Adjustable Rotor Diameter Motor for UAV Noise Reduction
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Solution Overview
Problem
Unmanned aerial vehicles (UAVs) with multiple motors and propellers generate significant noise due to the periodic operation of traditional brushless DC motors, which is a drawback for applications like surveillance where noise reduction is desirable.
Innovation Solution
The solution involves a brushless DC motor with non-uniformly spaced rotor magnets and electromagnetic coils, allowing for adjustable rotor diameter through heating or mechanical means, which alters the back-electromotive force (EMF) and torque, enabling quieter operation by optimizing motor properties for specific flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional brushless DC motors are used in multiple motors and propellers for UAV flight and navigation, then flight capability and maneuverability are improved, but noise generation increases significantly
Solution Approach 1:
The rotor diameter is made dynamically adjustable through heating elements that cause thermal expansion of the rotor material. This allows the motor to transition between different operational states (contracted and expanded positions) to optimize performance for different flight conditions, reducing noise while maintaining flight capability
Solution Approach 2:
The physical parameter of rotor diameter is changed through controlled heating, which alters the back-EMF and torque characteristics of the motor. This parameter change enables the motor to operate more quietly by optimizing the magnetic field interaction for reduced periodic noise generation
2Object-generated harmful factors
If the rotor diameter is increased to reduce back-EMF and noise, then noise reduction is achieved, but torque decreases
Solution Approach 1:
The rotor diameter is dynamically adjusted based on operational requirements. During phases requiring high torque (takeoff, maneuvering), the rotor is in the contracted position. During transit flight where noise reduction is prioritized, the rotor expands to reduce back-EMF and noise, demonstrating dynamic adaptation to operational context
Solution Approach 2:
The motor operates in periodic cycles, transitioning between contracted and expanded states depending on flight phase. This periodic adjustment of rotor diameter allows the system to alternate between high-torque mode and low-noise mode, optimizing overall performance
3Force
If the rotor diameter is decreased to increase torque, then torque is improved, but maximum RPM decreases
Solution Approach 1:
The rotor diameter is made dynamically adjustable to optimize the torque-RPM tradeoff for different flight conditions. The heating elements enable real-time adjustment of rotor size, allowing the motor to achieve high torque when needed while maintaining the capability for high RPM operation
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 approach reduces noise by altering the motor's sound profile to broadband noise and allows for adjustable torque and RPM, optimizing motor performance for different UAV operations such as takeoff, transit, and maneuvering, thereby enhancing operational efficiency and reducing noise pollution.
Implementation Method 1
a heating coil coupled to a surface of the rotor and configured to heat the rotor, wherein when the rotor is heated the rotor transitions from a contracted position in which the rotor has a first diameter to an expanded position in which the rotor has a second diameter that is larger than the first diameter
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
The described apparatus and method enable alteration of motor properties during operation of a motor. For example, the rotor of the motor may be adjustable, during motor operation, between a first diameter and a larger, second diameter. When the diameter of the rotor increases, the distance between the electromagnetic coils of the stator and the magnets of the rotor increases, thereby reducing the back-electromotor force (back-EMF) of the motor. When the back-EMF of the motor decreases, the torque of the motor decreases but the maximum revolutions per minute (RPM) increases. When the diameter of the rotor decreases, the distance between the electromagnetic coils of the stator and the magnets of the rotor decreases, thereby increasing the back-EMF of the motor. When the back-EMF of the motor increases, the torque of the motor increases but the maximum RPM decreases.