Analysis and Optimization of Inside-Cushion Structure in High-Speed Hydraulic Cylinders

An inside-cushion structure with sidestep and taper-shaped plungers is studied to address the problems of high impact and vibration in high-speed hydraulic cylinders. First, the three stages of cushion processes are discussed according to the varying flow area as the piston moves. Then, to establish a precise mathematical model, the states of the flow field are estimated in terms of the Reynolds number. Accordingly, the simulation model parameterized against measured data is developed and verified by experiment. Last, the average velocity, peak cushion pressure, and terminal velocity are defined to evaluate cushion performance. According to these optimized objectives, the non-linear programming by quadratic Lagrange (NLPQL) algorithm is applied to optimize the structure parameters. The optimization results indicate that the peak cushion pressure is reduced by 28% and terminal velocity is reduced by 21% without reduction of average velocity.