JP3366248B2 - Robot control method and device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method and control device for a robot that performs force control.

[0002]

2. Description of the Related Art Conventionally, most industrial robots are intended for high-speed and highly accurate position control. When an assembly work or a component positioning work is performed by a robot that performs such position control, even if an external force acts due to the contact between the robot and the component, jig, etc. Therefore, problems such as breakage of parts and jigs and deterioration of line operation rate due to the alarm stop of the robot occur.

Therefore, many techniques have been disclosed, including Japanese Patent Application Laid-Open No. 8-155868, regarding the force control of a robot which operates a manipulator by following the external force when the external force is applied to the robot.

In the above-mentioned prior art example, when there is a positional error between the jig and the grasped component when the work of fixing the component grasped at the tip of the robot to the jig is performed,
The robot is operated in such a direction that the parts and the jig come into contact with each other to generate an external force, and the external force generated as the force control decreases. As a result, even if there is a position error, the position error is absorbed, and it is possible to achieve the target work of fixing the gripped object to the jig.

However, if the position error is excessive, even if the tip position of the robot deviates from the taught position by force control, it is not possible to judge whether or not the intended work has been achieved.

[0006]

In the above prior art example, when the tip position of the robot is deviated from the taught position by force control, it is impossible to judge whether or not the intended work is achieved. For example, if the position error between the jig and the gripped part is too large and the work cannot be achieved even if the force control is performed, the jig or the gripped object is forcibly moved to the next work. It had the drawback of damaging the robot and the need to turn off the power to the entire line when the robot alarm stopped.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a control method and control device for a robot capable of determining whether or not a desired work has been achieved.

[0008]

In order to achieve the above object, the first method of the present invention changes the trajectory of a robot by following the external force when the external force is applied to the robot. In a control method of a robot that performs force control, the position deviation that occurs between the current position of the robot tip moved by force control and the teaching point is detected, and the work purpose is achieved.
A threshold value that is determined as a possible position deviation , the detected value and the threshold value are compared, and if the detected value is larger than the threshold value, at least the robot control that abnormally processes the robot Is the way.

Further, according to the second method of the present invention, when an external force is applied to the robot , the robot follows the external force and
A method of controlling a robot for performing a force control for changing the trajectory, that detects the tip position of the robot moved by the force control, the difference between the position and the position command trajectory and the detected is calculated to achieve the purpose of working wherein the threshold value <br/> predetermined as a position deviation can, the calculated value and then
A method of controlling a robot, which compares threshold values and at least abnormally processes the robot when the calculated value is larger than the threshold value.

Further, a third method of the present invention is a robot control method in which a threshold value can be designated by a robot teaching program.

Further, according to the first configuration of the present invention, when an external force is applied to the robot , the robot follows the external force and
A control unit that controls the force to change the trajectory , a detection unit that detects the position deviation of the tip position of the robot moved by the force control, and a position deviation that can achieve the purpose of the work.
As the threshold value and the signal from the detection unit.
A determination unit for comparing the item, receiving a signal from the determination unit, wherein
It is a control device for a robot having an abnormality processing unit for abnormally processing the robot at least when the detected value is larger than the threshold value .

The second configuration of the present invention is such that when an external force is applied to the robot , the robot follows the external force and
A control unit that controls the force to change the trajectory , a detection unit that detects the position of the tip position of the robot moved by the force control, and a difference between the detected position and the position command trajectory is calculated to achieve the purpose of the work. As a position deviation that can be performed, a determination unit that compares a predetermined threshold value with the calculated value, and the detected value when a signal from the determination unit is received.
Is greater than the threshold value, the robot controller has at least an abnormality processing unit that abnormally processes the robot.

A third configuration of the present invention is a robot control device having a threshold value setting unit capable of designating a threshold value in a robot teaching program.

[0014]

With the above configuration, according to the first method and configuration of the present invention, the position deviation of the tip position of the robot generated by the force control is detected, and the value is determined from a predetermined threshold value. When it is large, it judges that the target work is not achieved and at least handles the robot abnormally,
The jig and the gripped object can be prevented from being damaged, and there is an effect that it is not necessary to turn off the power supply of the entire process line and the deterioration of the operating rate of the line can be prevented.

Further, according to the second method and configuration of the present invention, the tip position of the robot moved by force control is always detected, and when the difference from the position command trajectory becomes larger than a predetermined threshold value. Since at least the robot is abnormally processed, it is possible to prevent the jig or the gripped object from being damaged, and to prevent the operation rate of the line from being deteriorated because it is not necessary to turn off the power of the entire process line.

Further, according to the third method and configuration of the present invention, the threshold value can be set by the teaching program of the robot so that the threshold value can be set according to the contents of the work performed by the robot. It has the effect that

As the abnormal processing, the operation of the robot or the robot and peripheral equipment is temporarily stopped, the defective portion during work is removed by the robot or other equipment, and the abnormal state is displayed. This refers to the process for resolving a defect that allows the operator to deal with the problem.

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) First, an embodiment of the first method and configuration of the present invention will be described.

FIG. 1 is considered as an application example of the present invention.
It is a figure explaining the fitting work seen in an assembly process, a component positioning process, etc. Originally 3 of XYZ
This is a work in a dimensional space, but for simplicity here X-
The description will be given by replacing it with the two-dimensional Z plane. In FIG. 1A, 1 is a robot whose force can be controlled, 2 is a hand attached to the tip of the robot, 3 is a work held by the hand 2, and 4 is a work for fixing the work 3 at a predetermined position. It is a jig and has a structure that moves on a line and stops at a predetermined point. And 5 has shown the conveyor which moves a jig. T on work 3
CP is a tool tip point. The line segment L on the jig 4 is the jig 4
Represents the center line of. This is a work of attaching the work 3 to the jig 4 by lowering the work 3 gripped by the hand 2 along the center line of the jig 4.

In the case of such work, a robot capable of force control generally sets the softness with respect to the external force in the X direction to be large and the softness with respect to the external force in the Z direction to be smaller than that in the X direction. Is. The reason is that, as described in the section of the prior art, if the softness is not specified in all directions, the robot tries to realize the predetermined command position against the external force, and This is because the jig may be damaged.

FIG. 1 (b) illustrates when this task is accomplished. For the sake of simplicity, the robot 1
The hand 2 is omitted from the figure. P1 and P2
Are the standby position and the work end position in the reference coordinate system. It is assumed that the robot is taught and moves so that the trajectory of the tool tip point moves on the line segment connecting P1 and P2. The state shown in the figure is a state in which the robot is on the standby position. Since the figure shows a state in which the fixed position on the conveyor 5 of the jig 4 has a slight error from the regular position, the work 3 and the jig 4 come into contact with each other in the state, and the trajectory changes due to force control. As a result, in the state, a deviation Δd1 occurs between the tool tip point and P2, but in terms of fitting work, the work achieves its purpose.

FIG. 2 illustrates a case where the same fitting work as in FIG. 1 has not been achieved yet. As compared with FIG. 1B, the fixed position of the jig 4 has a large error with respect to the regular position. Therefore, in the state ', the work 3 is caught by the jig 4 and further progresses, and even in the state' in which all position commands for moving to the work end point according to the teaching trajectory are output, the state is changed to the state 'by the Z direction force control. It stops at almost the same position, and the positional deviation Δd between the tool tip point and the work end point P2 at that time is Δd.
2 is considerably larger than Δd1 described in FIG. 1, and the work itself is not achieved. If the next work is performed in this state, the next process is also adversely affected.

FIG. 3 is a flow chart showing the processing contents of the first method of the present invention. When all the position commands for the work end point are output, the process of the flowchart in the figure is started. In step 1, a position deviation Δd between the position of the tool tip point and the position of the work end point shown in the same coordinate system as the position of the tool tip point is obtained.

In step 2, a comparison is made with a preset threshold value Δd max according to the work, and Δ
If d is smaller than Δd max, it is determined that the work has been accomplished in step 3, and the process proceeds to the next step. △ d
Is larger than Δd max, it is judged that the work is not achieved in step 4, and the robot or the robot and peripheral devices are abnormally processed. This Δd max can also be designated in the robot teaching program.

FIG. 4 is a block diagram showing a first configuration example of the present invention. In the figure, 6 is a robot, 7 is a control unit, 8 is a detection unit, 9 is a determination unit, 10 is an abnormality processing unit, 11
Is a peripheral device such as a conveyor, and 12 is a threshold value setting unit.

The mutual relationship and operation of the above components will be described. The control unit 7 controls the position and force of the robot and communicates with or controls peripheral devices. The robot 6 operates according to a command from the control unit. When all the position commands from the control unit 7 to the work end point are output to the robot 6, the detection unit 8 outputs the work end point indicated by the same coordinate system as the position of the tool tip point and the position of the tool tip point. The position deviation Δd from the position of is calculated and output to the determination unit 9. The determination unit 9 compares Δd with a threshold value Δd max preset according to the work, and Δd is Δd ma
If it is smaller than x, it is determined that the work has been accomplished, and a work continuation signal is directly or indirectly output to the control unit 7, and Δd is Δ.
If it is larger than d max, it is determined that the work has not been achieved, and the work unachieved signal is output to the abnormality processing unit 10. The abnormality processing unit 10 receives the work non-attainment signal and outputs an abnormality processing instruction signal to the robot or the robot and peripheral devices to the control unit 7. When the control unit 7 receives the work continuation signal, it outputs a command for executing the next work to the robot and the peripheral device, and when it receives the abnormal processing instruction signal, it abnormally processes the robot or the robot and the peripheral device.

(Embodiment 2) Next, an embodiment of the second method and configuration of the present invention will be described.

FIG. 5 is a graph showing the change over time in the command trajectory in the work shown in FIG. 1 and the actual positional deviation Δe between the tool tip points. The horizontal axis represents the elapsed time, and the vertical axis represents the position deviation amount indicating the difference between the command trajectory and the position of the tool tip point at that time.

FIG. 5A shows the time variation of the position deviation amount when the work is completed. As shown in FIG. 1A, a minute position deviation exists due to the tracking delay of the robot until the workpiece 3 and the jig 4 come into contact with each other. The force control increases the deviation amount of the position for a certain time from the state, but the deviation does not increase thereafter, and the work end point is reached with a substantially constant amount.

FIG. 5B shows the case where the work has not been achieved. As shown in FIG. 2, up to the state where the work 3 and the jig 4 are in contact with each other, there is a minute position deviation due to the tracking delay of the robot, as in FIG. 5A. From state'to state ', the robot cannot move in the -Z direction, so the position deviation Δe will continue to increase.

FIG. 6 is a flow chart showing the processing contents of the second method of the present invention. The processing of the flowchart in the drawing is executed every control cycle of the control unit. In step 21, a position deviation Δe between the position of the tool tip point and the position command trajectory shown in the same coordinate system as the position of the tool tip point is obtained.

In step 22, a comparison is made with a preset threshold value Δe max according to the work,
If Δe is smaller than Δe max, it is determined in step 23 that the work is being performed well, the process is terminated, and the process proceeds to the next control cycle. If Δe is larger than Δe max, it is determined that it is difficult to continue the work in step 24, and the robot or the robot and peripheral devices are abnormally processed.

FIG. 7 is a block diagram showing the second configuration of the present invention. In the figure, 6 is a robot, 24 is a control unit, 25 is a detection unit, 26 is a determination unit, 27 is an abnormality processing unit,
Reference numeral 11 denotes a peripheral device such as a line, and 28 denotes a threshold value setting unit.

The mutual relationship and operation of the above components will be described. The control unit 24 controls the position and force of the robot and communicates with or controls peripheral devices. The robot 6 operates according to a command from the control unit. When the processing of each control cycle of the control unit 24 is completed, the detection unit 25 determines the position deviation Δe between the position of the tool tip point and the position command trajectory indicated by the same coordinate system as the position of the tool tip point. The calculated value is output to the determination unit 26. The determination unit 26 compares Δe with a threshold value Δe max preset according to the work, and if Δe is smaller than Δe max, it is determined that the work is performed well. The work continuation signal is directly or indirectly output to the control unit 24. If Δe is larger than Δemax, it is determined that it is difficult to continue the work, and the work unachieved signal is output to the abnormality processing unit 27. The abnormality processing unit 27 receives the work non-attainment signal and outputs an abnormality processing instruction signal of the robot or the robot and peripheral devices to the control unit 24. Control unit 2
In No. 4, when the work continuation signal is received, the process of the next control cycle is executed, and when the abnormal process instruction signal is received, the robot or the robot and peripheral devices are abnormally processed.

(Embodiment 3) Next, an embodiment of a third method and structure of the present invention will be described.

As described with reference to FIGS. 3 and 6, if the positional deviation is larger than the threshold value set in advance according to the work, it is determined that the work has not been achieved, and the robot and the peripheral equipment are temporarily stopped. This threshold is specified in the robot teaching program.

FIG. 8 is a block diagram showing the third configuration of the present invention. In the figure, 6 is a robot, 7 is a control unit,
Reference numeral 8 is a detection unit, 9 is a determination unit, 10 is an abnormality processing unit, and 11 is a peripheral device such as a conveyor, which is common to the configuration described in FIG. Reference numeral 12 indicates a threshold value setting unit.

The mutual relationship and operation of the above-mentioned components are also common to the description of FIGS. 4 and 7. The threshold value is designated by the threshold value setting unit 12 by a teaching program.

It is needless to say that the respective constituent elements and their operations of these three embodiments can be realized by the program operation of the microcomputer.

Further, as the abnormal processing described in each of the embodiments, in order to eliminate the trouble, the robot and the peripheral equipment are temporarily stopped or the work 3 and the jig 4 for which the work cannot be achieved are removed from the conveyor 5. , Etc. are performed by a worker or the like, and the occurrence of an abnormality is reported to the worker or other equipment.

[0041]

According to the first method and configuration of the present invention, the positional deviation of the tip position of the robot generated by the force control is detected, and when the value is larger than a predetermined threshold value, it is an object. Abnormal processing of the robot or robot and peripheral equipment is judged as the work has not been achieved, so damage to jigs and gripping objects is prevented, and it is not necessary to turn off the power of the entire process line, which deteriorates the operating rate of the line. Can be prevented.

According to the second method and configuration of the present invention, the tip position of the robot moved by force control is always detected,
When the difference from the position command trajectory exceeds a predetermined threshold, the robot or robot and peripheral devices are abnormally processed, so damage to jigs and gripped objects is prevented, and the power to the entire process line is turned off. It is not necessary to prevent the deterioration of the operating rate of the line.

According to the third method and configuration of the present invention, the threshold value can be set by the teaching program of the robot so that the threshold value can be set according to the contents of the work performed by the robot. You can

[Brief description of drawings]

FIG. 1 is a diagram illustrating a case where a fitting work is achieved.

FIG. 2 is a diagram for explaining a case where the fitting work has not been achieved.

FIG. 3 is a flowchart showing the processing contents of the control method according to the first embodiment.

FIG. 4 is a block diagram showing the configuration of the control device according to the first embodiment.

FIG. 5 is a graph showing a change with time of a positional deviation Δe between a command trajectory and an actual tool tip point in a fitting operation.

FIG. 6 is a flowchart showing the processing contents of the control method according to the second embodiment.

FIG. 7 is a block diagram showing a configuration of a control device according to a second embodiment.

FIG. 8 is a block diagram showing a configuration of a control device according to a third embodiment.

[Explanation of symbols]

1 robot Two hands 3 work 4 jigs 5 conveyors 6 robots 7 control unit 8 detector 9 Judgment section 10 Pause processing section 11 peripherals 12 Threshold setting section 24 Control unit 25 Detector 26 Judgment section 27 Pause processing section 28 Threshold setting section

Front page continuation (72) Inventor Atsumi Hashimoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Takashi Nakatsuka 1006 Kadoma, Kadoma City Osaka Prefecture Matsuda Electric Industrial Co., Ltd. (56 ) References JP-A-6-99371 (JP, A) JP-A-10-264080 (JP, A) JP-A-8-155868 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) G05D 3/00-3/20

Claims (6)

(57) [Claims] 1. A robot control method for performing force control for changing a trajectory of a robot by following the external force when an external force is applied to the robot , and a current position of a robot tip moved by the force control and a teaching point. detecting a positional deviation occurring between the, positions that can achieve the purpose of working
A method of controlling a robot, which compares a predetermined threshold value as a positional deviation with the detected value, and abnormally processes at least the robot when the detected value is larger than the threshold value. 2. A robot control method for performing force control for changing the trajectory of a robot when the external force is applied to the robot, wherein the tip position of the robot moved by the force control is detected, calculating the difference between the position command trajectory and the detected position, to achieve the purpose of the work
A method of controlling a robot, which compares a predetermined threshold value as a possible position deviation with the calculated value, and at least abnormally processes the robot when the calculated value is larger than the threshold value. 3. The robot control method according to claim 1, wherein the threshold value can be designated by a robot teaching program. 4. A control unit for controlling a force to change the trajectory of the robot by following the external force when the external force is applied to the robot, and a detection for detecting a positional deviation of a tip position of the robot moved by the force control. receiving the parts, and a judging unit for comparing the signals from the predetermined threshold and the detection unit as a position deviation that can achieve the purpose of the work, a signal from the determination unit, the detected value is above From threshold
A control device for a robot having an abnormality processing unit for abnormally processing the robot when the size is large . 5. A control unit for controlling the force to change the trajectory of the robot by following the external force when the external force is applied to the robot, and a detection unit for detecting the position of the tip position of the robot moved by the force control. When the difference between the position and the position command trajectory and the detected calculation, to achieve the purpose of the work
And the above-mentioned threshold value as a possible position deviation
A robot controller having a judging unit for comparing the calculated value and an abnormality processing unit for receiving a signal from the judging unit and abnormally processing the robot at least when the detected value is larger than the threshold value. . 6. The robot controller according to claim 5, further comprising a threshold value setting unit capable of designating the threshold value with a robot teaching program.