Surgical Robotic Arm Torque Observation for Collision Compensation
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Solution Overview
Problem
Surgical robotic arms are affected by various external forces during minimally invasive medical procedures, necessitating effective monitoring and compensation to improve their operation.
Innovation Solution
The surgical robotic arm incorporates a joint torque sensor to measure torque imparted on its links, a controller to calculate input motor torque commands, determine estimated and environmental torque values, and detect collisions by comparing these values. The controller adjusts the motor torque command to prevent oversaturation and compensate for friction, gravity, and inertia.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a joint torque sensor is added to measure torque imparted on the robotic arm links, then measurement precision of external forces is improved, but device complexity increases
Solution Approach 1:
The joint torque sensor acts as an intermediary device that measures the torque imparted on the robotic arm links without requiring direct measurement of all external forces. The sensor is integrated into the joint structure, allowing indirect measurement of external forces through torque measurement, thus improving measurement precision while avoiding the complexity of multiple sensors.
2Stability of the object's composition
If the controller calculates and compensates for friction, gravity, and inertia effects, then stability of robotic arm operation is improved, but use of energy increases
Solution Approach 1:
The controller performs preliminary calculations of friction, gravity, and inertia effects before executing robotic arm movements. By pre-computing these compensatory torques based on the current joint positions and velocities, the system stabilizes the robotic arm operation while minimizing energy consumption during actual movement execution.
3Reliability
If the controller adjusts the input motor torque command to prevent oversaturation, then reliability of actuator operation is improved, but productivity of robotic arm movement decreases
Solution Approach 1:
The controller dynamically adjusts the input motor torque command based on real-time feedback from the joint torque sensor and the current operational state of the robotic arm. This dynamic adjustment prevents actuator oversaturation and ensures reliable operation while maintaining optimal movement speed by adapting torque commands to actual load conditions rather than using fixed conservative limits.
Data Source
AI summary
A surgical robotic arm includes a first link; a second link coupled to the first link at a first joint such that at least one of the first link or the second link is movable relative to each other; and a first actuator configured to move at least one of the first link or the second link. The surgical robotic arm also includes a joint torque sensor disposed within the first joint and configured to measure torque imparted on at least one of the first link or the second link to obtain a measured torque value. The surgical robotic arm further includes a controller configured to: determine an estimated joint torque value; compare the estimated joint torque value to the measured torque value; and determine an environmental torque value based on a comparison of the estimated joint torque value and the measured torque value.