Sensorless UAV Motor Startup Using Back-EMF Direction Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Unmanned aerial vehicles (UAVs) with sensorless motors face challenges in determining and adjusting the rotation rate and direction, especially when starting up with unknown conditions, which can lead to inefficient or unsafe operation.
Innovation Solution
A system utilizing a microcontroller to measure the frequency of back electromotive force (EMF) generated by the sensorless motor, allowing it to determine the rotation rate and direction, and adjust the motor's operation accordingly, enabling the UAV to start and maintain the desired rotation rate and direction without sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless motors are used in UAVs to reduce device complexity, then device complexity is reduced, but the ability to determine and adjust rotation rate and direction deteriorates
Solution Approach 1:
The motor system uses itself to provide the measurement function. The back-EMF generated by the motor during rotation is measured to determine rotation rate and direction, eliminating the need for external sensors. The motor's own electrical characteristics are exploited for self-diagnosis and self-regulation.
Solution Approach 2:
The system measures the back-EMF frequency and uses this feedback to determine the actual rotation rate and direction. This feedback information is then used by the microcontroller to adjust the motor operation, creating a closed-loop control system without requiring mechanical sensors.
2Ease of operation
If the motor starts with unknown rotation rate and direction, then ease of operation is improved, but reliability deteriorates due to unsafe operation
Solution Approach 1:
Before the motor is started or during startup, the system performs preliminary measurements of the back-EMF frequency to determine the current rotation rate and direction. This preliminary information is used to prepare the appropriate control actions, ensuring safe operation from the beginning of the startup sequence.
Solution Approach 2:
The system proactively identifies and counteracts potential unsafe conditions during startup by measuring back-EMF and determining the actual rotation state before full power is applied. If the rotation direction or rate is incorrect, the system takes corrective action in advance to prevent unsafe operation.
3Measurement precision
If back-EMF frequency measurement is used to determine rotation rate, then measurement precision is improved, but device complexity increases due to additional measurement requirements
Solution Approach 1:
The existing microcontroller and its built-in frequency measurement capabilities are used for dual purposes: controlling the motor and measuring the back-EMF frequency. The same hardware resources are leveraged for both control and sensing functions, avoiding the need for dedicated measurement circuitry.
Solution Approach 2:
The back-EMF signal serves as an intermediary that carries information about the motor's rotation state. By measuring this electrical signal, the system indirectly obtains mechanical rotation information without direct mechanical contact or additional sensors.
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
Enables the UAV to efficiently and safely start and operate its propellers by determining and adjusting the rotation rate and direction, even when the motor is unknown, improving the reliability and efficiency of the UAV's propulsion system.
Implementation Method 1
determine a rotation rate of the at least one propeller based on a measured frequency of a back electromotive force (EMF) generated by the at least one sensorless motor
Data Source
AI summary
Systems, devices, and methods for: an unmanned aerial vehicle (UAV); at least one sensorless motor of the UAV, the at least one sensorless motor comprising a set of windings and a rotor; at least one propeller connected to the at least one sensorless motor; a microcontroller in communication with the at least one sensorless motor, wherein the microcontroller is configured to: determine a rotation rate of the at least one propeller; determine a rotation direction of the at least one propeller; provide an output to stop the at least one propeller if at least one of: the determined rotation rate is not a desired rotation rate and the determined rotation direction is not a desired rotation direction; and provide an output to start the at least one propeller if the at least one propeller is stopped at the desired rotation rate and the desired rotation direction.