Pull-Wire Articulation Control Under Tension Limits and Friction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Flexible elongate medical devices face difficulties in reaching desired regions due to impaired articulation caused by friction, leading to incomplete or failed articulation commands.
Innovation Solution
A medical system with a manipulator assembly and control system that controls articulation states of flexible elongate devices by managing tensions applied to pull wires, using an upper-bounded tension control scheme to achieve commanded articulation without exceeding tension limits, and adjusting tensions with additional actuators if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single actuator controls articulation of the flexible elongate device, then the control system is simple, but the desired articulation cannot be achieved when friction is severe
Solution Approach 1:
The control system is segmented into multiple independent actuators, each responsible for controlling tension in specific pull wires. This segmentation allows the system to distribute the articulation control across multiple actuators, enabling the device to overcome friction and achieve desired articulation states that a single actuator cannot accomplish.
Solution Approach 2:
Multiple actuators are employed to perform the same function of controlling articulation through different pull wires. Each actuator can independently apply tension to its associated pull wire, and collectively they provide redundant and complementary control capabilities, ensuring reliable articulation achievement even when friction is severe.
2Strength
If upper-bounded tension control is applied to each pull wire, then the pull wires are protected from excessive tension, but the commanded articulation state cannot be achieved without exceeding tension limits
Solution Approach 1:
The control system dynamically adjusts the tension distribution among multiple pull wires controlled by different actuators. By dynamically coordinating the tension applied by each actuator, the system achieves the commanded articulation state while keeping individual pull wire tensions within their upper bounds, thus protecting wire integrity while maintaining articulation precision.
Solution Approach 2:
The system changes the tension parameters of multiple pull wires simultaneously through different actuators to achieve the desired articulation state. By adjusting the tension parameters of individual pull wires within their acceptable ranges, the system can achieve precise articulation control without any single wire exceeding its tension limit.
3Adaptability or versatility
If friction is present in the pull wire system, then the device can navigate through tight spaces, but the articulation becomes impaired and struggling motion occurs
Solution Approach 1:
The control system incorporates feedback mechanisms that monitor the tension and position of pull wires controlled by multiple actuators. This feedback allows the system to detect struggling motion and adjust the tension distribution in real-time, compensating for friction effects and maintaining ease of articulation control while preserving the ability to navigate tight spaces.
Solution Approach 2:
Multiple actuators serve as intermediaries between the control system and the pull wires, distributing the control effort across multiple channels. This intermediary approach allows the system to overcome friction by coordinating multiple actuators, each applying controlled tension to different pull wires, thereby maintaining articulation control while enabling navigation through friction-prone environments.
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 complete execution of commanded articulations by detecting and resolving struggling motion, ensuring accurate navigation and operation of flexible elongate devices in minimally invasive procedures.
Implementation Method 1
controlling a second actuator of the plurality of actuators to change an amount of tension applied to a second pull wire of the plurality of pull wires
Implementation Method 2
an articulation of the flexible elongate device may be impaired by friction. When the friction becomes too severe, the desired articulation may become unachievable for the elongate device
Data Source
AI summary
A medical system includes a manipulator assembly and a control system. The manipulator assembly includes actuators that control an articulation state of a flexible elongate device by changing tensions applied to pull wires of the flexible elongate device. The control system controls the actuators to change the articulation state of the flexible elongate device using a control scheme that defines an upper-bounded tension applied to each of the pull wires. The control system further determines that a commanded articulation state of the flexible elongate device cannot be achieved by control of a first actuator without the first actuator applying more than the upper-bounded tension to a first pull wire. The control system also controls a second actuator to change an amount of tension applied to a second pull wire to achieve the commanded articulation state without the first actuator applying more than the upper-bounded tension to the first pull wire.