JPS6320510A - Positioning device for servo-motor - Google Patents

Abstract

PURPOSE:To accurately control a rotary driving quantity based upon integral rotations of a servo-motor by detecting a rotating speed from the specific code signal of an absolute position detecting means and detecting a rotating speed commanded with movement data, and then controlling the step of the servo-motor on the basis of the code signal. CONSTITUTION:The rotating speed of the servo-motor 1 is known by allowing a down counter 2 to count one-turn signals Grid generated by detecting a specific code in an absolute code signal from an absolute code encoder 3 by a grid detecting circuit 5. Then when the counted value of the down counter 2 reaches zero, an open loop signal Open from a control circuit 9 rises with a zero-detecting signal and an analog switch 6 is switched to supply a command voltage VLP for position correction to a servo-motor driving unit 7. The motor is stopped where this position correcting voltage VLP becomes 0, and consequently the motor can be made to have accurately integral rotations, so that stepwise positioning operation is accurately performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a servo motor positioning device that is effective in digitally controlling a servo motor for driving a machine tool or the like.

(Prior art) In order to digitally control machine tools, the amount of rotation of the servo motor must be accurately detected. A resolver that detects the amount of movement is one type of angular position detector. This type of resolver constitutes a type of electromagnetic transformer that outputs a voltage as a function of the angular position of the rotor.It has a simple structure and is resistant to vibrations and shocks, and the feedback signal from this resolver can be used for analog calculation. It is possible to position the rotor at a specific rotational angle by obtaining a position correction voltage, and such simple positioning devices have been commonly used in the past.

(Problems to be Solved by the Invention) However, although such a resolver as an angular position detector has high detection accuracy, it requires an excitation circuit, and also requires a 7-analog circuit for digitally processing the detection signal. A digital conversion circuit was required. For this reason, when realizing a positioning device at a low cost, a position detector based on a digital angle signal such as an optical rotary encoder is adopted, but a device having such a position detector is used to function as the above-mentioned simple positioning device. In order to do this, a resolver must be added, which poses a problem in that it becomes expensive.

The present invention solves the problems of the prior art,
The purpose of this invention is to provide a positioning device with a simple configuration that uses digital positioning and detection functions that correspond to the rotation angle of a servo motor.

(Means for solving the problem of source points) The present invention provides absolute position detection means that outputs a code signal corresponding to the rotational position of a servo motor, and a voltage that generates a command voltage for correcting the stop position based on the code signal. a generating means, a counting means for counting the number of revolutions of the servo motor from a one-rotation signal included in the code signal, and a speed voltage generating means for generating a speed command voltage to the servo motor;
A positioning device for a servo motor, characterized in that it comprises switching control means for switching the speed command voltage to the servo motor to the command voltage for correcting the stop position at the end of counting the predetermined number of rotations. This solves the problems of the prior art.

(Function) The present invention detects the rotation speed from a specific code signal among the code signals output from the absolute position detection means, detects the rotation speed commanded by movement data, and then converts the rotation speed to the code signal. Since the servo motor is controlled to stop based on the command voltage for position correction based on the above, the rotational drive amount of the servo motor by an integral number of rotations can be controlled with high accuracy.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an example of a servo motor positioning device. Movement data serving as a drive command for a servo motor 1 is supplied to a down counter 2 as a 12-bit digital signal DO to Dll.

The servo motor l above has a 4-bit gray code C0~
Absolute encoder 3 with output code of C5
is directly connected to the shaft, and this absolute code signal is supplied to the position correction voltage generation circuit 4 and the grid detection circuit 5. This position correction voltage generation circuit 4 operates to control the servo motor l based on the code signal, as will be described in detail later.
This command voltage VLP is supplied to the servo motor drive unit 7 via the analog switch 16 when the servo motor 1 is controlled to stop.

The down counter 2 is supplied with the data set signal D set along with the 12-bit movement data, and is also supplied with the one-rotation signal Grid generated by the grid detection circuit 5 based on the absolute code signal. 8
is a detection circuit connected to the down counter 2, and the movement data DO~Dll set in the down counter 2 is 1.
It is subtracted by the rotation signal Grid and outputs a zero detection signal Z when it becomes zero. A control circuit 9 for controlling the analog switch 8 is connected to the detection circuit 8, and when the data set signal Dset is input, the control circuit 9 outputs an open loop signal Open to connect the analog switch 6 to the terminal. I am trying to switch it to terminal a. Then, when the zero detection signal Z is supplied to the control circuit 9, the analog switch 6 is inverted again.

Reference numeral 10 denotes a feed speed voltage generation circuit that supplies a speed voltage VCa that defines the feed speed during rotation of the servo motor 1 as a speed command voltage to the servo motor drive unit 7 via an analog switch 6 .

FIG. 2 is a timing chart showing an example of the operation timing of the positioning device having the above configuration.

Movement data DO to D11 are stored in each digit of the down counter 2.
is set by the data set signal D set,
The contents of the down counter 2 are set from zero to a predetermined number of revolutions at which the servo motor 1 should rotate, for example "6", and the open loop signal Open from the control circuit 9 is output from the analog switch 6 to the terminal. a, the servo motor drive unit 7 is supplied with the speed voltage Vca. The servo motor drive unit 7 uses this speed voltage V
ca to the speed command voltage v cxo by a predetermined acceleration/deceleration circuit
In addition, the servo motor 1 is rotationally controlled. The number of rotations of the servo motor 1 is determined by writing the one rotation signal Grid generated by detecting a specific code from the absolute code signal outputted from the absolute encoder 3 in the grid detection circuit 5 in -. It is counted by counting with the down counter 2.

Then, when the count value of the down counter 2 reaches zero, the open loop signal Open from the control circuit 9 falls due to the zero detection signal Z, and the analog switch 6 is switched to set the servo motor drive unit to the position of the unit 7. Supply command voltage VLP for correction.

FIG. 3 shows an example of the position correction voltage generation circuit 4 that outputs the command voltage VLP. This position correction voltage generation circuit 4 includes a conversion circuit 41 that converts the Gray code CO-C into a normal binary code, and a D/A converter 4 that outputs an analog signal corresponding to the converted binary data.
It consists of 2. As shown in FIG. 4, when the servo motor 1 is rotating, the command voltage VLP is always output as an output of the D/A converter 42, for example, as a linear function value with respect to the rotation angle of the servo motor 1, and
The code detection circuit 5 outputs a one-rotation signal Grid that is synchronized with the rising timing of the gray code C3.

FIG. 5 is a diagram illustrating a specific configuration of the grid detection circuit 5. As shown in FIG. Here, two clocks operating on the same clock CLK are used.
A gray code c2. The one-rotation signal Grid shown in FIG. 4 is obtained from c3, but by changing the decoding method of the above-mentioned absolute code signal, the one-rotation signal Grid can be taken out at any position within one cycle. .

In addition, a code signal output according to the rotation angle is obtained by an absolute position detection means such as an absolute encoder directly connected to the output shaft of the servo motor l, and this code signal is
By performing the A conversion, the position correction voltage VLP can be generated as a function value of the motor rotation angle, so the servo motor 1 can be stopped at a rotation angle position where the position correction voltage LP becomes 0. In this manner, by counting the one-rotation signal and stopping the motor at the point where the position correction voltage VLP becomes O, the motor can be accurately rotated by an integer number of rotations, so that step-like positioning can be performed with high precision.

Note that the functional relationship between the motor rotation angle and the output voltage in the position correction voltage generation circuit 4 may be any function as long as it is proportional to the displacement at (near) the stop position and generates voltages with opposite signs before and after the stop position. , -order number, but may be a trigonometric function such as a sine waveform, for example.

(Effects of the Invention) As explained above, according to the positioning device of the present invention, the servo motor can be stopped at an angle where the position correction voltage becomes 0 by the code signal from the absolute position detection means, and the servo motor can be stopped for one more rotation. By counting the signals, step-like positioning for each rotation can be performed with high precision. Furthermore, such a positioning device can be applied to all servo systems that have an absolute position detection means that outputs the rotation angle in the form of a code.

[Brief explanation of the drawing]

Fig. 1 is a circuit configuration diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing a time chart explaining the operation of the embodiment, and Fig. 3 is an example of a position correction voltage generation circuit. FIG. 4 is a timing explanatory diagram showing the relationship between the code signal, one revolution signal, and command voltage, and FIG. 5 is a block diagram showing an example of a grid detection circuit. 1... Servo motor, 2... Down counter, 3...
... Absolute encoder, 4 ... Position correction voltage generation circuit, 6 ... Analog switch, 9 ... Control circuit. Patent applicant: Representative of FANUC Co., Ltd. Patent attorney: Minoru Tsuji Figure 3C. GrRIC)

Claims (4)

[Claims] (1) Absolute position detection means that outputs a code signal corresponding to the rotational position of the servo motor, and voltage generation means that generates a command voltage for correcting the stop position based on this code signal;
a counting means for counting the number of rotations of the servo motor from a one-rotation signal included in the code signal; a speed voltage generation means for generating a speed command voltage to the servo motor; A servo motor positioning device comprising: switching control means for switching a speed command voltage to the motor to a command voltage for correcting a stop position; (2) Positioning of the servo motor according to claim 1, further comprising a decoder that converts the code signal into a voltage signal proportional to the rotation angle of the servo motor, at least in the vicinity of the stop position. Device. (3) The servo motor positioning device according to claim 2, wherein the voltage signal is output as a sine function value with respect to the rotation angle of the servo motor. (4) The servo motor positioning device according to claim 2, wherein the voltage signal is output as a linear function value with respect to the rotation angle of the servo motor.