Dual-Actuator Instrument Control With Minimum Tension Compensation
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Solution Overview
Problem
Existing computer-assisted instruments face challenges in controlling degrees of freedom (DOFs) due to the limitations of force or torque transmission mechanisms that are either too rigid or require larger actuators, which are not suitable for minimally invasive procedures with limited workspace access.
Innovation Solution
A control system using two actuators with opposing force or torque transmission mechanisms to maintain minimum tensions in both directions, compensating for external disturbances and dynamics, allowing precise control of DOFs in instruments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a single actuator with a force or torque transmission mechanism is used to actuate a degree of freedom in both directions, then the actuator size can be reduced, but the transmission mechanism becomes too rigid and requires larger actuators that are not suitable for minimally invasive procedures
Solution Approach 1:
The single actuator system is segmented into two separate actuators, each responsible for actuating the degree of freedom in one direction. This segmentation allows each actuator to be smaller and less rigid, eliminating the need for complex rigid transmission mechanisms while maintaining bidirectional control capability.
2Manufacturing precision
If two actuators with opposing force or torque transmission mechanisms are used to maintain minimum tensions, then control precision is improved, but the system complexity increases
Solution Approach 1:
The system changes the control parameter from single-actuator force control to dual-actuator tension control, where each actuator maintains a minimum tension in its transmission mechanism. This parameter change enables precise control of the degree of freedom while the control system manages the complexity through coordinated actuation commands.
3Stability of the object's composition
If rigid force or torque transmission mechanisms are used, then structural stability is improved, but the actuators required become larger and less suitable for minimally invasive procedures
Solution Approach 1:
The patent replaces rigid force or torque transmission mechanisms with flexible transmission mechanisms that maintain structural stability through continuous tension. The flexible nature of these mechanisms allows for smaller actuator sizes while preserving the stability needed for precise instrument control in minimally invasive procedures.
Data Source
AI summary
Systems and methods of controlling instruments include first and second actuators configured to actuate a degree of freedom (DOF) in first and second directions using respective transmission mechanisms and a control unit. The control unit is configured to determine positions of the first and second actuators; determine an actuation command based on the positions of the first and second actuators, and a desired state of the DOF; determine respective actuation levels of the first and second actuators so as to maintain tensions in the transmission mechanisms above respective minimum tensions by: using a model based on the force or torque command, the minimum tensions, and the first and second actuator positions; and command actuation of the first and second actuators at the respective actuation levels. The model compensates for an external disturbance on the DOF and for dynamics of the first and second actuators.