Most research papers about parallel kinematic chainmechanisms investigate symmetric robot manipulators, in which all the limbs connecting the end-effector to the fixed based are composed by the same sequence of links ...Most research papers about parallel kinematic chainmechanisms investigate symmetric robot manipulators, in which all the limbs connecting the end-effector to the fixed based are composed by the same sequence of links and joints. Contrarily, in some manipulation tasks the velocity and stiffness requirements are anisotropic. In such cases, the asymmetric parallel kinematic chain mechanisms may offer advantages. This work objective is to present the synthesis, dynamic modeling and analysis of a 3-dof asymmetric parallel chain mechanism, conceived as a robot manipulator for pick-and-place operations. Firs＇t, a structural synthesis, resulting in a three translations end-effector, and a kinematic modeling are carried out. Then, the inverse dynamic modeling is developed by employing the virtual work principle. Based on the model equations and on the saturation of the mechanism actuators, a maximum acceleration analysis is performed and shows that although the mechanism has a parallel architecture its actuators influences on the 3-dof are quite decoupled.展开更多
In this paper, the author examines the possibilities of leisure （studies） in Mozambique. First, the author suggests that leisure can he looked at as a social construct which resulted from the colonial regulation of ...In this paper, the author examines the possibilities of leisure （studies） in Mozambique. First, the author suggests that leisure can he looked at as a social construct which resulted from the colonial regulation of native labour, particularly between 1890s and 1974. Secondly, the author proposes that people look at the conditions of possibility of leisure in a context dominated by the new moral code of conduct, a cathartic purification of the colonial mentality, introduced through the ideology of the ＂New Man＂ created by the ruling party, Frelimo. Thirdly, the author examines the possibility of leisure in the context of Mozambique＇s adherence to neo-liberalism and market-driven economy after the collapse of socialism. The author concludes by providing the ground to establish lines of inquiry for an eventual field of leisure studies.展开更多
文摘Most research papers about parallel kinematic chainmechanisms investigate symmetric robot manipulators, in which all the limbs connecting the end-effector to the fixed based are composed by the same sequence of links and joints. Contrarily, in some manipulation tasks the velocity and stiffness requirements are anisotropic. In such cases, the asymmetric parallel kinematic chain mechanisms may offer advantages. This work objective is to present the synthesis, dynamic modeling and analysis of a 3-dof asymmetric parallel chain mechanism, conceived as a robot manipulator for pick-and-place operations. Firs＇t, a structural synthesis, resulting in a three translations end-effector, and a kinematic modeling are carried out. Then, the inverse dynamic modeling is developed by employing the virtual work principle. Based on the model equations and on the saturation of the mechanism actuators, a maximum acceleration analysis is performed and shows that although the mechanism has a parallel architecture its actuators influences on the 3-dof are quite decoupled.
文摘In this paper, the author examines the possibilities of leisure （studies） in Mozambique. First, the author suggests that leisure can he looked at as a social construct which resulted from the colonial regulation of native labour, particularly between 1890s and 1974. Secondly, the author proposes that people look at the conditions of possibility of leisure in a context dominated by the new moral code of conduct, a cathartic purification of the colonial mentality, introduced through the ideology of the ＂New Man＂ created by the ruling party, Frelimo. Thirdly, the author examines the possibility of leisure in the context of Mozambique＇s adherence to neo-liberalism and market-driven economy after the collapse of socialism. The author concludes by providing the ground to establish lines of inquiry for an eventual field of leisure studies.
