Method for measuring displacement of large-range moving platform

A method for measuring linear displacement of a large-range moving platform, characterized in that, the method comprising:

• an optical path distribution device (201) is fixed on the moving platform (101), in which multiple beams of first measuring light (204) parallel to one another are generated by the optical path distribution device (201) and the beams of first measuring light (204) are parallel to the horizontal surface;
• a plurality of position sensitive detectors (301) are formed into a linear array and fixed on a base platform (102), in which the working surface of the position sensitive detectors (301) is perpendicular to the horizontal surface of the base platform (102);
• the multiple beams of first measuring light (204) and the linear array of position sensitive detectors (301) are arranged in such a manner that at least one beam of first measuring light (204) is detected by the linear array of position sensitive detectors (301) when the moving platform (101) is within a moving area, wherein the arranging manner is calculated as follows:
• when the beams of first measuring light (204) are arranged in equal spacing and the position sensitive detectors (301) are arranged periodically, given that the spacing between the adjacent beams of first measuring light (204) is τd, the number of the beams of first measuring light (204) is m, the number of the position sensitive detectors (301) in each period is k, and the measurement range of the position sensitive detector (301) is d, then:
• k
• ≥
• τ
• d
• d
• when the beams of first measuring light (204) are arranged in unequal spacing and the position sensitive detectors (301) are arranged in equal spacing, given that the spacing between the adjacent position sensitive detectors (301) is τp, the number of the beams of first measuring light (204) is m, and the measurement range of the position sensitive detector (301) is d, then:
• m
• ≥
• τ
• p
• d
• ;
• a linear array formed by multiple pairs of detection headers (401) for emitting multiple beams of second measuring light (402) parallel to one another is fixed on the base platform (102), in which the linear array formed by the detection headers (401) is configured for detecting whether the beams of second measuring light are shaded by the moving platform (101) to obtain a rough position of the moving platform (101) according to the shaded situation of the beams of second measuring light distributed within the moving area of the moving platform (101);
• and
• the array of position sensitive detectors (301) and the linear array of detection headers (401) are arranged along a same direction at the same time, and the large-range displacement of the moving platform (101) in the direction is calculated according to the measurements of the position sensitive detectors (301) and the rough position of the moving platform (101) obtained by the detection headers (401), in which the calculating is as follows:
• given that the moving platform (101) performs linear motion along the y-direction;
• at the same time, the first measuring light (204) is detected by the nth position sensitive detector of the array of position sensitive detectors (301), in which, the coordinates of the measuring origin of the nth position sensitive detector is (x0, y0, z0) in respect to the coordinate system of the base platform (102), and the coordinates of the detected beam of first measuring light (204) is (0, y1, z1) in respect to the measuring origin of the nth position sensitive detector in the coordinate system of the base platform (102);
• the spacing between the adjacent detection headers (401) is τω, and ω beams of light are shaded in the array of detection headers (401), with the coordinate in the y-direction of the center of the ω pairs of detection headers (401) being yω, and the mass center of the moving platform (101) which is at its centroid is l in length;
• then the position error of the mass center of the moving platform (101) measured by the detection headers (401) is
• ±
• l
• -
• ω
• ·
• τ
• ω
• 2
• ,
• and the relative position in the y-direction of the detected beam of first measuring light (204) emitted at the moving platform (101) is y0+y1−ym in respect to the mass center of the moving platform (101) with an error being
• ±
• l
• -
• ω
• ·
• τ
• ω
• 2
• ;
• and then the accurate position of the detected beam of first measuring light (204) and its relative position in respect to the mass center of the moving platform (101) are determined in connection with the fixing position of the optical path distribution device (201);
• given that the position in respect to the mass center is (xr, yr, zr), then the displacement of the moving platform (101) in the y-direction is y0+y1−yr.