Automatic Assembly Technology of Dense Small Screws for Flat Panel Parts

Screw assemblies of radar are characterized by numerous densely distributed small screws of various types, rendering their manual assembly difficult and inefficient. To improve the assembly quality and efficiency, an automatic assembly system was developed. First, the position and attitude relationships among the workpiece, camera, and base coordinate systems of the manipulator were obtained using three-point location and nine-point calibration methods. Second, a visual servoing strategy is designed for guiding the manipulator such that its position can be adjusted adaptively to achieve the high-precision positioning of threaded holes. Third, a method for evaluating assembly quality is developed. The templates of angle-torque curves of various screws were produced by fitting experimental data. Furthermore, the assembly quality was determined by calculating the similarity between the angle-torque curves and templates based on the Frechet distance. Finally, the feasibility was verified using a flat plate component with five threaded holes.

Automated summary

An automatic assembly system was developed to improve the assembly quality and efficiency of screw assemblies of radar. The system obtained the position and attitude relationships among the workpiece, camera, and manipulator coordinate systems using three-point location and nine-point calibration methods. A visual servoing strategy was designed to guide the manipulator for high-precision positioning of threaded holes. An evaluation method for assembly quality was developed based on angle-torque curves and templates.