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International audienceDuring the last three decades, several active damping strategies have been proposed, based on the so-called passivity concept, or equivalently, on the power port concept. One of them, known as Integral Force Feedback (IFF) is reviewed in this paper. Actually, the main drawback of the IFF is that high active damping is obtained at the cost of a degradation of the compliance at low frequency, compromising the capability of disturbance rejection. Classically, a trade-off between damping and stiffness can be reached by adequately high pass filtering the control signal. However, the high pass filter poles and zeros often interfere with the plant dynamics, which in turn compromises the guaranteed stability of the IFF. In this paper, a novel type of high pass filter is proposed. It is shown that this modification makes the controller unconditionally stable, and increases drastically the achievable modal damping. Analytic formulas are derived, and illustrated using simple numerical models. The characteristics of the proposed controller are discussed in terms of maximum modal damping and transmissibility

Modal active control, based on a state model, is an efficient method of increasing the lifetime of electronic boards by using piezoelectric components. In the case of industrial mass production, dispersions lead to changes in mechanical and electromechanical properties. Moreover, initial operating conditions such as boundary conditions can change during the lifetime of the control and modify its efficiency and stability. Therefore, a semi-adaptive modal control strategy in deferred time is proposed to attenuate these problems. Firstly modal control gains are calculated by using a classical linear quadratic Gaussian algorithm with the nominal model including mode shapes. Then control I/O data are collected by an identification system that uses on-board piezoelectric components. A subspace method is implemented to estimate modal matrices in order to update the controller. The sensitivity of control performance to modal parameter variation is presented. Estimated control frequencies and modal damping are finally used to update modal control gains. The effectiveness of the proposed method is examined through numerical simulation and experimental tests in the case of boundary condition modifications. This adaptive modal control/identification design greatly increases the nominal robustness of the controller in the case of frequency shifts.