860 research outputs found
The Effect of Internal Damping on Locomotion in Frictional Environments
The gaits of undulating animals arise from a complex interaction of their
central nervous system, muscle, connective tissue, bone, and environment. As a
simplifying assumption, many previous studies have often assumed that
sufficient internal force is available to produce observed kinematics, thus not
focusing on quantifying the interconnection between muscle effort, body shape,
and external reaction forces. This interplay, however, is critical to
locomotion performance in crawling animals, especially when accompanied by body
viscoelasticity. Moreover, in bio-inspired robotic applications, the body's
internal damping is indeed a parameter that the designer can tune. Still, the
effect of internal damping is not well understood. This study explores how
internal damping affects the locomotion performance of a crawler with a
continuous, visco-elastic, nonlinear beam model. Crawler muscle actuation is
modeled as a traveling wave of bending moment propagating posteriorly along the
body. Consistent with the friction properties of the scales of snakes and
limbless lizards, environmental forces are modeled using anisotropic Coulomb
friction. It is found that by varying the crawler body's internal damping, the
crawler's performance can be altered, and distinct gaits could be achieved,
including changing the net locomotion direction from forward to back. We will
discuss this forward and backward control and identify the optimal internal
damping for peak crawling speed
Legged locomotion over irregular terrains: State of the art of human and robot performance
Legged robotic technologies have moved out of the lab to operate in real environments, characterized by a wide variety of unpredictable irregularities and disturbances, all this in close proximity with humans. Demonstrating the ability of current robots to move robustly and reliably in these conditions is becoming essential to prove their safe operation. Here, we report an in-depth literature review aimed at verifying the existence of common or agreed protocols and metrics to test the performance of legged system in realistic environments. We primarily focused on three types of robotic technologies, i.e., hexapods, quadrupeds and bipeds. We also included a comprehensive overview on human locomotion studies, being it often considered the gold standard for performance, and one of the most important sources of bioinspiration for legged machines. We discovered that very few papers have rigorously studied robotic locomotion under irregular terrain conditions. On the contrary, numerous studies have addressed this problem on human gait, being nonetheless of highly heterogeneous nature in terms of experimental design. This lack of agreed methodology makes it challenging for the community to properly assess, compare and predict the performance of existing legged systems in real environments. On the one hand, this work provides a library of methods, metrics and experimental protocols, with a critical analysis on the limitations of the current approaches and future promising directions. On the other hand, it demonstrates the existence of an important lack of benchmarks in the literature, and the possibility of bridging different disciplines, e.g., the human and robotic, towards the definition of standardized procedure that will boost not only the scientific development of better bioinspired solutions, but also their market uptake
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