Sliding Mode Analysis of a Counterbalance Valve Induced Instability in an Electrohydraulic Drive

This paper analyzes dynamic effects of an electro-hydraulicdrive which uses a counter-balance valve for rod volumecompensation. It shows that local stability analysis is notsufficient in this particular case to get general statements ofthe system’s chattering properties. A reduced-order switchedsystem is proposed to gain deeper insights in system dynamicswith saturation effects such as the end-stop of a valvepoppet and solutions are compared numerically to the fullsystemdynamics which incorporates pressure built-up, pistonand valve dynamics as well as motor dynamics. It isshown that in cases of e.g. fast valves with small crackingpressures undesirable chattering of the full system existswhich can be easily understood in terms of the reduced-ordersystem in form of sliding mode solutions. The paper also describesunder which conditions such sliding modes exist, howthey behave and how they can be interpreted in terms of thefull system.