Use Of Disturbance Observer Research Articles

Maximum power tracking of variable‐speed wind energy conversion systems based on a near‐optimal servomechanism control system

AbstractIn this article, integral servomechanism based state‐dependent Riccati equation (SDRE) nonlinear output feedback control for wind energy conversion systems (WECSs) has been proposed. The numerical off‐line solving the proposed SDRE control requires to formulate algebraic Riccati equation and algebraic Lyapunov equation. This method approximates the solution of SDRE with Taylor series expansions which are solved with MATLAB solvers. The maximum power point tracking is achieved by defining relation between the optimal angular shaft speed and maximum power providing optimal tip speed ratio in variable‐speed WECSs. The proposed control can significantly reduce the angular shaft speed errors of the permanent magnet synchronous generator (PMSG)‐based WECSs without use of disturbance observers to compensate model uncertainties, modeling errors and noise as in the conventional SDRE control method. The simulation results demonstrate the superior results under mean average errors and root mean square error evaluation methods of the angular shaft speed of PMSG. The performance of the proposed integral servomechanism based SDRE control system has been improved by 80.67% and 80.05% in both scenarios compared to the conventional SDRE control based on compensation technique with disturbance observers.

Novel SMC control design for path following of autonomous vehicles with uncertainties and mismatched disturbances

The article propose a novel robust, accurate, and fast control strategy with uncertainties/mismatched disturbances for path following control of autonomous vehicles using an innovative sliding mode control (SMC).The molded SMC is based on gain scheduling with fuzzy system, the algorithm of a radial basis function neural networks (RBFNN) and disturbance observer (DOB). The fuzzy system provide an automatic adjustment of the gain of SMC in order to compensate variations of system parameters; the use of DOB is to estimate the mismatched disturbances, and the RBFNN is for assessing the uncertainties. In addition, the stability of the closed-loop system is proved by the Lyapunov stability theorem. The proposed controller is applied to the path following of autonomous vehicle in extreme driving condition at high speed and under different road adhesion conditions. To show the effectiveness of our controller, simulation results have been compared with other robust strategies.

Offset-Free Model Predictive Control for the Power Control of Three-Phase AC/DC Converters

This paper describes an offset-free model predictive control (MPC) algorithm using a disturbance observer (DOB) to control the active/reactive powers of a three-phase ac/dc converter. The strategy of this paper is twofold. One is the use of DOB to remove the offset error, and the other is the proper choice of the weighting matrices of a cost index to provide fast error decay with small overshoot. The DOB is designed to estimate the unknown disturbances of the ac/dc converter following the standard Luenberger observer design procedure. The proposed MPC minimizes a one-step-ahead cost index penalizing the predicted tracking error by performing a simple membership test without any use of numerical methods. A systematic way for choosing the weights of the cost index, which guarantees the global stability of the closed-loop system, is proposed. Use of the DOB eliminates the offset tracking errors in the real implementation. Using a 25-kW ac/dc converter, it is experimentally shown that the proposed MPC enhances the power tracking performance while considerably reducing the mutual interference of the active/reactive powers as well as the output voltage.

불변집합에 기반한 삼상 인버터 시스템의 모델예측제어

This paper provides an efficient model predictive control for the output voltage control of three-phase inverter system which includes output LC filters. Use of SVPWM (Space Vector Pulse-Width-Modulation) and the rotating d-q frame is made to obtain an input constrained dynamic model of the inverter system. From the measured/estimated output current and reference output voltage, corresponding equilibrium values of the inductor current and the control input are computed. Derivation of a feasible and invariant set around the equilibrium state is made and then a receding horizon strategy which steers the current state deep into the invariant set is proposed. In order to remove offset error, use of disturbance observer is made in the form of state estimator. The efficacy of the proposed method is verified through simulations.

Pointing Stability Improvement of Astronomy Satellites by Integration of Actuators.

As pointing requirements of astronomy satellites become more demanding, a conventional momentum-exchange scheme for attitude-pointing control is sometimes not enough to satisfy stringent stability requirements. This paper presents a new attitude control system for improving the attitude-pointing stability of astronomy satellites/and earth-observation satellites. In our proposed control system, an actuator system is composed of wheel-rotor drive motors and magnetic torquers driven by a newly devised “cooperative drive law.” The pointing stability is improved by torque control of the actuator system so that the total torque acting on the satellite body is minimized with the use of disturbance observers and in a way that shortcomings of the actuators are compensated for by each other. In the torque control, attitude control and momentum management are both treated consistently. In this paper, the mathematical formulation of our proposed scheme is presented, and the results of numerical simulations are also presented to demonstrate the stability improvement.

On the use of disturbance observers for the digital control of robots

A decentralized digital control system consisting of single-input-single-output proportional derivative controllers and disturbance observers is proposed for the positional control of multidegree of freedom manipulators. Stability of this control system is analysed and relationships between the manipulator characteristics, the closed-loop bandwidths, the bounds on the stability region and the sampling period of the digital control system are derived.

Robots positioning control revisited

Positioning control systems for robot arms are presented within a general framework in view of unification and classification. Treating coupling torques from other links as an external disturbance reduces the design of the control system to that of SISO servomechanisms driving each of the robot axes individually. A short survey of many control strategies proposed in the literature presents them as different methods aiming at attenuation of this disturbance. The use of disturbance observers is shown to provide a nice and simple way for that purpose. This could be applied to the improvement of actual industrial robots at the cost of slight software modifications.