HYDRA: Humanoid Robot with New Hydraulic Actuation
The development of force-sensitive driving system has been the main open research field for over 30 years in robotics. Since Prof. Hiroshi Kaminaga joined and started his Ph.D study at YNL in 2006, study of hydrostatic transmission for force-sensitive actuators of robots has been a main research topics of YNL. The hydrostatic transmission is an old technology of 1909 US patent and has been used for many applications including flight control system of aircraft. Our point of idea is to reinvent the hydrostatic transmission based on the recent technologies of precision machining, materials, surface treatments and so on.
The top left is a hydraulic pump using trochoid gears powered by a blushless DC motor. Pressured oil generated by the pump goes to the hydraulic cylinder (the second left) and drives its piston. Likewise, the hydraulic system does not use a valve and the pressured oil is generated on demand by a motor assigned to the cylinder. This system is called Electro Hydrostatic Actuator (EHA). The pressure drop by a valve creates loss of energy and is the major reason of large friction of hydraulic systems. By removing a valve and its friction, EHA has a chance to be an ideal force-sensitive driving system. The third left is a vane motor for rotary motion used instead of a cylinder. The bottom left is a cluster actuators (five small cylinders) for a robot hand. The EHA actuators in the left are recent model designed by Prof. Kaminaga, Satoshi Otsuki, and Tianyi Kang based on the early studies of Hirokazu Tanaka and Kouhei Odanaka.
The top right are the robot hands driven by EHA, which were the subjects discussed and developed in the Ph.D dissertation of Prof. Kaminaga in 2009. The hand of the second right was developed by Yuto Shimoyama. The bottom right is a robot hand developed by Tianyi Kang for the humanoid robot, Hydra. The hand has four underactuated fingers and driven by five small EHAs. The third right is an underactuated five-fingered hand with higher degrees of freedom designed prototyped by Treratanakulwong Tanut before the Hydra hand.
Hydra, the large photo in the center, is a humanoid robot with 40 joints all actuated by EHA. Only the three types of EHA in the left are used. The Hydra project started in July 2014 and many members at YNL have contributed. Prof. Kaminaga, Ryo Masumura, Tianyi Kang, Mitsuo Komagata, Shunsuke Sato, and Satoshi Yorita worked on mechanism, structure and electronics including the detailed adjustments of all the actuators. The software for motion planning and teleoperation were developed by Stephane Caron and Yasuhiro Ishiguro. Masaki Hayashi and Taira Miyatake developed electronics for sensing system.
The Hydra project (2014.07-2016.02, NEDO) was a joint project with Chiba Institute of Technology, Osaka University and Kobe University. Kiyoshi Irie (Chiba Institute of Technology) developed the Laser scanning system and the software for geometry reconstruction from it. Prof. Tomomichi Sugihara (Osaka University) and his students developed the software for biped control and IMU sensing. Prof. Yasuyoshi Yokokohji (Kobe University) and his students developed the master arm for teleoperation and the software for network communication.
The goal of Hydra project was to develop a humanoid robot for disaster response. It was an important mile stone to participate in the final competition of the DARPA Robotics Challenge on June 5-6th, 2015. Unfortunately Hydra was not completed by the time of the final and is still under development at YNL.
Hydraulics is known for high-power and heavy-duty. The specification of Hydra is focused on precision of force control and not on high-power. Hydraulic systems are robust and heavy-duty, because the fluid power is distributed by the oil pressure and does not cause intensive stress due to mechanical contacts seen in gears. The design and selection of clearance, structure, surface treatment and oil seals for low friction have been the key factors. Hydra is named not only after “hydaulics” but also after “hydrogen” of the fuelcell system used in the power system.
Structure and mechanism of humanoid robots have been a long standing study at YNL. UT-theta and UT-theta2 are two adult-size humanoid robots developed in 2003 and 2004 by Prof. Masafumi Okada (Tokyo Institute of Technology), Shigeki Ban, Tatsuya Goto, Tetsuya Shinohara, Naoyuki Hihara, and Yusuke Yamamoto. Biped control of UT-theta was accomplished by Prof. Dirk Wollherr (Technical University of Munich) and Dr. Fabio Zonfrilli (Procter&Gamble). The focused issues of research on mechanism design were closed kinematic chains for joint drive systems, passive-elastic components in driving systems, and fabrication of structural components by magnesium-alloy casting. UT-mu:mighty and UT-mu2:magnum are two small size (60cm tall) humanoid robots. UT-mu:mighty was designed and developed by Prof. Tomomichi Sugihara (Osaka University) for his Ph.D dissertation in 2004. Prof. Ko Yamamoto (University of Tokyo) designed and developed in his Ph.D study a new humanoid robot, UT-mu2:magnum, which was exhibited at Aichi EXPO in 2005. Tatsuhito Aono developed in 2005 UT-mu3:guchida which had a skinny body allowing soft-exterior. The issues of research were on modular design of joint-drive mechanism, integration of electronics for sensing, motor-drive, and control, and experimental study of biped locomotion.