Mathematical model of operating processes of the chocker-free trip with energy-saving hydraulic drive

Chokerless hauling devices are often used in combination with wheeled agricultural tractors for thinning operations in the forest-steppe zone of Russia. Negative fluctuations often occur during the movement of the tractor with the above-mentioned unit along uneven terrain in clearings. They cause jumps in the working fluid in the hydraulic system and general high dynamic loads, which in turn reduce the reliability of both technological equipment and the traction unit. One of the options for reducing dynamic loads and energy consumption is the use of an energy-saving (recuperative) hydraulic drive with a hydraulic accumulator. The aim of the study was to develop a new chokerless hauling grip and a mathematical model that took into account external and internal forces acting on a skidded bundle of wood, as well as the parameters of an energy-saving hydraulic drive that allowed reducing the dynamic loading and energy intensity of work processes. The authors of the article proposed a new design and technological scheme for a chokerless hauling grip with an energy-saving hydraulic drive, protected by a patent of the Russian Federation for an invention. A mathematical model is presented that takes into account not only the external and internal forces acting on the skidding pack of wood, but also the parameters of an energy-saving hydraulic drive. The working processes of gripping together with a pack of wood during transient acceleration and deceleration modes are described by the equation of motion of the recuperation hydraulic cylinder piston and by the equation of the hydraulic fluid consumption of the recuperation hydraulic cylinder, taking into account leakages into the accumulator at a pressure higher than the pre-charge one. The Cauchy problem for a nonlinear system of differential equations of a hauling grip motion with an energy-saving hydraulic drive was considered. Theoretical time dependences of the working fluid pressure and the stroke of the recuperation hydraulic cylinder were obtained, their adequacy was confirmed by the results of experimental studies on an operating laboratory stand for a chokerless gripper with an energy-saving hydraulic drive with the following design parameters: hydraulic accumulator pre-charge pressure 5 MPa; hydraulic accumulator working volume 0.005 m3; hydraulic cylinder piston diameter 0.1 m; hydraulic cylinder rod diameter 0.04 m. It has been established that the energy recovery system of the hauling grip reduced bursts of the working fluid pressure during transient processes by 1.4…1.7 times and allowed reserving power in the range of 1.7 ... 2.1 kW.