Analysis of an ‘on–off’ regenerative electromechanical damper

Abstract

The design concept of an electromechanical regenerative damper is proposed to achieve variable asymmetric damping, similar to ‘high–low’ and ‘on–off’ semi-active damping, in a passive manner, while providing the energy-harvesting potential. The proposed design consists of two overrunning clutches and a planet gear mechanism which provides a low effective inertia and transforms the bidirectional linear motion across the damper to an asymmetric unidirectional rotation of the generator. An analytical model of the proposed electromechanical regenerative damper is developed to derive its damping properties during compression and rebound in terms of the inertia and electromagnetic generator force components considering slippage of the clutches. For this purpose, the conditions for slippage of the clutches are established. The influences of the transmission system and electromagnetic circuit parameters on the damping properties are analysed under different harmonic excitations. The results showed that the proposed transmission design helps to limit the inertial damping force, and the rebound to compression damper asymmetry is directly related to the gear ratio, while slippage of the clutches yields a high–low or on–off type of damping. The on- or off-cycle duration could be easily tuned through the electromagnetic and charging circuit parameters. The vibration isolation properties of the proposed damper are subsequently investigated considering a base-excited single-degree-of-freedom system. The model is further applied to evaluate the energy-harvesting potential of the damper. The results showed that the proposed damper with slippage of the clutches offers superior tuning flexibility to achieve improved vibration isolation and an improved relative displacement performance, while the energy-harvesting potential is strongly dependent upon the armature resistance and the charging capacitor voltage, as well as the damper velocity.