element, but since it is an incremental type over a wide range, It is not a practical solution. The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a servo positioning device in which the response speed is not limited and errors due to noise are not accumulated. do.

[Means to solve the problem]

The present invention is a servo positioning device that automatically controls the relative positions of two members that move relative to each other along a drive shaft in which a servo motor is involved by feeding back a speed signal and a position signal to a ':# control circuit of a servo motor. A scale having a scale formed of an aperiodic pattern along the drive shaft is disposed on one member, and a detector for reading the amount of displacement from the aperiodic pattern is disposed on the other member,
The above object is achieved by using the detected value as a position signal. Further, in embodiment R of the present invention, the aperiodic pattern is composed of reference edges arranged at a constant pitch and a position pattern for identifying the reference edges. Further, in another embodiment of the present invention, the servo motor is driven by the servo motor. This is a linear servo motor with the IJ axis as the secondary conductor.

[Effect]

In the present invention, instead of position feedback using a conventional incremental displacement detector, position feedback is performed using an absolute displacement detector. Therefore, there is no limit to the response speed, and even if noise is mixed in, the error will not be reduced to Wtn and a positioning error will not occur. Furthermore, if the aperiodic pattern is composed of reference edges arranged at a constant pitch and a position pattern for identifying the reference edges, the structure is simple. Furthermore, when the servo motor is a linear servo motor in which the drive shaft is a secondary conductor, the effects of the present invention are particularly great.

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. In the first embodiment of the present invention, as shown in FIG. 1, a main scale 18 is arranged parallel to a rod 14 of a linear servo motor 12 similar to the conventional one. The main scale 18 is provided with a first grating 19 consisting of a periodic scale similar to the conventional one, and a second grating 60 consisting of an aperiodic absolute scale. The first grating 19 consists of a bright and dark striped pattern with a predetermined pitch, and the first detector 20, similar to the conventional one, is provided with an index scale of a corresponding pattern. Therefore, according to the displacement of the moving table 10, two-phase sine wave signals a1 and bl of a predetermined pitch are output. The sine wave signals a+ and bl are input to a conversion circuit 62 to generate a speed signal q proportional to the speed, which is fed back to the motor drive circuit 34. As shown in detail in FIG. 2, there are Schmitt circuits 64 and 66 that binarize the sine wave signals a1 and bl into binary signals a2 and bl, respectively, and a JK flip-flop for discriminating the traveling direction of the moving table 10. A direction discrimination circuit 68 consisting of a 70.72 and an AND 4.76
, b3) into pulses a,, b, of equal length, and a rectifier diode 84,86 for converting the pulses a,, b4 into DC signals.
The rectifier circuit 82 including the difference! It is comprised of a differential amplifier 88 that amplifies the lJ signal and outputs the speed output q. Note that the differential amplifier 88 may have a filter effect. A time chart of each signal in the f/v conversion circuit 62 when the moving table 10 moves from right to stop to left is as shown in FIG. That is, the two-phase sine wave signals a, , b are binarized by Schmitt circuits 64 and 66 to become 2ftg signals a2 and bl. The zero order pulses are converted into pulses a3 or b3 by the pulsing circuits 78 and 80, which are converted into pulses a4 and b4 of equal length by the rectifying circuit 82, respectively, and the difference amplification value is the speed. Output (becomes 1.In principle, when the moving table 10 moves quickly in one direction, the frequency of pulse a4 or b< becomes higher and the rectification value also becomes larger. are positive and negative. Also, the second grating 6 formed on the main scale 18
0, as shown in detail in FIG. 1, includes a reference pattern 90 with a width of 1 inch per line including reference edges 90At arranged at a constant pitch P, and a reference pattern 90 for distinguishing the reference patterns from each other. The B-IJ pattern placed in between is composed of a position pattern 92 consisting of a binary pattern with a line width of srn bits, which indicates the number of patterns from the left side of the reference pattern on the left side of the figure. The second detector 94 disposed opposite to the second grating 60 has a light receiving length capable of simultaneously receiving light from at least two reference edges 90A, as shown in FIG. , pixel pitch ℃, image L
A QN line sensor 96 is included, and is used to identify the reference pattern 90 and to identify, for example, the leftmost pixel 9 of the line sensor 96.
Based on the length Y from 6A to the reference pattern, the distance from the origin to the current position in FIG. 1 can be detected in minutes sg: 1 μm. The pitch P in Figure 2 is 5n.
1. If the position pattern 92 is provided up to 9 bits, approximately 2.
Absolute values can be detected up to a range of 51. Distance detection based on the output of the second detector 94 is performed by an absolute detection circuit 98, and the value thereof is directly input to the CPU 30 as position R18. Unlike the incremental type, this absolute detection circuit 98 requires about 100 μsec in total to determine the value, so the value is held in the latch circuits 2 and 1 every time the calculation is completed. Regarding absolute position detection using reference edges arranged at a constant pitch and a position pattern for identifying the reference edges, the applicant has already proposed in Japanese Patent Application No. 157581/1983, so details are not provided. , see this earlier application. In this first embodiment, the present invention is applied to a linear servo motor 12 whose drive shaft is a secondary scale body, and the present invention is particularly effective. Note that the scope of application of the present invention is not limited to this, and as in a second embodiment shown in FIG.
By applying the present invention to an NC servo device that performs positioning,
It is also possible to use an absolute type length measuring device similar to that of the first embodiment as the position feedback element. In FIG. 0, 104 is a gear box. The other points are the same as those of the first embodiment, so the explanation will be omitted. In each of the above embodiments, an optical scale was used as the second grating 60 and the second detector 94 of the absolute method, but the absolute method length measuring device is not limited to this, and the length measuring device of about 11 is used. It is also possible to use other scales, such as a capacitive scale, as long as the range can be measured with a resolution of about 10 μm.

【Effect of the invention】

As explained below, according to the present invention, since an absolute type position feedback element is used, there is no limit to the response speed, and even if noise is mixed, the error is calculated and the position is determined. y) It has the advantage of eliminating the possibility of errors.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of a first embodiment of a servo positioning device according to the present invention, and FIG. 2 shows an example of the top configuration of an f/v conversion circuit used in the first embodiment. FIG. 3 is a diagram showing examples of signal waveforms of each part of the f/v conversion circuit shown in FIG. 2, and FIG. 2. FIG. 5 is a block diagram showing the structure of the second embodiment. FIG. 6 is a diagram showing the structure of an example of a conventional closed loop servo positioning device. It is a block diagram. 10...Moving table, 12...Linear servo motor, 14...Rod (secondary conductor), 16...Stator, 18...Main scale, 19.60 River grid, 20.94...・Detector, 98... Absolute detection circuit, 100... Servo motor.

Claims (3)

[Claims] (1) In a servo positioning device that automatically controls the relative positions of two members that move relative to each other along a drive shaft involving a servo motor by feeding back a speed signal and a position signal to the control circuit of the servo motor, one A scale with a scale formed of a non-periodic pattern is placed on one member, and a detector that reads the amount of displacement from the non-periodic pattern is placed on the other member, and the detected value is used as a position indicator. A servo positioning device characterized by being used as a signal. (2) The servo positioning device according to claim 1, wherein the non-periodic pattern is composed of reference edges arranged at a constant pitch and a position pattern for identifying the reference edges. (3) The servo positioning device according to claim 1 or 2, wherein the servo motor is a linear servo motor in which the drive shaft is a secondary conductor.