Structural Control and Health Monitoring

Crolet, J. M.; Preumont, A.

doi: 10.1002/stc.4300030101pmid: N/A

Battaini, M.; Casciati, F.

doi: 10.1002/stc.4300030102pmid: N/A

Attention is focused on low‐damping‐rubber base‐isolators. Instead of thinking in terms of intelligent materials, this paper pursues the definition of conditions of behaviour which result intelligent in view of a coupling with an active control device (hybrid control). In particular, situations which show a chaotic behaviour of the dynamic response to external excitations are promising in terms of control efficiency. The regions of chaotic behaviour are identified by evaluation of the corresponding Lyapunov exponents.

Breitbach, E.; Büter, A.

doi: 10.1002/stc.4300030103pmid: N/A

This paper deals with the sources of helicopter vibration and noise emissions. It shows and evaluates adaptive concepts to reduce them. The main reasons for these emissions are aerodynamic effects such as blade‐vortex‐inter action (BVI), aerodynamic hysteresis, and local transonic effects at the forward moving blade.

de Man, Pierre; Preumont, André

doi: 10.1002/stc.4300030104pmid: N/A

This paper evaluates a hybrid feedback‐feedforward controller for vibration suppression. The synergy between the two types of controllers is pointed out. The feedforward control extends the bandwidth of the controller for steady state disturbances with a correlated reference, while the feedback control reduces drastically the impulse response of lightly damped structures, avoiding the problems associated with truncation. The hybrid controller does not require additional actuator and sensor. Two applications are presented in the area of vibration attenuation and precision pointing. In each case the theoretical advantage of the hybrid controller is confirmed by experiments.

Jenkins, D. F. L.; Cunningham, M. J.; Clegg, W. W.

doi: 10.1002/stc.4300030105pmid: N/A

An active vibration control system has been developed based upon analogue feedback and optical vibration sensing. Composite piezoelectric films have been deposited directly onto the cantilever to provide a means of actuation and micro‐positioning. The system operates such that unwanted vibrations in the cantilever are removed and yet it remains possible to deflect the cantilever statically or dynamically as required. Results are presented for such a system.

Lenczner, Michel

doi: 10.1002/stc.4300030106pmid: N/A

The Besançon “Matériaux Intelligents” group is working on theoretical and practical aspects of design of dynamical stabilizers for realistic distributed systems. This paper is related to the modelling of an elastic multilayered plate including distributed piezoelectric actuators and a distributed electrical circuit. The derivation of the model is based on asymptotic methods. It is shown that the electrical circuit is a dynamical stabilizer for plate vibrations. An optimization procedure of circuit parameters is formulated and numerical results are discussed.

Loix, Nicolas; Kozanek, Jan; Foltete, Emmanuel

doi: 10.1002/stc.4300030107pmid: N/A

This paper shows that, in some circomstances, conservative systems may possess complex zeros. The presence of these complex zeros seems to reduce the robustness of the control system with respect to parameter variations.

Mace, B. R.; Jones, R. W.

doi: 10.1002/stc.4300030108pmid: N/A

The control of bending waves in a thin beam using a collocated feedback method is discussed with special reference to the case of a system comprising a displacement sensor and a force actuator. Control strategies involving vibration isolation (i.e. reducing wave transmission) and energy absorption (i.e. reducing scattered energy) are considered. Digital implementation is discussed and some results presented.

Maćkiewicz, Andrzej; Almansa, Francisco López; Inaudi, José A.

doi: 10.1002/stc.4300030109pmid: N/A

The classical Rosenbrock's algorithm (based on the Gauss elimination method) for n‐dimensional linear time invariant state equation matrices is analysed and modernized. The method of orthogonal similarity reduction to block Hessenberg form is used to assure numerical stability. The updated version of the Rosenbrock's algorithm is then justified in a very easy way using properties of Krylov matrices. Additionally, this algorithm can be used to determine an equivalence transformation which converts an n‐dimensional linear state equation into a controllable form (or a time invariant one into an equivalent observable form). It is advantageous for big and medium size problems and can be easily parallelized. Numerical examples are presented.

Petitjean, B.; Legrain, I.

doi: 10.1002/stc.4300030110pmid: N/A

The aim of the present paper is to investigate two strategies for the active control of plate vibrations, using distributed sensors and actuators (PVDF patches) working on a wide frequency band. The two strategies correspond to the two ends of a spectrum ranging from very robust/less efficient schemes (analog static output feedback) to less robust/very efficient schemes (here ‘frequency shaped LQG’).