A robot system for the control of fabric tension for inspection

This paper describes the performance of a stepper-motor-based robot system that exerts a prescribe tension on fabrics to facilitate inspection process. In fact, inspection is an important part of quality control in the textile and clothing industry. It is a useful tool to safeguard the quality and ensure that the product can meet the customer expectation and the relevant stipulated standard. Obviously, before the automated inspection process, it is necessary to expand the fabrics being tested to have certain tension. Due to the nonlinear nature of fabric stiffness, it is essential that an adaptive force feedback control be employed to regulate the applied tension.A pair of symmetrical two-link mechanisms with a revolute joint, driven by a stepper motor, in conjunction with an adaptive controller, constitutes the robot system proposed in the present work. The two mechanisms are responsible for stretching the fabrics to be inspected, while the controller regulates the stretching force to the desired value by sensing the reaction force exerted on the links by the fabrics. In order to update the controller parameters so as to account for the nonlinear change of the fabric stiffness, a Model-Reference Adaptive System (MRAS) based on the augmented error is designed. The performance of MRAS is compared with a Proportional-plus-Integral (PI) control. A short-sleeved T-shirt made of knitted fabric is considered for the demonstration of the system. Besides, a prescribed value of tension is set to the system. Numerical simulations are conducted to illustrate the feasibility and performance of the proposed system. Successful outcomes of the present work establish a foundation for the real implementation of the hanger.