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This communication deals with the problem of fault detection for a class of nonlinear systems using unknown input observers. Sufficient conditions for existence and stability of such observers are investigated. Based on linear matrix inequality (LMI) approach a design algorithm is proposed. The procedure includes constraints on detection performances and robustness to unknown inputs. Simulations results...
A robust observer is considered for a class of discrete, singular, descriptor systems subject to unknown inputs. Firstly, existence and causality of solutions are addressed. Then an observer is proposed which is based on the solution of a Riccati equation and on the use of a quadratic Liapunov function. A design algorithm is given and is illustrated by a practical example.
Variable Structure Control(VSC) with sliding mode is a special type of control technique that is capable of making a control system very robust with respect to system parameter variations and external disturbances. The chattering of the VSC signal can be reduced by several methods. One way is to augment the system with an integrator to isolate the system from the VSC control signal which causes the...
This paper proposes a new approach for detecting and isolating faults in a non-linear dynamic process using the multiple model approach. The necessary conditions for the assignability of eigenvalues to a region in the s-plane and the necessary conditions to guarantee the stability of fuzzy models for Takagi-Sugeno (T-S) fuzzy observers are derived. The paper is structured in two stages. The first...
In this paper, we are interested in missile autopilot design. Our objective is to seek the approaches which significantly enhance the ability of a control engineer to deal with practical nonlinear control problem. For this purpose, two nonlinear methods are considered: «approximate feedback » and « approximate dynamic feedback » with two time-scale separation. Both methodologies are applied in order...
This paper describes the design of an estimator for wind gusts acting on an airplane during flight. The linearised longitudinal model of the airplane for steady state rectilinear flight is presented. It is shown, how wind gusts, which are considered to be unknown inputs to the airplane, can be estimated in general, if the unknown inputs appear in the output equation. The unknown inputs are removed...
A multirate controller for the coupled mass benchmark problem is presented. A robust controller with full state feedback is designed using LMI techniques, and the transfer properties of state feedback control are approximately recovered by using a very simple fast output sampling control law. The proposed controller is compared to a state feedback / loop transfer recovery solution reported in the...
The paper deals with the design of an integral variable structure systems that enable to achieve the asymptotic reference signal tracking and unmeasured disturbances rejection in MIMO plants. The sliding mode equivalence principle and inverse model control method are used to determine the required dynamic switching surfaces with integral parts ensuring disturbances estimation and compensative control...
Contraction theory is a recent tool enabling to study the stability of nonlinear systems trajectories with respect to one another, and therefore belongs to the class of incremental stability methods. In this paper, we extend the original definition of contraction theory to incorporate in an explicit manner the control input of the considered system. Such an extension, called universal contraction,...
In the context of aircraft engineering and maintenance, No Fault Found (NFF) is a chain of events that develops from a pilot experiencing a system malfunction with post-flight maintenance failing to reproduce the reported symptoms. Without any repair being undertaken, the malfunction may be experienced again on subsequent flights. This present significant cost impacts to the industry that includes...
This paper introduces a method to locate simultaneous leaks in a pipeline when only the inflow and outflow of the fluid are available. It is assumed that the fluid in the duct with fixed leaks positions can be described by an approximated finite dimensional model considering pressure at the end of the duct as control variables. This model is used to design a vector called residual pattern in steady...
The problem of observer design for robust residual generation in nonlinear discrete-time systems is considered. The method is proposed to solve this problem involving nonlinear time-dependent transformation of state-space system model into strict feedback form. To make this transformation practicable, algebra of time-dependent functions is developed.
A robust multi-model design approach is used to control a four-link lightweight manipulator arm. The nonlinear plant model is linearized in a number of operating points, and recent LMI methods are employed to design a linear state feedback controller that places the closed-loop poles in a desired pole region simultaneously for all models. Only the joint angles are available for feedback, however,...
The fact that the feedback interconnection of strictly positive real (spr) systems leads to an asymptotically stable closed loop can be used for the synthesis of robust observer-based state-space controllers. Since most control plants originally are not spr structural modifications must be done to establish this property even under parameter variations. Going that way one gets a modified spr plant...
This paper proposes a design framework for robust control system design. The approach is based on improving the robustness of a previously existing controller instead of the design of a Robust Controller: therefore the consideration of the Controller Robustification problem. The method is based on the generation of a complement to the control signal of the initial controller by means of a Robustification...
The paper presents some results on parametric identification of linear systems applied to robust Fault Diagnosis schemes. In our approach, an equation error model is derived from input- output data. In particular, the error term takes into account disturbances (non measurable inputs), nonlinear and time-variant terms, measurement errors, etc. In this manner, state-space realization of the equation...
This article is concerned with the design and implementation of a robust position trajectory tracking controller for a permanent magnet synchronous motor (PMSM). The information on the angular position, provided by a classical resolver, is here complemented with an observer based phase lock loop (PLL) circuit which accurately renders the position and the angular velocity of the rotor. A Backstepping...
An encoderless predictive control method for doubly fed induction generator is proposed in this paper. Doubly fed induction generators are commonly used in wind turbine applications because of fast dynamic response and grid synchronizing capability. Dependency on speed measurement is an important drawback in wind turbine applications. A reduced order model based observer is used to estimate the torque,...
This paper investigates the automatic control problem of high speed train systems under uncertain resistance conditions such as time-varying resistance, unknown aerodynamic drag and wind gust. A sliding mode observer (SMO) based control method is designed for tracking given position-velocity profile precisely. The control method is disturbance rejective that does not rely on specific resistance coefficient...
Recently in many countries the efforts of researchers are directed to the design of low cost, accurate and robust controllers for small Unmanned Aerial Vehicle (UAV) using the minimum number of on-board sensors. The basic problem of such kind of design is to restore the unknown (unmeasured) states. The approach proposed in the paper consists of two procedures: state restoration by the reduced-order...
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