Surgery-Assisting Robot Arm Tolerance Control for Distal Accuracy
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Solution Overview
Problem
Existing surgery-assisting devices face challenges in maintaining safety and positional accuracy of surgical instruments without increasing manufacturing costs, particularly due to external forces affecting movable bodies and complications from torque sensors.
Innovation Solution
The device incorporates a configuration where distal-side movable bodies have higher operation tolerance than proximal-side movable bodies, using a combination of electric and pneumatic actuators to manage external forces, ensuring simplified operation control and maintaining positional accuracy at the surgical instrument's distal end.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If torque sensors are installed to detect external forces, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts the torque sensor from the system and replaces it with a simpler external force detection mechanism. The control unit directly calculates external forces based on actuator commands and positional deviations, eliminating the need for complex torque sensors while maintaining detection capability.
Solution Approach 2:
The patent replaces the mechanical torque sensor system with a computational approach where the control unit calculates external forces through mathematical models based on actuator commands and observed positional deviations, substituting physical measurement hardware with software-based calculation.
2Device complexity
If all movable bodies have the same operation tolerance, then device complexity is reduced, but safety is worsened due to inability to distinguish critical and non-critical components
Solution Approach 1:
The patent applies local quality by assigning different operation tolerances to different movable bodies based on their criticality. Critical movable bodies (directly connected to the surgical instrument) have lower tolerances, while non-critical movable bodies have higher tolerances, optimizing safety without requiring uniform strict control across all components.
Solution Approach 2:
The patent segments the movable bodies into critical and non-critical categories based on their position and function in the series connection. This segmentation allows differential tolerance assignment, where critical components near the surgical instrument receive stricter control parameters than distal components.
3Ease of operation
If operation tolerance is uniformly applied to all movable bodies, then ease of operation is improved, but positional accuracy at the distal end worsens due to cumulative errors
Solution Approach 1:
The patent implements local quality in tolerance assignment, where movable bodies closer to the surgical instrument (critical bodies) have lower operation tolerances to maintain positional accuracy, while movable bodies farther away (non-critical bodies) have higher tolerances, creating a gradient of precision requirements that preserves overall accuracy without unnecessarily constraining all components.
Solution Approach 2:
The patent segments the chain of movable bodies into critical and non-critical segments based on their distance from the surgical instrument. This segmentation enables differentiated tolerance control where the critical segment (proximal to the instrument) maintains high precision while the non-critical segment (distal to the instrument) allows greater flexibility, reducing cumulative error propagation.
Data Source
AI summary
A surgery-assisting device includes a robot arm that includes plural movable bodies that are operably connected in order in a connecting direction, a surgical instrument connected to a distal end of the robot arm, and one or more actuators that generate a driving force that operates one or more of the movable bodies. The movable bodies include one or more distal-side movable bodies that is provided distally in the connection direction, and one or more proximal-side movable bodies that is provided proximally in the connection direction. An operation tolerance of the one or more distal-side movable bodies is higher than an operation tolerance of the one or more proximal-side movable bodies.