Modeling and Adaptive Nonlinear Disturbance Observer for Closed-Loop Control of In-Ground-Effects on Multi-Rotor UAVs

2017 ◽  
Author(s):  
Xiang He ◽  
Marc Calaf ◽  
Kam K. Leang
Keyword(s):  
Flight Control ◽  
Disturbance Observer ◽  
Closed Loop ◽  
Ground Effect ◽  
Flight Behavior ◽  
Nonlinear Disturbance Observer ◽  
Loop Control ◽  
Confined Spaces ◽  
Nonlinear Disturbance ◽  
Ground Effects

This paper focuses on modeling and nonlinear control of in-ground-effect (IGE) on multi-rotor aerial vehicles such as quadrotor helicopters (quadcopters). As the vehicle flies and hovers near obstacles such as the ground, walls, and other features, the IGE which is a function of the distance between the rotor and the obstacle induces a thrust that drastically affects flight behavior. This effect on each rotor can be vastly different as the vehicle’s attitude varies. Furthermore, IGE limits the ability for precision flight control, navigation, and landing in tight and confined spaces. A nonlinear model is proposed to predict the IGE for each rotor. To compensate for the IGE, an adaptive nonlinear disturbance observer (ANDO) is designed to enhance closed-loop PID control. The observer and controller are implemented in a simulation framework, where results show significant improvement in performance compared to the case without observing and compensating for the IGE. In particular, it is shown that the ANDO PID closed-loop controller improves the settling time by approximately 60%.

scholarly journals In-Ground-Effect Modeling and Nonlinear-Disturbance Observer for Multirotor Unmanned Aerial Vehicle Control

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Xiang He ◽  
Gordon Kou ◽  
Marc Calaf ◽  
Kam K. Leang
Keyword(s):  
Flight Control ◽  
Disturbance Observer ◽  
Tracking Error ◽  
Ground Effect ◽  
Exponential Model ◽  
Flight Behavior ◽  
Nonlinear Disturbance Observer ◽  
Loop Control ◽  
Modeling And Control ◽  
Nonlinear Disturbance

This paper focuses on modeling and control of in-ground-effect (IGE) on multirotor unmanned aerial vehicles (UAVs). As the vehicle flies and hovers over, around, or underneath obstacles, such as the ground, ceiling, and other features, the IGE induces a change in thrust that drastically affects flight behavior. This effect on each rotor can be vastly different as the vehicle's attitude varies, and this phenomenon limits the ability for precision flight control, navigation, and landing in tight and confined spaces. An exponential model describing this effect is proposed, analyzed, and validated through experiments. The model accurately predicts the quasi-steady IGE for an experimental quadcopter UAV. To compensate for the IGE, a model-based feed-forward controller and a nonlinear-disturbance observer (NDO) are designed for closed-loop control. Both controllers are validated through physical experiments, where results show approximately 23% reduction in the tracking error using the NDO compared to the case when IGE is not compensated for.

Robust Attitude Control for Quadrotors Based on Parameter Optimization of a Nonlinear Disturbance Observer

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Shatadal Mishra ◽  
Todd Rakstad ◽  
Wenlong Zhang
Keyword(s):  
Flight Control ◽  
Attitude Control ◽  
Disturbance Rejection ◽  
Disturbance Observer ◽  
Control Unit ◽  
Nonlinear Disturbance Observer ◽  
Wave Disturbances ◽  
Active Disturbance Rejection ◽  
Exogenous Disturbances ◽  
Nonlinear Disturbance

This paper presents a nonlinear disturbance observer (NDOB) for active disturbance rejection in the attitude control loop for quadrotors. An optimization framework is developed for tuning the parameter in the NDOB structure, which includes the infinity-norm minimization of the weighted sum of noise-to-output transfer function and load disturbance sensitivity function. Subsequently, the minimization generates an optimal value of the parameter based on the tradeoff between disturbance rejection and noise propagation in the system. The proposed structure is implemented on PIXHAWK, a real-time embedded flight control unit. Simulation tests are carried out on a custom built, high-fidelity simulator providing physically accurate simulations. Furthermore, experimental flight tests are conducted to demonstrate the performance of the proposed approach. The system is injected with step, sinusoidal, and square wave disturbances, and the corresponding system tracking performance is recorded. Experimental results show that the proposed algorithm attenuates the disturbances better compared to just a baseline controller implementation. The proposed algorithm is computationally cheap, an active disturbance rejection technique and robust to exogenous disturbances.

Disturbance observer based dynamic surface flight control for an uncertain aircraft

2017 ◽  
Vol 232 (4) ◽  
pp. 729-744 ◽  
Author(s):  
Jianjun Ma ◽  
Peng Li ◽  
Zhiqiang Zheng
Keyword(s):  
Flight Control ◽  
Disturbance Observer ◽  
Sliding Mode ◽  
Tracking Error ◽  
Small Neighborhood ◽  
Dynamic Surface ◽  
Nonlinear Disturbance Observer ◽  
Actuator Dynamics ◽  
Highly Nonlinear ◽  
Nonlinear Disturbance

To handle the flight control problem of an uncertain aircraft with highly nonlinear characteristics, internal uncertainties and external disturbances, an adaptive dynamic surface controller based on nonlinear disturbance observer is designed in this paper. A novel nonhomogeneous nonlinear disturbance observer is designed to approximate the uncertainties and disturbances, which can exactly estimate the disturbances in finite time. Dynamic surface control is utilized to avoid the explosion of complexity in traditional backstepping design. Through Lyapunov synthesis, the closed-loop control system is demonstrated to be semi-globally uniformly ultimately bounded and the tracking error converges to a small neighborhood of origin. Besides, actuator dynamics are taken into account, and the controller for actuator dynamics with consideration of limitation is developed based on sliding-mode control theory. The effectiveness of the proposed control is shown by simulation experiments.

Disturbance observer-based control for a class of strict-feedback nonlinear systems with derivative-bounded disturbances

2020 ◽  
Vol 42 (14) ◽  
pp. 2601-2610
Author(s):  
Huifeng Zhang ◽  
Xinjiang Wei ◽  
Lingyan Zhang ◽  
Jian Han
Keyword(s):  
Stability Analysis ◽  
Nonlinear Systems ◽  
Disturbance Observer ◽  
Closed Loop ◽  
Closed Loop System ◽  
Nonlinear Disturbance Observer ◽  
Control Scheme ◽  
Bounded Disturbances ◽  
Nonlinear Disturbance ◽  
Strict Feedback

An anti-disturbance control problem is investigated in this paper. The disturbance observer plus back-stepping (DOPBS) control scheme is proposed for a class of strict-feedback nonlinear systems with derivative-bounded disturbances. A nonlinear disturbance observer is designed to estimate the derivative-bounded disturbances. By combining the disturbance observer with back-stepping method, the DOPBS controller is designed to reject and attenuate the disturbances. Stability analysis proves that all the signals in the the closed-loop system are uniformly ultimately bounded (UUB). Finally, simulation examples demonstrate the feasibility and effectiveness of the proposed approach compared with existing methods.

scholarly journals Robust Predictive Functional Control for Flight Vehicles Based on Nonlinear Disturbance Observer

2015 ◽  
Vol 2015 ◽  
pp. 1-16
Author(s):  
Yinhui Zhang ◽  
Huabo Yang ◽  
Zhenyu Jiang ◽  
Fan Hu ◽  
Weihua Zhang
Keyword(s):  
Flight Control ◽  
Disturbance Observer ◽  
Linear Structure ◽  
Flight Vehicle ◽  
Nonlinear Disturbance Observer ◽  
Flight Vehicles ◽  
Predictive Functional Control ◽  
State Dependent ◽  
Functional Control ◽  
Nonlinear Disturbance

A novel robust predictive functional control based on nonlinear disturbance observer is investigated in order to address the control system design for flight vehicles with significant uncertainties, external disturbances, and measurement noise. Firstly, the nonlinear longitudinal dynamics of the flight vehicle are transformed into linear-like state-space equations with state-dependent coefficient matrices. And then the lumped disturbances are considered in the linear structure predictive model of the predictive functional control to increase the precision of the predictive output and resolve the intractable mismatched disturbance problem. As the lumped disturbances cannot be derived or measured directly, the nonlinear disturbance observer is applied to estimate the lumped disturbances, which are then introduced to the predictive functional control to replace the unknown actual lumped disturbances. Consequently, the robust predictive functional control for the flight vehicle is proposed. Compared with the existing designs, the effectiveness and robustness of the proposed flight control are illustrated and validated in various simulation conditions.

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