Hydraulics is a traditional technology with a long history of contribution to heavy plants and large power machines. In addition to the traditional features of hydraulics, new hydraulic components are recently being developed for robots, which aim for compactness, low weight, high energy-efficiency, multi-DOF drives, dexterity, smartness, silence, cleanliness, etc. All these advancements have great potential to be expanded for a new discipline of ‘tough robotics’.
‘Toughness’ is a keyword for recent robots working practically in real fields such as hazardous outdoor environments and unknown disaster scenes. While ‘toughness of a robot’ includes various aspects, this special issue focuses on mechanical and functional ‘toughness’ of hydraulic robots, which are difficult to be realized by conventional robots driven by electric motors and gears. This includes: (1) high power with a light and compact body, (2) strength and durability for heavy loads, impacts, and vibration, (3) shock and vibration absorption, (4) stationary positioning with no energy consumption, and (5) resistance for applications in special environments, e.g. radiation-hardened, waterproof, fire-safe.
This volume includes one survey paper and four full papers. We wish to share the state of art on new hydraulics components for tough robotics through these papers.
The survey paper by K. Suzumori et al. shows the hydraulic trends in tough robotics applications which focus on legged robots. Additionally, new innovations of hydraulic components such as actuators, pumps, and other accessories and trends are discussed for future hydraulics in tough robotics applications.
The first full paper by I. Davliakos et al. describes the development and the control for an eighteen degree-of-freedom electrohydraulic hexapod robot for subsea operations. The developed electrohydraulic hexapod can be equipped with a trenching machine and move over obstacles and on sloped terrain.
The second full paper by H. Osaki et al. proposes small hydraulic flow control valve. A small three-way valve by particle excitation using a piezoelectric transducer has been developed. This valve consists of two transducers and can switch the inlet and outlet ports by applying an AC voltage of different driving frequencies to each transducer.
The third full paper by R. Morita et al. proposes a new rotational compliant mechanism that allows the coexistence of strong force and compliance. The proposed mechanism has compliance in an active rotational direction and in two directions orthogonal to the direction. For this mechanism, a novel hydraulic artificial muscle has been developed.
The last paper by H. Nabae et al. proposes novel hydraulic actuators that realize lightweight with a multidirectional forging magnesium alloy and have high controllability by low friction pistons.
Prototypes were developed to examine the fundamental characteristics of the actuators.
The guest editors would like to thank all the authors who submitted to this special issue. The editors also thank all the reviewers and the editorial office of Advanced Robotics.
Tokyo Institute of Technology, Japan Sang-Ho Hyon
Ritsumeikan University, Japan Claudio Semini
Istituto Italiano di Tecnologia, Italy Jouni Mattila
Tampere University of Technology, Finland Takefumi Kanda
Okayama University, Japan