A proposal of a new rotational-compliant joint with oil-hydraulic M cKibben
artificial muscles
Ryusuke Morita, H iroyuki N abae, G en Endo and K oichi S uzumori
Department of Mechanical Engineering, Tokyo Institute of Technology, Tokyo, J apan
ABSTRACT
Conventional h ydraulic actuators can generate a s trong force due to high pressure. H owever, most of them are h eavy and h ard b ecause they are m ade o f m etal. It is d ifficult to use s uch actuators in robots r equired t o b e as light as possible. Moreover, t he joint m echanisms o f t hese actuators h ave p r o b l e m s wi t h int r i n s i c s a f e t y a n d r o b u s t n e s s b e c a u s e t h e co m p l i a n c e is ac q u i r e d u s i n g d e l i c a t e sensors and advanced controls. Therefore, we propose a new r otational-compliant mechanism t hat allows the coexistence of strong force and compliance. The p roposed mechanism h as compliance in an active rotational d irection and in t wo directions orthogonal t o it. To realize t his m echanism, we have developed a Hydraulic Artificial Muscle ( HAM), which is very lightweight and able t o g enerate strong force. Furthermore, the H AM has compliance without any advanced control. By exploiting the characteristics of the H AM, t he function of the p roposed mechanism can be realized even in conditions of compact dimensions. In t his p aper, b y constructing a simple experimental s ystem that imitates the p roposed mechanism, and b y modeling it, we verify its compliance f rom both a theoretical and an experimental point of view. W e d emonstrate that the m echanism has compliance in the t hree rotational d irections.
KEYWORDS
H y d r a u l i c a r t i fi c i a l m u s c l e ; hydraulic a ctuator; a n t a g o n i s t i c d r i v e ; r o t a t i o n a l c o m p l i a n t m e c h a n i s m ; t o u g h ro b o t i c s
A small three-way valve using particle excitation with piezoelectric transducers
for hydraulic actuators
Hayato Osakia, Takefumi Kandaa, Shoki Ofujia, Norihisa Senoa, Koichi Suzumorib, Takahiro Ukidab and
Hiroyuki Nabaeb
aGraduate school of national science and technology, okayama University, okayama, Japan; btokyo institute of technology, tokyo, Japan
ABSTRACT
Robots composed of hydraulic actuators have been utilized in various filds and at disaster sites. However, the hydraulic control system for multiple-degree-of-freedom mechanisms is large because such systems require many control components. The purpose of this research was to develop a small hydraulic flw control valve. This paper describes the fabrication and evaluation of a small
three-way valve by particle excitation using a piezoelectric transducer. This valve consists of two transducers and can switch the inlet and outlet ports by applying an AC voltage of diffrent driving frequencies to each transducer because each transducer has diffrent resonant frequencies. The flw rate was controlled by applying a voltage to the piezoelectric transducer. We evaluated the
vibration characteristics of the fabricated three-way valve. The vibration velocity exhibited peaks at 120 and 155 kHz for the inlet and outlet port, respectively, and that of each transducer increased with the applied voltage. Therefore, this three-way valve can switch the opening port by changing the driving frequencies and continuously controlling the flw rate. As a result, we have succeeded in driving the novel small three-way valve.
KEYWORDS
Flow rate control; hydraulic actuators; particle excitation; piezoelectric transducer; three-way valve
Design, development, and control of a tough electrohydraulic hexapod robot for
subsea operations
I. Davliakosa, I. Roditisb, K. Likaa, Ch.-M. Brekib and E. Papadopoulosa
aschool of Mechanical engineering, national technical University of Athens, Athens, Greece; binnora sA, Koropi, Greece
ABSTRACT
In this paper, the design, the development, and the control for an 18 degree-of-freedom electrohydraulic hexapod robot for subsea operations are presented. The hexapod, called HexaTerra, can be equipped with a trenching machine, and move over obstacles and on sloped terrain. Optimization techniques are employed to size the robot legs. Rigid body equations of motion and hydraulic dynamics are developed. Compact electrohydraulic components are sized and selected taking into account the leg kinematics and system dynamic analysis. A model-based control system design is implemented in a real-time environment, able to produce the overall functionality and performance. Experimental results obtained from preliminary tests with the developed electrohydraulic hexapod show good controlled performance and demonstrate excellent system stability over obstacles.
KEYWORDS
Hexapod robot; electrohydraulic mobile robot; underwater hydraulics; model-based hydraulic control; hexapod stability and control
Super-low friction and lightweight hydraulic cylinder u sing multi-directional
forging magnesium alloy and its application to r obotic leg
Hiroyuki N abae, Morizo Hemmi, Y oshiharu Hirota, Tohru Ide, Koichi Suzumori and G en Endo
Department of Mechanical Engineering, Tokyo Institute of Technology, Tokyo, J apan
ABSTRACT
O n e o f t h e m o s t im p o r t a n t m i s s i o n s f o r r o b o t s is t o o p e r a t e i n s e v e r e e n v i r o n m e n t s , a n d these s ituations require robots t o h ave ‘toughness’ which can overcome large s hocks, d egraded communication quality, unexpected condition, and o ther critical accidents. Although there are many k i n d s o f a p p r o a c h e s t o r e a l i z e t o u g h r o b o t i c s y s t e m s , d e v e l o p i n g a t o u g h a c t u a t o r s is o n e o f t h e key technologies for them. W e focus on hydraulic actuators and attempt to develop a tough robotic actuator with greater t oughness than the electromagnetic actuators used in conventional robotic s y s t e m s . I n g e n e r a l , h y d r a u l i c a c t u a t o r s h a v e e n o u g h t o u g h n e s s f o r s e v e r e e n v i r o n m e n t s , b u t t h e i r c o n t r o l l a b i l i t y an d l i g h t n e s s a r e in s uffi c i e n t f o r r o b o t s y s t e m s . H e r e i n , we p r o p o s e n o v e l h y d r a u l i c actuators that r ealizes lightweight with a multidirectional-forging magnesium alloy and have high controllability b y low friction pistons. Prototypes were d eveloped t o examine the fundamental characteristics o f t he actuators and compare the t wo approaches for the low-friction p istons: one i s b a s e d o n a p a c k i n g m e c h a n i s m u s i n g an e l a s t i c r e s t o r i n g p r e s s u r e , an d t h e o t h e r u t i l i z e s a flui d bearing technology. A fter basic experiments, t he prototype was applied to a robotic leg to verify
their potential in actual robotic systems. The r obotic leg successfully jumped 260 mm in height with 21 MPa.
KEYWORDS
H y d r a u l i c ; a c t u a t o r ; c y l i n d e r ; t o u g h ro b o t ; robotic l eg
Trends in hydraulic actuators and components in legged and tough robots: a
review
Koichi Suzumoria and Ahmad Athif Faudzia,b,c
aschool of engineering, tokyo institute oftechnology, tokyo, Japan; bcentre for Artifiial intelligence and Robotics, Universiti teknologi Malaysia, Johor bahru, Malaysia; cFaculty of electrical engineering, Universiti teknologi Malaysia, Johor bahru, Malaysia
ABSTRACT
Hydraulics is an old technology which is being applied in many applications including large machinery, heavy industries, and early robotics. The traditional features of hydraulics that possess a high power to weight ratio compared to other power transmission system make it suitable to work in a tough and robust environment. However, the trend of hydraulic system has decreased since the introduction and mass usage of the powerful brushless motor and rare earth magnetic motor in industrial sector since the 1980s. Recently, hydraulic systems have shown incremental demand where the innovation of hydraulic actuators and components was actively conducted aimed at compactness, lightweight with higher energy-effiency, clean and friendly features for many applications in both mobile and industrial hydraulics. This review shows the hydraulic trends in tough robotics applications which focus on legged robots such as humanoid, search and rescue robot and large machinery. New innovations of hydraulic components such as actuators, pump, and other accessories and trends are discussed for future hydraulics in tough robotics applications.
KEYWORDS
Hydraulic components; tough robots; trends in future hydraulics
