جستجوی مقالات مرتبط با کلیدواژه « disturbance observer » در نشریات گروه « برق »

The control of unmanned aerial vehicles is a challenging problem due to their lightweight and intense coupling between longitudinal and lateral motion. Considering this issue, in this article, an automatic landing system for a fixed-wing unmanned aircraft exposed to wind disturbances and parametric uncertainties is designed using the backstepping algorithm and the disturbance observer-based sliding mode control. Two controllers are designed based on the backstepping algorithm and sliding mode control to stabilize the attitude angles. The longitudinal speed controller uses the sliding mode technique to maintain the total speed relative to the ground at a constant desired value in all landing phases. A nonlinear disturbance-observer is considered in the sliding mode controller structure to estimate wind disturbance and parametric uncertainty. The new robust automatic landing system is software implemented, and its performance is investigated by several numerical simulations; Lateral deviation relative to the runway is eliminated while the unmanned aerial vehicle maintains its desired trajectory slope angle in all phases of the landing at the desired value. Therefore, the results of numerical simulations prove that the new control structure is stable and robust against different initial conditions, different types of wind disturbances (wind shear and discrete gust), and parametric uncertainty.

Permanent magnet synchronous motors are widely used motors in various industries. Speed ​​control of these motors is of special importance that can be done using a closed loop control system. Due to the nonlinear dynamics of this type of motor, in recent years, nonlinear controllers have been used to control permanent magnet synchronous motors. One solution for controlling uncertain nonlinear systems is to use an observer-based nonlinear controller. In this method, uncertainty estimation is provided to the controller using an extended state observer. Another challenge in controlling a permanent magnet synchronous motor is the two input- two output of the dynamic system of this type of motor. Therefore using multivariate control techniques will be desirable for the design of the control input vector. In this paper, a combined vector observer-based nonlinear method is used to control the two inputs - two outputs system of a permanent magnet synchronous motor. For this purpose, using an extended observer, the load torque, which is assumed to be uncertain, is estimated, and then the smooth multi-input-multi-output sliding mode method is used to design the control input vector. The proposed hybrid method has the advantages of nonlinear, robustness to uncertainty, finite time convergence, and vector based controller design. These features are demonstrated analytically as well as using computer simulations.

In this paper, a new adaptive fractional-order sliding mode controller is designed for a Permanent Magnet Synchronous Generator (PMSG) to track the maximum power point. The controller objective is to track the desired generator speed to extract the maximum power from the wind turbine system in the presence of parametric uncertainty and external disturbances. First, a new fractional order sliding surface is defined. To ensure the stability of the closed-loop system in the sliding model controller it is required to know the upper bounds of uncertainties and disturbances, where it is difficult to calculate these bounds for practical applications such as wind turbines. Therefore, the control signal parameters are estimated online by the proposed adaptive laws, in order to increase the convergence rate of the state variables to the reference value and reduce the chatting phenomenon, also to increase the system robustness against external disturbances and parametric uncertanity. On the other hand, due to the unknown disturbance dynamics, a disturbance observer is designed to estimate external disturbances and parametric uncertainty. Then, the stability of the general closed-loop system together with the disturbance observer is performed using Lyapunov's theory. Finally, the simulation results considering two different scenarios; first for step wind changes with external disturbance, second for changes in sine wind speed with parametric uncertainty. The results are compared with conventional sliding mode controller and results show the effective performance of the proposed controller in tracking the reference value, increasing its robustness against uncertainty and disturbance and reducing the chatting phenomenon.

In this paper, the trajectory tracking control problem for a team of nonholonomic tractor-trailer wheeled mob ile robots has been investigated based on the leader-follower strategy in the presence of structural uncertainties and external disturbances. For this purpose, the kinematic and dynamic equations of the formation of tractor-trailer robots are presented and leader-followerchr(chr('39')39chr('39'))s model is produced by defining the state error vector at first. Then, a nonlinear disturbance observer is designed by using the formation dynamic model to estimate and compensate the external disturbance and a new model of the system is obta ined. In the following, a finite-time dynamic surface controller has been designed and presented by con sidering an observer-based model. The proposed scheme ensures closed-loop signals boundedness and fast c o n v er gence of tracking errors in a limited time. Furthermore, the par a m etric uncertainties are estimated by using a fuzzy adaptive estimator with a great accuracy. Finally, the finite time stability of the closed-loop control system is proved by Lyapunov theory and the effectiveness of proposed algorithm is sho w n by simula tions.

The design of integrated guidance and control system for flying objects is one of the research fields in the aerospace that is considered by researchers in recent years. Due to the nonlinearity of the kinematic and dynamic equations of the homing interceptors in the terminal phase and also existence of uncertainties such as target maneuvers, external disturbances and variations in aerodynamic coefficients, siding mode control theory is a suitable method for designing integrated guidance and control system. One of the most problem of sliding mode is the presence of high frequency oscillations in the control signal that is called chattering, which makes it impossible to implement this controller. A method for smoothing the control signal in a sliding mode is to use a disturbance observer. In this paper, the control signal is completely smooth, with having the disturbances estimation and using a different scheme compared with standard sliding mode. Also, the finite time convergence is guaranteed in the presence of uncertainty. The proposed guidance and control system are evaluated in computer simulation.