Surgical Robot Arm Control System Spread Angle Calibration
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Solution Overview
Problem
Current surgical robot arm control systems face challenges in accurately reflecting surgeon inputs due to discrepancies between predicted and actual spread angles between end effector elements, leading to issues like over-closed or open configurations, which affect the precision and ease of use during minimally invasive procedures.
Innovation Solution
The control system employs a processor and memory to adjust instrument drive forces and positions based on determined spread offset and interface position offset values, using kinematic equations and force/sensor data to calibrate and compensate for lost motion and manufacturing variability, ensuring accurate reflection of surgeon inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the surgical robot arm uses standard control systems with predicted spread angles, then the device complexity is reduced and ease of manufacture is improved, but the manufacturing precision and measurement precision deteriorate due to discrepancies between predicted and actual spread angles
Solution Approach 1:
The control system performs preliminary calibration by actuating the robotic surgical instrument through its full range of motion before surgery to measure actual spread angles. These measurements are stored and used to create calibration data that compensates for manufacturing variations, eliminating the need for complex real-time adjustments during surgery.
Solution Approach 2:
The system implements feedback by comparing predicted spread angles from kinematic equations with actual measured spread angles from sensors. This feedback loop allows the control system to identify discrepancies and apply compensation based on calibration data, improving accuracy without requiring overly complex real-time control mechanisms.
2Measurement precision
If the control system applies compensation for lost motion and manufacturing variability, then the measurement precision of spread angles is improved, but the device complexity and ease of operation worsen due to additional calibration procedures
Solution Approach 1:
The control system performs self-calibration by automatically actuating the robotic surgical instrument through its full range of motion, measuring actual spread angles using integrated sensors, and generating calibration data without requiring external intervention. This automated process reduces the burden on surgeons and operating room staff.
Solution Approach 2:
The calibration procedure is performed in advance before surgery begins, during which the system automatically measures and stores compensation data. This preliminary action ensures that all subsequent surgical operations benefit from the calibrated data without requiring repeated calibration procedures, simplifying the surgical workflow.
3Reliability
If the system uses kinematic equations to predict spread angles, then the ease of manufacture is improved, but the manufacturing precision and reliability deteriorate due to accumulated errors from link length and angle variations
Solution Approach 1:
The system uses feedback by measuring actual spread angles with sensors and comparing them to predicted values from kinematic equations. The differences are used to generate calibration data that compensates for manufacturing variations in link lengths and joint angles, maintaining control accuracy without requiring extremely tight manufacturing tolerances.
Solution Approach 2:
The control system dynamically adjusts operational parameters based on calibration data. Instead of relying solely on fixed kinematic equations with nominal parameters, the system uses measured parameters from calibration to calculate actual spread angles, effectively adapting to the specific physical characteristics of each robotic instrument.
Data Source
AI summary
A control system for controlling a surgical robot arm, the surgical robot arm having a drive mechanism configured for driving a robotic surgical instrument, said robotic surgical instrument comprising a first end effector element and a second end effector element, the drive mechanism comprising one or more interface elements configured to interface with the robotic surgical instrument for controlling a spread angle between the first end effector element and the second end effector element, the control system being configured to: cause an instrument drive force applied at the one or more interface elements to be varied; measure, at each of a plurality of times, the instrument drive force applied at the one or more interface elements; determine, for each of the plurality of times, a force behaviour value using a derivative of the measured instrument drive force with respect to the time at that time; determine an offset value in dependence on the plurality of determined force behaviour values; and control, in dependence on the offset value, the surgical robot arm to control the spread angle between the first end effector element and the second end effector element of the robotic surgical instrument.