Robotica (2008) volume 26, pp. 55–62. © 2007 Cambridge University Press doi:10.1017/S026357470700358X Printed in the United Kingdom Development of a new buffing robot manipulator for shoes Hyeung-Sik Choi ∗ , Gyu-Deuk Hwang and Sam-Sang You Division of Mechanicl and Information Engineering, Underwater Vehicle Research Center, Korea Maritime University, Dongsam-Dong, Yeongdo-Ku, Pusan, Korea. (Received in Final Form: May 16, 2007. First published online: August 28, 2007) SUMMARY This paper presents analysis and experimental verifications of a new robot manipulator with five degrees of freedom developed for the buffing operation of shoes. First, the forward and inverse kinematics are analyzed. Next, an analytic closed-form solution is rigorously derived for the joint angles corresponding to the position and orientation of the end-effector in Cartesian coordinates. A control system, including input/output interfaces and the related electronic system, is designed for the control of the mechanical structure of the buffing robot. Then, peripheral systems integrated with the conveyer, transfer device, and fixture device are designed for the sequential buffing process of shoes. Also, a graphic user interface (GUI) program including the forward/inverse kinematics, control algorithm, and communication program to interact the robot with the peripheral systems is developed by using visual C++ language. A new flexible toolholder (FTH) is proposed to compensate for the excessive applied force between deburring tools and shoes. Finally, the test results are provided to demonstrate the effectiveness of the proposed scheme. KEYWORDS: Robot manipulator; Buffing; Shoe uppers; Kinematics; Control system; Flexible toolholder. 1. Introduction In general, shoe processing tasks are tedious and relatively complicated such that several machines have been applied to tasks in footwear production factories. In one of the processing tasks, the leather uppers of the shoe exterior are glued to the outsole. Since the leather uppers of the shoe exterior are treated with various dyes or they have slippery surfaces, it is not easy to maintain a high level of adhesion between the leather uppers and the outsole of the shoes. Hence, the side of the uppers covering the sole should be mechanically buffed to enhance the adhesive power. This task is tedious and hazardous to human health because of the amount of dirt involved, and demands higher labor costs as well. In this sense, developing automatic buffing machines for processing of the shoe uppers has been actively pursued in the shoemaking industry. Considerable attention has been paid to the development and applications of industrial robots in shoe manufacturing for tasks such as the buffing task of shoes. Many commercially available industrial robots have been used in manufacturing and assembly tasks in several shoe companies. * Corresponding author. E-mail: hchoi@hhu.ac.kr The early work done by Tectors Company in England was noticed by many shoe manufacturers. In 1989, this company introduced the PUMA 700 commercial robot for buffing the uppers of shoes. Recently, the ABB Robot Company in Sweden has conducted similar tasks for shoe buffing. In addition, the robot system applied to shoe manufacturing was investigated by Spencer. 1 It has been recognized that the shoe industry is turning more and more toward the robot-based automation system capable of autonomous and repetitive operations. Furthermore, several other shoe companies such as ACTIS (France), DESMA (Germany), and Intelligent Machines (USA) have used industrial robots for shoe manufacturing. 2 Research on various types of robots applied to shoe processing tasks such as outsole buffing has been conducted for real applications. However, most of these robots are applied to formalized shoes, and the existing 6-axis industrial robots have been utilized for the buffing tasks. It has been observed that industrial robots are often too expensive and not appropriate for the buffing operation of irregular shoes such as public sneakers. Furthermore, to apply industrial robots to the buffing operation of shoes, a user-oriented program is required to achieve easy interface between operators and robots. For this reason, practical dedicated robots with user- oriented programs are required for buffing the outsole of shoes including public sneakers. The purpose of this study is to develop a new 5-degree-of- freedom (DOF) buffing-oriented robot capable of performing buffing operations for general shoes. The forward and inverse kinematics of the developed robot are completely analyzed, and the peripheral devices and control system for sequential process tasks are designed. A trajectory control program for the robot is developed to automatically follow a desired buffing task line, and a communication system between the robot and the peripheral system is developed as well. Furthermore, the program for a graphic user interface (GUI) based on the visual C++ language is designed for the buffing robot, so that the user can conveniently manipulate and teach the robot via the operating screen. In addition, a new structure of the flexible toolholder (FTH) is proposed and analyzed to compensate the interacting forces between the buffing tools and shoes. 2. Kinematics of the Robot 2.1. Forward kinematics analysis of robot In this study, a new robot system is proposed for the buffing tasks of shoe uppers as shown in Fig. 1(a) and (b),