Teleoperated Robot Haptic Feedback Force Limiting
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Solution Overview
Problem
Existing tele-operation systems for industrial robots face challenges in effectively limiting contact forces, leading to potential damage to workpieces or equipment due to communication delays and limited force/torque output, which can result in unstable haptic loops and unrealistic feedback.
Innovation Solution
A system comprising an operator input device that applies and outputs feedback force, with a dual threshold hysteresis control mechanism to impose force constraints on the industrial robot, using a position/velocity-force bilateral haptic control loop with a force limiting control function, providing virtual constraint force feedback to the operator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If force limiting control is implemented in tele-operated robot systems, then contact force damage is prevented, but communication delays and limited force/torque output cause unstable haptic loops and unrealistic feedback
Solution Approach 1:
The system dynamically switches between two control modes based on contact force conditions: impedance control mode during contact (to limit force) and position control mode during non-contact (to maintain stability). This dynamic mode switching resolves the contradiction by adapting the control strategy to real-time operational needs, ensuring both force limitation and haptic loop stability.
Solution Approach 2:
The controller changes control parameters (impedance parameters vs. position parameters) based on contact detection. By modifying control parameters dynamically according to contact state, the system achieves stable haptic feedback while preventing excessive contact forces, thus resolving the stability-reliability contradiction.
2Loss of information
If larger feedback gains are used to enhance operator transparency, then feedback realism improves, but contact forces increase causing potential damage to workpieces or equipment
Solution Approach 1:
The feedback gain is dynamically adjusted based on contact state. During non-contact operations, high feedback gains are applied to maintain operator transparency and realism. During contact operations, the system switches to impedance control with reduced effective gain to limit contact forces. This dynamic adjustment resolves the contradiction between feedback realism and contact force safety.
Solution Approach 2:
The system uses force feedback to monitor contact conditions and automatically adjusts control parameters to prevent excessive forces. The feedback mechanism detects contact events and triggers appropriate control mode changes, ensuring that operator transparency is maintained when safe while preventing damage when contact occurs.
3Device complexity
If simple force limiting control is applied, then implementation complexity is reduced, but communication delays result in unrealistic haptic feedback and unstable control
Solution Approach 1:
The control system is segmented into distinct operational modes (contact mode and non-contact mode) with dedicated control strategies for each. This segmentation allows the system to apply appropriate control complexity only when needed, maintaining simplicity during non-contact operations while ensuring realistic haptic feedback during contact operations through impedance control.
Solution Approach 2:
The system pre-defines two control modes with optimized parameters for different operational conditions. By preparing these control strategies in advance and switching between them based on contact detection, the system avoids the complexity of continuously adapting parameters while maintaining haptic feedback realism, thus resolving the contradiction between simplicity and reliability.
Data Source
AI summary
One exemplary embodiment is a system comprising an operator input device structured to move in response to operator-applied force and to selectably output feedback force to the operator. A first computing system is structured to receive input from the operator input device and provide an output. A second computing system is structured to receive the output and provide a robot control command subject to a force constraint. An industrial robot system is in operative communication with the second computing system and comprises a robotic arm structured to move in response to the command. The second computing system is structured process the output to impose a force constraint using a dual threshold hysteresis control. The first computing system is structured to apply a feedback force to the operator input device correlated to force associated with the industrial robot system.