The field of robotics and mechatronics can benefit greatly from the development of its peripheral elements. At the time when the author began studies on legged locomotion robots in 1984, many researchers in the fields of mechanical engineering, control engineering, and electrical engineering became interested in this subject, and it was becoming possible to carry out not only the theoretical discussions on the basis of simulations but also the experimental discussions using actual machines. This is because, at that time, computers were rapidly increasing their performance and were becoming relatively inexpensive so that they were being introduced into work even at research laboratories of universities. Needless to say, without such development of computer technology, the advances not only in the legged locomotion robots but also in a number of mechatronic devices would have been hampered. For us who have gotten hold of high-performance computers, one of the present overriding issues is an appearance of new high-performance actuators. Almost every legged locomotion robot uses either an electric motor or a hydraulic actuator. However, its energy sources are placed outside the robot, and these actuators themselves have not really been miniaturized to any remarkable extent up to now. Computer control is indispensable for mechatronic devices that are equipped with actuators. At present, various control theories are being proposed in an effort to raise control performance by compensating restrictions on hardware (such as power-weight ratio, responsiveness, nonlinearity, etc.) as many as possible. It is necessary to continue such control-theoretic discussions in the future as well. On the other hand, however, rapid progress in hardware involving actuators and sensors may have a possibility of raising such performance drastically all at once. In the future, it is hoped that researchers are not well versed in the robotics or mechatronics may participate to develop the actuators based on new principles. The fact that an electro-rheological fluid may be used as actuators is attracting attention, for example. In actually developing devices incorporating with the electro-rheological fluid, various experimental data must be fed back skillfully to the chemists as developers of the fluids. In other words, the cooperation of both sides is extremely important. The author feels through his own studies the importance of developing high-performance actuators. In addition, since the debugging (improvement) of hardware (actuators) takes a longer time than the debugging of software, a patient and steady R&D is considered necessary. In this special issue, Prof. Takamori (Kobe University) was requested to provide a general overview as an expert engaged in studies of the actuators over a long period of time; he presented an explanation on what are new, hopeful actuators and also on the latest achievements that are considered promising in the future, now that the 21st century is so close. Other researchers were kind enough to introduce their very creative and advanced studies as well.
Numerical algorithms for high-performance computational science