Robotic End Effector Joint Control With Null-Space Redundancy
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Solution Overview
Problem
Surgical robotic systems face challenges in achieving precise control and redundancy in joint movements, particularly in minimally-invasive surgeries, where existing systems often lack the ability to optimize multiple motor positions for desired joint positions, leading to inefficiencies in torque delivery and tension maintenance.
Innovation Solution
The introduction of a redundant degree of freedom (DoF) for end effector joints, driven by two actuators, allows for calculating position displacements 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 of actuators and processors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single actuator drives a joint directly, then the control system is simple and direct correlation between motor position and joint position is maintained, but the system lacks redundancy and cannot optimize multiple motor positions for desired joint positions
Solution Approach 1:
The control system segments the actuation of a single joint into multiple independent actuators. Instead of one actuator directly driving the joint, the patent employs multiple actuators (e.g., two or more motors) that can independently contribute to the joint's movement, enabling redundancy while maintaining manageable control through modular architecture
Solution Approach 2:
The patent adds an additional dimension to the control space by introducing redundant actuators. This transforms the control problem from a direct one-to-one mapping to a many-to-one relationship, where multiple actuator positions (adding a dimension of choice) can achieve the same joint position, enabling optimization of torque delivery and tension maintenance
2Adaptability or versatility
If multiple actuators drive a joint, then redundancy is achieved and multiple motor positions can be optimized for desired joint positions, but the control system complexity increases
Solution Approach 1:
The patent implements feedback mechanisms where the control system continuously monitors joint position, actuator positions, and system state (such as tension and torque). This feedback enables the controller to calculate optimal actuator configurations and adjust them in real-time, managing the complexity of multiple actuators through closed-loop control
Solution Approach 2:
The control system dynamically changes parameters such as actuator positions, torque distribution, and tension levels to optimize performance. By adjusting these parameters based on the null space of the redundant actuators, the system achieves multiple control objectives (position accuracy, torque optimization, tension maintenance) without proportionally increasing complexity
3Reliability
If redundant actuators are used to drive a joint, then torque delivery and tension maintenance are optimized, but the device requires additional actuators and control calculations
Solution Approach 1:
The patent employs dynamic control of redundant actuators, where the system continuously adjusts actuator positions and torque distribution based on real-time requirements. This dynamic allocation allows the system to maintain consistent torque delivery and tension across varying surgical tasks, with actuators transitioning between active and redundant roles as needed
Solution Approach 2:
The control system changes operational parameters such as torque magnitude, actuator engagement state, and tension levels to optimize reliability. By modifying these parameters within the null space of the redundant actuator system, the patent achieves consistent torque delivery and tension maintenance without requiring all actuators to operate at maximum capacity simultaneously
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.