## 1 Introduction  
Plasma-based pharmaceuticals are extensively applied in various medical fields, including for anemia treatment, clotting factor replacement, and immunotherapy. As the demand for blood products has consistently increased over the years, the number of plasma stations in China has continuously expanded, leading to an expansion in the market and supply scale. The market size reached $39 billion as of 2021, and is expected to remain high in the upcoming years. Therefore, improving the plasma recovery rate and efficiency has become a pressing concern for the blood-product pharmaceutical industry. Currently, the existing plasma-bag-splitter machines face two major issues, namely a low working efficiency and low plasma recovery rates. As a result, the process of extracting plasma still relies heavily on manual labor. With the continuous expansion of the blood-product market, the cost of using manual labor to extract plasma is too high, and there are issues with low efficiency and hygiene safety. Therefore, there is a need in the market for a highly efficient and high plasma recovery rate plasma-bag-splitter machine. The aim of this paper is to address the above two issues considering our designed plasma-bag-splitter machine. To address the issue of working efficiency, we adopt a pipeline workstation-style design, splitting different procedures apart. The procedures that need to be stopped before completion are placed on the workstation, while the procedures that can be completed during the movement process are placed on the moving path. The system can recognize the residual-input tube-end position of the plasma bag and cut the residual-input tube end during the movement process. The experimental section of this paper only includes the recognition of the input tube's endpoint and the cutting of the input tube's endpoint during the plasma bag's movement process. This part is crucial for determining whether the plasma bag splitter machine can improve the recovery rate. The residual-input tube contains plasma and the endpoint of the input tube will be sealed. To extract all of the blood inside, the endpoint of the input tube must be cut as close to the edge as possible to allow both sides to have contact with the outside air pressure. However, the difficulty lies in the fact that the input tube is irregularly placed in the freezing process, causing a significant difference in the endpoint's position, and the plasma bag is continuously moving. Therefore, it is necessary to develop a system that can accurately identify the endpoint of the input tube during the movement process and cut it. This will enable the residual plasma to be taken out of the input tube, making the endpoint-cutting system for the plasma bag an essential technology component of the automatic plasma-bag splitter. As the residual-input tube is a flexible tube and its position varies randomly, non-contact measurement methods are necessary to detect the distance of the input tube's endpoint. Non-contact measurement methods include laser triangulation, eddy current testing, ultrasonic measurement, and machine vision measurement. However, laser triangulation and ultrasonic measurement also face the challenge that the position of the residual-input tube is random and changes as the plasma bag moves, making it difficult to identify the accurate position of the tube's endpoint. The accurate position is the relative position of the input tube's end in the plasma bag. Additionally, eddy current testing requires a conductor, which is not suitable for use with a plasma bag. Visual measurement is a non-contact method with a high accuracy and extensive uses, and is especially suitable for detecting the position of the residual-input tube of the plasma bag. Based on machine vision, processing equipment has been widely used, providing a new approach for accurate identification of the cutting position of the input tube of the plasma bag. [PERSON] et al.