Reciprocating seals are vital components in hydraulic systems. As a kind of reciprocating seal, the glyd-ring is commonly used as a piston seal. For the sealing characteristics of aircraft glyd-ring under severe working conditions, systematic research and experimental verification are not sufficient. The liquid-solid coupling model based on mixed lubrication theory is established in order to analyze the characteristics of the glyd-ring seal in the cylinder piston. The contact stress distribution on the glyd-ring under different fluid pressures or temperatures is discussed through finite element analysis. The mechanical analysis of solids and fluids are carried out separately, and the thickness of the fluid film is continuously updated until the results of the deformation analysis converged. According to the calculation results obtained by this model, three characteristics of the glyd-ring seal (static contact pressure, film thickness, friction force) are discussed. As the fluid pressure rises, the contact pressure in the sealing area increases by a rate which is greater than that of the corresponding fluid pressure, the seal length is shortened, the fluid film thickness is reduced, and the frictional force gradually increases, this force increase is proved by test data. As the temperature rises, the contact pressure in the seal area (near the O-ring) increases by a rate which is greater than that of the corresponding fluid pressure, the seal length increases, the oil film thickness decreases, and the frictional force increases significantly.

The electro-hydrostatic actuator (EHA) is a kind of power-by-wire (PBW) actuator that converts the electrical power into localized hydraulic power for flight control. In order to solve the problem of flow mismatching in the asymmetric cylinder, this paper presents a novel EHA which applies a three-ports fixed displacement pump to work with the asymmetric cylinder. The working principle of the novel EHA is introduced, and its nonlinear mathematical model is built. The sliding-mode control is proposed to control the position loop of the EHA. The controller structure of EHA is built including the position control using sliding-mode control, the speed control using PI, and the current control using PI. The model of mechanical parts including the permanent magnet synchronous motor (PMSM), controller and hydraulic parts are built in the SIMULINK. Simulation results show that the sliding-mode control improves the dynamic response and control accuracy compared with the traditional classic PID.