Robust Adaptive Tracking Control for Quadrotors by Combining PI and Self-Tuning Regulator

This brief is concerned with the robust adaptive tracking control problem of quadrotors. Considering the practicality of control laws to be designed, the self-tuning regulator (STR) for discrete-time systems is employed as our inner loop adaptive tracking mechanism and the classical proportional–integral (PI) control is designed for the outer loop to guarantee the robustness of the whole system. The main contributions of our work include: 1) we design the control laws for the actuator inputs (pulsewidth modulation signals) directly, which removes the need to measure the motor speeds and 2) the proposed PI-STR method can reduce the large overshoot of a single STR and retain the adaptability of the STR and the robustness of the PI control simultaneously. Furthermore, the outer loop PI controller and inner loop STR can easily be implemented in the digital form. The stability analysis is also provided. Simulations indicate that the PI-STR-based control structure can cope with the situations where vehicles are disturbed or have time-varying parameters. Our preliminary experiments show its practicality.