A 2D high-precision motion unit plays an important role in an automatic optical inspection (AOI) system, and its
positioning accuracy and speed have an decisive effect on the inspection accuracy, efficiency and stability of the AOI
system, but the present AOI systems cannot ensure the high speed and high-precision at the same time. To solve this
problem, an automatic optical platform is developed, using the whole-closed-loop, fast, high-precision positioning
technology to construct the mathematical models of its motion control unit, including models of current loop, velocity
loop and position loop from inside to outside. Experiments were made on the motion platform using a laser
interferometer. Experimental results show that the 2D motion platform can be used to reach a scanning speed of 20m/s
and a positioning accuracy of 9ìm in a work area of 300mm * 3000mm with a load of 5kg.