This paper addresses a difficult problem of high-accuracy control for quadrotor unmanned aerial vehicles (UAVs) subject to external disturbance force and unknown disturbance torque. An observer-based full control scheme is presented. In the strategy, two observer-based estimators are first designed to estimate external disturbance force and torque, respectively. With the application of the precise estimation value, a nonlinear tracking controller is then proposed with compensated disturbance. It is shown by the Lyapunov stability analysis that the entire controller–observer system is asymptotically stable. The key feature of the scheme is that it not only has the superior capability to attenuate unknown external disturbance torque and external force generated by the wind, but also it is able to achieve full control (i.e., six degrees-of-freedom) of the quadrotor UAVs with position and attitude successfully controlled. The effectiveness of the approach is verified on a quadrotor UAV example.

A New Disturbance Attenuation Control Scheme for Quadrotor Unmanned Aerial Vehicles

This paper proposes a novel adaptive sliding-mode-based control allocation scheme for accommodating simultaneous actuator faults. The proposed control scheme includes two separate control modules with virtual control part and control allocation part, respectively. As a low-level control module, the control allocation/reallocation scheme is used to distribute/redistribute virtual control signals among the available actuators under fault-free or faulty conditions, respectively. In the case of simultaneous actuator faults, the control allocation and reallocation module may fail to meet the required virtual control signal, which will degrade the overall system stability. The proposed online adaptive scheme can seamlessly adjust the control gains for the high-level sliding mode control module and reconfigure the distribution of control signals to eliminate the effect of the virtual control error and maintain the stability of the closed-loop system. In addition, with the help of the boundary layer for constructing the adaptation law, the overestimation of control gains is avoided, and the adaptation ceases once the sliding variable is within the boundary layer. A significant feature of this study is that the stability of the closed-loop system is guaranteed theoretically in the presence of simultaneous actuator faults. The effectiveness of the proposed control scheme is demonstrated by experimental results based on a modified unmanned multirotor helicopter under both single and simultaneous actuator faults conditions with comparison to a conventional sliding mode controller and a linear quadratic regulator scheme.

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An Adaptive Fault-Tolerant Sliding Mode Control Allocation Scheme for Multirotor Helicopter Subject to Simultaneous Actuator Faults

Quadrotors are well suited for executing fast maneuvers with high accelerations but they are still unable to follow a fast trajectory with centimeter accuracy without iteratively learning it beforehand. In this paper, we present a novel body-rate controller and an iterative thrust-mixing scheme, which improve the trajectory-tracking performance without requiring learning and reduce the yaw control error of a quadrotor, respectively. Furthermore, to the best of our knowledge, we present the first algorithm to cope with motor saturations smartly by prioritizing control inputs which are relevant for stabilization and trajectory tracking. The presented body-rate controller uses LQR-control methods to consider both the body rate and the single motor dynamics, which reduces the overall trajectory-tracking error while still rejecting external disturbances well. Our iterative thrust-mixing scheme computes the four rotor thrusts given the inputs from a position-control pipeline. Through the iterative computation, we are able to consider a varying ratio of thrust and drag torque of a single propeller over its input range, which allows applying the desired yaw torque more precisely and hence reduces the yaw-control error. Our prioritizing motor-saturation scheme improves stability and robustness of a quadrotor's flight and may prevent unstable behavior in case of motor saturations. We demonstrate the improved trajectory tracking, yaw-control, and robustness in case of motor saturations in real-world experiments with a quadrotor.

Thrust Mixing, Saturation, and Body-Rate Control for Accurate Aggressive Quadrotor Flight

Position and attitude control of multi-rotor aerial vehicles: A survey

Disturbance observer-based adaptive fault-tolerant control for a quadrotor helicopter subject to parametric uncertainties and external disturbances

Active fault-tolerant control for a quadrotor helicopter against actuator faults and model uncertainties

Sliding mode control (SMC) is known as a robust control method to maintain system performance and keep it insensitive to system uncertainties. To achieve this objective, the knowledge of the uncert...

Ban Wang

Papers

An Adaptive Fault-Tolerant Sliding Mode Control Allocation Scheme for Multirotor Helicopter Subject to Simultaneous Actuator Faults

Disturbance observer-based adaptive fault-tolerant control for a quadrotor helicopter subject to parametric uncertainties and external disturbances

Active fault-tolerant control for a quadrotor helicopter against actuator faults and model uncertainties

Adaptive Sliding Mode Fault-Tolerant Control for an Unmanned Aerial Vehicle

Effective optimization on Bump inlet using meta-model multi-objective particle swarm assisted by expected hyper-volume improvement