Rotorcraft Autorotation Control Using Differential Electrical Braking
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Solution Overview
Problem
Current electrically powered rotorcraft designs, particularly those with four or more rotors, lack the capability to safely autorotate and land in the event of a power failure, posing safety risks for passengers and those on the ground due to high descent rates and limited landing options.
Innovation Solution
The implementation of a method enabling autorotation of at least four rotors through mechanical and electrical braking mechanisms, allowing differential control of rotor orientation and pitch adjustments to maintain a safe descent rate, combined with a separate power system for autorotative operations, enables controlled autorotative landing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If electrically powered rotorcraft with four or more rotors are used, then productivity and versatility are improved, but the ability to safely autorotate and land in case of power failure deteriorates
Solution Approach 1:
The control system is segmented into multiple independent rotor controllers, each capable of autonomous electrical braking control. This allows individual rotor management during autorotation, enabling safe landing while maintaining the multi-rotor transportation platform.
Solution Approach 2:
Traditional mechanical pitch control systems are replaced with electrical braking control systems. The electrical motors that drive the rotors are repurposed to provide electrical braking during autorotation, eliminating the need for complex mechanical pitch adjustment mechanisms while enabling safe landing.
2Ease of operation
If fixed rotors with independent rotation speed control are used, then ease of operation is improved, but the capability to control descent rate during autorotation deteriorates
Solution Approach 1:
The electrical motors serve dual functions: driving the rotors during normal operation and providing electrical braking during autorotation. This self-service capability allows the same system to maintain simple operation while enabling precise descent rate control through electrical braking.
Solution Approach 2:
The control parameter changes from mechanical pitch angle adjustment to electrical braking torque application. This parameter change maintains operational simplicity while enabling precise control of rotor speed and descent rate during autorotation through electrical means.
3Reliability
If autorotation is enabled through mechanical means, then reliability is improved, but device complexity increases
Solution Approach 1:
The electrical motor system performs multiple functions: propulsion during normal flight and braking during autorotation. This multi-functionality enables autorotation capability without adding separate mechanical systems, thus improving reliability while minimizing complexity increase.
Solution Approach 2:
The electrical motor acts as an intermediary between the rotor and the control system. During autorotation, the motor provides electrical braking torque to control rotor speed, serving as a mediator that simplifies the control mechanism compared to direct mechanical pitch control while maintaining reliable autorotation.
4Ease of operation
If differential electrical braking is applied to control orientation, then ease of operation is improved, but use of energy increases
Solution Approach 1:
The natural drag and energy dissipation during autorotation, which would normally be harmful by causing uncontrolled descent, is converted into a beneficial control mechanism. The electrical braking system utilizes the rotor's kinetic energy and converts it to electrical energy through regenerative braking, controlling orientation while recovering energy.
Solution Approach 2:
The system discards the need for separate autorotation power sources by recovering energy from the rotor's natural deceleration. Electrical braking converts the kinetic energy of the rotating rotors back into electrical energy, which can be stored or used, thus managing orientation control while minimizing net energy consumption.
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 allows for a safe and controlled autorotative descent with a descent rate less than 10 meters per second, enhancing safety by providing a mechanism for emergency landings in urban areas and reducing the burden on pilots through semi-autonomous or fully autonomous control.
Implementation Method 1
causing, by the system controller, differential control of electrical braking of the set of rotors
Implementation Method 2
The ability to descend and land safely using autorotation requires the helicopter's rotor system and controls be designed to support autorotation
Implementation Method 3
drag from the rotor blades' motion through the air will quickly drain the rotational energy of the rotors
Implementation Method 4
If the rotors are spinning when the engine is disengaged (for example, due to engine failure in mid-flight), the angular momentum of the rotors ensures they will initially continue to spin
Data Source
AI summary
A method of operating an electrically powered rotorcraft of the type having a fuselage and a set of N rotors driven by a set of electric motors and coupled to the fuselage, N≥4, under a failure condition preventing ordinary operation of the rotorcraft. The method includes entering a failsafe mode of operation wherein autorotation of at least four of the rotors is enabled. The method also includes using electrical braking associated with a selected group of the rotors to control pitch, roll and yaw of the rotorcraft.