Robot Force Control Tuning for Non-Vertical Hole Insertion
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Solution Overview
Problem
Existing robot control systems fail to accurately insert components into holes when the insertion direction is not vertical, as they do not account for forces perpendicular to the insertion direction, leading to incomplete insertion due to normal and frictional forces from the hole walls.
Innovation Solution
A method for adjusting force control parameters in a robot system that includes a force detector and an end effector, where the robot performs insertion or pull-out operations while measuring external forces, optimizing parameters to account for forces orthogonal to the insertion direction, and repeating the process to determine suitable force control parameters for effective insertion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the target force in the direction perpendicular to the inserting direction is set to zero, then the control is simplified and follows conventional impedance control methods, but the component cannot be appropriately inserted into the hole when the inserting direction is not vertical
Solution Approach 1:
The patent changes the parameter setting for target force in the perpendicular direction from zero (conventional) to a non-zero value that accounts for normal and frictional forces. This parameter change enables appropriate insertion control for non-vertical directions while maintaining the overall simplicity of the impedance control framework.
2Measurement precision
If the force sensor detects force in the direction perpendicular to the inserting direction due to sensor characteristics, then the detection accuracy is affected, but control for reducing the force to zero is still performed
Solution Approach 1:
The patent uses force sensor feedback to detect forces in the perpendicular direction and incorporates this information into the impedance control. By setting the target force to a non-zero value based on detected forces, the system compensates for sensor characteristics and ensures accurate insertion control.
3Reliability
If the robot performs insertion operations with optimized force control parameters, then the insertion accuracy is improved, but the operation time increases due to repeated measurement and optimization processing
Solution Approach 1:
The patent performs measurement and optimization processing before the actual insertion operation to determine appropriate force control parameters. This preliminary action allows the system to have optimized parameters ready, improving insertion accuracy while minimizing time loss during the actual insertion task.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate and efficient insertion of components into holes by setting appropriate force control parameters, including those in directions orthogonal to the insertion, reducing operation time and preventing excessive force application, even when the insertion direction is not vertical.
Implementation Method 1
a force detector provided in the robot and configured to measure an external force
Data Source
AI summary
A robot system includes a robot, a force detector, and an end effector. When the robot is caused to execute a following operation, force control is performed based on a measurement value by the force detector. The following operation is an operation in which a first target object held by the end effector is inserted into a void included in a second target object or pulled out from the void while coming into contact with the second target. The adjustment method includes a measuring step for causing the robot to perform the following operation using candidate values of the force control parameters including a target force in a direction orthogonal to a direction of the insertion or the pull-out and obtaining a force measurement value, a parameter updating step for performing optimization processing using the force measurement value and obtaining new candidate values of the force control parameters, and a step of repeating the measuring step and the parameter updating step to determine force control parameters and outputting the force control parameters.