Collaborative Robot Contact Release Using Multi-Strategy Arm Control
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Solution Overview
Problem
Collaborative robots may unintentionally cause discomfort or injury to humans due to contact, necessitating safe and efficient strategies to release such contact.
Innovation Solution
The robot is equipped with sensors to detect external forces and a controller that employs multiple release strategies to minimize discomfort, including adjusting movement paths based on environmental data and joint manipulations to safely disengage from contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the robot limits the speed of its arm to ensure safe contact energy levels, then safety is improved, but the productivity and efficiency of the robot deteriorates
Solution Approach 1:
The robot implements dynamic speed adjustment based on real-time contact detection. The controller continuously monitors sensor data and adapts the arm's speed during operation - maintaining higher speeds during normal operation for productivity, and automatically reducing speed when contact is detected for safety. This dynamic adaptation resolves the contradiction by making safety and efficiency context-dependent rather than fixed.
Solution Approach 2:
The system changes the speed parameter dynamically based on operational conditions. During normal operation, the robot operates at optimal speeds for productivity. Upon detecting external forces or contact through sensors, the controller modifies the speed parameter to lower values to ensure safe energy transfer levels. This parameter adaptation allows the system to achieve both high productivity during normal operation and safety during contact scenarios.
2Reliability
If the robot stops motion immediately upon detecting contact, then safety is improved, but the comfort and minimal disruption for the person deteriorates
Solution Approach 1:
The robot applies preliminary anti-action by moving in the direction of the detected external force rather than simply stopping. When contact is detected, the controller analyzes the force vector and commands the arm to move along that vector, which naturally releases the contact by following the person's motion. This preliminary action in the direction of the force prevents the harsh stopping effect while still ensuring safety through controlled movement.
Solution Approach 2:
Instead of the conventional approach of stopping or reversing motion upon contact detection, the system inverts the response by moving in the direction of the applied force. This inversion allows the robot to release contact smoothly by accommodating the person's movement rather than resisting it, thereby improving comfort while maintaining safety through controlled, force-aligned motion.
3Device complexity
If the robot uses a single release strategy upon contact detection, then the device complexity is reduced, but the reliability of contact release deteriorates due to potential malfunctions
Solution Approach 1:
The contact release function is segmented into multiple independent strategies rather than relying on a single method. The controller implements at least two distinct release strategies: one based on moving along the external force vector and another as a backup option. This segmentation ensures that if one strategy fails or is inappropriate for the specific contact scenario, the alternative strategy can still achieve safe contact release, thereby improving reliability without requiring overly complex hardware.
Solution Approach 2:
The control system dynamically selects and switches between different release strategies based on real-time sensor feedback and contact characteristics. The controller evaluates which strategy is most appropriate for the current situation and can switch strategies during operation if needed. This dynamic strategy selection maintains relatively simple device architecture while achieving high reliability through adaptive control logic that responds to actual contact conditions.
4Loss of time
If the robot moves rapidly to release contact, then the response time is improved, but the discomfort and potential injury risk to the person worsens
Solution Approach 1:
The robot applies preliminary anti-action by moving in the direction of the external force rather than rapidly reversing or stopping. This approach naturally releases contact by following the person's motion trajectory, preventing additional discomfort from sudden deceleration or reverse movement. The speed is controlled to be sufficient for timely release but moderated to avoid causing harm, achieving a balance between response time and comfort through force-aligned motion.
Solution Approach 2:
The controller dynamically adjusts the speed parameter during contact release based on the detected external force characteristics. Rather than using a fixed high speed that might cause discomfort, the system modifies the speed parameter to be appropriate for the specific contact scenario - fast enough to ensure timely release but controlled enough to prevent additional harm. This parameter adaptation resolves the contradiction between response time and comfort.
Data Source
AI summary
A robot comprises at least one articulate arm having members including a base, an end effector and a plurality of links, wherein each link is movably connected to two others of said members by respective joints, at least one sensor for detecting an external force acting on any one of the members, and a controller for controlling movements of the joints, so as to move the end effector along a pre-programmed path. In case of the sensor detecting an external force, the controller is adapted to adopt a first release strategy for escaping from the external force, to evaluate whether the first strategy is successful, and if not, to adopt a second release strategy.