Robotic End Effector Joint Null-Space Control With Redundant Actuation
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Solution Overview
Problem
Surgical robotic systems face limitations in achieving precise control and redundancy in joint movements, particularly in minimally-invasive surgeries, where direct correlation between motor and joint positions can lead to reduced flexibility and additional control objectives being unmet.
Innovation Solution
The implementation of a redundant degree of freedom (DoF) for end effector joints using two actuators, allowing for position displacement calculations and secondary movements within a null space to achieve desired end effector movements while maintaining additional control objectives, such as pre-tension and torque, through a system comprising a tool driver with processors and actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single actuator directly drives a joint, then the system structure is simple and direct correlation between motor position and joint position is achieved, but the system lacks flexibility and cannot meet additional control objectives
Solution Approach 1:
The control system segments the actuation function by separating the primary position control from secondary control objectives. The single actuator's control is divided into independent components: one for joint position and another for additional objectives like pre-tension maintenance, allowing simultaneous achievement of multiple goals without adding physical actuators
Solution Approach 2:
The patent introduces a null space dimension in the control space to accommodate additional control objectives. By operating in this extra dimensional space, the system can achieve secondary objectives (such as maintaining pre-tension or optimizing torque distribution) without affecting the primary joint position control, effectively adding versatility without physical complexity
2Adaptability or versatility
If multiple actuators drive a single joint, then flexibility and additional control objectives are achieved, but the system complexity increases
Solution Approach 1:
The single actuator is designed to perform multiple functions simultaneously through sophisticated control algorithms. It handles both primary joint position control and secondary objectives like pre-tension maintenance and torque optimization, making the actuator universal and eliminating the need for multiple specialized actuators
Solution Approach 2:
The control system dynamically adjusts control parameters including null space vectors, weighting factors, and constraint conditions to balance between position accuracy and additional objectives. By changing these parameters in real-time, the system achieves flexibility and adaptability without adding physical complexity to the actuator configuration
Data Source
AI summary
The disclosed embodiments relate to systems and methods for a surgical tool or a surgical robotic system. One example method includes providing a redundant degree of freedom (DoF) for an end effector joint of one DoF by driving the joint with two actuators, calculating a position displacement of the joint to effect a desired end effector movement in response to an input command, calculating a first movement of the two actuators based on the position displacement of the joint and a second movement of the two actuators based on a second control objective in a null space corresponding to the redundant DoF, and driving the joint according to the first movement and the second movement to effect the desired end effector movement while accomplishing the second control objective in the null space.