## 1 Introduction  
Space propulsion systems are important subsystems of various spacecrafts, such as satellites, spacecraft, and probes; their mission is to provide the orbit and attitude control force and torque of the spacecraft [1]. The composition of the propulsion system includes propellant storage units (gas cylinders, tanks), fluid control components (various electric and mechanical valves), and liquid engines [2]. The electric valves in fluid control components account for the largest proportion of the entire propulsion system. They provide precise fluid control for the propulsion system and precise impulse for the liquid engine as an actuator. The electric valves in space propulsion systems are divided into solenoid valves, self-locking valves, proportional valves, etc., based on their functions. Most of them are solenoid axial flow structures with a compact structure and high accuracy [3,4]. The overall weight of some products is only a few tens of grams. A schematic diagram of the composition and structure of a typical electric valve is shown in Figure 1.  
In order to meet the requirements of miniaturization and lightness, and to avoid material wastage during the assembly process, the electric valve components used in the space propulsion system are all of a threaded structure. Finally, the valve parts are welded and fixed via electron beam welding. The unthreaded structure of electric valve productsdetermines that all processes until welding and fixation require the use of tooling for fixation. The assembly process is more complex and cumbersome than that for general industrial products. Due to the diverse and small-scale production needs of aerospace valve products, the assembly process has always relied mainly on manual labor. The main process steps in the assembly process of electric valve products are as follows:  
Parts assembly \(\rightarrow\) valve stroke measurement \(\rightarrow\) electrical performance testing \(\rightarrow\) running-in \(\rightarrow\) beam welding  
The traditional assembly process has the following problems:  
1. In terms of production, efficiency is low and management is cumbersome. 1. The product needs to be transferred between different workstations or positions, such as assembly, measurement, and testing, resulting in low efficiency. 2. Each set of products requires the entire process of tooling to follow, and during the valve assembly process, the amount of tooling used is large with high costs and cumbersome maintenance. 3. Before electron beam welding of the shell, spot welding and fixation should be carried out through the reserved holes in the fixture. After removing the fixture, circumferential welding should be carried out. One circumferential weld seam needs to be welded in two stages, which is low in efficiency and doubles the welding cost. 2. In terms of quality, there is a higher dependence on personnel, and measurement errors and assembly consistency are greatly affected by personnel factors, making it difficult to ensure quality consistency. 1. The disc spring that provides the flipping force and suspension effect during the valve assembly process is compressed by the screw of the fixture. The loading force is indirectly applied through the tightening of the thread. Due to the large discreteness of thread loading, it directly affects the response performance of valve opening and closing, and the influence of this factor cannot be decoupled, requiring repeated disassembly and debugging. 2. As an important indicator parameter, the valve stroke needs to be measured indirectly through a measuring rod using measuring tools. The small pressure exerted by the measuring tool on the adapter rod and the error introduced by manual operation result in low measurement accuracy. With the rapid development of the aerospace industry, the quantity of aerospace products has significantly increased, and the drawbacks of traditional assembly methods in terms of valve product delivery deadline and quality stability have become prominent.