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.

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%.

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.

scholarly journals Aerodynamic analysis and control for a novel coaxial ducted fan aerial robot in ground effect

2020 ◽  
Vol 17 (4) ◽  
pp. 172988142095302
Author(s):  
Tianfu Ai ◽  
Bin Xu ◽  
Changle Xiang ◽  
Wei Fan ◽  
Yibo Zhang
Keyword(s):  
Disturbance Observer ◽  
Ground Effect ◽  
System Stability ◽  
Bench Test ◽  
Nonlinear Disturbance Observer ◽  
Modeling And Control ◽  
Ducted Fan ◽  
Aerial Robot ◽  
Nonlinear Disturbance ◽  
And Control

Modeling and control for a novel coaxial ducted fan aerial robot in-ground-effect is presented in this article. Based on experiments using the ducted fan bench test, the fitting curve of the ground effect thrust of the ducted fan aerial robot at different heights is obtained. In addition, the flow field simulation results of the prototype with ground effect at different heights can be obtained using computational fluid dynamics software. A simplified model of the prototype for control can be designed based on several reasonable hypotheses that are established using blade element and momentum theory. To compensate for the disturbance associated with ground effect, a nonlinear disturbance observer is designed to estimate the disturbance, and control structure of the closed-loop system is composed of a nonlinear disturbance observer combined with a double-loop proportion–integration–differentiation controller. The results of several numerical simulations and experiments demonstrate the effectiveness of this controller structure. The performances of tracking trajectory and system stability are improved significantly, compared to the situation that the ground effect 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.

scholarly journals Research on control technology of tip-tilt mirror system in adaptive optics

2021 ◽  
Vol 2087 (1) ◽  
pp. 012056
Author(s):  
Dechun Zhao ◽  
Yansong Song ◽  
Yang Liu ◽  
Baishuo Zhang ◽  
Tianci Liu
Keyword(s):  
Sliding Mode Control ◽  
Disturbance Observer ◽  
Control Method ◽  
Sliding Mode ◽  
Tracking Error ◽  
Mirror System ◽  
Nonlinear Observer ◽  
Nonlinear Disturbance Observer ◽  
Mode Control ◽  
Nonlinear Disturbance

Abstract In order to solve the control problem of the tip-tilt mirror under the unknown disturbance, a nonlinear disturbance observer with adaptive ability based on the sliding mode control is designed.Firstly, the sliding mode control method of the tip-tilt mirror system is established with Lyapunov functions. Secondly, an adaptive nonlinear disturbance observer is developed on a basis of observer model. Finally, the proposed sliding mode control method is combined with a nonlinear observer with adaptive capability to achieve the goal of improving the control accuracy of the system, while also reducing the chattering caused by the system. The experiment proves that this method is achievable. The experimental results show that the tracking error of the azimuth axis is reduced from 1.637μrad to 1.083μrad, and the accuracy is improved by about 51.2%. The tracking error of the pitch axis is reduced from 1.966μrad to 1.614μrad, and the accuracy is improved by about 21.8%. This method can greatly weaken the inherent chattering and external disturbance of the system, and improve the stability of the tip-tilt mirror system.

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