Search

The mechanical impedance of the human arm can be measured to quantitatively assess the motor function. In this paper, an adaptive least square estimation method is proposed for online measurement of the mechanical impedance of the arm, without force or acceleration sensors, which extremely reduces the expenses and complexity of rehabilitation robots. The proposed strategy may also be used for monitoring the dynamic changes of the mechanical impedance. Estimation of time-varying force is also the other capability of the algorithm. The closed-loop stability of the system is analytically shown using the Lyapunov stability theorem. To show the applications of the proposed scheme, two main scenarios are described which can be used for the rehabilitation robots to assess the motor recovery of the patients undergoing the rehabilitation sessions. To validate the scheme, a 2-DOF manipulator is adopted to illustrate the accuracy of the impedance and force estimations in noiseless and noisy conditions. [ABSTRACT FROM AUTHOR]

This paper proposes a cascade high-gain observer for a class of triangular nonlinear systems with large and diverse time delays at states and output equation. Compared with some existing results in the literature, the main contribution is to consider the simultaneous and diverse delays in both states and output and further, to propose a cascade observer in dealing with arbitrarily large delayed measurements. By choosing a suitable Lyapunov-Krasovskii functional, the sufficient condition is presented that guarantees the exponential convergence of observation error to the origin. Simulation results on a numerical example and a practical case study involving inverted pendulum are finally given to illustrate the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

An observer-based controller for Lipschitz nonlinear systems is presented. The necessary and sufficient condition to ensure stability of state-observer as well as nonlinear system with state-feedback control law is derived. According to the separation principle, the closed-loop stability is guaranteed based on dual problems concerning stability of state-observer and stability of state-feedback parts. Also, the stability region for locally Lipschitz nonlinearities is obtained. A practical synthesis approach to achieve controller parameters is then given which yields the closed-loop convergence with less conservative results. The effectiveness of the proposed synthesis method is finally demonstrated by simulation results. [ABSTRACT FROM AUTHOR]

The problem of designing an observer for nonlinear Lipschitz systems affected by system and sensor noises is addressed. Related to the system nonlinearity, the stability of observer dynamic with static and dynamic gain is considered. The advantage of using dynamic gain to deal with large Lipschitz nonlinearity is discussed and it is proved that no dynamic gain can stabilise the observer for a larger Lipschitz constant as compared with the static gain. However, a nonlinear observer with dynamic gain has some additional degrees of freedom which can be utilised to attenuate noise effect on the observer behaviour. Using mixedandcriteria, this article introduces a method to obtain a dynamic gain which can deal with system nonlinearity and noise simultaneously. The effectiveness of the proposed method is finally demonstrated by some simulation results. [ABSTRACT FROM AUTHOR]