Multi-Rotor UAV's used in applications such as inspection, interaction with humans or environment such as cleaning of glass, writing on a board or tasks which include hovering in a closed room or in presence of gust and ground effect needs precision and robustness because of uncertainties caused due to change in velocity of wind flow to the propeller.
The present UAV's use a static map which converts individually desired wrenches(thrust) to its respective PWM output which is sent to an electronic speed controller to control the speed of brushless direct current motors(BLDC).
The static map is an estimator which relates thrust and PWM signals designed by placing the BLOC motor at the center of the room. In the presence of disturbance such as ground effect, propeller effect, surroundings effect, the thrust varies and is not compensated because of open loop thrust control. In-order to overcome this issue a closed loop thrust controller is needed.