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Parallel Manipulators Towards New Applications Part 15

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Nhiều chương trình CAD hiện nay cho phép tạo ra các mô hình ba chiều để có thể nhìn từ mọi góc độ. Các chương trình CAD mô hình hóa vật thể đặc tiên tiến là một hệ thống thiết kế hiện thực ảo. Những mô hình đặc như vậy có thể được dùng làm cơ sở cho các phân tích phần tử hữu hạn (FEA) và / hoặc tính toán động lực dòng chảy (CFD) của thiết kế. Cho đến ứng dụng gia công với trợ giúp máy tính (CAM), những mô hình này cũng có thể được dùng. | A Novel 4-DOF Parallel Manipulator H4 413 DOFs which are obviously compatible with the motions offered by the first meta-chain . Such mechanical structures are named asymmetrical H4 Pierrot Company 1999 Company Pierrot 1999 . An asymmetrical design of H4 using two P-U-Us and two P-U-S s is shown in Fig.7 a . The P-U-U s can be replaced by P- U-S 2 s as shown in Fig.7 b . 2.2 Evolution of H4 A new trend in the researches on parallel robotics is the development of lower mobility manipulators. Indeed a lot of applications do not need six DOFs. A classification proposed by Brogardh Brogardh 2002 gives the necessary number of DOF for different industrial applications. He shows that applications such as pick-and-place assembly cutting measurement etc. just need from three up to five DOFs. The parallel manipulator H4 can provide three translations and one rotation about a fixed axis which are also called Schonflies motions Hervé 1999 . SCARA robots were the first manipulators developed to produce these movements. Due their serial architecture these robots involve high moving masses which are not suitable for high dynamics. Parallel architecture can overcome this problem. Delta robot is first introduced by Clavel to execute Schonflies motions Clavel 1988 . This architecture is able to produce three translations and one rotational motion is obtained using a central telescopic leg built with universal and prismatic joints. This RUPUR chain suffers from a short service life and involves a bad stiffness of the rotation motion. Orthoglide Chablat 2002 is another parallel robot that can provide Schonflies motions using linear actuators. Its particularity is to be isotropic at the center of its workspace. The machine tool HITA STT has been proposed to produce Schonflies motions Thurneysen et al 2002 . The particularity of this architecture is to use additional parts in the traveling plate in order to amplify the rotational motion. Other Schonflies motion generators include Gross