JP4985135B2 - Cooperative robot system - Google Patents

Description

  The present invention relates to a technique for automating a fitting operation required in a part assembling process, and more particularly to a cooperative robot system used for automating a heavy object fitting operation.

The mating operation is one of the basic operations included in many assembly processes, and automation of the mating operation using a robot has already been performed. In a fitting operation using a robot, one workpiece (fitting workpiece) is gripped by the robot and inserted into a predetermined portion (usually a recess) of the other workpiece (fitting workpiece). In many cases, a force control robot is used as a robot that holds a fitting workpiece.
Force-controlled robots are favorably used for mating work by absorbing variations in the position and orientation relationship between the mating workpiece and mating workpiece and controlling the force or moment during the insertion operation under specified conditions. Because there is a function to do. However, there are cases where the fitting operation is not smoothly performed even when a force-controlled robot is used. For example, when the shape / size of the concave part on the mating work and the shape / size of the convex part of the mating work are in a narrow gap, the frictional force between the contact surfaces of both works is large, or When the insertion operation must be performed against the elasticity of the combined workpiece, the resistance force acting during the insertion operation is increased, and a situation in which the pressing force of the fitting workpiece by the robot is insufficient is likely to occur. As described above, in the conventional robot system used for the mating operation, the force necessary for the insertion operation is exclusively required for the single robot that holds the mating workpiece, and thus is expected to be necessary for the insertion operation. A robot capable of outputting a force that surely exceeds the force had to be prepared, which was a difficulty in introducing the robot system in the mating operation.
As a robot system for solving such a problem, there is disclosed a system composed of two robots, in which one robot performs a mating work and another robot assists the work (for example, see Patent Document 1). . The conventional robot system is composed of two robots, the robot grips the mating work, and the robot on the side not gripping the mating part attaches a pressing tool to the tip via a force sensor, When the robot inserts the fitting workpiece, the robot supports the insertion by pressing with the pressing tool.
JP-A-10-124121

The reason why the collaborative robot system is put in the assembly line and the fitting work is performed is that it can be performed continuously faster, more accurately than manually. If it is attempted to manually handle heavy objects, the work efficiency decreases due to a decrease in concentration due to fatigue while working continuously. For this reason, robots are applied to lines with a large production volume. Robots that change to humans are required to improve throughput rather than work efficiency.
However, in the conventional cooperative robot system, the slave robot is mainly intended to compensate for the pressing force that is insufficient for the insertion operation, and does not match the actual situation when the system is introduced for the purpose of reducing the actual work time. . In other words, there is no merit to make one robot stand by just for support of insertion, and it has enough work requirements to handle a heavy work with both arms like a human double arm and insert it as it is at high speed. Therefore, in the conventional robot system used for mating work, the force required for the insertion operation is exclusively required for a single robot that grips the mating work, and is expected to be necessary for the insertion operation. It was necessary to prepare a robot capable of outputting a force that surely exceeded the required force, and could not solve the difficulties in introducing the robot system for the mating work.
The present invention has been made in view of such problems, and it is an object of the present invention to provide a cooperative robot system for smoothly and rapidly inserting a fitting work that has been subjected to high-speed cooperative handling.

In order to solve the above problems, the present invention is configured as follows.
The invention according to claim 1 is a robot system that works while monitoring each other's work status as force information when holding one work at the same time with at least two robots and performing one fitting work , A force sensor provided in each of the two robots; and an operation control unit that controls the operations of the two robots based on a work program. The operation control unit includes a signal of the force sensor. And a force control means for performing force control on each of the two robots.
The invention according to claim 2 is characterized in that the operation control means includes a pressing operation control means for controlling an operation of pressing the one work held by the two robots against a work to be fitted; A pushing operation control means for simultaneously pushing the one workpiece held by the two robots, and a pushing action completion means for ending the pushing action under a preset condition are provided.
According to a third aspect of the present invention, there is provided force control monitoring means based on information of a robot force sensor.
According to a fourth aspect of the present invention, the force control monitoring means controls the time after the pressing force becomes equal to or greater than a preset threshold as the control effective time of the first force control means. Is.
According to a fifth aspect of the present invention, the force control monitoring unit adjusts the control effective time according to an operation speed.
Further, in the invention described in claim 6, the force control monitoring means determines the time from the time point when the force sensor signal of any one of the two robots is equal to or greater than a preset threshold value as a control effective time. Is to be monitored.
Further, in the invention according to claim 7, when the pressing operation control means exceeds the effective control time from the time when the force sensor signal becomes equal to or higher than a preset threshold, the force control is performed. By switching from force control by means to position control in advance, the position is held.
In the invention according to claim 8, the pressing operation control means is controlled to increase the pressing force of the robot when the force sensor signal is equal to or less than the preset threshold value. Is.
According to a ninth aspect of the invention, the threshold value of the pressing force and the control effective time are described in the work program and read into the operation control means.

According to the first aspect of the present invention, in order to cooperatively operate two or more robots, the information of each robot's force sensor is taken into the operation control means of each robot, so that two or more independent robots can be operated. When the robots perform coordinated operations, each robot can work while monitoring each other's work status as force information, so that two or more robots can work simultaneously, improving work efficiency.
According to the second aspect of the present invention, the pushing operation is performed while monitoring the working state of the pushing operation, and the pushing operation is performed while monitoring the working state of the pushing operation, so that the desired work can be reliably achieved. It becomes possible.
According to the inventions of claims 3 to 9 , since the effective time of force control after contact can be monitored, the force control state can be canceled, and the transition to the position control state can be performed. In the state of being pressed by operation, it can be stopped quickly without oscillating, and the working efficiency can be greatly improved. In addition, since a force exceeding the threshold does not act, it is possible to prevent malfunction such as biting.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Examples of the present invention will be described below. FIG. 1 is an overall configuration diagram of a cooperative robot system showing a first embodiment. In FIG. 1, 1 is a first robot serving as a master, 2 is a second robot serving as a slave, and a first hand 5 is attached to the tip of the first robot 1 via a force sensor 3. 2 A second hand 6 is attached to the tip of the robot 2 via a force sensor 4.
Reference numeral 9 is a control device for controlling the first robot 1 and the second robot 2, and executes the work program 10 stored in a non-volatile memory while decoding the work program step by step. The work program decoding execution control unit 11 to be controlled, the pressing operation control means 12 executed based on the programming pattern of the work program 9, the pushing operation control means 13, and the first force control for controlling the force of the first robot. Unit 14, a second force control unit 15 that controls the force of the second robot 2, a first position / speed control unit 16 that controls the position of the first robot, and a second position / speed control unit 17 that controls the position of the second robot. And the output of the first servo amplifier 18 that drives the servo motor of the first robot according to the output of the first position speed controller 16 and the output of the second position speed controller 17. And a second servo amplifier 19 for driving the servo motor of the second robot according.
In the first robot 1, a control command obtained by decoding the work content written in the work program 10 by the work program decoding execution control unit 11 is sent to the pressing operation control means 12. The control command includes information on the movement amount, speed, pushing force, operation direction, and control parameters (force control effective time TC, threshold FC) of the force control monitoring means 12A described later. According to the control command sent, the pressing operation control means 12 generates the target position and the impedance shown in FIG. 3 for realizing the pressing force to the first force control unit 14 and the second force control unit 15. The control parameter of the model unit 612 is set, and the first robot 1 and the second robot 2 operate so as to be impedance controlled. When the pushing operation is started, the force control monitoring unit shown in FIG. 2 provided in the pressing operation control unit 12 starts the operation.
The force control effective time TC written in the work program 10 and the threshold value FC of the reaction force of the pressing force are acquired from the work program decoding execution control unit. At this time, the force control effective time is set to a time that has a correlation so as to be short if the operation speed is high, in accordance with the operation speed of the robot written in the work program 10. As described above, the force control effective time TC and the reaction force threshold value FC of the pressing force are set, and then the workpiece is pressed against the work to be fitted, and the force sensor of the first and second robots when the workpiece is being pushed in. If the force information is smaller than the force information, force control output processing is performed so as to increase the pushing force to the second robot and the pushing force of the first robot, and the force information from the force sensor is greater than the threshold FC. For example, during the force control effective time TC, the first and second robots are force-controlled, and thereafter, the force control is invalidated. After invalidation, the first and second robots are in the position control state and hold their positions. Although the pushing operation control means has been described here, the pushing operation means is also provided with a force control monitoring means 13A of the same process.
The first force control unit 14 and the second force control unit 15 have the configuration shown in FIG. That is, the output from the force sensor 3 is converted into an operating force in the control point coordinate system by the sensor coordinate conversion unit 611 and output to the impedance model unit 612. Here, the impedance model of the impedance model unit 612 is expressed by Equation 1.

However, F: Fd-Fr (Fd: target force, Fr: force sensor output)
M: Inertia coefficient B: Viscosity coefficient K: Spring coefficient

By adjusting the inertia coefficient M, the viscosity coefficient B, and the spring coefficient K, the direct operation performance of the robot 1 can be adjusted. Since impedance control is a known technique, further detailed description is omitted.
The output of the impedance model unit 612 is added to the control point position calculated by the forward conversion 614 from the current feedback position, and the target pulse of each joint of J1 to L6 is calculated by the inverse conversion 613, and the position / velocity servo system To 62.
Next, based on the work program 10, the first robot 1 and the second robot 2 press and insert the first fitting component 7 held by the first hand 5 and the second hand 6 into the second fitting component 8. The robot system according to the present invention will be described with reference to the case of working.
FIG. 5 shows a program of the work program 10. The work program decoding execution control unit 11 inputs the work program 10 and first positions the first fitting component 7 at an initial position where it is pressed. In the next step, the work program decoding execution control unit 11 recognizes the operation command of the pressing operation, outputs an execution request to the pressing operation control means 12, and sets a threshold value and an impedance parameter. In the pressing operation control unit 12, the force control monitoring unit 12a monitors the outputs of the force sensor 3 and the force sensor 4 based on the set threshold, and the force sensor 3 and the force sensor 4 are monitored. When one of the threshold values reaches the threshold, the control outputs of the first force control means 14 and the second force control means 15 are continuously enabled for a set time, and the set time is reached. At the time, the control outputs of the first force control means 14 and the second force control means 15 are invalidated, and the position control state is set based on the outputs of the first position speed control section 16 and the second position speed control section 17. Stop. FIG. 4 shows a response waveform of the force and speed at that time. In the case of only normal force control, if the speed exceeds a certain level, contact stability cannot be maintained due to impact force and oscillation occurs, but the control device according to the present invention switches to position control immediately before oscillation, so it is extremely stable. Response can be obtained.

  The object of the present invention is to provide a fitting robot that has been subjected to high-speed cooperative handling, and a cooperative robot system for smooth and high-speed insertion.

The figure which shows the whole structure of this invention The figure which shows the structure of the force control part of this invention The figure which shows the Example of this invention Transition diagram of working state for explaining an embodiment of the present invention The figure which shows the structure of the control point position change means of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st robot 2 2nd robot 3 Force sensor 4 Force sensor 5 1st hand 6 2nd hand 7 1st fitting component 8 2nd fitting component 9 Control apparatus 10 Work program 11 Work program decoding execution control part 12 Pushing Operation control means 12A Force control monitoring means 13 Pushing action control means 13A Force control monitoring means 14 First force control section 15 Second force control section 16 First position speed control section 17 Second position speed control section 18 First servo amplifier 19 Second servo amplifier 611 Sensor coordinate conversion unit 612 Impedance model unit 613 Inverse conversion 614 Forward conversion

TC Force control effective time FC Threshold value F1 Force information from force sensor 3 F2 Force information from force sensor 4

Claims (9)

A robot system that works while monitoring each other's work status as force information when holding one work at the same time with at least two robots,
A force sensor provided in each of the two robots;
Operation control means for controlling the operations of the two robots based on a work program,
The operation control means includes
A cooperative robot system comprising force control means for performing force control on each of the two robots based on a signal from the force sensor. The operation control means includes
A pressing operation control means for controlling an operation of pressing the one workpiece held by the two robots against a workpiece to be fitted;
Push-in operation control means for simultaneously pushing in the one workpiece held by the two robots;
The cooperative robot system according to claim 1 , further comprising: a pushing operation completion unit that finishes the pushing operation under a preset condition. 3. The cooperative robot system according to claim 1, further comprising force control monitoring means based on information from a force sensor of the robot. 4. The cooperation according to claim 3, wherein the force control monitoring means controls the time after the pressing force becomes equal to or greater than a preset threshold as a control effective time of the first force control means. Robot system. 5. The cooperative robot system according to claim 3, wherein the force control monitoring unit adjusts the control effective time according to an operation speed. 4. The force control monitoring means monitors the time from when the force sensor signal of any one of the two robots becomes equal to or greater than a preset threshold as a control effective time. The cooperative robot system according to any one of? The pressing operation control means includes
When the control effective time from the time when the force sensor signal becomes equal to or greater than the preset threshold is exceeded, the position is maintained by switching from force control by the force control means to position control in advance. The cooperative robot system according to any one of claims 3 to 6. The pressing operation control means includes
The cooperation according to any one of claims 3 to 7, wherein when the force sensor signal is equal to or less than the preset threshold value, the pressing force of the robot is controlled to be increased. Robot system. The cooperative robot system according to any one of claims 4 to 8, wherein the threshold value of the pressing force and the control effective time are described in the work program and read into the operation control unit.