JPS62176736A - Linear position control method - Google Patents

Abstract

PURPOSE:To make it possible to perform accurate position control by a milli- meter unit by setting a pitch (p)mm of a toothed belt X the number of a drive pulley (n)/an objective minimum travel amount (s)mm so as to become a nearly integral number in a device converting a motor revolution to linear motion by a milli-meter unit by the use of a tooth belt pitched in inch and by detecting the rotational position of a motor by a position detecting means outputting pulses of (p)X(n)/(s) per one revolution. CONSTITUTION:In an industrial robot, when (p)mm is taken as pitch of a toothed belt 18 for driving a slider 20, (n) is taken as the number of teeth of a drive pulley, and (s)mm is taken as an objective minimum travel amount, each of them is set so that the result of (p)X(n)/(s) may become a nearly integral number. And the rotational position of a motor 24 for driving a drive pulley 14 is detected by a rotary encoder 26 for outputting same number of pulses as (p)X(n)/(s) per one revolution. And the servo motor 24 is controlled on the basis of the difference between the output pulse (b) and commanded travel quantity through a counter 28, D/A 30, and a driver 32. The linear position control by the milli-meter unit can thus become possible by using the toothed belt pitched in inch.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a linear position control method for converting the rotation of a servo motor into a linear motion in mm units using a toothed belt with an inch pitch.

(Background of the Invention) In industrial robots and the like, rotation of a servo motor is sometimes converted into linear motion by a toothed belt. In this case, a position detector such as an optical rotary encoder is used to detect the amount of linear movement of the belt from the rotation angle of the servo motor.

On the other hand, while toothed belts with inch pitches have been widely used, linear position control is often performed in mm units. Further, the conventional rotary encoder is made to output a number of pulses with a sharp decimal number such as 250°500.1000, 2000 (7) or a pulse number of nff1 of 2 per revolution. For this reason, there was a problem in that it was not possible to precisely control the inch pitch toothed belt in mm units. So m m
This problem does not occur if a toothed belt with a pitch of t1 is used, but belts with a pitch of mm are conventionally custom-made products and are difficult to insert.

(Purpose of the Invention) The present invention was made in view of the above circumstances, and when converting the rotation of a servo motor into linear motion via a toothed belt with a widely used inch pitch, The purpose of this invention is to apply a linear position control method that can accurately control the amount of linear movement.

(Structure of the Invention) According to the present invention, this object is to provide a linear position control method for converting the rotation of a servo motor into a linear movement in units of mm via a toothed belt with an inch pitch. The unit is expressed as p, the number of teeth of the drive boob is n, the target minimum movement amount is S, p X n / s is set to be approximately an integer, and the rotational position of the motor is p per rotation. A straight line characterized in that the servo motor is detected by a position detecting means that outputs a pulse number of X n /s, and the servo motor is controlled based on the difference between the output of the position detecting means and a command pulse indicating a commanded movement amount. This is achieved by a position control method.

Here, an optical rotary encoder is suitable as the position detection means, but is not limited to this. For example, a high-resolution position 1δ detector may be used, and its output pulses may be converted into the above (p×n/s) by a conversion means such as an arithmetic unit. ) may be converted to match.

(Example) The drawing is a conceptual diagram of an example of the present invention. In this figure, reference numeral 10 denotes a base, and this base 10 has upright portions 12, 12 at both ends. A driving pulley 14 and a driven pulley 16 are held on both of these upright portions 12.12, and an inch-pitch southern bell 18 is wound around both pulleys 14.16.

Reference numeral 20 denotes a slider, which is slidably held by a guide 22.22 which is passed between the upright portion 12.12 of one car and the belt 18 and the other. This slider 20 has a belt 1
8 is fixed.

24 is a servo motor, and the rotating shaft of this motor 240 is fixed to the drive pulley 14.

26 is a position detector that detects the rotation angle of this motor 24, and for example, an optical incremental rotary encoder is used.

Reference numeral 28 denotes an up-counter (U/D counter), and a number of command pulses a proportional to the commanded movement amount of the slider 20 is input to its up-input terminal. Further, the output pulse b of the encoder 26 is input to the down input terminal. The counter 28 is a,! The difference (a-b) between 1 and 1 is calculated, and the signal C indicating the difference is converted into an analog signal d by the D/A converter 30. The driver 32 rotates the motor 24 based on this analog signal d.

Here, the encoder 26 outputs the number of pulses determined as follows per revolution of the motor 24. That is, the south pitch of the belt 18 is expressed in mm as p, the number of teeth of the drive pulley 14 is n, and the target minimum movement (lY
When is S, (p x n /s) is determined to be approximately an integer, and the encoder 26 outputs the same number of pulses as this (p x n/s) per revolution.

For example, when p=115 inches=5.08 mm n=15 s=0.1 mm, (p×n/5)=762. Therefore, the encoder 26 is set to output 762 pulses per revolution.

Note that the pinch p may be an irrational number that cannot be expressed as a fraction, so if an attempt is made to determine the target minimum movement j7s to a well-rounded value, (p×n/s) will not strictly be an integer. Therefore, in relation to control accuracy, even if it is not a strictly integer,
In other words, there is no problem even if it is set so that it can be approximately regarded as an integer.

(Effects of the Invention) As described in 1- below, the present invention provides a pulse that changes the rotational position of the motor by a pulse of (p×n/s) per rotation, which makes (p×n/s) almost an integer. Since the position is detected by the position detecting means that outputs the number, it is possible to control the position in mm width while using a toothed belt with inch pitch.

[Brief explanation of drawings]

The drawings are conceptual diagrams of embodiments of the present invention. 14... Drive pulley, 18... belt with ridges, 24... Servo motor, 26... As a position detection means Rotary encoder.

Claims (1)

[Claims] In a linear position control method for converting the rotation of a servo motor into linear motion in units of mm via an inch-pitch toothed belt, the pitch of the toothed belt is expressed in units of mm and is expressed as p;
Let the number of teeth of the drive pulley be n, the target minimum movement amount be s, set so that p×n/s is approximately an integer, and set the rotational position of the motor to the number of pulses p×n/s per rotation. A linear position control method, characterized in that the servo motor is controlled based on a difference between an output pulse of the position detection means and a command pulse indicating a commanded movement amount while detecting the position by an output position detection means.