Modeling of dynamic characteristics for hydraulic drive under nonstationary load

The methodology for estimating the transient response and frequency characteristics for volumetric hydraulic drive under nonstationary load is proposed. The methodology is based on obtaining the transfer function for the speed of movement for the drive output link according to the load. To obtain the transfer function, the nonlinear mathematical model of translational hydraulic drive has been compiled, including the motion equations for the hydraulic cylinder piston, the equations of continuity in the pressure and drain cavities, taking into account compressibility of the working fluid. Hydraulic losses are described by quadratic dependence. In addition to the generally arbitrary load acting on the hydraulic cylinder rod, the resistance force proportional to the speed of movement of the hydraulic cylinder piston is also considered. By linearization of the mathematical model, the transfer function for the speed of movement on load is established in the form of fractional rational function of the third order. The dependences for calculating the coefficients of the transfer function is determined. The example of calculating the transient response, amplitude and phase frequency characteristics is given. The presented results can be used in the design and modernization of technological equipment with hydraulic drives.