Vol.4 No.2 2011
Research paper : Toward the use of humanoid robots as assemblies of content technologies (S. Nakaoka et al.)−89−Synthesiology - English edition Vol.4 No.2 (2011) as the future prospects will be explained.3 Robot hardware3.1 Issues of the form and appearance of the robotWhile many conventional humanoids claimed to have “human form”, most of them could be identified as robots from their form and appearance. While these were effective in the contents that intentionally featured the “robot-like form and appearance”, such contents were for minor audiences. If a robot has the form and appearance like humans and possessed expressive ability like humans, it can be used in many categories of contents.Considering the above points, we set the following two conditions as the issues for robot hardware. The robot:(1) must be life-sized and capable of stable bipedal motion, and(2) must have an appearance similar to humans throughout its entire body.Advanced technology is necessary to fulfill the condition (1), and many humanoids do not fulfill this condition. Some of the examples are humanoids supported by stands and wheels, those connected by cables to external devices, and those that are small in size. While these robots may not possess expressive abilities similar to humans in terms of the whole body action and scale, many robots that fulfill the condition (1) have recently been developed by robotics institutions-. However, the appearances of these robots are very “robot-like”, and do not fulfill the condition (2). We present examples of the conventional bipedal humanoid that our research group had developed in Fig. 2. Albert HUBO, a bipedal humanoid with a realistic head, was developed, but this had the conventional robot-like appearance except for the head. On the other hand, looking only at condition (2), robots that are so close to humans in appearance, so much so that one may not be able to make the distinction, have been developed. However, only the upper body moved in such robots and they do not fulfill the condition (1). Therefore, this issue could be cleared if the two technologies were integrated in one robot.The reason why the robot that fulfills the condition (1) has a robot-like appearance is not only because it was designed so intentionally, but also it is due to the mechanical limitations of size and form of the torso, appendages, and joints. In the conventional robots that fulfill the condition (2), the controller and the power source that drove the multiple joints at high speed to ensure human-like appearance were placed externally to the robot body. To fulfill the two conditions simultaneously by incorporating the mechanism for autonomous bipedal motion in a slender human body to give them a human-like appearance is a difficult technological issue.The mechanical dolls, as exemplified by the “Audio-Animatronics” of Disneyland, may be called humanoids used in the context of content technology. However, these do not fulfill the condition (1) as they are limited to specific motions and are set in specific places, and do not have the general-use capacity that allow them to be used outside of their original settings. Therefore, they are different from the “content technology” that we have in mind.3.2 Development of cybernetic human HRP-4CWe set out to solve these issues, and succeeded in the development of cybernetic humanNote 1) HRP-4C as shown in Fig.3. As seen in Fig. 3, HRP-4C is a life-size (height 158 cm) humanoid with an appearance similar to a human being throughout the body. Moreover, HRP-4C has all the mechanisms necessary for motions contained within its body, and is an autonomous robot with bipedal motion. The size and form of the body is close to the average young Japanese woman. It has a slender body compared to a conventional bipedal humanoid. Its total weight is 47 kgNote 2).There is an 8 degrees-of-freedom (DOF) in the head, 3 in the neck, 6 in each arm, 2 in each hand, 3 in the waist, and 7 in each leg. The total joint freedom is 44 ways. The 8 DOF in the head allows changes in the facial expression, movement of the line of sight, and movement of the mouth when speaking. The 3 DOF in the waist allows its smooth movement. In terms of movement, these allow expressive ability close to humans compared to the conventional robots.As mentioned earlier, the creation of such hardware was a technologically difficult issue. For the development of HRP-4C, a small distributed motor driver combined with a distributed control system, and newly developed ankle joint driving mechanisms were introduced to the design technology nurtured in the development of HRP-2 and HRP-3. The actuator and battery were downsized to enable the design with reduced weight capacity. As a result of the integrated effort, we solved the issues and Fig. 2 Conventional biped humanoid robotsFrom left, HRP-2, HRP-3P, and HRP-3.