JP2597977B2 - Reference point setting method for position detection circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference point setting method for a position detection circuit using a pulse generator as an incremental type position detector.

2. Description of the Related Art For example, a method of combining a DC servomotor and a pulse generator and detecting the position of a moving body driven by the DC servomotor with the pulse generator is known in the field of machine tools and the like.

Taking the servo control type slide unit of FIG. 5 as an example, the position of the slide table 3 driven by the CD servo motor 1 and the ball screw 2 is generated by the pulse generator 4 according to the rotational displacement of the DC servo motor 1. The output signal is detected by counting the number of pulses.

Reference numeral 5 denotes an NC control device, 6 denotes a servo control circuit, 7 denotes a tacho generator, and 8 denotes a limit switch for detecting an origin position.

Then, in order to eliminate the accumulated error due to the backlash of the machine feed system and maintain its position detection accuracy, it is necessary to return to the origin position every cycle and set the coordinate system to zero. Has taken.

As shown in FIG. 6, the output of the pulse generator 4, that is, the A-phase output signal a having a 90 ° phase shift in electrical angle
The rise of the pulse is counted by the coordinate register in the NC control device 5 for the B-phase output signal b. The pulse generator 4 generates one pulse z (one rotation signal) for one rotation of the pulse generator 4 as a Z-phase (C-phase) output in addition to the A-phase and B-phase outputs.

Therefore, the slide table 3 shown in FIG. 5 is moved backward at a low speed until the slide table 3 hits the limit switch 8, and the logical product is obtained by the origin set signal c output from the limit switch 8 and the Z-phase output z of the pulse generator 4, and the logical product By resetting the count data of the coordinate register at the timing of the output (origin position signal) e, the origin of the coordinates of the machine feed system is set.

Problems to be Solved by the Invention In the conventional method, the origin is set by moving the slide table 3 to a specific one mechanical origin and turning on the limit switch 8, so that the power supply
If the slide table 3 is stopped at a position other than the machine origin at the time of OFF or emergency stop, the slide table 3 must be returned slowly until it hits the limit switch 8 to set the origin. Lower.

The present invention provides a method in which the initial zero reset position can be set as a reference point regardless of whether the moving body is moved in any of the forward and reverse directions from an arbitrary position. .

Means for Solving the Problems The present invention detects an absolute position of a predetermined moving body in an analog manner by a potentiometer attached to a moving body driving motor, and detects the analog output when the pulse generator makes one rotation. While digitizing and outputting with a resolution corresponding to the moving amount of the moving body, the incremental position of the moving body is also detected by counting the number of pulses of the A-phase output of the pulse generator also attached to the motor, A reference point setting method for a position detecting circuit, wherein a sum of the digitized absolute position data and the incremental position data obtained as the pulse count value is output as absolute current position data of the moving body. AND of Z-phase output and A-phase output including one pulse generated for one rotation of the pulse generator It is characterized in that the count value of the pulse generator is reset to zero at the generation timing of the reference point signal generated under the condition.

According to the present invention, since the absolute position of the moving body is constantly monitored by the potentiometer,
Even if a situation such as OFF occurs, the current position of the moving object does not become unknown.

Since the zero point is reset each time on the condition of the reference point signal generated once for each rotation of the pulse generator, an arbitrary zero reset position can be set as the reference point. Even when the pulse generator is turned off, the reference point can be set only by moving the moving body within the range where the pulse generator makes one rotation.

Embodiment FIGS. 1A and 1B show an embodiment of the present invention. FIG. 1A is different from FIG. 5 in that a potentiometer 10 is added via a speed reduction mechanism 9. Is different.

The potentiometer 10 and the pulse generator 4 have a rotation speed ratio of 1: 100, and when the motor 1 and the pulse generator 4 make 100 rotations, the potentiometer 10 makes one rotation. That is, if the pitch (lead) of the ball screw 2 is 10 mm, the potentiometer 10
One revolution of has an effective working distance of 1 m.

Here, regarding the output waveform of the pulse generator 4, as shown in FIGS. 2 and 3, it is assumed that the pulse width of the A-phase output a is straddled by the pulse width of the Z-phase output z, and T ₁ ≧
Add a condition such that (1/2) · T ₂ and T ₃ ≧ (1/2) · T ₂ .

The potentiometer 10 detects and outputs the absolute position of the slide table 3 as a moving body in an analog manner. The output of the aronag is digitized with the resolution of the pitch of the ball screw 2, and the unit width is D. (Mm). For example the unit width D in FIG. 1 (B) and 10 mm, the D ₃ is 30.000mm if D ₂ data instruction 20.000mm, D ₄ will be instructs respectively 40.000 mm.

Further, in order to detect the incremental position of the slide table 3, the rising edge of the A-phase output a of the pulse generator 4 is counted and represented in a coordinate register in the NC control device 5, and the unit width is d (mm).

The output of the potentiometer 10 is output as the absolute current position data of the slide table 3 as the sum of the digitized absolute position data and the incremental position data obtained as the pulse count value of the pulse generator 4. creating a home position signal (reference point signal) e ₁ ANDed with the pulse rise of the pulse rise and Z-phase output z of the a-phase output a of the generator 4, the above-described the origin position signal e ₁ as a reset signal Reset the contents of the coordinate register.

Assuming that the slide table 3 is stopped at an arbitrary position on the reciprocating path of the slide table 3 for turning off the power or the like, when the home position is set after the power is turned on, the slide table 3 is moved from the stopped position. Forward or backward (forward rotation or reverse rotation operation for the pulse generator 4). Then, for example, if during the pulse generator Figure 1 in the forward direction of the 4 (B) are shown Q ₁ point and that rises pulse of the origin position signals e _1, d on the coordinate corresponding to the rise of the pulse Consider position ₈ as origin "0".

That is, to reset the coordinate register at the rising edge of the pulse origin position signal e _1, zero-set the contents of coordinate register. In this case, since the absolute position of the slide table 3 is indicated by the value of the potentiometer 10, as its coordinate is in within the width of the D _3, With D × P (pitch of the ball screw) + "0" The origin position on the coordinate register is obtained. This also applies to Q ₂ points in the reverse direction of the pulse generator 4.

Thus, one rotation of the pulse generator 4
At the time of zero reset that occurs twice, the zero reset position is
In order to make the output of the potentiometer 10 a position specified by the digitized absolute position data, the absolute position data is output as the current position data of the slide table 3 each time. In particular, even if the power is turned on again at an arbitrary position when the power is turned off, the first zero reset is performed only by moving the slide table 3 within the range where the pulse generator 4 makes one rotation. The position can be set as the origin position, and finally the origin position can always be determined within the range of the resolution of the potentiometer 10.

Here, FIGS. 4A and 4B show reset timings when the pulse generator 4 rotates forward and when the pulse generator 4 rotates reversely, and are located at the same position as a machine. As is clear from the figure, the reset timing is shifted by a half pulse between the forward rotation and the reverse rotation, but there is no problem with the origin position.

According to the present invention, the absolute position data obtained by digitizing the analog output of the potentiometer and the incremental position data obtained as the count value of the output pulses of the pulse generator is used as the absolute current position data of the moving object. In the position detection circuit, the pulse generator counts at the timing of generation of the origin position signal generated under the logical product condition of the Z-phase output and the A-phase output including one pulse generated for one rotation of the pulse generator. Since the numerical value is reset to zero, the first zero reset position can be set as the reference point only by moving the slide table 3 within the range where the pulse generator 4 makes one rotation. Sometimes,
The reference point can be set at an arbitrary position and regardless of the moving direction of the moving body.

As a result, it is not necessary to return to the machine origin every time as in the conventional case, the reference point can be set during the execution of the program, and the current position does not become unknown even if the power is turned off.

[Brief description of the drawings]

FIG. 1 (A) is a conceptual diagram of a slide unit showing an embodiment of the present invention, FIG. 1 (B) is a time chart of FIG. 1 (A), and FIGS. 2 and 3 are explanations of waveforms of main signals. Figure, 4th
FIG. 1 is an explanatory view of a main part of FIG. 1 (B), FIG. 5 is a conceptual diagram of a conventional slide unit, and FIG. 6 is a time chart of FIG. 1. DC servo motor (moving body driving motor) 2.
Ball screw, 3 ... Slide table as moving body, 4 ... Pulse generator, 10 ... Potentiometer.

Claims (1)

(57) [Claims] An absolute position of a predetermined moving body is detected in an analog manner by a potentiometer attached to a moving body driving motor, and the analog output is detected as a moving amount of the moving body when the pulse generator makes one rotation. While outputting by digitizing with the corresponding resolution, the incremental position of the moving body is detected by counting the number of pulses of the A-phase output of the pulse generator also attached to the motor, and the digitized absolute position data is detected. A reference point setting method for a position detection circuit that outputs a sum of the pulse count value and incremental position data obtained as the pulse count value as absolute current position data of the moving object, wherein the pulse generator performs one rotation. The reference point signal generated under the condition of the logical product of the Z-phase output and the A-phase output including one generated pulse Reference point set process of the position detection circuit, characterized in that the zero-reset the count value of the pulse generator in generation timing of.