Research on Unmanned Aerial Vehicles (UAVs) has been carried out for a few years. Different kinds of sensor models and control strategies have been developed and applied to increase the flying stability. However, due to several constraints, motors used on small UAVs are usually not under closed loop control. Space limitation of the UAVs and mechanical shape of the motors mainly cause this limitation.

An attitude controller of a UAV is used to control the motor output in order to keep the desired attitude. The problem is that the performance of the controller will change or even fail once the motors are replaced or the performance of the motors changes. The worst case will be failing in managing the attitude of the UAVs. This is because the thrust provided by propellers is related to th...[ Read more ]

Research on Unmanned Aerial Vehicles (UAVs) has been carried out for a few years. Different kinds of sensor models and control strategies have been developed and applied to increase the flying stability. However, due to several constraints, motors used on small UAVs are usually not under closed loop control. Space limitation of the UAVs and mechanical shape of the motors mainly cause this limitation.

An attitude controller of a UAV is used to control the motor output in order to keep the desired attitude. The problem is that the performance of the controller will change or even fail once the motors are replaced or the performance of the motors changes. The worst case will be failing in managing the attitude of the UAVs. This is because the thrust provided by propellers is related to their rotation speed while the speed is managed by the motors. Even for motors with the same model number, there will be deviation in performance owing to the deviation in terms of the mechanical structure and electrical characteristics of the motors. Additionally, the rotation speed of different motors with the same voltage supply will be different.

The dynamics of the UAVs are closely related to the rotation speed of the motors. But it is the truth that this important element is not under proper control. In this thesis, a closed loop control system of the motors implemented on the UAVs is proposed. This helps to solve the feedback sensing problem of three-phase brushless DC motors with a fast response time and accurate readings. The hardware setting consists of few basic electronic components therefore it is small in size and can easily be installed on the UAV. The detection algorithm does not require high computational power.

This system can be easily adopted by different UAV systems with different designs. With the help of this approach, a more robust control system for UAVs can be built.