In this paper we begin by assuming that an observer with a corresponding quadratic-type Lyapunov function has been designed for a given nonlinear system. We then consider the problem that arises when the output of that nonlinear system is not directly available; instead, it acts as an input to a second, linear system from which a partial-state measurement is in turn available. We develop an obs...

We derive an exact deterministic nonlinear observer to compute the continuous state of an inertial navigation system based on partial discrete measurements, the so-called strap-down problem. Nonlinear contraction is used as the main analysis tool, and the hierarchical structure of the system physics is systematically exploited. The paper also discusses the use of nonlinear measurements, such as...

In this paper, further results are proposed that concern the design and the convergence of receding horizon nonlinear observers. The key feature is the de nition of observability-radius in relation with a pre-speci ed compact set of initial con gurations. This enables a semi-global convergence result to be derived that turns to be a global convergence result when appropriate regularity assumpti...

There exist several approaches to the design of observers for nonlinear systems, including the separation of the nonlinear system into a linear part and a nonlinear perturbation of the system with a bounded condition [2], the use of Lie derivatives and the inversion of the Jacobian of a coordinate transformation to obtain the gain of the nonlinear observer [10] and the use of a Lyapunov equatio...

This paper puts forward a fault isolation method for nonlinear dynamic systems. The method based on nonlinear observers and using parameter partition. It fits many kinds of nonlinear dynamic systems and its fault isolation speed is satisfying.

This paper provides some new developments in the design of unknown input observers for nonlinear systems. An algorithm which states if the state and the unknown input of the system can be recovered in finite time is introduced. This algorithm leads to the transformation of the system into an extended block triangular observable form suitable for the design of finite time observers. The proposed...

We conduct full-scale experimental validation and comparison of three different nonlinear attitude observers, two of them with inherent heave estimation, in two different operational scenarios encountered by an offshore vessel in the North Sea. Two different microelectro-mechanical inertial measurement units are the primary sensors for driving the nonlinear observers, which are aided by gyrocom...

This paper presents the application of two nonlinear observers in order to estimate the absolute orientation angle of a quadruped walking robot. The designed observers are based on high gain and high order sliding mode approaches. A loss of observability during the robot step appears: this problem is dealed by using two different observers structures.

This paper is about necessary conditions for the existence of an observer in the case of nonlinear systems. Those conditions are first highlighted in terms of detectability, for observers ensuring asymptotic state reconstruction. They then take the form of stronger observability notions, for the case of tunable observers, that is observers with a tunable rate of state reconstruction.

Motivated by a class of nonlinear regulator problems associated with systems that experience actuator failure, this work discusses the construction of nonlinear observers in normal form using a systematic and elegant method of transformation, namely Lie Transforms. It is shown how the transformation, which is the solution of a Homological Equation, and the observer gain matrix, which is a serie...