پیشرفت فناوری اگزواسکلتون انسانی و بحث هایی در مورد تحقیقات آینده Proceeding of Human Exoskeleton Technology and Discussions on Future Research

۱ Introduction The human exoskeleton is a kind of electromechanic system originally coming from comic stories. It can give human an extra strength to resist fatigue or to take more weight, to run faster or to jump higher. These kind facilities are drawn to be a lightweight armor worn by human, and its power system will output energy instantly whenever any muscles need some assistance to perform hard works than usual. Conceivably, the achievement of exoskeletons will be actively involved in life, especially for peoples disabled or wounded, and it might be evolved to be sport or amusement tools with great commercial value. Inspired by this promising outlook, studies of the fantastic wearable equipment have been going on for more than fifty years. Among the most enthusiastic are defense departments, who were willing to invest millions to such development. The more a soldier could carry, the more combat ability he had. According to the US military standard, a soldier is allowed to carry up to 30% of his overall weight when marching, and this limit is set to 245 N for PLA[1]. However, thanks to modern powerful firearms and equipment, soldiers’ loads tend to significantly exceed these limits. This is particularly true in the case of Special Forces, who usually carry out tasks in difficult situations with little logistic support. In the late 1960s, the General Electric Research developed and tested a body amplifier prototype based on master-slave system, called “Hardiman”[۲–۳]. It was a huge hydraulically driven system (weighting more than 5900N), and was only able to raise one arm. This system remained incomplete at the time of its termination. Several research projects were conducted by Prof. Vukobratovic in Serbia in around 1970s[4–۵], and similar works were done at MIT beginning from around 1980s[6]. However, few studies were done during the next 20 years because of fundamental technological insufficiencies, especially in control hardware. At the end of the 20th century, with the rapid progress in computer science, as well as control and drive technologies, DARPA believed that the technological basis was already sufficient to restart the exoskeleton project. They launched a 7-year project called EHPA[7], with a total investment of 50 million dollars, and expected it to enter service within the next decade. Since then, the research of exoskeleton has seen a major revival. Besides the U.S. army, many other colleges and institutes in Japan, Russia, the U.K., German, Korea and Singapore also started their own projects. Hundreds of exciting results were published during the first several years of 21st century, which fostered a general optimism that the “Iron Man” would soon be seen walking the streets. However, development of the exoskeleton was bogged down and few achievements were reported during the following years. Several reviews in 2008 and 2009 introduced latest progress [8–۱۰], and discussed directions of future developments in an optimistic tone still. However, the technological difficulties were far greater than expected: many engineering problems previously regarded as nonessential turned out to be major challenges. So what exactly is exoskeleton? Why are there always some “small” problems keeping it from being practical relevant? It is time to look back and critically reconsider the researching routes that have led to this predicament. The concept of exoskeleton and the range of its research should be redefined to adapt accurately to the current human science and technology level. This article maps the developing history of exoskeletons, both active and passive, focusing on several most important achievements. Some key difficulties in control algorithm, driver system, power source, and man-machine interface, which, from the very beginning, have prevented researchers from creating the perfect exoskeleton, have been summarized and discussed. At the end of the article, a critical assessment of the traditional robotics-oriented researching methods and contemplations about possible future directions of research are presented. ۲ Researches on Exoskeleton At present, research directions of exoskeletons can be divided into two categories: active and passive, based on the criterion whether the system has a portable power supply or not. This section introduces developments in both categories.