In the control systems literature, it is well known that a separation principle holds locally for nonlinear control systems, when exponential feedback stabilizers and exponential observers are used. In this paper, we present a counterexample to show that the global separation principle need not hold for nonlinear control systems. Our example demonstrates that global stability might be lost when...

This letter extends bipedal trajectory tracking methods to prostheses enable construction of a class model-dependent prosthesis controllers using locally available sensor information. The rapidly exponentially stabilizing control Lyapunov functions (RES-CLFs) developed for robots guarantee stability the hybrid zero dynamics in presence impacts that occur walking. These cannot be directly applie...

This paper is endeavoured to the problem of local feedback dissipativity and the use of feedback dissipativity for stabilization purposes in the nonlinear discretetime setting. Sufficient conditions under which a class of non-affine discrete-time control systems can be rendered locally dissipative are derived. A methodology in order to render nonlinear single-input single-output discrete-time s...

This contribution is concerned with the observability and accessibility analysis of implicit discrete-time dynamic systems. The presented approach is motivated by a geometric representation of discrete-time systems and the crucial observation that the Lie group investigations known for implicit continuoustime dynamic systems is also appropriate in the discrete-time scenario. The obtained formal...

This paper analyzes the stability of nonlinear systems with quantized feedback in the presence of exogenous disturbances. This paper is an extension of [Liberzon, Nešić (2007)] to nonlinear systems. Under appropriate assumptions using nonlinear modification of the scheme proposed in [Liberzon, Nešić (2007)], it is shown here that it is possible to achieve input-to-state and nonlinear gain l2 st...

In this letter, we consider a problem of global stabilization of a class of approximately feedback linearized systems. We propose a new nonlinear control approach which includes a nonlinear controller and a Lyapunov-based design method. Our new nonlinear control approach broadens the class of systems under consideration over the existing results. key words: approximate feedback linearization, g...

This paper addresses the stabilization problem of nonlinear feedback systems with quantized measurements in the presence of bounded disturbances. This paper is an extension of [Liberzon, Nešić (2007)] to nonlinear systems. Using the scheme proposed in [Liberzon, Nešić (2007)], we show that input-to-state stability with respect to bounded disturbances is achievable for nonlinear systems with qua...

A framework for system analysis and design is described based on nonlinear system models and nonperiodic signals generated by nonlinear systems. The proposed approach to analysis of nonlinear systems is based on excitability index a nonlinear counterpart of magnitude frequency response of linear system. It can be used for stability analysis of fully nonlinear cascade systems similarly to absolu...

control of robotic systems is an interesting subject due to their wide spectrum applications in medicine, aerospace and other industries. this paper proposes a novel continuous control mechanism for tracking problem of a 5-dof upper-limb exoskeleton robot. the proposed method is a combination of a recently developed robust integral of the sign of the error (rise) feedback and neural network (nn...