In Eq. (22), the
x
symbol was incorrectly represented by an @ symbol, therefore the equation should correctly read as
\begin{eqnarray*}
\dot x &=& {f_v}(x) + {g_v}(x)u,\\
{y_v} &=& y_v^a(x) - ...y_v^d(x).
\end{eqnarray*}
Similar errors were also found in the sentence following Eq. (22). In this sentence, the correct math symbol should be
y
v
a
(
x
) and
y
v
d
(
x
) instead of
y
v
a
(@) and
y
v
d
(@).
Stegosaur tracks were unknown until the identification of Deltapodus more than 20 years ago. Currently, the Iberian Peninsula, especially Teruel Province, is one of the areas globally with the most ...occurrences of these tracks. However, their identification, based on the global record, is problematic due to their similarities with sauropod tracks. A review of the largest number of analyzed Deltapodus tracks globally, including the holotype of D. ibericus and a description of new occurrences, has been carried out. Our research shows substantial morphological variations, but all the studied tracks can be considered D. ibericus based on the manus morphology and the morphometric data. These variations are related to substrate differences and/or different dynamic foot postures (possibly ontogenetically related) during locomotion, as evidenced by changes within the same trackway. We provide detailed comparisons via 3D modeling with sauropod tracks, and our data show that they generally have proportionally longer manus and wider pes because of the differences in the metapodial bones. The scarcity of stegosaur trackways in the fossil record has prevented the identification of gregarious behavior in this group of herbivorous dinosaurs. Two of the studied tracksites show evidence of this behavior, being the only examples among stegosaurs described thus far in the fossil record.
Insect-sized (<inline-formula><tex-math notation="LaTeX">\sim</tex-math></inline-formula>100 mg) aerial robots have advantages over larger robots because of their small size, low weight, and low ...materials cost. Previous iterations have demonstrated controlled flight but were difficult to fabricate because they consisted of many separate parts assembled together and were also unable to perform locomotion modes besides flight. This article presents a new design of a 74-mg flapping-wing robot that dramatically reduces the number of parts and simplifies fabrication. The robot also has a lower center of mass, which allows the robot to additionally land without the need for long legs, even in case of unstable flight. We also show that the new design allows for wing-driven ground and air-water interfacial locomotion, improving the versatility of the robot. During surface ambulation, forward thrust is generated by increasing the speed of the upstroke relative to the downstroke of the flapping wings. Adjusting relative wing stroke amplitudes also allows for steering. The ability to land and subsequently move along the ground first presented here allows the robot to negotiate extremely confined spaces and underneath obstacles. We present results demonstrating these capabilities, as well as hovering flight and controlled landing.
While research into the biology of animal behaviour has primarily focused on the central nervous system, cues from peripheral tissues and the environment have been implicated in brain development and ...function
. There is emerging evidence that bidirectional communication between the gut and the brain affects behaviours including anxiety, cognition, nociception and social interaction
. Coordinated locomotor behaviour is critical for the survival and propagation of animals, and is regulated by internal and external sensory inputs
. However, little is known about how the gut microbiome influences host locomotion, or the molecular and cellular mechanisms involved. Here we report that germ-free status or antibiotic treatment results in hyperactive locomotor behaviour in the fruit fly Drosophila melanogaster. Increased walking speed and daily activity in the absence of a gut microbiome are rescued by mono-colonization with specific bacteria, including the fly commensal Lactobacillus brevis. The bacterial enzyme xylose isomerase from L. brevis recapitulates the locomotor effects of microbial colonization by modulating sugar metabolism in flies. Notably, thermogenetic activation of octopaminergic neurons or exogenous administration of octopamine, the invertebrate counterpart of noradrenaline, abrogates the effects of xylose isomerase on Drosophila locomotion. These findings reveal a previously unappreciated role for the gut microbiome in modulating locomotion, and identify octopaminergic neurons as mediators of peripheral microbial cues that regulate motor behaviour in animals.
Mammals walk in different directions, such as forward and backward. In human infants/adults and decerebrate cats, one leg can walk forward and the other backward simultaneously on a split‐belt ...treadmill, termed hybrid or bidirectional locomotion. The purpose of the present study was to determine if spinal sensorimotor circuits generate hybrid locomotion and if so, how the limbs remain coordinated. We tested hybrid locomotion in 11 intact cats and in five following complete spinal thoracic transection (spinal cats) at three treadmill speeds with the hindlimbs moving forward, backward or bidirectionally. All intact cats generated hybrid locomotion with the forelimbs on a stationary platform. Four of five spinal cats generated hybrid locomotion, also with the forelimbs on a stationary platform, but required perineal stimulation. During hybrid locomotion, intact and spinal cats positioned their forward and backward moving hindlimbs caudal and rostral to the hip, respectively. The hindlimbs maintained consistent left–right out‐of‐phase alternation in the different stepping directions. Our results suggest that spinal locomotor networks generate hybrid locomotion by following certain rules at phase transitions. We also found that stance duration determined cycle duration in the different locomotor directions/conditions, consistent with a common rhythm‐generating mechanism for different locomotor directions. Our findings provide additional insight on how left–right spinal networks and sensory feedback from the limbs interact to coordinate the hindlimbs and provide stability during locomotion in different directions.
Key points
Terrestrial mammals can walk forward and backward, which is controlled in part by spinal sensorimotor circuits.
Humans and cats also perform bidirectional or hybrid locomotion on a split‐belt treadmill with one leg going forward and the other going backward.
We show that cats with a spinal transection can perform hybrid locomotion and maintain left–right out‐of‐phase coordination, indicating that spinal sensorimotor circuits can perform simultaneous forward and backward locomotion.
We also show that the regulation of cycle duration and phase duration is conserved across stepping direction, consistent with a common rhythm‐generating mechanism for different stepping directions.
The results help us better understand how spinal networks controlling the left and right legs enable locomotion in different directions.
figure legend Simultaneous control of forward and backward locomotion by spinal sensorimotor circuits. Sensory feedback from the hindimbs interacts with neuronal circuits of the lumbosacral cord to coordinate the left and right hindlimbs, allowing one hindlimb to step forward while the other steps backward on a split‐belt treadmill.
The goal of this research is to develop a generic earthworm-like locomotion robot model consisting of a large number of segments in series and based on which to systematically investigate the ...generation of planar locomotion gaits and their correlation with a robot’s locomotion performance. The investigation advances the state-of-the-art by addressing some fundamental but largely unaddressed issues in the field. These issues include (a) how to extract the main shape and deformation characteristics of the earthworm’s body and build a generic model, (b) how to coordinate the deformations of different segments such that steady-state planar locomotion can be achieved, and (c) how different locomotion gaits would qualitatively and quantitatively affect the robot’s locomotion performance, and how to evaluate them. Learning from earthworms’ unique morphology characteristics, a generic kinematic model of earthworm-like metameric locomotion robots is developed. Left/right-contracted segments are introduced into the model to achieve planar locomotion. Then, this paper proposes a gait-generation algorithm by mimicking the earthworm’s retrograde peristalsis wave, with which all admissible locomotion gaits can be constructed. We discover that when controlled by different gaits, the robot would exhibit four qualitatively different locomotion modes, namely, rectilinear, sidewinding, circular, and cycloid locomotion. For each mode, kinematic indexes are defined and examined to characterize their locomotion performances. For verification, a proof-of-concept robot hardware is designed and prototyped. Experiments reveal that with the proposed robot model and the employed gait controls, locomotion of different modes can be effectively achieved, and they agree well with the theoretical predictions.
We present a single trajectory optimization formulation for legged locomotion that automatically determines the gait sequence, step timings, footholds, swing-leg motions, and six-dimensional body ...motion over nonflat terrain, without any additional modules. Our phase-based parameterization of feet motion and forces allows to optimize over the discrete gait sequence using only continuous decision variables. The system is represented using a simplified centroidal dynamics model that is influenced by the feet's location and forces. We explicitly enforce friction cone constraints, depending on the shape of the terrain. The nonlinear programming problem solver generates highly dynamic motion plans with full flight phases for a variety of legged systems with arbitrary morphologies in an efficient manner. We validate the feasibility of the generated plans in simulation and on the real quadruped robot ANYmal. Additionally, the entire solver software TOWR, which used to generate these motions is made freely available.
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