Design of a Low-Frequency Harmonic Rotary Piezoelectric Actuator

Piezoelectric actuators usually operate under a high frequency driving signal. Here we report a harmonic rotating piezoelectric actuator by coupling a harmonic wave generator and a friction rotor, in which the actuator can be actuated by a low-frequency sinusoidal signal with positive bias. The harmonic wave is generated by a two-stage magnifying mechanism consisting of a displacement amplifier and a harmonic rod. Applying piezoelectricity theory, the actuator’s output characteristic equations are deduced. What is more, the output characteristics of piezoelectric actuators are tested with the established experimental system. Results show that the generated harmonic displacements can drive the actuator to work normally at a driving voltage of larger than 90 V and the maximum total harmonic displacement of the piezoelectric actuator comes up to 427.6 μm under the driving voltage of 150 V. Meanwhile, the error between the measured and calculated values of the harmonic displacement is less than 7%. Furthermore, the rotational speed of the piezoelectric actuator reaches 5.45 rpm/min at 150 V voltage and 5 Hz driving frequency.

On the Nonlinear Dynamics of a Vibro-Impacting Cantilever With End Mass

A theoretical and experimental dynamic analysis of a vibro-impacting cantilever with end mass is presented in this paper. The cantilever is excited by transverse harmonic displacement given at its fixed end with the help of a shaker. Nonlinearity in dynamics due to impact of cantilever on a motion limiting stop only on one side is considered. Experiments revealed quite interesting nonlinear hysteresis, jump, and drop phenomena in this case. Phenomena are experimentally characterized by varying the position and the gap between the stop and cantilever on a custom-built setup. Vibrating cantilever is modeled using assumed modes method while spring damper model for impacting stop is considered. Simulation and experimental results show close match for the same parameters under various cases of stop position and gap. Results are presented in terms of frequency response curves for range of parameters in non-dimensional form to enable their use in similar other cases.

Active Control of Rotor Vibrations by Means of Piezoelectric Actuators

This work deals with the development of an adaptive hydrodynamic bearing made of a mobile housing mounted on piezoelectric actuators. The device is placed near one of the two bearings supporting a slender shaft. Imposing a harmonic displacement on the mobile bearing, in two orthogonal directions, a rotating force, and hence a correcting moment, can be produced on the shaft so as to reduce the bending caused by the unbalance. The first tests carried out are encouraging and the agreement of experimental and numerical results is satisfactory.