On developing lightweight robot-arm of anthropomorphic characteristics

Human arm is one of the most sophisticated biological limbs known in a wildlife, capable to accomplish the most different and delicate sensory-motor tasks such as for example, lifting and carrying of payload, precise manipulation, symbolic gesticulation up to a fine sensitivity and tactile perception, pressure feeling, texture, temperature, moisture, fluid stream sensing, etc. A human arm with hand has an exceptional dexterity and physical capabilities (weight carrying, doing impact, pulsation, etc.) by virtue of its own naturally adjusted structure of the muscular-skeletal system, sensitive perceptive system and fast and reactive nervous system whose peripheral terminations reach up the every segment of the limb. By virtue of such a sophisticated structure, the arm enables humans accomplishing the most complex and delicate manipulative tasks that require high speed and precision, perceptive capabilities, but also natural robustness and durability of operation even under load. Due to the fore mentioned reasons the robots have incurred at the beginning just as an imitation of human arm/hand (e.g. Programmable industrial manipulators) but afterwards by introducing full automatization and adding artificial intelligence within controllers, it became a smart bionic device that find its’ implementation more and more in the service and medical robotics, rehabilitation and therapy, building prosthetics of new generation, etc. Contemporary service robots use today the lightweight robot-arms due to intention to make robot arm/hand as similar as possible to the human limb by its structure and functionality, in sense of decreasing the weight of the arm, increasing the payload up to the human physical capabilities, achieving desired compliance of joints (soft joints), decreasing energy consumptions for operation, etc. Industrial lightweight robot arms rely to the contemporary technological, miniature powerful actuators, miniature embedded electronics, new light and durable composite materials, harmonic-drives, integrated mechanics and electronics, etc. In spite of that, the overall mass of the lightweight robots is still higher than a human limb and also the payload fraction (coefficient that quantifies robot weight and payload ratio) overcome those that is with human arm. Due to these facts the energy consumptions are still high because of actuator imperfection in spite of the high progress of technology. From another side, in spite of advancement in micro-sensors technology still it did not find solution for replacement of human skin and perceptive system with artificial ones. There are some attempts of developing artificial skin, but still not satisfactory to replace natural one. Bearing in mind the fore mentioned, this paper represents an attempt to make a next step towards a new concept of design lightweight robot arms of anthropomorphic characteristics.