Purpose: The purpose of this paper is to reduce the drag loss and study the effects of operating conditions and groove parameters such as flow rate and temperature of automatic transmission fluid, clearance between plates, groove depth and groove ratio on the drag torque of a wet clutch for vehicles, parametric analysis of the drag torque model of wet multi-plate friction clutch with groove consideration. Design/methodology/approach: Both experimental and numerical research was carried out in this work. Parametric groove models, full film lubrication flow model and pressure distribution model are established to investigate the effects of the grooves on drag torque of a wet clutch. Multigrid method is used to simplify the solution. Findings: In this paper, a drag torque model of a wet multi-plate friction clutch based on the basic theory of viscous fluid dynamics is examined through experimental and numerical methods that take grooves into account, and the change trend of drag torque with operating conditions and groove parameters is analyzed. Originality/value: Multigrid method is used to solve the governing equations, which simplifies the solution process because of the restrictions and interpolation operations between the adjacent layers of coarser and fine grids. These works provide insight into the effect regularity of operating conditions and groove parameters on drag torque of a wet multi-plate friction clutch. Furthermore, variable test conditions and sufficient experimental data are the main functions in the experimental research.

A numerical model is established to investigate the effects of the influencing factors such as design parameters and operating conditions on the performance and behavior of the engagement process of the wet clutch based on the Navier–Stokes equations, contact mechanics, and heat transfer theory. A finite element contact model called KE contact model is used to analyze the rough contact during engagement process and thermal effect on the viscosity is considered based on heat transfer theory. The integration of the grooving into the simulation and the method of coupled finite element by domain decomposition of groove and ungrooved areas are put forward to facilitate the analysis. The experimental results agree well with the numerical model which takes the normal pressure, the temperature of ATF, relative revolution speed, the permeability and the groove geometry into account. The results of numerical simulation and the experiment indicate that the applied pressure not only affects the engagement time, but also has influence on the value of the engagement torque. Besides, the engagement time is roughly proportional to the relative revolution speed. The influencing factors such as the temperature of ATF, the permeability, grooves, the torque judders and effects of PID control parameters are also discussed in the paper. The performance and behavior of the engagement of the wet clutch were studied by two methods of numerical calculation and experimental research, which make the working process of the wet clutch more detailed.

Aimed at the unattended requirements of the heavy launch vehicle filling and launching support system, this paper focuses on the propellant filling and discharge automatically. This paper adopts the parametric variable frequency and amplitude variation equation to simulate the motion of the launch vehicle under wind load conditions. The equivalent spring damping model is used to simulate the real flexible umbilical arm of the rocket. In this paper, the compound active disturbance rejection control and robust integral sign control (CADRCRISC) method is proposed, including feedforward compensation control, linear feedback control, robust control, and extended state observer (ESO) control. This method can adapt to external disturbances and achieve high‐precision follow‐up control, which is verified through experiments and simulations. The method can adaptively realize fast‐following responses and regulate against any disturbance. The research on the automatic docking control technology of the combined connector is of great significance to the unattended launch support system for heavy launch vehicles. Besides, the control method proposed in this paper can be applied in other similar automatic docking applications.