Abstract
Electrical and hybrid vehicles require increasingly amounts of electrical power that might be harvested from different systems, such as the vehicle suspension. A vehicle suspension able to generate electrical power transforms the kinetic energy of vertical bound-rebound movement excited by the road roughness into electrical energy. If an electromagnetic motor and generator is used to produce electrical power, the translational bound-rebound movement has to be transformed into a rotational movement, by employing an appropriate mechanism, such as: ball screw and nut; rack and gear; hydraulic cylinder and hydraulic motor, etc. Such systems are costly, complex from a structural standpoint, and have relatively low efficiency, robustness and reliability. Oppositely, if electromagnetic induction and/or piezoelectric elements are used to produce electrical power, there is no need to transform the translational bound-rebound movement. Such systems are relatively inexpensive and simpler from a structural standpoint. In this work, a piezoelectric stack is placed inside the cylinder of an oil or colloidal damper. Working fluid produces a cyclical compression-decompression on the surface of the piezoelectric disks, and in this way the mechanical energy recovered from the rough road excitation can be partially transformed into electrical energy. Piezoelectric stack is serially mounted together with a compression helical spring in order to obtain a vehicle suspension. From excitation tests performed on a ball-screw shaker one determines the power generation performances. Thus, for a piezoelectric stack consisted of 55 annular disks with an outer diameter of 60 mm, excited at a frequency of 1-10 Hz, the generated electrical power was about 1-100 W.
