Robot Force Control Using Learned Contact Trajectories
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Solution Overview
Problem
Existing robot control methods require longer working times and increased motion velocity to ensure accurate contact between the tool and workpieces, leading to inefficiencies when performing repetitive tasks on multiple workpieces due to the need for precise positioning and force control.
Innovation Solution
A control method for a robot system that performs first work on a workpiece by force control based on a predetermined position command value, stores position information of the trajectory, and updates the position command value for subsequent workpieces to reduce the difference between target and actual contact positions, allowing for higher motion velocity and reduced working time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the target position is set to a position at a distance longer than the actual distance between the tool and the object member to ensure reliable contact, then the reliability of contact is improved, but the working time increases and productivity decreases
Solution Approach 1:
The patent applies preliminary action by storing the actual contact position information detected during the first work on a workpiece, and then using this stored information to update the target position for subsequent works. This preliminary storage and reuse of contact position data eliminates the need to repeatedly set conservative target positions, thereby reducing working time while maintaining reliable contact.
Solution Approach 2:
The patent implements feedback by detecting the actual contact position between the tool and the workpiece during operation, and using this detected information to correct and update the target position for subsequent operations. This closed-loop feedback mechanism allows the system to learn from actual contact experiences and optimize future operations, resolving the contradiction between reliable contact and productivity.
2Manufacturing precision
If the robot arm is operated at a lower velocity to ensure accurate contact between the tool and the object member, then the manufacturing precision is improved, but the working time increases and productivity decreases
Solution Approach 1:
The patent stores the actual contact position information detected during the first work, and uses this pre-stored accurate position data to set the target position for subsequent works. This preliminary acquisition and reuse of precise contact position information allows the robot arm to operate at higher velocities while maintaining accurate contact, thereby improving productivity without sacrificing manufacturing precision.
Solution Approach 2:
The patent uses feedback from the detected actual contact position to update the target position for subsequent operations. This feedback mechanism enables the system to achieve accurate contact positions based on actual measurements rather than conservative estimates, allowing for higher operating velocities and improved productivity while maintaining manufacturing precision.
3Productivity
If the target position is updated based on stored position information from previous work, then the working time is reduced and productivity is improved, but the device complexity increases due to memory and update mechanisms
Solution Approach 1:
The patent applies preliminary action by storing contact position information in memory during the first work, and then reusing this stored information for subsequent works. This preliminary storage and reuse mechanism simplifies the control logic compared to real-time detection and adjustment, as the system only needs to retrieve and apply pre-stored position data, thereby improving productivity without significantly increasing device complexity.
Solution Approach 2:
The patent uses copying by storing the actual contact position information from the first work and copying this position data for use in subsequent works. This copying approach allows the system to reuse verified contact position information without complex real-time calculations or adjustments, improving productivity while keeping the control system relatively simple through straightforward data retrieval and application.
4Productivity
If the robot arm operates at higher velocity for subsequent workpieces, then the productivity is improved, but the risk of inaccurate contact increases
Solution Approach 1:
The patent applies preliminary action by storing the actual contact position information detected during the first work, and using this pre-stored accurate position data as the target position for subsequent works. This preliminary acquisition of precise contact position information enables the robot arm to operate at higher velocities while maintaining accurate contact, thereby improving productivity without compromising manufacturing precision.
Solution Approach 2:
The patent implements feedback by using the detected actual contact position from previous work to update and correct the target position for subsequent operations. This feedback mechanism ensures that even when operating at higher velocities, the robot arm can achieve accurate contact by referencing the corrected target position derived from actual contact experiences, thus maintaining manufacturing precision while improving productivity.
Data Source
AI summary
A control method for a robot includes a first working step of executing first work on a first working object by operating a robot arm by force control based on a predetermined position command value, a first memory step of storing first position information of a trajectory in which a control point set for the robot arm passes at the first working step, and a second working step of updating a position command value for the robot arm based on the first position information stored at the first memory step, and executing second work on a second working object by operating the robot arm by the force control based on an updated value as the updated position command value.