Cable-Driven End-Effector Control for Maintaining Cable Tension
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Solution Overview
Problem
Existing robotic surgical systems face challenges in effectively controlling the tension in cables to manipulate end effectors during minimally invasive procedures, necessitating improved methods for precise manipulation and maintaining desired poses.
Innovation Solution
A method and controller system for end effectors using a primary controller to generate motor torques and null torques, combined with a secondary controller to maintain cable tension, and a tertiary controller to adjust torques, ensuring precise manipulation in yaw, pitch, and jaw degrees-of-freedom, while utilizing a differential drive mechanism with springs to bias the end effector to a predetermined pose.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional open loop cable control system is used to manipulate end effectors, then the system structure is simple, but the control precision and ability to maintain desired poses is insufficient
Solution Approach 1:
The control system is divided into multiple independent controllers (primary controller, secondary controller, tertiary controller) that each handle specific control functions. The primary controller manages motor torques, the secondary controller maintains cable tension, and the tertiary controller adjusts torques, allowing for precise control while keeping each controller's function simple and modular.
Solution Approach 2:
A secondary controller is introduced as an intermediary between the primary and tertiary controllers to specifically maintain cable tension. This intermediary component resolves the conflict by handling the tension maintenance function separately, enabling the primary controller to focus on position control and the tertiary controller to focus on torque adjustment.
2Reliability
If multiple controllers are used to maintain cable tension and adjust torques, then control precision is improved, but the device complexity increases
Solution Approach 1:
The control system is divided into multiple independent controllers (primary controller, secondary controller, tertiary controller) that each handle specific control functions. The primary controller manages motor torques, the secondary controller maintains cable tension, and the tertiary controller adjusts torques, allowing for precise control while keeping each controller's function simple and modular.
Solution Approach 2:
The secondary controller automatically maintains cable tension by continuously monitoring and adjusting motor torques, without requiring external intervention. This self-service capability improves reliability by ensuring consistent cable tension maintenance while keeping the control architecture manageable through automation.
3Measurement precision
If calibration and encoders are extensively used to achieve precise control, then positioning accuracy is improved, but operational complexity and setup time increase
Solution Approach 1:
The system replaces complex mechanical calibration procedures and extensive encoder usage with a control-based approach. The multiple controllers work together to achieve precise positioning through software control and feedback mechanisms, eliminating the need for physical calibration hardware and reducing setup complexity.
Solution Approach 2:
The control system performs self-calibration and self-adjustment through the coordinated action of the primary, secondary, and tertiary controllers. The system automatically maintains desired poses and adjusts torques without requiring external calibration equipment or complex setup procedures, improving ease of operation while maintaining precision.
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
Enables precise and efficient control of end effectors, reducing the need for calibration and encoder usage, maintaining desired poses, and facilitating seamless tool attachment, thereby enhancing surgical precision and reducing operational complexity.
Implementation Method 1
utilizing a differential drive mechanism with springs to bias the end effector to a predetermined pose
Data Source
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AI summary
A method of controlling an end effector of a surgical robot includes receiving a desired pose, generating motor torques, transmitting the motor torques, generating null torques, generating desired torques, and transmitting the desired torques to an IDU such that the IDU moves the end effector to the desired pose. A primary controller receives the desired pose of the end effector in three DOF. The primary controller generates the motor torques in response to receiving the desired pose. The primary controller transmits the motor torques which are received in a secondary controller. The secondary controller generates null torques to maintain tension in cables of a differential drive mechanism of the IDU. The desired torques are generated for each motor of the IDU to include a sum of the motor torques and the null torques.