Pneupard: A biomimetic musculoskeletal approach for a feline-inspired quadruped robot

Feline locomotion combines great acrobatic proficiency, unparalleled balance and higher accelerations than other animals. Capable of accelerating from 0 to 100 km h−1 in three seconds, the cheetah (Acinonyx jubatus) is still a mystery which intrigues scientists. Aiming for a better understanding of the source of such higher speeds, we develop a biomimetic platform, where musculoskeletal parameters (range of motion and moment arms) from the biological system can be evaluated with air muscles within a lightweight robotic structure. We performed experiments validating the muscular structure during a treadmill walk, successfully reproducing animal locomotion while adopting an EMG based control method.This work was partially supported by KAKENHI Kiban(S) 23220004.This is the accepted manuscript. The final version is available at http://dx.doi.org/10.1109/IROS.2013.6696540

Producing alternating gait on uncoupled feline hindlimbs: Muscular unloading rule on a biomimetic robot

Studies on decerebrate walking cats have shown that phase transition is strongly related to muscular sensory signals at limbs. To further investigate the role of such signals terminating the stance phase, we developed a biomimetic feline platform. Adopting link lengths and moment arms from an Acinonyx jubatus, we built a pair of hindlimbs connected to a hindquarter and attached it to a sliding strut, simulating solid forelimbs. Artificial pneumatic muscles simulate biological muscles through a control method based on EMG signals from walking cats (Felis catus). Using the bio-inspired muscular unloading rule, where a decreasing ground reaction force triggers phase transition, stable walking on a treadmill was achieved. Finally, an alternating gait is possible using the unloading rule, withstanding disturbances and systematic muscular changes, not only contributing to our understanding on how cats may walk, but also helping develop better legged robots.The authors acknouledge the Japanese Research Grant KAKENHI Kiban 23220004 and 25540117.This is the author accepted manuscript. The final version is available from Taylor & Francis via http://dx.doi.org/10.1080/01691864.2013.87049

Exploring muscular contribution during stepping of biomimetic feline hindlimbs

Although robotic locomotion have greatly advanced over the past years, the abyss that separates such locomotion from even the simplest animal locomotions prompt us to approach robotic locomotion taking cues from animals. The animal musculoskeletal structure, often ignored by roboticists due to its high redundancy and complexity, might hold the secret for self-stable locomotion observed in bipeds and quadrupeds. Aiming to better understand how muscles contribute to selfstable locomotion we take the feline structure as a model on a biomimetic approach. Using 6 air muscles per hindlimb to mimic real muscles, this robot walks stably on a treadmill while supported by a slider, simulating forelimbs. We individually evaluate muscle contribution to walking stability, performing a comparison between mono and biarticular synergistic muscles at the ankle and concluding that a higher compliance on the biarticular muscle improved walking stability. A better understanding of such complex phenomena may help on the development of better legged robots in the future, truly taking advantage of concepts developed by nature over the years.This work was partially supported by KAKENHI Kiban(S) 23220004.This is the accepted manuscript. The final version is available at http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6739573&tag=1

Stable reflex-based walking of forelimbs of a bio-inspired quadruped robot-modeled cheetah

In contrast to the high movement adaptability of quadruped animals in many environmental conditions, it is hard for conventional quadruped robots to operate in complex environment conditions. We investigate the adaptability of animals’ musculo-skeletal systems, by building a bio-inspired quadruped robot named ”Pneupard” which duplicates a feline musculo-skeletal system. In this study, we built Pneupard’s forelimb which has 14 active muscles, 4 passive muscles and 8 degrees of freedom (DOF). We propose sole reflex-based control and verify its effectiveness by conducting walking experiments, in which the robot performed stable walking with a two-dimensional restriction.This work was partially supported by a Grant-in-Aid for Scientific Research(23220004) from the Japanese Ministry of Education, Culture, Sports, Science and Technology.This is the accepted manuscript. The final version is available at http://dx.doi.org/10.1109/ROBIO.2013.673973

Electronic structure and molecular orientation of a Zn-tetra-phenyl porphyrin multilayer on Si(111)

The electronic properties and the molecular orientation of Zn-tetraphenyl-porphyrin films deposited on Si(111) have been investigated using synchrotron radiation. For the first time we have revealed and assigned the fine structures in the electronic spectra related to the HOMOs and LUMOs states. This is particularly important in order to understand the orbital interactions, the bond formation and the evolution of the electronic properties with oxidation or reduction of the porphyrins in supramolecular donor-acceptor complexes used in photovoltaic devices.Comment: text 11 pages, 4 figures submitted for publicatio