Redundant Force Sensing in Surgical Robots
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Solution Overview
Problem
Surgical robots with single force/torque sensors are prone to failures due to environmental conditions, leading to inaccurate measurements and potentially unsafe robot movements during surgeries, necessitating improved force sensing systems for reliability and safety.
Innovation Solution
A cooperatively controlled robotic system with redundant force sensing, incorporating a second force sensor between the arm assembly and the main robot assembly, allowing for cross-validation of force measurements and detection of sensor failures, collisions, and user-robot interactions, enhancing safety and usability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single force/torque sensor is used in the surgical robot, then the device complexity is reduced, but the reliability of force sensing deteriorates due to susceptibility to failure from environmental conditions, accidents, or misuse
Solution Approach 1:
The patent places force sensors at multiple specific locations within the robotic arm structure (between the last joint and surgical instrument adapter, and between the first joint and base). This distributed sensor placement ensures that local force measurements can be cross-validated, improving overall system reliability without requiring a completely complex redundant system throughout the entire robot.
Solution Approach 2:
The control system continuously compares force measurements from multiple sensors before executing surgical operations. This preliminary validation of sensor data ensures that any faulty readings are detected and corrected before they can cause harmful actions, proactively preventing reliability issues rather than reacting to them after failure occurs.
2Device complexity
If a single force/torque sensor is used, then the manufacturing cost is reduced, but the measurement precision deteriorates due to temperature changes, electrical noise, or permanent mechanical deformations
Solution Approach 1:
The control system uses force measurements from multiple sensors to continuously monitor and validate each other's readings. When discrepancies are detected that indicate temperature drift, electrical noise, or mechanical deformation, the system can compensate for these errors using data from the other sensors, maintaining measurement precision without requiring expensive individual sensor improvements.
Solution Approach 2:
The patent combines data from multiple force sensors to create a composite measurement that is more reliable than any single sensor reading. This composite sensing approach allows the system to filter out noise and errors from individual sensors, achieving higher effective measurement precision through data fusion rather than relying on a single expensive high-precision sensor.
3Reliability
If redundant force sensing with multiple sensors is implemented, then the reliability and safety of force measurements is improved, but the device complexity increases
Solution Approach 1:
The robotic arm is segmented into multiple sections with force sensors placed at specific segments (between joints and at the end effector). This segmentation allows each sensor to measure forces locally, and the control system to combine these segmented measurements into a complete picture of system forces, achieving high reliability through modular sensor placement rather than a monolithic complex sensor system.
4Reliability
If multiple force sensors are used for cross-validation, then the safety against unexpected robot movement is improved, but the ease of operation deteriorates due to more complex sensor comparison and failure detection
Solution Approach 1:
The control system automatically performs the complex task of comparing sensor readings and detecting failures without requiring manual intervention. The system self-monitors its own sensor health by continuously validating measurements against each other, automatically detecting discrepancies that indicate sensor failure or collisions, and taking appropriate safety actions without burdening the surgeon with complex monitoring tasks.
Data Source
AI summary
A cooperatively controlled robotic system includes a main robot assembly, and an arm assembly comprising a proximal end and a distal end. The arm assembly is connected to the main robot assembly at the proximal end. The system also includes a tool assembly connected to the arm assembly at the distal end, a first force sensor between the distal end of the arm assembly and the tool assembly, and a second force sensor between the proximal end of the arm assembly and the main robot assembly. The system includes a control system that is configured to determine a force applied at the first force sensor based on a force detected by the second force sensor, and to compare the determined force to a force detected by the first force sensor to detect a failure of at least one of the first and second force sensors.