JPH02205488A - Searching method for original point - Google Patents

Abstract

PURPOSE:To perform an original point search without performing a large rotation operation by rotating a rotating shaft in the other direction different to one direction, and after its output is turned to be under a first state and then to be in a second state once again, rotating the rotating shaft in one direction until it is turned to be under the first state, thereby searching an original point. CONSTITUTION:The output of a detecting member 5 takes a second state as an initial position and a rotating shaft is rotated in one direction (e.g. right direction) at a specific angle (e.g. 90 deg.). In the case the output of the detecting member 5 is not set in a first state during the above rotation, the processing is made by reversing the rotation direction by recognizing that there is no notch part between the specific angles in the one part direction from the initial position. Namely, this rotating shaft is rotated in the other direction reverse to one direction, the output is set in the first state. After it is set in the second state again, the rotating shaft is rotated until it is set in the first state in one direction, so that the original point is searched.

Description

[Detailed Description of the Invention] [Summary] Regarding the origin search for joint angles performed after the robot is powered on, when the notch of the disc of the range sensor is smaller than a semicircle, a large rotational movement is performed during the origin search. The present invention aims to prevent this from occurring, and includes a disc that rotates by a rotating shaft and has a notch, and a detection member that detects the arrival of the notch, and the output of the detection member detects the notch. The origin search method includes searching for an origin by rotating the rotating shaft in one direction from a second state in which the notch is not detected to a first state in which the notch is detected. When the output is in the second state and the output does not change even if the rotating shaft is rotated by a predetermined angle in the one direction, rotating the rotating shaft in the other direction opposite to the one direction, After the output is in the first state and again in the second state, the rotating shaft is rotated in the one direction until the output is in the first state to search for the origin.

[Industrial application field]

The present invention relates to robot control, and more particularly to an origin search for joint angles performed after the robot is powered on.

Robots used in factories for assembly, welding, painting, etc. often use a method called the teaching playback method. The teaching playback method is a method in which a person first teaches the robot a motion sequence by directly moving a teaching pendant or the tip of the robot, and then the robot repeats the motion sequence according to the taught data.

In this teaching playback method, in order to maintain the reproducibility of the data taught to the robot, it is necessary that the origin of each joint of the robot does not change.

[Conventional technology]

Generally, joint angles and positions of a robot are detected by encoders. There are two types of encoders: an absolute type that detects absolute angles and an incremental type that detects relative angles.

As shown in FIG. 4, the joints of a robot are generally such that an encoder is directly connected to a motor, and the motor is connected to an output shaft through a speed reducer. Therefore, while the output shaft rotates once, the motor shaft rotates several tens of times, so the encoder is generally of an incremental type. Since this detects relative angles, it is suitable when the motor rotation speed is high, but it has the disadvantage that the angle cannot be reproduced if the robot is powered off.

Therefore, it is common practice to perform an "origin search" after turning on the power to the robot, mechanically position the robot at a certain position, and then set the encoder count to a certain value to maintain data reproducibility. ing.

The origin search is normally carried out using the mechanism shown in FIG. 4, in which a Z phase is provided on the encoder that generates one pulse per revolution as shown in FIG. 5, and as shown in FIG. It is necessary to install a range sensor on the output shaft side whose sign reverses near the origin.

This range sensor outputs OFF when a disk crosses the optical axis of the optical sensor, and outputs ON when there is nothing blocking the optical axis.

FIG. 7 is a diagram showing a procedure for origin search according to a conventional example.

FIG. 7(a) shows the flow of processing, and FIG. 7(b) shows the relative positions of the disk of the range sensor and the optical sensor in each state. The origin search procedure is performed as follows.

(1) As shown in (1) in Figure 7 et al., when the range sensor is on, the shaft rotates to the right, and when the range sensor is off, it stops. Skip this step if the range sensor is off from the beginning.

(2) Since the state shown in FIG. 7(b) is reached, the shaft is rotated to the left and stopped when the range sensor is turned on.

(3) As a result of (1) and (2), the state shown in (■) in Figure 7(b) is reached, so the shaft is now rotated slowly to the right and stops when two phases of the encoder are detected.

[Problem to be solved by the invention]

The origin search is performed using the procedure described above, but SCARA type robots (two joints at the base that rotate horizontally, corresponding to the shoulders and arms, and an axis that slides vertically at the end) (a robot with a rotating shaft at the end and a hand at the end) has an asymmetrical fan-shaped disc used as a range sensor on the rotating shaft at the end of the robot, as shown in Figure 8(a). . The range sensor is originally intended to indicate the range of motion of a joint, and is generally used for origin search. Therefore, for an axis having a movable range as shown in FIG. 8(a), this type of range sensor is used for origin search.

When performing an origin search using a range sensor shaped like the one shown in FIG. 8(a), when the disc and the optical sensor are in the relationship as shown in FIG. 8(b), if the above procedure is followed, Steps (2)
), it will make a large movement as shown by the arrow in the figure.

On the other hand, a sensor and a hand are attached to the tip of the robot, and cables that drive them and transmit signals are connected from the robot body to the sensor and hand. Therefore, if a large movement as shown in FIG. 8(B) is repeated, the cable will become entangled with the tip of the robot, as shown in FIG. 9, and the robot will become unable to operate or the cable will break.

The problem to be solved by the present invention is to provide an origin search method that eliminates such conventional problems.

[Means to solve the problem]

FIG. 1 is a diagram showing the configuration of the present invention.

In the figure, (2-1), (2-2), (2-
3), (2-4), and (2-5) are each processing step.

(2-1) is a process of placing the rotating shaft at a position where the output of the detection member is in the second state.

(2-2) is a process of rotating a predetermined angle in one direction, and ends the process when the first state is reached halfway.

(2-3) is to rotate the detection member in the other direction until the output reaches the first state when the second state remains even after rotating to a predetermined angle in step (2-2). It is processing.

(2-4) is a process of rotating the detection member in the other direction until the output of the detection member returns to the second state.

(2-5) is a process of changing the rotation direction, rotating in one direction until the output of the detection member reaches the first state, and then stopping.

[For production]

According to the process according to the present invention, the output of the detection member is set in the second state as the initial position, and from there the axis is rotated by a predetermined angle (for example, 90 degrees) in one direction (for example, rightward), and during this period, the output of the detection member is When the output reaches the first state, the shaft is stopped and processing ends. If one output of the detection member does not reach the first state even after rotating by a predetermined angle, the shaft is rotated for a predetermined angle in one direction from the initial position. Recognizing that there is no notch, the rotation direction is reversed and processed.

That is, the shaft is rotated in the other direction until the output of the sensing member is in the first state, rotated until the output of the sensing member is again in the second state, and then the shaft is rotated in the other direction until the output of the sensing member is in the second state. It is rotated until the output reaches the first state.

The subsequent process, like the process (3) in the conventional example, is to slowly rotate the shaft and stop when the Z phase of the encoder is detected.

According to the above processing, large rotational movements are not performed (,
Even in the worst case, there is no rotation movement exceeding 270 degrees.

This will prevent cables from getting entangled.

〔Example〕

The present invention will be explained in more detail below with reference to embodiments shown in FIGS. 2 and 3.

FIG. 2 is a diagram showing the main configuration of an embodiment of the present invention, with FIG. 2(a) showing the hardware configuration and FIG. 2(b) showing the software configuration.

In FIG. 2(a), l is a control processor,
The robot is controlled via the robot control circuit 2.

3 is an encoder provided on a motor shaft that rotates the rotary shaft at the tip of the robot arm, and 4 is a Z-phase signal processing circuit that processes the Z-phase signal of the encoder 3.

5 is a range sensor provided on the rotation axis at the tip of the robot arm, and 6 is a range sensor processing circuit. The range sensor 5 rotates once for every 500 rotations of the encoder 3.

An interrupt is generated from the Z-phase signal processing circuit 4 and the range sensor processing circuit 6 to the control processor 1 every time the state changes.
The control processor 1 reads the state in response to an interrupt.

The control processor 1 recognizes the state of the robot by reading the state from the Z-phase signal processing circuit 4 and the range sensor processing circuit 6 and the other states of the robot from the robot control circuit 2, and controls the robot accordingly. An instruction of control values for operation is given to the robot control circuit 2.

FIG. 2(b) shows programs related to the present invention among the control programs held in the control processor 1. As shown in FIG.

The origin search sequence program is a program that controls the origin search sequence.

The robot stop program is a program that starts when an interrupt occurs and stops the robot.

FIG. 3 is a flowchart showing processing according to an embodiment of the present invention, and is the processing content of the origin search sequence program shown in FIG. 2(b).

The operation will be explained below according to the processing steps in the flowchart of FIG.

■Cancel the interrupt mask and enable the program that advances the processing steps by interrupts from the sensor.

■Identify whether the range sensor is on or not. If it is on, go to step ■; if it is off, jump to step ■.

■Rotate the shaft to the left.

■Monitor the range sensor until it changes from on to off. If it turns off, proceed to step ■.

■Stop the rotation of the shaft.

■The current state is that the range sensor is off. Rotate the shaft to the right.

■Watch the range sensor change from off to on.

If it turns on, proceed to step ■; if it remains off, proceed to step ■.

■Stop rotating the shaft and jump to step [phase].

[Phase] Since it remained off even after rotating 90 degrees, it was rotated 90 degrees to the left and returned to the initial state of step (2).

■Rotate the shaft further to the left.

@Watch the range sensor change from off to on.

If it is turned on, proceed to step ■, and if it is turned off, continue monitoring.

■Stop rotating the shaft and proceed to step 0.

■Rotate the shaft further to the left.

[Phase] Monitor the range sensor changing from on to off. If it turns off, proceed to step ■, and if it turns on, continue monitoring.

■Stop the rotation of the shaft and proceed to step ■.

■Rotate the shaft to the right.

■Watch the range sensor change from off to on.

If it turns on, step ■ advances negatively, and if it turns off, continue monitoring.

[Phase] Stop the rotation of the axis and proceed to step @.

[Phase] Rotate the axis slowly to the right.

■Monitor whether the encoder Z-phase signal detection interrupt has been raised. If an interrupt is received, the process proceeds to step 0. Continue until receiving a 2-phase signal detection interrupt.

Among the above processing steps, processing steps (2-1) to (2-5) shown in FIG.
).

〔Effect of the invention〕

As is clear from the above description, according to the present invention, even when the notch of the range sensor disk is smaller than 180 degrees,
This has a remarkable industrial effect in that it is possible to search for the origin without making a large rotational movement, and it is possible to avoid the robot going down or cable breakage due to cable entanglement.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of the present invention, Fig. 2 is a diagram showing the main part configuration of an embodiment of the present invention, and Fig. 3
FIG. 4 is a flowchart showing processing according to an embodiment of the present invention, FIG. 4 is a diagram showing a joint mechanism of a robot, FIG. 5 is a diagram showing an encoder with a Z phase, and FIG. 6 is a diagram showing an example of the configuration of a range sensor. , Fig. 7 is a diagram showing the origin search procedure according to the conventional example, Fig. 8 is a diagram showing an asymmetric range sensor disk, and Fig. 9 is a diagram showing a state where the cable is entangled at the end of the robot arm. . In the figure, 1 is a control processor, 2 is a robot control circuit, 3 is an encoder, 4 is a Z-phase signal processing circuit, 5 is a range sensor, 6 is a range sensor processing circuit, (1), (2
), (3), (2-1) to (2-5), ■ to @ are processing steps. shows. Hardware configuration (a) Figure 1 Encoder 2 Figure 2 Encoder position (b) Diagram showing the origin search procedure according to the conventional example

Claims (1)

[Scope of Claims] A second disc comprising a disc rotated by a rotating shaft and having a notch, and a detection member for detecting the arrival of the notch, wherein the output of the detection member does not detect the notch. The origin search method includes searching for an origin by rotating the rotating shaft in one direction from the state to a first state in which the notch is detected, the output of the detection member being a second state. In this state, if the output does not change even if the rotating shaft is rotated by a predetermined angle in the one direction, the rotating shaft is rotated in the other direction opposite to the one direction, and the output is the first. The origin search method is characterized in that, after the first state is reached and the second state is reached again, the rotation shaft is rotated in the one direction until the first state is reached, and the origin is searched for.