Tiltrotor Rotor Speed Control for Lower Transient Torque Loads
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Solution Overview
Problem
Existing methods for changing rotor speeds in tiltrotor aircraft often result in abrupt transient torque loads, leading to stress, wear, and increased maintenance costs, as well as requiring operators to reduce payload for safety margins.
Innovation Solution
A method and system that use a controller to automatically change rotor speeds from one flight mode to another by implementing an acceleration-rate profile that varies over time, reducing the abruptness of rotor speed changes and minimizing transient torque loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If rotor speed is changed rapidly from initial steady state to transitional steady state and then to final steady state, then the transition time is reduced, but abrupt transient torque loads are generated causing stress, wear, and increased maintenance costs
Solution Approach 1:
The patent applies dynamics by making the rotor speed change profile variable rather than fixed. The acceleration rate is dynamically adjusted during the transition, allowing the system to optimize between transition speed and torque load management. The controller continuously modifies the acceleration rate based on current rotor speed and target speed differences, creating an adaptive transition profile that reduces transient torque loads while maintaining reasonable transition time.
Solution Approach 2:
The patent changes the parameter of acceleration rate from constant to variable during the transition process. By modifying the acceleration rate parameter dynamically - increasing it when the rotor speed difference is large and decreasing it when the difference is small - the system achieves smoother transitions with reduced transient torque loads. This parameter change approach allows optimization of both transition time and torque load characteristics.
2Reliability
If transient torque loads are reduced through slower rotor speed changes, then stress and wear are minimized, but the transition time increases
Solution Approach 1:
The system uses dynamic control to adjust the acceleration rate in real-time during rotor speed transitions. By making the acceleration profile adaptive rather than static, the system can achieve reliable, low-stress transitions without unnecessarily extending transition time. The dynamic adjustment allows the system to be aggressive when safe and conservative when needed.
Solution Approach 2:
The patent implements feedback control where the controller continuously monitors the difference between actual rotor speed and target rotor speed, then adjusts the acceleration rate accordingly. This feedback mechanism ensures that transient torque loads are kept within safe limits while minimizing transition time. The feedback loop allows the system to respond to actual conditions rather than following a predetermined rigid profile.
3Device complexity
If a fixed acceleration rate is used for rotor speed changes, then the control system is simple, but abrupt transient torque loads occur at the beginning and end of transitions
Solution Approach 1:
The patent changes the acceleration rate parameter from fixed to variable based on the rotor speed difference. The controller calculates the difference between target and actual rotor speeds and adjusts the acceleration rate accordingly - higher when the difference is large, lower when the difference is small. This parameter change approach eliminates abrupt transient torque loads while maintaining relatively simple control logic.
Solution Approach 2:
The patent changes the parameter of acceleration rate from constant to variable during the transition process. By modifying the acceleration rate parameter dynamically - increasing it when the rotor speed difference is large and decreasing it when the difference is small - the system achieves smoother transitions with reduced transient torque loads. This parameter change approach allows optimization of both transition time and torque load characteristics.
Data Source
AI summary
A method and system to control a rotor system includes automatically changing a rotor speed of the rotor system of the tiltrotor aircraft while moving the rotor system from a first position and a first rotor speed to a second position and a second rotor speed over a time period in accordance with an acceleration-rate profile that varies over the time period using a controller communicably coupled to the rotor system of the tiltrotor aircraft.