Haptic Input Feedback for Manipulator Stability Under Variable Stiffness
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Solution Overview
Problem
Computer-assisted systems face challenges in stabilizing control of manipulator arms due to phase loss, resonance, and environmental stiffness changes, leading to instabilities and reduced usability.
Innovation Solution
A controller determines environmental stiffness and applies feedback forces to the input device based on this stiffness, compensating for changes in the operating environment to maintain stability and improve tracking accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback force is applied to compensate for environmental stiffness changes, then stability and tracking accuracy are improved, but device complexity increases
Solution Approach 1:
The controller implements a feedback mechanism that continuously monitors environmental stiffness changes and adjusts the feedback force applied to the input device accordingly. This closed-loop control compensates for stiffness variations in real-time, maintaining system stability and tracking accuracy without requiring hardware modifications.
Solution Approach 2:
The system dynamically changes the feedback force parameter based on detected environmental stiffness conditions. When stiffness exceeds a threshold, the controller modifies the feedback force magnitude and characteristics to maintain optimal performance, allowing adaptation to varying operational environments.
2Ease of operation
If damping is reduced to improve responsiveness, then usability and tracking accuracy are improved, but instabilities increase
Solution Approach 1:
The system employs dynamic damping adjustment where the damping characteristics are not fixed but adapt in real-time based on operational conditions and environmental stiffness. This allows the system to maintain low damping for responsiveness during normal operation while automatically increasing damping when instabilities are detected, achieving both responsiveness and stability.
Data Source
AI summary
A computer-assisted system includes a manipulator arm configured to support an instrument, an input device configured to accept user commands to move the instrument, and an actuator system coupled to the input device. A controller of the computer-assisted system is configured to determine a component of a change in force at the instrument, the component correlating with a direction of motion of the input device. The controller also determines a feedback force based at least in part on the environmental stiffness and the component of the change in force if the environmental stiffness experienced by the instrument exceeds a threshold stiffness. The controller causes the actuator system to drive the input device to apply the feedback force.