In this paper, the problem of estimating the frequency of a harmonic signal embedded in broad-band noise is considered. The paper focuses on the extended Kalman filter frequency tracker, which is the application of the extended Kalman filter (EKF) framework to the frequency estimation problem. The EKF frequency tracker recently proposed in the literature is characterized by a vector of three design parameters , whose role and tuning is still a controversial and unclear issue. In this paper it is shown that a wise parameterization of the extended Kalman frequency tracker is characterized by just one parameter: as a matter of fact must be set to zero to achieve the basic property of unbiasedness in a noise-free setting; moreover, the performances of the tracker are not influenced independently by and ; what really matters is the ratio = only. The proposed simplification of the extended Kalman filter frequency tracker allows an easier and more transparent tuning of its tracking behavior.
The problem considered in this paper is the design and analysis of control strategies for semiactive suspensions in road vehicles. The most commonly used control framework is the well-known Sky–Hook (SH) damping. Two-state or linear approximation of the SH concept are typically implemented. The goal of this paper is to analyze the optimality of SH-based control algorithms, and to propose an innovative control strategy, named Acceleration-Driven-Damper (ADD) control. It is shown that ADD is optimal in the sense that it minimizes the vertical body acceleration (comfort objective) when no road-preview is available. This control strategy is extremely simple; it requires the same sensors of the SH algorithms, and a simple two-state controllable damper. In order to assess and to compare the closed-loop performance of the SH and ADD control strategies, both a theoretical and a numerical analysis of performance are proposed.
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