Quadrupédie | EPFL Graph Search

vignette|droite La quadrupédie est un mode de par lequel un organisme se meut préférentiellement sur quatre membres. Le terme de quadrupède ou quadripède désigne les espèces d’animaux qui marchent à quatre pattes. De nombreux animaux ambulatoires sont des quadrupèdes (particulièrement chez les Mammifères), mais la plupart ne le sont pas : Arthropodes à six pattes ou plus, comme les mille-pattes, Oiseaux (bipèdes), Poissons ou Cétacés (nageurs), Chauve-souris, Serpents ou humains. Quelques exemples courants de quadrupèdes sont les chats, les chiens, les bovidés, les batraciens et une grande quantité de lézards. Le groupe de « quadrupèdes » (qui n'a pas de valeur au niveau de la classification phylogénétique) se rapporte donc couramment aux mammifères qui marchent avec leurs quatre membres (qu'ils soient plantigrades, digitigrades ou ongulés). Tous les animaux qui possèdent quatre membres ne sont pas des quadrupèdes : les tétrapodes regroupent tous les animaux qui ont deux paires de membres munis de doigts. De nombreux tétrapodes n'utilisent pas leurs quatre membres pour marcher. Les humains, les oiseaux, les marsouins sont tous des exemples de tétrapodes non quadrupèdes. Il est possible que les ancêtres de ces animaux aient autrefois utilisé tous leurs membres pour marcher. Quelques autres animaux avaient peut-être des ancêtres quadrupèdes, mais leurs pattes sont devenues des structures vestigiales – c’est-à-dire que leurs membres n'ont plus de fonction contrairement à ceux de leurs ancêtres. Leopard africa.jpg| [[Léopard]]. Thomsons-gazelle.jpg| [[Gazelle]]. Six weeks old cat (aka).jpg| [[Chat]]. 2012 Suedchinesischer Tiger.JPG| [[Tigre]]. Actuellement, il y a aussi une controverse au sujet de l’existence d’humains quadrupèdes. En , des scientifiques ont découvert que les membres d'une famille en Turquie, la famille Ulas, marchaient naturellement sur leurs pieds et leurs deux mains, un récit corroboré par les cals sur leurs mains.

Towards Agility: Definition, Benchmark and Design Considerations for Small, Quadrupedal Robots

Peter Eckert

Agile quadrupedal locomotion in animals and robots is yet to be fully understood, quantified or achieved. An intuitive notion of agility exists, but neither a concise definition nor a common benchmark can be found. Further, it is unclear, what minimal level of mechatronic complexity is needed for this particular aspect of locomotion. In this thesis we address and partially answer two primary questions: (Q1) What is agile legged locomotion (agility) and how can wemeasure it? (Q2) How can wemake agile legged locomotion with a robot a reality? To answer our first question, we define agility for robot and animal alike, building a common ground for this particular component of locomotion and introduce quantitative measures to enhance robot evaluation and comparison. The definition is based on and inspired by features of agility observed in nature, sports, and suggested in robotics related publications. Using the results of this observational and literature review, we build a novel and extendable benchmark of thirteen different tasks that implement our vision of quantitatively classifying agility. All scores are calculated from simple measures, such as time, distance, angles and characteristic geometric values for robot scaling. We normalize all unit-less scores to reach comparability between different systems. An initial implementation with available robots and real agility-dogs as baseline finalize our effort of answering the first question. Bio-inspired designs introducing and benefiting from morphological aspects present in nature allowed the generation of fast, robust and energy efficient locomotion. We use engineering tools and interdisciplinary knowledge transferred from biology to build low-cost robots able to achieve a certain level of agility and as a result of this addressing our second question. This iterative process led to a series of robots from Lynx over Cheetah-Cub-S, Cheetah-Cub-AL, and Oncilla to Serval, a compliant robot with actuated spine, high range of motion in all joints. Serval presents a high level of mobility at medium speeds. With many successfully implemented skills, using a basic kinematics-duplication from dogs (copying the foot-trajectories of real animals and replaying themotion on the robot using a mathematical interpretation), we found strengths to emphasize, weaknesses to correct and made Serval ready for future attempts to achieve even more agile locomotion. We calculated Servalâs agility scores with the result of it performing better than any of its predecessors. Our small, safe and low-cost robot is able to execute up to 6 agility tasks out of 13 with the potential to reachmore after extended development. Concluding, we like to mention that Serval is able to cope with step-downs, smooth, bumpy terrain and falling orthogonally to the ground.

EPFL2018

Spinal joint compliance and actuation in a simulated bounding quadruped robot

Auke Ijspeert, Alexander Spröwitz, Soha Pouya, Mohammad Khodabakhsh

Spine movements play an important role in quadrupedal locomotion, yet their potential benefits in locomotion of quadruped robots have not been systematically explored. In this work, we investigate the role of spinal joint actuation and compliance on the bounding performance of a simulated compliant quadruped robot. We designed and conducted extensive simulation experiments, to compare the benefits of different spine designs, and in particular, we compared the bounding performance when (i) using actuated versus passive spinal joint, (ii) changing the stiffness of the spinal joint and (iii) altering joint actuation profiles. We used a detailed rigid body dynamics modeling to capture the main dynamical features of the robot. We applied a set of analytic tools to evaluate the bounding gait characteristics including periodicity, stability, and cost of transport. A stochastic optimization method called particle swarm optimization was implemented to perform a global search over the parameter space, and extract a pool of diverse gait solutions. Our results show improvements in bounding speed for decreasing spine stiffness, both in the passive and the actuated case. The results also suggests that for the passive spine configuration at low stiffness values, periodic solutions are hard to realize. Overall, passive spine solutions were more energy efficient and self-stable than actuated ones, but they basically exist in limited regions of parameter space. Applying more complex joint control profiles reduced the dependency of the robot's speed to its chosen spine stiffness. In average, active spine control decreased energy efficiency and self-stability behavior, in comparison to a passive compliant spine setup.

Springer2017

Hardware, software and control design considerations towards low-cost compliant quadruped robots

Alexandre Tuleu

Quadrupedal robots have been a field of interest the last few years, with many new maturing platforms. Many of these projects have in common the use of state of the art actuation and sensing, and therefore are able to handle difficult locomotion tasks very effectively. This work focuses on another trend of low-cost, quadrupedal robots, that features less precise actuators and sensors, but overcomes their limitations with strong bio-inspired designs to achieve state of the art locomotion. We aim here to further extend the achievements of this approach to handle more complex tasks and that require anticipation, We would like also to verify to which extent a close synergy between clever mechanics, sensorimotor coordination, and Central Pattern Generator models is able to handle these tasks. This thesis presents supporting work that was required to pursue this goal. A software architecture for the development of real-time drivers and low-level control for robotic applications, based on a clear separation of concerns is presented. An implementation of this architecture able to handle the specific requirements for small compliant quadruped robots is proposed. Furthermore, the development and integration of a communication protocol for inter-electronic devices communication on the Oncilla robot is discussed. As leg load is a key quantity in some of the sensory-motor coordination this thesis want to explore, a novel tactile sensing approach for its estimation is proposed, based on an Extended Kalman Filter data fusion of static and dynamic tactile sensor information. Then, to support the design of efficient interactions between the control and the bio-inspired mechanics, accurate dynamic modeling of the Advanced Spring Loaded Pantographic leg, equipping all robots considered here, is presented. We propose two approaches to this modeling with the presentation of their benefits and limitations. Finally, two Central Pattern Generator architectures are proposed, based on biologically inspired foot trajectories. The first is using a well-known method for inter-limb coordination with strong neural coupling, and the second, the Tegotae rule, relies only on limb physical coupling and strong sensory-motor coordination. These two approaches are compared on their capacity to handle dynamic footstep placement and it let to the conclusion that strong sensory-motor coordination is required for this task.

EPFL2016