Active damping

Position/Displacement sensors can be used in active damping systems of industrial washing machines in order to compensate for vibrations coming from unbalanced drums /laundry. These can work much like a simple automotive shock absorber. 

We now consider a duplexer like that described on pp. 395-397. The main elements are the two sets of crossed diodes and the A./4 line. After the cross diodes stop conducting, the decay rate will be determined by the unloaded Q of the tank circuit in the absence of any active damping. In a high Q circuit, especially at low frequencies, this could entail an intolerable wait, e.g., in excess of Tg. Lowering the tank... 

In summary, what we have described is a system which recovers from the transmitter pulse in two distinct steps. The first part takes place through some low impedance path usually, but not always, associated with the output circuitry of the transmitter. In order to improve the S/N, the transmitter circuit is passively disconnected by a set of series crossed diodes after which the second phase of recovery proceeds according to an active damping circuit which, if present, leads to better S/N because of the improved recovery even though it is a source of additional noise. Neither sets of... 

Process stability and achievable metal cutting volume limited by the low stiffness of the tool Active damping with feedback control Vibration-assisted machining... 

Overall, within a proper operational range of 0.7 V the Ni-doped MFR IPMCs showed good paramagnetic characteristics and excellent electric responsive properties. This makes the developed MFR IPMCs attractive not only for actuator applications but also potentially for active damping applications. It is yet to be researched how the ionic liquids as potential electrolytes can improve the material to extend the operational voltage range. 

Adaptronics and control can be implemented at different points or subsystems. In order to evaluate possible concepts from a system point of view, an overall end to end model is established. The elements of such an integrated simulation model are shown in Fig. 5.3. In the left part the reduced structure (dynamics) model together with control laws are used for assessing the effects of active damping introduced by adaptronics as described below. The right part contains the optical submodel together with the telescope drives. 

Fig. 5.6. Root locus curve (real and imaginary axis) for active damping via proof mass actuators in the secondary mirror support truss (Ci percentage of critical damping)...

Preumont, A. Dufour, J.-P. Malkian, C. Active damping by a local force feedback with piezoelectric actuators. AIAA J. Guidance, Control, and D5Tiamics, 15 (1992), pp. 390-395... 

Among several applications in space and machine tools, a nice application has been developed using this concept the active damping of a ski [19]. The first flexural vibration mode of the ski occurring at 14 Hz is actively damped (the initial quality factor of 100 is decreased down to 10) through a piezo actuator and an accelerometer (Fig. 6.26a). A special filter is necessary to avoid instabilities coming from the high order vibration modes. The piezo actuator is mounted in front of the shoe and the accelerometer is mounted at the top of the ski. This implementation is an important step to the adaptronic application, in which it is foreseen to adapt the quality factor of the ski as a function of the snow hardness. 

The curve of the absolute maximum strain against the frequency of the unloaded MAS (Fig. 6.38) has been calculated and tested taking into account both the field limit and the stress limit at each frequency. It defines a law of current that depends on frequency. This new strain curve is above the classical curve of strain at constant current, based on the maximum current acceptable at resonance. It possesses a large pass band, which might be used in several applications such as active damping, low frequency projectors, etc. 

Sosiucki, O. (et al.) Active damping of vibrations applied on ski structures. Proc. 10th Conf. Actuator, Bremen (2006), pp. 932-935... 

Integrated safety, active crash systems Active pre-crash and crash systems, reversible locking systems, adaptation of car structure, increased deformation zone, load control, active damping... 

Electro- and magnetorheological fluids are mainly used in semi-active damping devices, current car suspension systems in premimn class vehicles based on MRF [139]. Furthermore, shape memory alloys are imder investigation, especially for active pre-crash systems [141]. 

One approach to optimize weight and acoustic emission is to actively influence sheet metals via ASAC. A corresponding project example is an actively damped car roof structure which was part of the German Leitprojekt Adap-tronik [165]. Several distributed piezoceramic actuators have been attached... 

Active Damping and Reduction of Structural Oscillations. Under this heading, the research groups develop fundamental concepts of optimized positioning and integrating adaptronic components (actuators, sensors) in machine tool structures. Research focuses on approaches and implementations that will reduce structure-born noise by means of control techniques. 

Traina, M.I. et al. An experimental study of the earthquake response of building models provided with active damping devices. Proc. 9th World Conf. on Earthquake Eng., VIII 447-4522 (1988)... 

Shook, D. A., Roschke, P. N., Ozbulut, O. E. (2008). Superelastic semi-active damping of a base-isolated stmcture. Structural Control and Health Monitoring, 15, 746-768. doi 10.1002/ stc.276... 

N. Kodera, H. Yamashita, and T. Ando, Active damping of the scanner for high-speed atomic force microscopy. Rev. Sci. Instrum., 76, 053709 (2005). 

Disc-shaped rotor with integrated active damping system... 

Fig. 7.20 Test stand for the damping petfoimanee investigation of the fiber-reinforced rotor with integrated active damping systems.

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