Nonlinear Modeling and Analysis of Digital Hydraulic Cylinder

Based on comprehensive theoretical analysis of all parts of digital hydraulic cylinder, a nonlinear mathematical model was deduced. The model includes the dynamics of spool and feedback mechanism, and also covers factors such as backlash, radial leakage, overlap and dynamic friction, which make it more reasonable and perfect. Based on the model, simulation experiments were carried out to investigate the influence of backlash, radial leakage and overlap on system performance. The difference between the mechanical and electrical feedback was also explored. The results reveal that, overlap increases the steady-state error and transmission gap acts like this when no leak. The combination of backlash and valve radial leakage causes overshoots in both moving directions. The feedback mechanism increases system damping, which is helpful for restraint of speed vibration and stick-slip motion. The research supplies theoretical bases and guidelines for nonlinearities compensation control later.