Controller development and validation for a small quadrotor with compensation for model variation

The research discussed here proposes a control system with compensation to maintain consistent performance for quadrotors under system variations, specifically due to battery drainage and mass changes. This compensation control system is comprised of three subsystems. The first subsystem is a baseline PID controller, which generates a desired rpm for each motor. The second subsystem compensates for battery drainage. Based on a complete relationship of PWM-rpm-Voltage obtained from experiments, this compensation subsystem calculates an appropriate PWM command needed to obtain the rpm received from the PID controller, taking into account the current battery voltage. The last subsystem consists of an online mass estimator to estimate the total mass of the quadrotor and payload, and correspondingly adapts the output of the PID controller in order to maintain performance. Simulation and experiments were conducted, both with and without the compensation strategies. The results clearly show the effectiveness of the proposed approaches.