Markless Visual Servoing for 3C Product Assembly with Quotient Kinematics Manipulator

Due to the small size of 3C (Computer, Communication and Consumer electronics) parts and their high assembly accuracy requirements, traditional industrial robots cannot meet the needs of flexible assembly. To address manufacturing errors and uncertainties in part poses, this study proposes a markerless visual servoing method. Through analysis of assembled 3C parts and manual assembly movements, a high-precision and flexible assembly strategy has been designed. This strategy divides assembly into into long-range approaching phase and a short-range aligning phase. To adapt to these phases, a quotient kinematic manipulator (QKM) consisting of two parallel manipulator modules was developed, along with a well-designed camera hardware system. In the long-range approaching phase, an image moment-based visual servoing method with constrained model predictive control is employed, addressing robot motion collisions and end-effector velocity constraints, resulting in collision avoidance motion trajectories. In the short-range aligning phase, a weighted image brightness visual servoing method is proposed, utilizing surface texture features to replace geometric features, achieving high-precision alignment of components. Experimental results show the proposed servoing assembly strategy achieves high-precision collaborative manipulator assembly without artificial markers, with accuracy of 0.5mm/0.5°.