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Currently, robotics is one of the fields undergoing great scientific innovation and expansion. Automation, via robotic applications, in production industries has grown increasingly. In particular, multifunctional manipulators executing several industrial assembly tasks, i.e. large, fixed-base industrial robots executing “pick-and-place” tasks, with control strategies focused on precision end-effect positioning. Additionally, high precision robotic applications in the framework of medical (surgical) and microchips production are needed especially regarding high precision position control. Electrical motors combined with adapted reduction elements envelop the most commonly used actuator technology at the moment. The developed control algorithms are specifically optimized for position control, possibly in combination with force control. New developments in the area of robotics, however, have currently allowed for the development of multi-legged mobile robots and service robots oriented towards closer human/robot interaction. Especially in Japan, where a large number of corporations each work on a private humanoid robot, strong developments steer towards new applications in social service, domotics, rehabilitation and prosthesis. Important is that these domains require distinct features from the robotic system, such as special dynamical properties for reasons of chock absorption, energy consumption, and flexible and safe human/robot interaction. Present robots mainly are actuated with electrical drives, with the required reduction units, since this technology is well known. However, the use of these reduction units renders the joint to be more rigid, encompassing several disadvantages vis-a-vis applications of human/robot interactions. In this manner, the structure of the reduction elements is heavily burdened through jolting of highly reflected inertia values. Furthermore, this manner of actuation leaves small room for “soft” robot/human interaction and complicates the exploitation of the system’s natural dynamics. The latter encompasses generating robot movements closely associated to the natural, passive movement of the system. However, this requires compliant joints of which ideally stiffness can be manipulated. In a similar way, humans set up their joint stiffness, through relaxation of the muscles, according to the action or task performed. One of the positive consequences of movement within the natural dynamics |
