Active Tether Control for Multirotor UAS
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Solution Overview
Problem
Managing cable tension in tethered unmanned aerial systems (UAS) is challenging due to wind-induced stress and slack, which can interfere with flight controls and cause tangles, while excess tension can damage the UAS.
Innovation Solution
An active tether control system using a servomotor-driven reel with a tensioning pulley and spring, coupled with a linear displacement transducer, maintains constant tension by adjusting the tether's length based on feedback signals to ensure optimal tension levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the tether is used to provide power and control signals to the UAS, then the operating time and range are extended, but the cable tension becomes difficult to manage due to wind currents and motion
Solution Approach 1:
The system uses a transducer to measure the position of the tensioning pulley and generates a feedback signal proportional to the tensioning spring force. This feedback is fed to a tension controller that adjusts the servomotor output to maintain the desired tether tension, enabling automatic closed-loop control of cable tension during UAS operation.
Solution Approach 2:
The tensioning system automatically adjusts cable tension through the servomotor and feedback control without requiring manual intervention. The system self-regulates to maintain optimal tension levels, preventing both excessive tension and slack conditions that would require operator attention.
2Stability of the object's composition
If the tether tension is increased to prevent slack and tangling, then the cable remains taut during descent, but excess tension may interfere with flight controls and damage the UAS
Solution Approach 1:
The system dynamically adjusts the tether tension parameter within a predetermined range rather than maintaining a fixed tension value. The tension controller modifies the servomotor output based on feedback signals to keep tension within safe bounds, adapting to changing flight conditions while preventing both slack and excessive tension conditions.
3Ease of operation
If a tensioning spring is added to control cable tension, then the tension can be automatically regulated, but the device complexity increases
Solution Approach 1:
The tensioning spring acts as a mechanical intermediary that converts position changes of the tensioning pulley into a proportional force signal. This mechanical mediation simplifies the control task by providing a direct physical relationship between pulley position and tension force, which the transducer then converts into an electrical feedback signal for the controller.
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
The system automatically adjusts and maintains tension in real-time, preventing sagging and damage, allowing for stable and extended UAS operation with minimal resistance.
Implementation Method 1
The tensioning spring is arranged to generate a variable tension force on the active tether
Implementation Method 2
A transducer is connected adjacent to the tensioning spring to sense a linear displacement position of the tensioning pulley
Data Source
AI summary
A control system and method for tensioning an active tether for a multirotor unmanned aerial system is provided. The control system includes a tensioning pulley and a tensioning spring. The tensioning spring is arranged to generate a variable tension force on the active tether. A transducer is connected adjacent to the tensioning spring to sense a linear displacement position of the tensioning pulley and to transmit a position signal to a controller. The position signal is proportional to the linear displacement position. A servomotor in communication with the controller receives a control signal from the controller in response to the position signal. The servomotor drives a cable reel. The cable reel is rotatably mounted in the frame for spooling the tether in response to rotation of the servomotor. The cable reel is rotated by the servomotor to maintain a predetermined tension on the tensioning spring.