MR Clutch Tether Tension Control for Stable Payload Motion
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Solution Overview
Problem
Current systems for dynamic motion control of tethered payloads in aircraft and cable-driven systems face challenges in maintaining stable tension, particularly under windy conditions, leading to undesirable payload motion and potential damage due to uncontrolled tension distribution.
Innovation Solution
The implementation of a magnetorheological (MR) fluid clutch apparatus with sensors and a controller system that adjusts tether tension based on aircraft and payload acceleration, using MR fluid actuators to maintain desired tension and decouple payload motion from aircraft motion, thereby stabilizing the payload position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple tethers are used to lift payloads, then payload position delivery accuracy is improved, but the system becomes more sensitive to wind gusts causing large detrimental payload motion
Solution Approach 1:
The patent implements a control system that uses sensors to detect payload position and tension in real-time, then feeds this information back to adjust the tether forces dynamically. This feedback mechanism allows the system to compensate for wind gusts while maintaining precise payload positioning, resolving the contradiction between position accuracy and wind sensitivity.
Solution Approach 2:
The patent changes the tension parameter in the tethers dynamically using controllable actuators (such as winches or hydraulic systems). By adjusting tension levels in response to wind conditions and payload position, the system maintains both positioning accuracy and reduced wind sensitivity, transforming a static system into a dynamically adaptable one.
2Speed
If high-speed cable robot manipulations are used, then workspace coverage and speed are improved, but winch position tracking performance deteriorates due to tension distribution changes
Solution Approach 1:
The control system continuously monitors winch position, cable tension, and payload position, using this feedback to adjust winch commands in real-time. This compensates for tension distribution changes during high-speed maneuvers, maintaining accurate position tracking even at high speeds and large workspaces.
Solution Approach 2:
The system performs preliminary calculations of required tension distribution based on desired trajectory and current system state, preparing control commands in advance. This predictive approach allows the system to anticipate tension changes during high-speed maneuvers and adjust winch positions proactively, maintaining tracking accuracy.
3Force
If collaborative load lifting using multiple aircraft is used, then payload lifting capability is improved, but the system creates large detrimental payload motion under wind gust conditions
Solution Approach 1:
The patent merges the control systems of multiple aircraft into a coordinated system that shares the load and controls payload position collectively. By synchronizing the actions of multiple aircraft and using shared sensing and control, the system achieves both enhanced lifting capability and improved stability against wind gusts.
Solution Approach 2:
The coordinated control system uses real-time feedback from sensors on multiple aircraft and the payload to continuously adjust each aircraft's contribution to the lift. This feedback mechanism allows the system to maintain payload stability while distributing the lifting force across multiple aircraft, even in windy conditions.
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
This solution effectively isolates the payload from aircraft-induced accelerations and wind disturbances, maintaining stable tension and minimizing undesirable payload motion, ensuring precise positioning and safety during lifting operations.
Implementation Method 1
The MR fluid clutch apparatus has a driving member with radial disks, this assembly also known as input rotor. The MR fluid clutch apparatus also has a driven member with annular plates intertwined with the radial disks to define an annular chamber filled with an MR fluid. When a magnetic field is applied, the MR fluid increases its apparent viscosity, creating controllable friction between the disks and plates to transmit variable torque.
Implementation Method 2
An electromagnet is configured to vary the strength of the magnetic field such that the friction between the members is low enough to allow the driving member to freely rotate with the driven member and vice versa.
Data Source
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AI summary
A system for controlling a tension of a tether between an object and a load tethered to the object comprises magnetorheological (MR) fluid actuator unit(s) including at least one torque source and at least one MR fluid clutch apparatus coupled to the at least one torque source to receive torque from the at least one torque source, the MR fluid clutch apparatus controllable to transmit a variable amount of torque via an output of the MR fluid actuator unit. A tensioning member is connected to the output so as to be pulled by the output member upon actuation of the magnetorheological fluid clutch apparatus, a free end of the tensioning member adapted to exert a pulling action when being pulled by the output member. Sensor(s) provide information indicative of a relation between the object and the load tethered to the object. A controller controls the at least one MR fluid clutch apparatus in exerting the pulling action based on said information.