Instrument Drive Unit Torque Compensation Using IMU Pose Feedback
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Solution Overview
Problem
Robotic surgical systems face challenges in accurately compensating for the varying forces acting on instrument drive unit (IDU) motors as the pose of the linkage changes during minimally invasive procedures, affecting the precision and efficiency of tool manipulation.
Innovation Solution
Incorporating an inertial measurement unit (IMU) within the IDU, comprising a gyroscope, accelerometer, and compass, to determine the pose and generate corrected output signals for motor control, thereby compensating for forces such as gravity, and using torque sensors to measure motor torque, with a controller applying correction values to achieve precise tool manipulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the linkage moves the IDU about a workspace to manipulate tissue, then the versatility and adaptability of the surgical system is improved, but the forces acting on the motors vary with pose causing measurement precision and control accuracy to deteriorate
Solution Approach 1:
The system uses torque sensors to measure actual motor torque and IMUs to detect pose changes, then feeds this information back to a controller that calculates compensation values. This closed-loop feedback mechanism continuously corrects torque readings based on real-time pose data, maintaining measurement precision across the entire workspace.
Solution Approach 2:
The system changes the reference frame parameters for torque measurements based on the detected pose of the IDU. By dynamically adjusting the reference frame according to gravitational force directions at different poses, the system maintains accurate torque measurements regardless of the IDU's position in the workspace.
2Productivity
If the IDU operates the tool to manipulate tissue at various poses, then the productivity and efficiency of the surgical procedure is improved, but the varying gravitational forces on motors cause torque reading errors to increase
Solution Approach 1:
The system introduces an intermediary compensation mechanism between the torque sensors and the motor control system. The IMU acts as a mediator that detects pose changes and triggers compensation calculations, serving as an intermediary element that connects the mechanical system with the control system to eliminate gravity-induced errors.
Solution Approach 2:
The system performs preliminary compensation calculations based on predicted pose changes before they significantly affect torque measurements. By continuously monitoring IMU data and pre-calculating compensation values, the system prepares correction factors in advance, ensuring reliable motor control as the IDU moves through its workspace.
3Manufacturing precision
If torque sensors are used to measure motor torque, then the manufacturing precision and initial calibration are improved, but the torque readings become inaccurate when the pose of the IDU changes due to varying gravitational forces
Solution Approach 1:
The system applies a counterweight approach by calculating compensatory torque values that oppose the gravitational forces acting on the IDU at different poses. The controller computes these counter-torque values based on IMU-detected pose changes and adds them to the sensor readings, effectively canceling out gravity-induced measurement errors and achieving pose-invariant torque measurement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution significantly reduces torque reading errors, improving the accuracy and reliability of motor control, allowing for more precise and efficient tool manipulation by compensating for pose-related force variations, thereby enhancing the overall performance of robotic surgical systems.
Implementation Method 1
The inertial measurement unit may be configured to determine the pose of the instrument drive unit based on gravity acting on the inertial measurement unit
Data Source
AI summary
An instrument drive unit includes a housing defining a central longitudinal axis; an inertial measurement unit disposed within the housing and configured to determine a pose of the instrument drive unit; and a controller disposed within the housing, the controller configured to receive the pose of the instrument drive unit from the inertial measurement unit and to generate a corrected output signal which compensates for the pose of the instrument drive unit.