Jongwook Yang

Reduced-Order Dynamic Observer Error Linearization

Abstract For an unforced nonlinear single output system, we propose a new approach to observer error linearization called reduced-order dynamic observer error linearization (RDOEL), which is a modified version of dynamic observer error linearization (DOEL). While RDOEL also has an auxiliary dynamics and a generalized output injection like DOEL, it offers a lower dimensional observer than DOEL, and allows a complete constructive algorithm in contrast to DOEL when the auxiliary dynamics is a chain of integrators. For RDOEL whose auxiliary dynamics is a chain of integrators (RDOELI), we provide a complete constructive algorithm which presents not only a coordinate transformation between the original system and a nonlinear observer canonical form, but also the minimum number of integrators needed to perform RDOELI. Moreover, we show that if the original system is of dimension n , then the minimum number of integrators is less than or equal to n –- 2. In order to describe our algorithm well, we present an example that the auxiliary dynamics is a chain of two integrators.

Feedback passivity approach to output feedback disturbance attenuation for uncertain nonlinear systems

The problem of output feedback disturbance attenuation for a class of uncertain nonlinear systems is studied based on output feedback passification. Previous work on output feedback disturbance attenuation is extended to the case where (1) the nominal system is not transformable into the normal form and (2) the uncertainty is parameterized nonlinearly. An adaptive output feedback controller is also provided that makes a nonlinear system passive. The paper then considers the output feedback disturbance attenuation problem for a class of uncertain nonlinear systems in the normal form and of relative degree one. The difference is that the result is applicable to nonlinear systems that include the uncertainty in the input matrix and do not satisfy the matching condition.

Reduced-order dynamic observer error linearization for discrete-time systems

This paper addresses reduced-order dynamic observer error linearization (RDOEL) for discrete-time systems, which is a modified version of dynamic observer error linearization (DOEL). We define the concept of RDOEL and provide a necessary and sufficient condition for RDOEL. Moreover, we discuss the relation between RDOEL and DOEL when the auxiliary dynamics is an arbitrary linear controllable system. Using the relationship and an existing algorithm for DOEL, we also propose an algorithm for RDOEL that offers lower dimensional observers than DOEL. Finally, a simple example is included to illustrate the theory.

Geometric characterization of reduced-order dynamic observer error linearization for uncontrolled multi-output systems

In this paper, we introduce the concept of reduced-order dynamic observer error linearization (RDOEL) for uncontrolled multi-output systems, which is a natural extension of the (conventional) observer error linearization (OEL) as well as a modified version of dynamic observer error linearization (DOEL). We first state necessary conditions for RDOEL, and then provide a necessary and sufficient condition in terms of Lie algebras of vector fields, which has not yet been completely established even in OEL.

Synchronization of Linear Time-Varying Multi-Agent Systems with Heterogeneous Time-Varying Disturbances Using Integral Controller

This paper presents synchronization of LTV (Linear Time-Varying) MAS (Multi-Agent Systems) with heterogeneous time-varying disturbances under a fixed, connected, and undirected communication network. All the agents can collect only relative state information from their neighborhoods. To achieve synchronization of the MAS, an integral control scheme is proposed based on relative state information between agents.

Reduced-order dynamic observer error linearisation: a natural extension of observer error linearisation

This paper introduces the concept of reduced-order dynamic observer error linearisation (RDOEL) for multi-output systems, which is the problem of transforming a nonlinear system into a nonlinear observer canonical form with the aid of auxiliary dynamics. The proposed RDOEL framework is not only a modified version of dynamic observer error linearisation (DOEL) but also a natural extension of observer error linearisation (OEL). We provide three necessary conditions for the RDOEL problem, and then derive a necessary and sufficient condition described in terms of Lie algebras of vector fields. Furthermore, from the result, we also give a geometric necessary and sufficient condition for the OEL problem, which has not yet been completely established in the case where a diffeomorphism on the output of general form is considered.