3D Avian bipedal locomotion in even and unpredictable environments: an integrative study of locomotion control, body and leg proportions
Automation, Mechatronics, Control Systems, Intelligent Technical Systems, Robotics
Final Report Abstract
We primarily think of birds in terms of a flight animal, but many of them are skilled terrestrial bipeds with a 230-millon-year bipedal legacy inherited from dinosaurs. Among birds, there is a considerable variation in hindlimb morphology. Birds display, in addition, a great diversity of gaits like walking, grounded running (a running gait without aerial phases), aerial running, mixed gait (combination of walking and running) or skipping gaits (in humans used by children or astronauts on the moon). In this grant we have explored how birds, in comparison to other bipeds like humans or trained Japanese macaques, combine simple control rules, body proportions and sensorimotor control to achieve agile and stable locomotion. Periodic locomotion is important in birds and mammals. Our results added to the notion that finely tuned nervous systems in birds and mammals permits precise information about limb loading, which is a key feature for rhythmicity. Birds can walk but usually adopt grounded running. We found that this gait permits small birds with compliant legs to move, with both legs on the ground, at speeds at which walking becomes airborne. This permits them to move fast, to adapt to rough terrains and to change direction quickly. We further found that birds negotiating rough terrains use a simple strategy: the leg swinging forward is controlled to touch the ground in a similar fashion as it does during unperturbed locomotion (e.g., same length, angle). For this, the leg in contact with the ground adapts related to the type of perturbation. This strategy permit birds to regain in one or two steps periodic locomotion after a vertical shift in terrain. Interestingly, we found that humans using skipping gaits apply a similar strategy to negotiate visible drops, and that this strategy make this gait more robust. Japanese macaques are of interest because they are quadrupedal animals that are trained to walk bipedally. On two legs, they show a great versality of gaits like grounded running, aerial running or skipping. However, we found that they do not walk. Contrarily, our simulations showed that Japanese macaques should be dynamically able to walk. However, their hindlimb anatomy (highly adapted for quadruped locomotion) hampers larger hip extensions, which are necessary to adopt walking. Interestingly, after few months of training, they discovered the same control strategy used by humans or birds to balance the trunk. To understand the relationship between basic morphology and locomotion, we searched in simulations for the basic body and leg dimensions that assure stable bipedal gaits. The largest stability fields were found for relative body dimensions encountered in birds or bipedal dinosaurs. Surprisingly, the same simulations indicate that grounded running might be an ancestral gait that evolved with the first early archosaurs or dinosaurs, and not, as until now assumed, a new gait discovered by ground birds. This knowledge is being implemented as an algorithm for the construction of robust walking machines (see e-Nandu). Based on our experimental and simulation findings, we designed and constructed a bird-like robot called e-Nandu. We will use this robot to analyze bio-inspired locomotion strategies in the real world. Moreover, we expect this technology will open new pathways for development of more robust daily applications like companion robots or exoskeletons.
Publications
- (2017) Contributions to the biomechanics of bipedal locomotion – methods and models. Habilitation thesis, TU-Ilmenau
Andrada, E.
- (2018). Bipedal gait versatility in the Japanese macaque (Macaca fuscata). Journal of Human Evolution, 125, 2-14
Ogihara, N., Hirasaki, E., Andrada, E., & Blickhan, R.
(See online at https://doi.org/10.1016/j.jhevol.2018.09.001) - (2018). Global dynamics of bipedal macaques during grounded running and running. J. Exp. Biology, 221(24), jeb178897
Blickhan, R., Andrada, E., Hirasaki, E., Ogihara N.
(See online at https://doi.org/10.1242/jeb.178897) - (2018). Skipping on uneven ground: trailing leg adjustments simplify control and enhance robustness. Royal Society open science, 5(1), 172114
Müller, R., & Andrada, E.
(See online at https://doi.org/10.1098/rsos.172114) - (2020). Low leg compliance permits grounded running at speeds where the inverted pendulum model gets airborne. J Theor. Biology, 110227
Andrada, E., Blickhan, R., Ogihara, N., & Rode, C.
(See online at https://doi.org/10.1016/j.jtbi.2020.110227) - (2021). Trunk and leg kinematics of grounded and aerial running in bipedal macaques. J. Exp. Biology, 224(2), jeb225532
Blickhan, R., Andrada, E., Hirasaki, E., & Ogihara, N.
(See online at https://doi.org/10.1242/jeb.225532)
