In noise control, the reactance of a mechanical system needs to be minimized while the resistance is chosen suitably. This work illustrates the possibility of and the ease at which such design tasks may be accomplished by utilizing strong electromechanical coupling. Moving-coil loudspeaker is chosen as the vehicle of illustration and it is considered as a simple spring-mass system when operated below its first diaphragm mode. It is shown that the system mechanical property may be tuned easily by a simple R-LC circuit. In addition to the assigned resonance frequency, there can be a maximum of two other resonances. It is argued that the ability to tune the system mechanical resonance to any frequency, such as the ones at very low frequencies, can be very useful for noise and vibration control applications.

Les céramiques piézoélectriques présentent un couplage électromécanique leurdonnant la capacité de développer sous une contrainte mécanique une charge électrique proportionnelle à celle-ci et de se déformer en présence d'un champ électrique.Cette propriété est à la base des nombreuses applications telles que des actionneursou des capteurs. Pour des chargements plus importants, la réponse n'est pluslinéaire. Ce comportement s'explique par la rotation de zones uniformément polariséesqui engendre une polarisation et une déformation irréversibles responsablesdes comportements ferroélectrique et ferroélastique. L'exploitation de ces comportements non-linéairespermet des déplacements plus importants mais elle est freinée par la complexitédu comportement et l'absence d'outils de dimensionnement.Une modélisation phénoménologique décrivant la piézoélectricité, ferroélasticitéet ferroélectricité est présentée. Des cyclages électriques ainsi que le phénomène de dépolarisation mécaniquesont simulés sur la base de ce modèle.

When modeling the dynamics of robotic systems containing electric motors, the force generated by the motor is generally considered only as an applied torque or force that is independent of mechanical state variables such as velocity. Due to the electromechanical coupling effects in the motors, this approach leads engineers working on a robotic system to designing faulty controllers. In this paper, we propose a dynamics analysis model in which DC motor dynamics are embedded into a mechanical dynamics model such that the electromechanical coupling effects are included in the overall model. A model for the DC motor is developed based on its equivalent circuit model and incorporated into the generalized recursive dynamics formula previously developed by our group. The resulting dynamic numerical simulation program provides an effective and realistic approach for analyzing the electromechanical dynamics of robotic systems driven by DC motors. The developed numerical simulation tool is evaluated by applying to an industrial robot and a flexible antenna system driven by DC motors for a satellite.

A new category of piezoelectric ceramics with very high electromechanical coupling was discovered in a lead zinc niobate:lead titanate solid solution in a single crystal form. The maximum coupling factor k33 reaches 95%, which corresponds to the energy conversion rate twice as high as the conventional lead zirconate titanate ceramics. This paper reviews the previous studies on superior piezoelectricity in relaxor ferroelectric: lead titanate solid solutions and on the possible mechanisms of this high electromechanical coupling.