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A new approach for optimal observer design of nonlinear systems, the so-called Nonlinear Quadratic Estimator is proposed. This approach employs the minimisation of a quadratic cost functional, thereby comprising two design parameters: Selective weighting of specific error state components and estimated upper bound minimisation. The new approach works without dual system transformation, achieving significant...
This paper analyses the observer synthesis for a class of nonlinear systems represented by Takagi-Sugeno models with premise variables depending on unmeasurable system states. It is well known that in case of unmeasurable premise variables the time-varying difference of the membership functions with true and estimated premise variables has to be considered in general as external disturbances or unknown...
The reliability and functional safety of electrical drives is necessary for the use in safety-related systems such as electrical cars and aerospace applications. In this paper, a rotor flux oriented fault tolerant control scheme for induction machines with squirrel-cage rotor using the fault hiding approach is presented. Based on a proposed physical model of the induction machine in Takagi-Sugeno...
This paper studies the input-to-state stability (ISS) of nonlinear systems in Takagi-Sugeno's form. Following the definitions and ISS properties proposed by Sontag and Wang [1], a condition in terms of Linear Matrix Inequalities (LMIs) and predefined norm-bounded inputs is derived. Due to the convex property of the weighted sum of input matrices, the input field is bounded and the ISS property holds...
In this paper, two criteria for robust actuator fault reconstruction with sliding mode observation for a class of uncertain nonlinear systems are derived. It is known, even though the sliding mode technique is robust against unknown but bounded uncertainties, that the quality of fault reconstruction under real conditions is not as good as assumed in the design stage. This is often due to the fact...
A nonlinear control-oriented description of large scale wind turbines with hydrostatic transmission using convex weighted combination polytopic models is proposed. The complete mathematical model of a wind turbine takes into consideration the nonlinearity of the aerodynamic maps and the hydrostatic drive with variable displacement pump and variable displacement motor. The objectives of the model-based...
In this paper, a Takagi-Sugeno sliding mode observer is designed to detect, isolate and reconstruct three different sensor faults and an actuator fault in a specified wind turbine benchmark problem. An extension of the discontinuous observer term using a weighted combination of gains responsible for establishing the sliding motion is proposed. The weights are equivalent to the membership functions...
In this paper, Lyapunov-based stability criteria for Takagi-Sugeno models in a new coordinate system are derived. Two different cases are considered: First, a simple change of coordinates with a common similarity transformation matrix for each local model is considered. For this, a linear matrix inequality (LMI) stability criterion for the transformed system based on the original coordinates is presented...
In modern wind turbines the output power for wind speeds above the nominal wind speed is limited by the adjustment of the rotor blade angles. The adjustment is performed with the pitch system. For cost reasons, in small wind turbines simple mechanical pitch systems are used actuated by centrifugal force and thus depending on the rotor speed and the blade mass. With the help of the converter the generator...
To improve the dynamics in mechatronic systems an active friction compensation is usualy necessary. However, a poor friction compensation action in the control scheme may lead to significant tracking errors, especially at low velocities.
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