Asymmetric bistable shock isolators for repeated force-transfer nullification using optimal payload return

In this study, we propose an asymmetric bistable shock isolator (BSI) based on a new concept of repeated force-transfer nullification. The asymmetric BSI, with one potential well deeper than the other, benefits from symmetry breaking in its double-well potential dynamics, offering improved shock isolation when compared with a mirror-symmetric BSI. The proposed system operates near a nullcline, where force transfer to the protected platform is nullified, leading to significantly reduced shock transmissibility and slow, small intrawell oscillations. Additionally, the asymmetric BSI can accommodate mistuned shock inputs, offering a practical design margin. However, the superior isolation performance observed under the first shock does not persist in subsequent shocks, owing to payload escape. After the initial shock, following the nullcline causes the payload to escape from the deep potential well and become trapped in the shallow potential well. This escape alters the initial conditions of the payload for a subsequent shock and prevents repeated force-transfer nullification. To overcome this limitation, we further propose a payload-return mechanism that employs a haversine base motion and leverages symmetry-broken dynamics. By restoring the initial conditions, this mechanism enables repeated force-transfer nullification. The optimal payload-return condition is identified for minimizing force transfer during the return process, and it exhibits robustness against deviations from the optimal haversine signal, offering an additional design margin. Experimental verification confirms the effectiveness of the proposed asymmetric BSI in achieving repeated force-transfer nullification with the optimal payload-return mechanism.