Surgical Robot Jaw Control Using Motor Current Thresholds
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Solution Overview
Problem
Existing robotic surgical systems require load cells or torque sensors to measure cable tensions for generating desired grasping forces, leading to a complicated structure around elongate elements.
Innovation Solution
A robotic surgical system that includes a controller to determine if the drive part current exceeds a threshold value during closing operations, restricting the command jaw opening angle to prevent excessive grasping force without the need for load cells or torque sensors, thereby simplifying the structure around elongate elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If load cells or torque sensors are provided to measure cable tensions, then the desired grasping force can be generated, but the structure around the elongate elements becomes complicated
Solution Approach 1:
The patent extracts the measurement function from the elongate elements themselves and relocates it to the drive part. By measuring the current value of the drive part that drives the elongate elements, the system obtains information about cable tensions without adding sensors to the elongate elements, thus resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The drive part current value serves as an intermediary parameter that indirectly reflects the cable tensions and grasping force. Instead of directly measuring cable tensions with sensors on the elongate elements, the system uses the electrical current of the drive part as a proxy measurement, eliminating the need for complex sensor integration while maintaining measurement capability
2Ease of operation
If the drive part is driven without restriction to achieve full jaw closing, then the jaw opening angle can be maximized, but the grasping force may become excessive
Solution Approach 1:
The patent implements a feedback control mechanism where the controller continuously monitors the current value of the drive part during jaw closing operation. When the current exceeds a predetermined threshold, the controller restricts further jaw closing, creating a closed-loop control system that prevents excessive grasping force while allowing full jaw closing under normal conditions
Solution Approach 2:
The system dynamically adjusts the jaw closing operation based on real-time current measurements. The restriction of command jaw opening angle is applied conditionally - only when the drive part current exceeds the threshold - allowing the system to adapt its operation mode between unrestricted and restricted states based on actual loading conditions
Data Source
AI summary
A robotic surgical system according to an embodiment may include: a surgical instrument including a pair of jaw members; an operation handle; and a surgical robot that includes a robot arm to which the surgical instrument is attached and which includes motors, and a controller configured to drive the motors based on a command jaw opening angle. The controller is configured, based on determining that a current value of the motors exceeds a predetermined threshold value during a closing operation of the pair of jaw members, to drive the motors in a restriction mode in which a magnitude of the command jaw opening angle is restricted.