Muscle roles on directional change during hopping of a biomimetic feline hindlimb

Cats, from tiny domestic cats (Felix Catus) to big tigers (Panthera Tigris), are well known for their great acrobatic skills and hunting ability. Aiming to better understand how the feline family interacts with the environment, we adopt a biomimetic approach on a hopping feline hindlimb. Using air muscles to simulate the compliance of biological muscles, this robotic hindlimb has seven muscles and changes hopping direction. We individually evaluate and estimate muscles contribution to the jumping direction. Finally, we successfully control the hopping direction using a non-linear curve fitting from experimental results, hopefully contributing to the understanding of our biological counterpart.This work was partially supported by KAKENHI Kiban(S) 23220004This is the accepted manuscript. The final version's available at http://dx.doi.org/10.1109/ROBIO.2012.6491108

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

Development of a minimalistic pneumatic quadruped robot for fast locomotion

In this paper, we describe the development of the quadruped robot ”Ken” with the minimalistic and lightweight body design for achieving fast locomotion. We use McKibben pneumatic artificial muscles as actuators, providing high frequency and wide stride motion of limbs, also avoiding problems with overheating. We conducted a preliminary experiment, finding out that the robot can swing its limb over 7.5 Hz without amplitude reduction, nor heat problems. Moreover, the robot realized a several steps of bouncing gait by using simple CPG-based open loop controller, indicating that the robot can generate enough torque to kick the ground and limb contraction to avoid stumbling.This work was partially supported by KAKENHI 23220004, KAKENHI 24000012 and KAKENHI 23700233.This is the accepted manuscript. The final version is available at http://dx.doi.org/10.1109/ROBIO.2012.6490984

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

Barrier formation at metal/organic interfaces: dipole formation and the Charge Neutrality Level

The barrier formation for metal/organic semiconductor interfaces is analyzed within the Induced Density of Interface States (IDIS) model. Using weak chemisorption theory, we calculate the induced density of states in the organic energy gap and show that it is high enough to control the barrier formation. We calculate the Charge Neutrality Levels of several organic molecules (PTCDA, PTCBI and CBP) and the interface Fermi level for their contact with a Au(111) surface. We find an excellent agreement with the experimental evidence and conclude that the barrier formation is due to the charge transfer between the metal and the states induced in the organic energy gap.Comment: 7 pages, Proceedings of ICFSI-9, Madrid, Spain (September 2003), special issue of Applied Surface Science (in press

Growth, Yield and Mineral Composition of Three Rice Varieties Cultivated under Salt-Affected Conditions

A pot experiment was conducted to study the relative performance of IR 6,KS 282 and IR 10198-66-2 rice varieties cultivated under salt-affected conditions at EC of 6.0,9.0 12.0 dS m(-1) in a sandy clay loam soil havig ECe of 1.6 dS m(-1) treated as control. Six seedlings of 39-day old transplaned to each pot having 12 kg soil. The fertilizer as nitrophos and potassium sulphate at the rate of 57.0, 25.0 and 50.0 mg N,P and K kg(-1) soil respectively was applied at the time of transplanting while zinc sulphate at the rate of 5 mg Zn kg(-1) soil and 43.0 mg N kg(-1) of soil as additional dose were applied 19 and 30 days after transplanting respectively. Normal plant protection measures like number of tillers, panicles, paddy grains, filled and unifilled grains, yield per plant and sterility were recorded and shoot and straw samples were analysed for sodium, potassium, calcium and chloride contents. It was observed that growth and yield of all the varieties were reduced significantly with increasing soil salinity. Na/K and Na/Ca rations in shoot and straw increased significantly with increasing soil salinity. It was also observed that higher values of Na/K and Na/Ca rations in shoots affected growth parameters while higher values of these rations in straw affected yield components and grain yield. However, IR 6 having relatively lower values of Na/K and Na/Ca rations proved to be the most salt-tolerant rice among the three varieties studied