Counterbalance valves are widely used in hydraulic deck machinery to balance the overrunning loads. However, as is well known, counterbalance circuit designed with poor choice of counterbalance valve tends to introduce instability to the system. This paper investigates the dynamic behavior of a pilot operated counterbalance valve which can operate at a flow rate about 2000L/min. A linearized stability analysis of such a hydraulic circuit which consists of a slip in cartridge, a pilot counterbalance valve and a hydraulic winch is presented. Pole-zero plots are employed to reveal the effect of the volume of control cavity, the hydraulic resistance on pilot line and counterbalance valve pilot area ratio on the stability of the system. The analysis results indicate that such a system will be unstable within the normal range of each parameter. An alternative approach that guarantees system stability by adding an accumulator on the pilot line is put forward. The approach stabilizes the pilot pressure by reducing the hydro-stiffness of pilot control cavity, thus the system can reach its stability condition. Finally, a numerical optimization method is putted forward, with the optimized parameters, the dynamic performance of considered system become better.

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