acquiring a target image at a target position;

obtaining a pixel information corresponding to the target image;

comparing the pixel information with a pixel database of the piston rod, wherein a full-stroke pixel information of the piston rod and a relationship between the full-stroke pixel information of the piston rod and a displacement of the piston rod are stored in the pixel database of the piston rod, and the full-stroke pixel information at least comprises the pixel information within a range in which the piston rod is configured to move relative to the target position; and

determining a position information of the piston rod based on a comparison result;

wherein the piston rod is provided with a plurality of coding units along a moving direction, the plurality of the coding units are provided in sequence throughout the piston rod and are different from each other to form a full-stroke feature coding, and the target image comprises at least one coding unit on the piston rod; and

before comparing the pixel information with the pixel database of the piston rod, the method further comprises:

determining a target coding feature segment from a coding feature database based on the coding unit of the target image, wherein the coding feature database comprises coding feature segments corresponding to all the coding units on the piston rod, and each of the coding feature segments in the coding feature database is mapped to the pixel information of the pixel database of the piston rod; and

obtaining a corresponding target pixel information in the pixel database of the piston rod based on the target coding feature segment.