JPS623305A - Method for setting original point position of robot - Google Patents

Abstract

PURPOSE:To control the original point of a coordinate system with a numerical control system by storing the count value of an encoder which delivers the number of pulses proportional to an angle in the form of the position information of a robot when the pulse sent from a position detecting sensor for robot has a rise. CONSTITUTION:The signals produced from an encoder are divided into A and B phases and the zero phase respectively and then supplied to an up-down counter through terminations and filters. The number of pulses is increased with a single revolution and in proportion to the revolving angle and N pulses are produced. Thus the count number of A and B phases are reset with input of the zero phase. When an arm is turned and the ON signal of a sensor is supplied while the pulses sent from the encoder are counted, the count number (d) of the encoder is stored in a rise mode and displayed on a CRT screen of a controller. At the same time, an original point is set with numerical control without moving the arm back to a point (a) which is moved back from the relevant position by the number (d).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for setting the origin position of a robot's coordinate system by numerical control.

(Prior Art) There is a conventional robot as shown in FIG. This allows a working tool 3 provided at the tip of the second arm to be two-dimensionally positioned by a first arm 1 and a second arm 2 that rotate about two mutually parallel axes θ□ and θ2. 4
is a column that supports the robot. A servo motor 6 with an encoder 5 connected to the θ1 axis is fixed to the column 4, and the servo motor 6 and the first arm 1 are connected via a speed reducer 7. or.

A servo motor 9 connected to an encoder 8 is connected to the θ2 axis.
is fixed to the tip of the first arm 1, and the servo motor 9 and the second arm 2 are connected via a speed reducer 1o. Sensors 11 and 12 are attached to the column 4 and the first arm 12, respectively, and detect the positions of the first arm 1 and the 27th arm 2 in an ON-FF manner.

With such a robot, the method of setting the origin in the robot's coordinate system is to slowly rotate the arm as shown in Figure 5, and set the origin when the sensors 11 and 12 are turned on, and when the encoders 5 and 8 rotate once. The arm returns to its home position in synchronization with the zero-phase signal that is output once (by setting it to a position where it turns ON at the same time). In this method, since the rotation of the motor is transmitted to the arm via the reducer, there are multiple arm rotation positions that correspond to the zero-phase signal position of one encoder. This is the method used to identify.

However, the ON range of the sensor changes depending on installation conditions such as the distance between the sensor and the target. Therefore, if the ON area of the sensor becomes too small, synchronization with the zero-phase signal of the encoder may not be achieved, and if the ON area of the sensor becomes too large, the zero-phase signal of the encoder may become 2 times in the ON area.
Since there is a risk that this occurs more than once and two origins appear, there is a problem in that the arm must always be rotated in the same direction to pick up the same zero phase signal when returning to the origin.

Furthermore, with the above method, when disassembled and reassembled to replace the motor or to clean the reducer lubricant, the relative position of the encoder and arm will become misaligned, and as a result, the zero phase signal of the encoder will also remain the same as before. There was a problem in that the robot would be shifted from the robot coordinate system and the robot would have to be taught again.

(Purpose) The purpose of the present invention is to make it possible to obtain robot position information without the need to synchronize the ON signal of a sensor and the zero-phase signal of an encoder, and to set the origin of a coordinate system by numerical control. It is said that

(Configuration) In order to achieve the above object, the present invention counts pulses from an encoder in which the number of pulses increases in proportion to the angle, and the number of pulse counts is reset to zero in one rotation. At the same time, a pulse signal from a sensor that detects the robot's position is input, the encoder count at the rise of the pulse signal is stored as the robot's position information, and the origin of the coordinate system is set based on the position information. It is characterized by

A detailed explanation will be given below based on the embodiment shown in FIGS. 1 to 3. The mechanical configuration is, for example, similar to that shown in FIG. FIG. 2 is a block diagram of the counter circuit of the robot.

The signal generated by the encoder is divided into human phase, B phase, and zero phase, and each passes through a termination and a filter circuit and is input to an up/down counter. Figure 3 shows, as an example, when an incremental encoder is used, the vertical axis is the number of A-phase and B-phase pulses generated by the encoder when the arm is moving at a constant speed during origin search, and the horizontal axis is the rotation angle. This is a diagram of the relationship taken. Assuming that N pulses are generated in one rotation of the encoder, the number of pulses increases in proportion to the angle, but after one rotation of the encoder, the number of pulse counts for A and B phases is reset from N to 0 by zero phase input. The circuit shown in FIG. 2 is constructed. A state in which the origin is set by counting pulses from the encoder using the method described above is shown in FIG.

Assume that the sensor ON signal is input at position b while the arm is rotating and counting pulses from the encoder. The count number d of the encoder when this ON signal rises is stored and displayed on the CRT screen of the control device. Then, the origin is set at point a, which is returned by the count number d from that position (that is, the position where the first zero-phase signal is received after returning from point b). In this case, if the position of the point is stored in the storage device, the origin can be set by numerical control, so it is not necessarily necessary to return the arm to the point a.

(Effects) The present invention detects the position of the robot while counting the pulses from the encoder, which increases the number of pulses in proportion to the angle and resets the pulse count to zero with one rotation. A pulse signal from a sensor is input, the encoder count at the rise of the pulse signal is stored as position information of the robot, and the origin of the coordinate system is set based on the position information.
Also, since there is no need to synchronize the sensor's ON signal and the encoder's zero-phase signal, the installation adjustment between the sensor and the target is simplified, and the sensor's ON signal can be a one-shot pulse, so the sensor's ON area can be made sufficiently small. By doing this, the zero phase signal of the same encoder can be reliably specified, so that the arm can be rotated in either direction when setting the origin.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the method of the present invention, FIG. 2 is a circuit diagram of an encoder used in the method of the present invention, FIG. FIG. 5 is a perspective view of an example of a robot that performs the process, and is an explanatory diagram of a conventional method. 1...First arm 2...Second arm 3...
・Work tools 4...Column 5.8...Encoder 6,9...Servo motor 11.12...
・Position detection sensor Pu Rotation angle (°) Figure 3 -

Claims (1)

[Claims] The number of pulses increases in proportion to the angle, and the number of pulses is reset to zero after one rotation.The pulse signal from the sensor that detects the robot's position while counting the pulses from the encoder. A method for setting the origin position of a robot, in which the count number of the encoder at the rising edge of the pulse signal is stored as position information of the robot, and the origin of the coordinate system is set based on the position information.