Tham khảo tài liệu 'parallel manipulators towards new applications part 17', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Mobility of Spatial Parallel Manipulators 473 _ _ _ 1 X .17 .2 A T T T m X m xớcosớ - J ml lớ v p 2v 7 21 The potential energy of the system is V mglcosd Therefore the Lagrange function of the system is 22 1 1 2 L - M- m x w xớcosớ yl J ml 0 -mglcosd 23 where L indicates the Lagrange function. The dynamics equations for the two-degrees-of-freedom system shown in Fig. 2 can be expressed as dt d_ dt 0L ÕL - - F ÕX X Í A ÕL ÕL T Õ0 24 where T represents the torque exerted to the revolute joint that connect the inverse pendulum and the vehicle. l parallel manipulator this chapter develops a general process to synthesize the manipulators with the specified mobility. The outstanding characteristics of the synthesis method are that the whole process is also analytical and each step can be programmed at a computer. Because of the restrictions of the traditional general mobility formulas for spatial mechanisms a lot of mechanisms having special manoeuvrability might not be synthesized. However any mechanism can be synthesized with this analytical theory of degrees of freedom for spatial mechanisms. 2. The valid means to investigate the mobility of a mechanism The quick calculation approaches based on the algebra summations of the number of the links joints and the constraints induced by the joints can not be completely perfected by itself. This is true even the analytical methods are applied in seeking the common constraints Hunt 1978 Waldron 1966 Huang 2006 . These problems are becoming more and more obvious with the advent of spatial parallel manipulators. The primary considerations of the designers for the parallel manipulators have been focused on nothing but the mobility of the end-effector and its controllability. Therefore the concept of general mobility of a mechanism should be divided into two basic concepts the degree of freedom of the end-effector and the number of actuations needed to control the end-effector. With this regard this chapter first introduces two .