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

This paper analyzes the dynamic effects of an electrohydraulic drive that uses a counterbalance valve for rod volume compensation. It shows that local stability analysis is not sufficient in this particular case to get general statements of the system's chattering properties. A reduced-order switched system is proposed to gain deeper insights in system dynamics with saturation effects such as the end-stop of a valve poppet and solutions are compared numerically to the full-system dynamics which incorporates pressure built-up, piston, and valve dynamics as well as motor dynamics. It is shown that in cases of, e.g., fast valves with small cracking pressures undesirable chattering of the full system exists which can be easily understood in terms of the reduced-order system in form of sliding mode solutions. The paper also describes under which conditions such sliding modes exist, how they behave, and how they can be interpreted in terms of the full system.