scholarly journals Robust Nonlinear Tracking Control for Unmanned Aircraft in the Presence of Wake Vortex

Electronics ◽  
2021 ◽  
Vol 10 (16) ◽  
pp. 1890
Author(s):  
Petr Kazarin ◽  
Vladimir Golubev ◽  
William McKunis ◽  
Claudia Moreno
Keyword(s):  
Nonlinear Control ◽  
Control Method ◽  
Unmanned Aircraft ◽  
Wake Vortex ◽  
Unmanned Aerial Systems ◽  
Computationally Efficient ◽  
Nonlinear Controller ◽  
External Disturbances ◽  
Robust Nonlinear Control ◽  
Nonlinear Tracking

The flight trajectory of unmanned aerial vehicles (UAVs) can be significantly affected by external disturbances such as turbulence, upstream wake vortices, or wind gusts. These effects present challenges for UAV flight safety. Hence, addressing these challenges is of critical importance for the integration of unmanned aerial systems (UAS) into the National Airspace System (NAS), especially in terminal zones. This work presents a robust nonlinear control method that has been designed to achieve roll/yaw regulation in the presence of unmodeled external disturbances and system nonlinearities. The data from NASA-conducted airport experimental measurements as well as high-fidelity Large Eddy Simulations of the wake vortex are used in the study. Side-by-side simulation comparisons between the robust nonlinear control law and both linear H∞ and PID control laws are provided for completeness. These simulations are focused on applications involving small UAV affected by the wake vortex disturbance in the vicinity of the ground (which models the take-off or landing phase) as well as in the out-of-ground zone. The results demonstrate the capability of the proposed nonlinear controller to asymptotically reject wake vortex disturbance in the presence of the nonlinearities in the system (i.e., parametric variations, unmodeled, time-varying disturbances). Further, the nonlinear controller is designed with a computationally efficient structure without the need for the complex calculations or function approximators in the control loop. Such a structure is motivated by UAV applications where onboard computational resources are limited.

scholarly journals Robust Nonlinear Control Scheme for Electro-Hydraulic Force Tracking Control with Time-Varying Output Constraint

Symmetry ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 2074
Author(s):  
Wanshun Zang ◽  
Qiang Zhang ◽  
Jinpeng Su ◽  
Long Feng
Keyword(s):  
Nonlinear Control ◽  
Time Varying ◽  
Parameter Uncertainties ◽  
Structural Vibrations ◽  
Robust Controller ◽  
External Disturbances ◽  
Robust Nonlinear Control ◽  
Hydraulic Force ◽  
Control Scheme ◽  
Output Constraint

This paper presents a robust nonlinear control scheme with time-varying output constraint for the electro-hydraulic force control system (EHFCS). Two typical double-rod symmetrical hydraulic cylinders are employed to simulate force environments in the EHFCS. Therefore, in order to improve the performance of the EHFCS, firstly, the model of the EHFCS is established with taking external disturbances, parameter uncertainties as well as structural vibrations into consideration. Secondly, in order to estimate external disturbances, parameter uncertainties and structural vibrations in the EHFCS and compensate them in the following robust controller design, two disturbance observers (DOs) are designed according to the nonlinear system model. Thirdly, with two estimation values from two DOs, a time-varying constraint-based robust controller (TVCRC) is presented in detail. Moreover, the stability of the proposed controller is analyzed by defining a proper Lyapunov functions. Finally, in order to validate the performance of the proposed controller, a series of simulation studies are conducted using the MATLAB/Simulink software. These simulation results give a fine proof of the efficiency of the proposed controller. What’s more, an experimental setup of the EHFCS is established to further validate the performance. Comparative experimental results show that the proposed controller exhibits better performance than the TVCRC without two DOs and a conventional proportional integral (PI) controller.

Nonlinear Control of SVG Based on Hamiltonian Energy Theory

2013 ◽  
Vol 331 ◽  
pp. 307-310
Author(s):  
Yun Bing Wei ◽  
Wei Jie Yang
Keyword(s):  
Nonlinear Control ◽  
Transient Stability ◽  
Control Method ◽  
Short Circuit ◽  
Synchronous Generator ◽  
Access Point ◽  
Mathematic Model ◽  
Nonlinear Controller ◽  
Energy Theory ◽  
Bus Voltage

Establish the practical mathematic model of Synchronous Generator in the static var generator (SVG) of single machine infinite bus power system. Based on Hamiltonian energy theory, the new nonlinear controller is designed between the SVG which is installed in the bus voltage of system and synchronous machine excitation. This controller directly use the energy as the storage function, compared to other nonlinear controllers, this controller has the advantage of the fast stability and the capability of quelling the disturbance. Since the nonlinear control structure retains all in this design, it does not need the linearization, the proposed SVG controller is more robust than linear control method. The simulation results show that the proposed controller can faster meet generator excitation and SVG access point voltage transient stability than conventional PID control when subjected to the three-phase short circuit fault.

scholarly journals Antidisturbance Control for Helicopter Stochastic Systems

2021 ◽  
Vol 2021 ◽  
pp. 1-28
Author(s):  
Dongping Li ◽  
Yankai Li
Keyword(s):  
Nonlinear Control ◽  
Stochastic Systems ◽  
Control Method ◽  
Stochastic Theory ◽  
Nonlinear Controller ◽  
Closed Loop System ◽  
Nonlinear Disturbance Observer ◽  
Control Techniques ◽  
Control Scheme ◽  
Nonlinear Control Method

In this paper, an antidisturbance controller is presented for helicopter stochastic systems under disturbances. To enhance the antidisturbance abilities, the nonlinear disturbance observer method is applied to reject the time-varying disturbances. Then, the antidisturbance nonlinear controller is designed by combining the backstepping control scheme. And the stochastic theory is used to guarantee that the closed-loop system is asymptotically bounded in mean square while the proposed control method is shown via some traditional nonlinear control techniques, which still show some common issues such as “dimension explosion” or others. The result of this paper can be regarded as a typical case of the nonlinear control method to help and promote the generation of advanced methods.

scholarly journals Disturbance Observer-Based Control for Trajectory Tracking of a Quadrotor

Electronics ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 1624
Author(s):  
Sang Wook Ha ◽  
Bong Seok Park
Keyword(s):  
Trajectory Tracking ◽  
Closed Loop ◽  
Control Method ◽  
Control Strategies ◽  
Hierarchical Control ◽  
Loop System ◽  
Nonlinear Controller ◽  
Closed Loop System ◽  
External Disturbances ◽  
Dynamic Surface

This paper presents a new control approach for the trajectory tracking of a quadrotor in the presence of external disturbances. Unlike in previous studies using hierarchical control strategies, a nonlinear controller is designed by introducing new state transformations that can use Euler angles as virtual control inputs. Thus, the proposed method can eliminate the timescale separation assumption of hierarchical control strategies. To estimate the external disturbances involved in the translational and rotational dynamics of the quadrotor, disturbance observers are developed. Using state transformations and estimates of external disturbances, we design a robust nonlinear controller based on the dynamic surface control method. The stability of the closed-loop system is analyzed without separation into two subsystems. From the Lyapunov stability theory, it is proven that all error signals in the closed-loop system are uniformly ultimately bounded and can be made arbitrarily small. Finally, simulation results are presented to demonstrate the performance of the proposed controller.

Robust finite-time trajectory tracking control for a space manipulator with parametric uncertainties and external disturbances

2021 ◽  
pp. 095441002110147
Author(s):  
Qijia Yao
Keyword(s):  
Trajectory Tracking ◽  
Finite Time ◽  
Tracking Control ◽  
Disturbance Observer ◽  
Control Method ◽  
Parametric Uncertainties ◽  
External Disturbances ◽  
Trajectory Tracking Control ◽  
Space Manipulator ◽  
Tracking Controller

Space manipulator is considered as one of the most promising technologies for future space activities owing to its important role in various on-orbit serving missions. In this study, a robust finite-time tracking control method is proposed for the rapid and accurate trajectory tracking control of an attitude-controlled free-flying space manipulator in the presence of parametric uncertainties and external disturbances. First, a baseline finite-time tracking controller is designed to track the desired position of the space manipulator based on the homogeneous method. Then, a finite-time disturbance observer is designed to accurately estimate the lumped uncertainties. Finally, a robust finite-time tracking controller is developed by integrating the baseline finite-time tracking controller with the finite-time disturbance observer. Rigorous theoretical analysis for the global finite-time stability of the whole closed-loop system is provided. The proposed robust finite-time tracking controller has a relatively simple structure and can guarantee the position and velocity tracking errors converge to zero in finite time even subject to lumped uncertainties. To the best of the authors’ knowledge, there are really limited existing controllers can achieve such excellent performance under the same conditions. Numerical simulations illustrate the effectiveness and superiority of the proposed control method.

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