The role of the hydraulic system is to increase the force by changing the pressure. A complete hydraulic system consists of five parts, namely power components, executive components, control components, auxiliary components (accessories) and hydraulic oil. Hydraulic systems can be divided into two categories: hydraulic drive systems and hydraulic control systems. The main function of hydraulic transmission system is to transmit power and movement. The hydraulic control system needs to make the output of the hydraulic system meet specific performance requirements (especially dynamic performance).