-The paper considers the problems of state estimation, unknown input and measurement disturbance reconstruction for a class of Lipschitz nonlinear system. By taking the measurement disturbance vector as an extended state vector, the original system is transformed into an augmented descriptor system. For the descriptor system, the necessary and sufficient condition of the existence of the unknow...

Integral action is required in many controllers in order to solve real world problems. Modeling errors and disturbances are examples of issues that can be dealt with by using controllers with integral action. This paper explores the use of disturbance observers to introduce integral action into an output feedback controller. In particular, the proposed solution is generalized to include the cas...

In this paper, a new method ofH∞ observer design for Lipschitz nonlinear systems is proposed in the form of an LMI optimization problem. The proposed observer has guaranteed decay rate (exponential convergence) and is robust against unknown exogenous disturbance. In addition, thanks to the linearity of the proposed LMIs in the admissible Lipschitz constant, it can be maximized via LMI optimizat...

This paper discusses the disturbance estimation problem for continuous-time multivariable dynamical systems with arbitrarily relative degrees. The disturbances, which are assumed bounded, refer to the combination of the external disturbances, the nonlinearities and the model uncertainties of the system. First, the disturbance observer is proposed for multivariable minimum phase systems. Then, t...

The disturbance observer (DOB) has been a popular robust control approach for servo enhancement in single-input single-output systems. This paper presents a new extension of the DOB idea to dualand multi-input single-output systems, and discusses an optimal filter design technique for the related loop shaping. The proposed decoupled disturbance observer (DDOB) provides the flexibility to use th...

This paper presents a disturbance estimation methodology on a Hexapod-type parallel kinematic machine tool of the Stewart platform. The disturbance estimation by monitoring an armature current of servo motors has been commonly done on conventional serial mechanism feed drives. On a parallel mechanism feed drive, a disturbance observer must have a more complex structure with a precise model of t...

A sliding mode synchronization controller is presented with RBF neural network for two chaotic systems in this paper. The compound disturbance of the synchronization error system consists of nonlinear uncertainties and exterior disturbances of chaotic systems. Based on RBF neural networks, a compound disturbance observer is proposed and the update law of parameters is given to monitor the compo...

This paper investigates the disturbance observer based composite fuzzy control for a class of uncertain nonlinear systems. With fuzzy logic system (FLS) approximating the unknown nonlinearities, composite learning is constructed on the basis of a serial-parallel identifier. By introducing the intermediate signal, the disturbance observer is developed to provide efficient learning of the compoun...

Robust control of nonlinear systems with disturbances and uncertainties is addressed in this paper using disturbance observer based control technique. In this framework, the “disturbance” is a generalized concept, which may include external disturbances, unmodeled dynamics, and system parameter perturbations. The existing disturbance observer based control (DOBC) methods were only applicable fo...

The rehabilitation exoskeleton is an effective piece of equipment for stroke patients and the aged. However, this complex human–robot system incurs many problems, such as modeling uncertainties, unknown interaction, external disturbance, actuator fault. This paper addresses adaptive fault-tolerant tracking control a lower limb joint driven by electro-hydraulic (EHA). First, model built consider...