Mechatronic design and implementation of a smart robotic hanger for garment inspection

The work in this paper, as continuation of previous research, improves the previous robot configuration and focuses on the mechatronic design and implementation of the robotic hanger system for garment inspection. In this improved 3-DOF smart hanger, three groups of linkages, body, shoulder, and sleeve links (joints), instead of the four-link robot consisting of three revolute joints and one prismatic joint in the previous design, can freely move in the 2D plane. In comparison with the previous design, the prismatic joint was removed. Link 2 and link 3 are replaced by the body link, and an extra shoulder link is added. Furthermore, the body link always keeps vertical status during motion, and the shoulder and sleeve links provide the convenience for holding the garment. Through these three pairs of improved links, the robotic hanger extends the garment effectively through several motion processes with position and force control where the force control was not considered in the previous design. Due to the hanger complexity and the inherent nonlinearity of the contact behavior, it is difficult, though not impossible, to build a model-based controller such as the proportional-derivative (PD) controller for the present application. Instead, a fuzzy proportional and integral (FPI) controller is applied for implementing the position and force control required for the motion processes. Additionally, for garments with different sizes and materials, the desired values in control system are different. To address this problem, an expert system for automatically selecting the desired position values in the control system is proposed. This intelligent module determines the proper desired positions for various garment sizes. The experimental results for one type of garment material validate the effectiveness of this improved novel smart robotic hanger system. In the future, the intelligent module for selecting different desired values will be further improved. The enhanced module is expected to provide the desired values of the control system when the factors of the garment size and material are considered simultaneously.