A low-cost control architecture for user-oriented service applications of Cassino parallel manipulator G. Carbone*, M. Ceccarelli*, T. Borangiu** *LARM: Laboratory of Robotics and Mechatronics, University of Cassino, Cassino, Italy (e-mail: carbone@unicas; ceccarelli@unicas.it) **Robotics Research Centre, University Politehnica of Bucharest, Bucharest, Romania (e-mail: borangiu@cimr.pub.ro) Abstract: This paper describes a low-cost control architecture that has been developed at LARM for operating the three-dofs parallel manipulator CaPaMan (Cassino Parallel Manipulator) in service applications. Main advantages of the proposed control architecture are outlined with emphasis to user- friendly features that have been achieved also via a suitable virtual instrument in Labview environment. Preliminary experimental tests show the feasibility of the proposed control architecture. Keywords: Parallel manipulators, low-cost, control architecture, service applications 1. INTRODUCTION Parallel robots have attracted the interest of many researchers, since they may overcome limits of serial robots, for example, in terms of payload to weight ratio, higher stiffness, higher accuracy, faster dynamic response. Several parallel robots have been conceived together with development of theoretical and practical investigations, (Merlet, 2005). However, also parallel architectures suffer of well-known drawbacks such as a complex design and control, an inherent relatively higher cost. Thus, several investigations have been carried out to achieve more low-cost user-friendly design solutions also in service tasks. A possible approach for reducing the design and control complexity is based on the reduction of the number of degrees of freedom (dofs) as proposed for example in (Kong and Gosselin, 2002; Karouia and Hervé, 2006; Itul and Pisla, 2008). CaPaMan (Cassino Parallel Manipulator) is a parallel manipulator, having three dofs, which has been conceived at LARM: Laboratory of Robotics and Mechatronics at Cassino, Italy, (Ceccarelli, 1997). A prototype has been built and a successful application of CaPaMan as a service platform for simulating earthquake phenomena is reported in (Carvalho and Ceccarelli, 1999; Ceccarelli et al., 2002). This paper describes a novel low-cost control architecture that has been recently developed at LARM in Cassino for operating the parallel manipulator CaPaMan. Main characteristics and advantages of the proposed control architecture are here described. Preliminary experimental tests are also described to show the feasibility and effectiveness of the proposed control hardware and software. 2. CAPAMAN PROTOTYPE CaPaMan architecture has been conceived at where a prototype has been built since 1996, (Ceccarelli, 1997). A schematic representation of the CaPaMan manipulator is shown in Fig.1, where the fixed platform is FP and the moving platform is MP. MP is connected to FP through three identical leg mechanisms and it is driven at points H1, H2, H3. An articulated parallelogram AP, a passive prismatic joint SJ and a connecting bar CB compose each leg mechanism. AP’s coupler carries the SJ and CB transmits the motion from AP to MP through SJ; CB is connected to the MP by a passive spherical joint BJ, which is installed on MP. CB may translate along the passive prismatic joint of SJ keeping its vertical posture and BJ allows MP to rotate in the space. Each plane, which contains AP, is rotated of π/3 with respect to the neighbour one. Figure 2 shows a built prototype whose main design parameters are listed in Table 1. Particularly, design parameters of the k-th leg are identified through: a k , which is the length of the frame link; b k , which is the length of the input crank; c k , which is the length of the coupler link; d k , which is the length of the follower crank; h k , which is the length of the connecting bar. The kinematic variables are: α k , which is the active dof input crank angle; s k , which is the stroke of the passive prismatic joint. Finally, the size of MP and FP are given by r P and r f , respectively, H is the center point of MP, O is the center point of FP, H k is the center point of the k-th BJ and Ok is the middle point of the frame link a k , Fig.1. The motion of MP with respect to FP can be described by considering a world frame O-XYZ, and a moving frame H-XpYpZp on MP that can be seen also as a tool reference frame for CaPaMan. Proceedings of the 14th IFAC Symposium on Information Control Problems in Manufacturing Bucharest, Romania, May 23-25, 2012 978-3-902661-98-2/12/$20.00 © 2012 IFAC 877 10.3182/20120523-3-RO-2023.00337