Robotic Arm Torque Sensing for Collision and Misalignment Detection
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Solution Overview
Problem
Surgical robotic systems face challenges in detecting undesirable forces on robotic arms during medical procedures, which can lead to collisions or misalignments, potentially causing unintended forces and compromising patient safety.
Innovation Solution
A system comprising a robotic arm with torque sensors and position sensors that measure and differentiate between torque values to determine gravitational and applied forces, allowing for the detection of collisions or misalignments by comparing these forces against threshold values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If torque sensors are used to detect forces on robotic arms, then collision detection capability is improved, but device complexity increases
Solution Approach 1:
The patent introduces torque sensors as intermediary devices that indirectly detect collisions by measuring torque at robotic arm joints. Instead of directly detecting collisions at the end effector, the system uses torque measurements from joint sensors as a mediator to infer collision events, thereby improving detection capability while avoiding the complexity of direct collision sensing throughout the entire arm structure
Solution Approach 2:
The patent replaces complex mechanical collision detection systems with electronic torque sensing and computational analysis. By using torque sensors combined with gravitational torque calculation and threshold comparison algorithms, the system substitutes elaborate mechanical switches or direct contact sensors with a more integrated electronic measurement approach that reduces overall device complexity
2Measurement precision
If gravitational torque is differentiated from applied torque, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent performs preliminary calculation of gravitational torque based on the robotic arm's known configuration and mass properties before comparing total torque measurements to detect collisions. By pre-computing the expected gravitational component and subtracting it from total torque measurements, the system isolates applied forces with high precision without requiring additional sensors, thus improving measurement precision while maintaining relatively simple device architecture
Solution Approach 2:
The system uses feedback from position sensors to continuously update the gravitational torque calculation as the robotic arm moves. The measured joint positions feed into the gravitational torque model, which then provides real-time compensation to the collision detection algorithm. This feedback loop enables precise force measurement throughout the range of motion while using existing sensor data rather than adding complex measurement equipment
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables real-time detection of collisions and misalignments, providing immediate feedback to users and preventing further procedure advancement until issues are resolved, thus enhancing safety and precision in surgical robotic systems.
Implementation Method 1
at least one torque sensor configured to detect torque between the at least two linkages
Implementation Method 2
determine a second torque value at the at least one joint based on a position of the first robotic arm, the second torque value indicative of a gravitational component of the torque between the at least two linkages
Data Source
AI summary
Certain aspects relate to systems and techniques for detection of undesirable forces on one or more surgical robotic arms. In one aspect, there is provided a system including a robotic arm, including: two linkages, a joint, a torque sensor, and an instrument device manipulator (IDM). The system may further include a processor configured to measure a first torque value at the joint based on an output of the torque sensor and determine a second torque value at the joint based on a position of the robotic arm. The second torque value may be indicative of a gravitational component of the torque between the two linkages. The processor may be further configured to determine a force at the IDM based a difference between the first and second torque values and determine whether the robotic arm has collided with an object or misaligned based on the force at the IDM.