Robot Emergency-Stop Motion Control for External Force Following
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Solution Overview
Problem
Existing robot systems face issues with unintended movements of movable members due to erroneous torque sensor readings or initial settings, leading to continued movement despite the cessation of external forces applied by workers, which can interfere with their motion.
Innovation Solution
A robot system with a control apparatus that includes an emergency stop controller, direction calculator, speed calculator, and movement controller to manage external forces on movable members, employing a variable coefficient to adjust movement speed over time and switch between modes based on force thresholds and elapsed time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the robot moves the movable members to follow the external force after emergency stop, then the worker can free themselves more easily, but the movable members may continue moving unintentionally if the external force detection is erroneous
Solution Approach 1:
The robot dynamically adjusts the movement speed of movable members based on the magnitude of detected external force. The speed calculator determines a moving speed in accordance with a function that includes a variable coefficient and the magnitude of external force, allowing the system to respond appropriately to different force levels while maintaining safety
Solution Approach 2:
The system continuously monitors external force through torque sensors and adjusts the movement control based on real-time feedback. The emergency stop controller stops operation when external force exceeds a threshold, and the speed calculator modulates movement speed based on the magnitude of detected force, creating a closed-loop feedback system that balances assistance and safety
2Reliability
If the robot stops the operation of movable members upon collision detection, then worker safety is ensured, but the worker needs to manually push the movable members away which increases their burden
Solution Approach 1:
The system converts the harmful external force (collision) into a beneficial signal for assisted movement. When the emergency stop is triggered and the worker continues to apply external force, the robot interprets this as a request for assistance and moves the movable members in the direction of the applied force, transforming the collision event into a helpful interaction
Solution Approach 2:
The control apparatus acts as an intermediary between the worker and the movable members. Rather than direct manual manipulation by the worker, the control system mediates the interaction by detecting external force and automatically moving the movable members in response, reducing the physical burden on the worker
3Device complexity
If the robot uses a fixed speed to move movable members after emergency stop, then the control is simple, but the system cannot adapt to varying external force magnitudes which may cause unintended movements
Solution Approach 1:
The system changes the speed parameter dynamically based on the magnitude of external force. The speed calculator determines moving speed in accordance with a function that includes a variable coefficient and the magnitude of external force, allowing the control system to adapt to varying force conditions without increasing overall system complexity
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A robot system (1) includes a robot (2) and a control apparatus (20) programmed to control the operation of the robot (2). The control apparatus (20) is programmed to implement an emergency stop controller (230) configured to stop the operation of movable members (11) of the robot (2) in response to an external force imposed on the movable members (11) during operation. The control apparatus (20) is further programmed to implement a direction calculator (240) configured to determine a moving direction to be adopted by the movable members (11). The control apparatus (20) is further programmed to implement a speed calculator (250) configured to determine a moving speed to be adopted by the movable members (11). The control apparatus (20) is further programmed to implement a movement controller (11) configured to move the movable members (11) in the determined moving direction at the determined moving speed.