Robotic Surgical Jaw Control Using Drive-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 a desired grasping force, 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 jaw closure, restricting the 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 by using a torque sensor at the drive part to measure the tension in the elongate elements indirectly. This removes the need to attach load cells or torque sensors directly to the elongate elements, thereby simplifying their structure while still enabling accurate tension measurement for grasping force control
Solution Approach 2:
The patent introduces a torque sensor at the drive part as an intermediary device to measure the tension in the elongate elements. Instead of directly measuring cable tension at multiple points along the elongate elements, the torque sensor measures the rotational torque at the drive part, which corresponds to the tension in the elongate elements, providing an indirect but effective measurement approach that simplifies the overall structure
2Force
If the drive part current is monitored and jaw opening angle is restricted when current exceeds threshold, then appropriate grasping force is achieved, but the control system becomes more complex
Solution Approach 1:
The patent implements a feedback control mechanism where the controller continuously monitors the current value of the drive part during jaw closure and compares it against a predetermined threshold. When the current exceeds the threshold, the controller restricts the jaw opening angle to prevent excessive grasping force. This feedback-based approach enables appropriate grasping force control using existing current measurement capabilities without requiring additional sensors or complex measurement systems
Solution Approach 2:
The patent utilizes the existing current measurement capability of the drive part for dual purposes: both for normal operation control and for grasping force control. By monitoring the drive part current, which naturally reflects the load and tension in the elongate elements, the system serves itself to provide grasping force control without requiring separate measurement devices, thereby minimizing additional system complexity
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 a drive part to drive a driven member, and a controller configured to drive the drive part based on a command jaw opening angle associated with an input to the input device for controlling an opening angle between the pair of jaw members. The controller is configured, when it is determined that a current value of the drive part excesses a predetermined threshold value during a closing operation of the pair of jaw members, to drive the drive part in a restriction mode in which a magnitude of the command jaw opening angle is restricted.