A semi-active shock isolation concept with a serial-stiffness-switch system

Abstract

This paper presents a novel semi-active shock isolation concept, which is referred to as a serial-stiffness-switch system. The system mainly consists of two serial elements, each of them composed of one spring and one switch in parallel with each other and connected to a protected payload. One spring acts as compression spring and the other as elongation spring. A velocity zero-crossing switching law allows to harvest vibrational energy and store it as potential energy in both springs. In order to realize the repositioning performance of the protected payload after shock, a position PID feedback controlled switching law is further introduced here. With the aim of isolating shocks having lower fundamental frequency than the serial-stiffness-switch system and reducing the maximal displacement response, both springs are slightly pre-stressed before shock. The approach is characterized and evaluated by numerical simulation results. It is proven that such a serial-stiffness-switch system shows much better shock isolation performance than a passive system and another semi-active shock isolation system. The study also investigates the effects of the system sampling frequency and potential energy pre-storage on shock isolation and residual vibration suppression performance.