Robotic hands grasp and manipulate objects through the contact forces between the fingers and the objects. The determination of contact forces in grasping is discussed in this paper. To systematically investigate the ...Robotic hands grasp and manipulate objects through the contact forces between the fingers and the objects. The determination of contact forces in grasping is discussed in this paper. To systematically investigate the characteristics of different grasps, the vector space of contact forces is decomposed into four subspaces and their basis is found by an efficient computational method. The vector of contact forces is then formulated into four components: active and passive grasping forces, controllable and uncontrollable internal forces. The dimensions of the subspaces identify uncontrollable internal forces. The contact force is further expressed into an explicit function of the external wrench and the joint torques. The resulting formulation simplifies the computation in the optimization of contact forces and makes the optimal variables controllable. Two numerical cases are given to show the simplicity and validity of the method.展开更多
Malaysia is the biggest crude palm oil exporter to the world market for the last 16 years. However this achievement is still be overshadowed by the harvesting method which is conventional and labor intensive. An attem...Malaysia is the biggest crude palm oil exporter to the world market for the last 16 years. However this achievement is still be overshadowed by the harvesting method which is conventional and labor intensive. An attempt to use mechanization into the harvesting system, in particular the cutting process of tall palm trees, has been unsuccessful. At the beginning of the oil palm＇s fruit bearing fife, i.e. 3 to 4 years of age, fi＇uit bunches are still accessible. For these palms, a chisel is used to cut the fiuit bunches. Growth is such 8-10 years, and the trees have already reached substantial height. In these cases a sickle mountedon flexible telescopic aluminum tube （pole） is used. This, however, exposes plantation worker to the risk of musculoskeletal discomfort and injury. This paper examines the problems by assessing the task posture and tool, and their implications for operators, using questionnaire survey and videotape analysis techniques. The result prevails that there is evidence to associate the problems of musculoskeletal disorders among the operators.展开更多
基金National Natural Science Foundation of China(59985001)
文摘Robotic hands grasp and manipulate objects through the contact forces between the fingers and the objects. The determination of contact forces in grasping is discussed in this paper. To systematically investigate the characteristics of different grasps, the vector space of contact forces is decomposed into four subspaces and their basis is found by an efficient computational method. The vector of contact forces is then formulated into four components: active and passive grasping forces, controllable and uncontrollable internal forces. The dimensions of the subspaces identify uncontrollable internal forces. The contact force is further expressed into an explicit function of the external wrench and the joint torques. The resulting formulation simplifies the computation in the optimization of contact forces and makes the optimal variables controllable. Two numerical cases are given to show the simplicity and validity of the method.
文摘Malaysia is the biggest crude palm oil exporter to the world market for the last 16 years. However this achievement is still be overshadowed by the harvesting method which is conventional and labor intensive. An attempt to use mechanization into the harvesting system, in particular the cutting process of tall palm trees, has been unsuccessful. At the beginning of the oil palm＇s fruit bearing fife, i.e. 3 to 4 years of age, fi＇uit bunches are still accessible. For these palms, a chisel is used to cut the fiuit bunches. Growth is such 8-10 years, and the trees have already reached substantial height. In these cases a sickle mountedon flexible telescopic aluminum tube （pole） is used. This, however, exposes plantation worker to the risk of musculoskeletal discomfort and injury. This paper examines the problems by assessing the task posture and tool, and their implications for operators, using questionnaire survey and videotape analysis techniques. The result prevails that there is evidence to associate the problems of musculoskeletal disorders among the operators.
