Fukuoka Institute of Technology

Abstract

Vehicle suspensions able to harvest electrical energy are usually using electromagnetic motor and generators. Since the bound-rebound translation has to be transformed into rotational motion by employing various mechanisms (ball screw and nut; rack and gear; hydraulic cylinder and motor, etc.), such systems are relatively complex, costly and unreliable. Alternatively, electromagnetic induction and piezoelectricity were used to produce electrical power. Such systems are cheaper and simpler, since there is no need to transform the motion. In this work, a piezoelectric stack is placed inside the cylinder of a colloidal damper. Working colloid produces a cyclical compression-decompression on the surface of the piezoelectric disks, and in this way mechanical energy recovered from the rough road excitation can be partially transformed into electrical energy. Electrical power harvestable from such system depends on the colloidal spring constant and rigidity of the piezoelectric stack that is serially mounted together with a spring in order to obtain a suspension able to support both compressive and tensile loads. From excitation tests carried on a ball-screw shaker, one determines the amount of harvestable power. Although the obtained power (1 − 100 W) is relatively modest, some applications such as, charge and recharge of a battery, or usage as electrical power source for the actuator of a fuel injection system can be considered.