Disturbance Rejection Mechanism Research Articles

Vibration and position tracking control for a flexible Timoshenko robot arm with disturbance rejection mechanism

PurposeThis paper aims to study the boundary disturbance rejection control design for a flexible Timoshenko robot arm to diminish external disturbances and achieve desired angle tracking, with system vibration and elastic deformation considered.Design/methodology/approachThis study introduces disturbance observer and disturbance rejection mechanism into the boundary control design for flexible Timoshenko robot arm systems. The uniform bounded stability of controlled systems is proved via Lyapunov analysis without any simplification of the infinite-dimensional system dynamics.FindingsThe proposed boundary disturbance rejection control scheme can effectively suppress vibrations and shear deformations, achieve the required angular positioning and reject external disturbances. Numerical simulations developed by the finite difference method are adapted to demonstrate the validity of the designed controller.Originality/valueThe originality of this study is to design boundary disturbance rejection control to suppress vibrations and shear deformations for the flexible Timoshenko robot arm, thereby improving the performance and control accuracy of the system.

Design, analysis and application of a new disturbance rejection PID for uncertain systems

In this paper, a new disturbance rejection proportional–integral–derivative (DR-PID) scheme is proposed for a class of minimum phase plants with low relative order. The essential active disturbance rejection (ADR) mechanism that is otherwise hidden in PID control structure has been illuminated and clarified in this paper for the first time.The proposed DR-PID scheme is derived on the basis of a modified disturbance observer to embed the active disturbance rejection mechanism seamlessly in the classical PID structure. Such a DR-PID scheme is implemented in a typical two-degree-of-freedom control structure that contains a standard PID controller and a pre-filter. The internal stability condition is established by investigating the closed-loop poles according to Rouche’s theorem. The ensuing internal stability condition provides effective guidelines for DR-PID design that has infinite gain margin with minimum plant information. Five numerical comparisons are performed to illustrate the effectiveness of the new DR-PID scheme. The physical realizability of the proposed DR-PID scheme is also demonstrated by experiments on a magnetic levitation system.

Constrained coordinated path-following control for underactuated surface vessels with the disturbance rejection mechanism

This note proposed a practical coordinated path-following algorithm for a group of underactuated surface vessels to achieve and maintain the desired formation pattern. The developed scheme consists of two envelopes. One is to stabilize the individual vessel to the virtual vessel moving along with the predefined path. The other is to synchronize the surge speed of virtual vehicles to guarantee the desired geometric formation. Within the design framework, a nonlinear disturbance observer (DOB) is constructed to estimate the lumped disturbance which includes the model uncertainty and the unknown disturbance. By virtue of the auxiliary system and the novel tan-type barrier Lyapunov function (BLF), the observer based control law is designed to eliminate the effect of the input and velocity constraints. Furthermore, on the basis of the undirected graph, the speed agreement is presented to ensure the motion synchronization of networked underactuated vessels. Compared with the existing results, the proposed algorithm is more applicable to the marine practice, e.g. the collaborative search and rescue scene. Through the Lyapunov analysis, it is proved that all the variables of the closed-loop system are with the uniform ultimate bounded stability. Finally, the scaling formation example and comparison simulation are conducted to illustrate the effective of the proposed algorithm.

Nonlinear optimal control with disturbance rejection for asteroid landing

This paper presents an optimal solution to asteroid soft landing problem, on the base of θ−D control technique and disturbance rejection mechanism. The control objective is to drive a probe to reach the surface of an asteroid with a desirable line-of-sight angle and zero velocity, eliminating the influence of external disturbance. Firstly, elementary θ−D technique is applied in the absence of disturbance to tackle the nonlinear optimal control problem. Secondly, the disturbance is estimated in the fast-estimation framework with explicitly bounded estimation error. Afterwards, an integrated control protocol is presented in a feed-forward structure by the aid of an additional variable-structure term to ensure stability under time-varying disturbance. Simulation results of the proposed approach compared with the results of elementary θ−D method and robust θ−D method are presented at the end of this paper, demonstrating the effectiveness of the proposed control protocol.

Real-Time Analysis of a Modified State Observer for Sensorless Induction Motor Drive Used in Electric Vehicle Applications

The purpose of this work is to present an adaptive sliding mode Luenberger state observer with improved disturbance rejection capability and better tracking performance under dynamic conditions. The sliding hyperplane is altered by incorporating the estimated disturbance torque with the stator currents. In addition, the effects of parameter detuning on the speed convergence are observed and compared with the conventional disturbance rejection mechanism. The entire drive system is first built in the Simulink environment. Then, the Simulink model is integrated with real-time (RT)-Lab blocksets and implemented in a relatively new real-time environment using OP4500 real-time simulator. Real-time simulation and testing platforms have succeeded offline simulation and testing tools due to their reduced development time. The real-time results validate the improvement in the proposed state observer and also correspond to the performance of the actual physical model.

A Modified Disturbance Rejection Mechanism in Sliding Mode State Observer for Sensorless Induction Motor Drive

This paper presents a modified sliding mode state observer for sensorless vector-controlled induction motor drive. The objective is to improve the dynamic performance of the sensorless drive subjected to parameter uncertainty, fault and disturbances. The sensorless drive along with the proposed observer is modeled and built in Simulink, and the dynamic behavior is obtained for different test cases such as flux-weakening region, variations in commanded speed and torque, low-speed operation and under faulty operation mode subjected to an electrical fault in the inverter. The conventional disturbance rejection mechanism is modified by constraining the estimated disturbance along with the stator current error in the sliding surface, thereby increasing the ability of the observer to reject the effect of the external load on the tracking performance. Extensive simulation results prove that the modified observer has a wide speed bandwidth compared to the conventional observer along with superior tracking, disturbance rejection characteristics and torque holding capability.

ステージ位置制御系における定盤加速度フィードバックの再解釈

In order to improve the positioning time of stage, base-plate acceleration feedback was proposed as described in the literature, and the effect of disturbance rejection was experimentally demonstrated. Since an explanation for the theoretical background of its feedback was insufficient, the disturbance rejection mechanism was clarified in our literature based on the mathematical model of stage including the base-plate dynamics. However, there is the question that what kind of controller can be derive by modern control theory. In this paper, the zeroing control theory, which is well-known as the disturbance rejection technique, is applied to the above mentioned mathematical model. As a result, it is clear that zeroing using the state feedback is impossible from the theoretical point of view. However, we can recognize through this examine that the base-plate acceleration feedback is equivalent to Master-Slave synchronization control. Since this analogical relationship is useful to progress the control performance, we describe the formulation and these relationship in detail.