eVTOL Propulsion Assembly With Regenerative Propulsor Braking
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Solution Overview
Problem
Battery-powered electric aircraft propulsion systems face inefficiencies due to varying DC voltage during flight, leading to increased current requirements and potential electrical losses, which can be mitigated but at the cost of added weight through the use of DC:DC converters.
Innovation Solution
An electric aircraft propulsion assembly that includes a DC:AC converter and a controller to operate in modes that allow the system to convert DC power to AC for propulsion and utilize idle motors to apply braking torque, reducing the need for mechanical brakes and optimizing energy use across flight phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If DC:DC converters are added to boost voltage as battery voltage reduces, then voltage stability is improved, but aircraft weight increases
Solution Approach 1:
The patent makes the converter system multi-functional by enabling it to operate in three different modes: DC:AC conversion for motor operation, DC:DC conversion for voltage boosting, and regenerative braking for energy recovery. This eliminates the need for separate dedicated components for each function, thereby reducing overall system weight while maintaining voltage stability throughout the flight cycle.
Solution Approach 2:
The converter system dynamically switches between different operating modes based on real-time flight conditions and battery state. The controller adjusts the converter operation from DC:AC mode during takeoff to DC:DC mode during cruise, and enables regenerative braking during descent, optimizing voltage stability adaptively without requiring fixed heavy infrastructure.
2Power
If higher current is used to compensate for reduced voltage, then power output is maintained, but electrical losses increase
Solution Approach 1:
The patent converts the harmful effect of aerodynamic drag on idle propellers into beneficial regenerative energy. During cruise phase, instead of allowing idle propellers to consume power or create drag, the system engages regenerative braking that converts the drag-induced rotation into electrical energy, feeding it back to the battery and reducing overall electrical losses.
Solution Approach 2:
The system maintains continuous useful action by ensuring that converters and motors remain actively engaged throughout all flight phases. Rather than idle components consuming power or creating drag, the regenerative braking mechanism ensures continuous energy recovery, eliminating wasted energy and maintaining optimal power utilization from takeoff through cruise to landing.
3Ease of operation
If mechanical brakes are used to hold idle propellers stationary, then propulsor control is improved, but device complexity and weight increase
Solution Approach 1:
The patent replaces the mechanical braking system with an electromagnetic braking system using the motor itself. The converter controls the motor to generate electromagnetic torque that counteracts aerodynamic drag, holding the propeller stationary during cruise. This substitution eliminates complex mechanical brake components while achieving the same control function through electrical means.
Solution Approach 2:
The motor serves dual functions: it acts as a drive motor during takeoff and landing, and as a regenerative brake during cruise. The system uses its own motor and converter infrastructure to provide braking functionality, eliminating the need for separate mechanical braking components and reducing overall system complexity.
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 reduces energy losses and weight by efficiently managing power distribution and utilizing idle motors for braking, enhancing the performance and efficiency of electric vertical takeoff and landing (eVTOL) aircraft.
Implementation Method 1
a first converter configured as a DC:AC converter having input connections connectable to the battery and output connections connected to the first electric motor, the first converter configured to convert a DC supply across the input connections to an AC supply across the output connections
Implementation Method 2
a first electric motor connected to power a first propulsor
Implementation Method 3
the second converter is operated to drive the second electric motor to provide a braking torque on the second propulsor
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
The disclosure relates to an electric aircraft propulsion assembly (300) for an electric vertical takeoff and landing, eVTOL, aircraft (100), the assembly (300) comprising: an electric storage unit (302); a first electric motor (303) connected to power a first propulsor (305); a first converter (307) configured as a DC:AC converter for driving the first electric motor (303) and a second electric motor (304) connected to power a second propulsor (306), a second converter (308). A controller (310) is connected to control operation of the first and second converters and is configured to operate in a first mode in which the first and second converters (307, 308) are operated as DC:AC converters to drive the first and second electric motors (303, 304) and a second mode in which the first converter (303) is operated to drive the first electric motor (303) to power the first propulsor (305) and the second converter (308) is operated to drive the second electric motor (304) to provide a braking torque on the second propulsor (306).