Method and device for detecting position of piston rod, hydraulic cylinder and working machine

A device for detecting a position of a piston rod, comprising:

• an acquiring module configured to acquire a target image at a target position;
• an obtaining module configured to obtain a pixel information corresponding to the target image;
• a positioning module configured to compare the pixel information with a pixel database of the piston rod, wherein a full-stroke pixel information of the piston rod, a corresponding 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 can move relative to the target position;
• and
• a detecting module configured to determine 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.