Behaviour Diversity in a Walking and Climbing Centipede-Like Virtual Creature.

Snakes are capable of moving in one of several ways depending on the substrate and medium being traversed. The locomotor velocities of neonate Brown Snakes (Storeria dekayi) during two modes of terrestrial locomotion (lateral undulation and concertina) and swimming were assessed at 10, 20, and 30 C. At all three temperatures, the fastest velocities were recorded during swimming while the slowest were recorded during concertina locomotion. Velocities of all three modes increased significantly with temperature but Q10 values differed greatly among locomotor modes indicating that the influence of temperature on velocity was mode dependent. Body length of neonates had no significant influence on velocities attained via any locomotor mode at any temperature. Neonate snakes displayed similar, but slightly lower, body length–relative velocities of terrestrial undulation and swimming compared to other snake species tested at the same temperatures. Previous studies have suggested that a trade-off exists between adaptations for aquatic and terrestrial locomotion in snakes, thereby suggesting that individuals that are fast swimmers will be slower on land and vice versa. In contrast to this prediction, significant positive correlations were detected between terrestrial and aquatic lateral undulation at 30 C, meaning that individuals that crawled faster via undulation on land were also faster swimmers. Future studies should relate performance via different modes of limbless locomotion to the actual use of these modes in nature.

The functional significance of the uncinate processes to the ventilatory mechanics of birds was examined by combining analytical modeling with morphological techniques. A geometric model was derived to determine the function of the uncinate processes and relate their action to morphological differences associated with locomotor specializations. The model demonstrates that uncinates act as levers, which improve the mechanical advantage for the forward rotation of the dorsal ribs and therefore lowering of the sternum during respiration. The length of these processes is functionally important; longer uncinate processes increasing the mechanical advantage of the Mm. appendicocostales muscle during inspiration. Morphological studies of four bird species showed that the uncinate process increased the mechanical advantage by factors of 2-4. Using canonical variate analysis and analysis of variance we then examined the variation in skeletal parameters in birds with different primary modes of locomotion (non-specialists, walking and diving). Birds clustered together in distinct groups, indicating that uncinate length is more similar in birds that have the same functional constraint, i.e. specialization to a locomotor mode. Uncinate processes are short in walking birds, long in diving species and of intermediate length in non-specialist birds. These results demonstrate that differences in the breathing mechanics of birds may be linked to the morphological adaptations of the ribs and rib cage associated with different modes of locomotion.

There is a growing interest in using robots in dangerous environments, such as for exploration, search-and-rescue or monitoring applications, in order to reduce the risks for workers or rescuers and to improve their efficiency. Typically, flying robots offer the possibility to quickly explore large areas while ground robots can thoroughly search specific regions of interest. While existing robotic solutions are very promising, they are often limited to specific use cases or environments. This makes them impractical for most missions involving complex or unpredictable scenarios, such as search-and-rescue applications. This limitation comes from the fact that existing robots usually exploit only a single locomotion strategy, which limits their flexibility and adaptability to different environments. In this thesis, a multi-modal locomotion strategy is investigated as a way to increase the versatility of mobile robots. We explore integrated design approaches, where the same actuators and structure are used for different modes of locomotion, which allows a minimization of the weight and complexity of the robot. This strategy is challenging because a single locomotor system must accommodate the potentially conflicting dynamics of multiple modes of locomotion. Herein, we suggest taking inspiration from nature, in particular the common vampire bat Desmodus rotundus. The goal being to make multiple modes of locomotion dynamically compatible (i.e. have compatible speeds and torques requirements), by optimizing the morphology of the locomotor system and even by adapting the morphology of the robot to a specific mode of locomotion. It is demonstrated in this thesis that the integrated design approach can be effectively implemented on a multi-modal aerial and terrestrial robot, and that two modes of locomotion can be made dynamically compatible by optimizing the morphology. Furthermore, an adaptive morphology is used to increase the efficiency of the different modes of locomotion. A locomotor system used both for walking on the ground and controlling flight, has been successfully implemented on a multi-modal robot, which further has deployable wings to increase its performances on the ground and in the air. By successfully exploiting the concepts of integrated design and adaptive morphology, this robot is capable of hovering, forward flight and ground locomotion. This robot demonstrates a very high versatility compared to state of the art of mobile robots, while having a low complexity.

Shrimp locomotion includes walking, swimming, and tail-flipping, all essential for survival. Understanding the pathway and use of energy during different modes of locomotion is important in understanding the strategy and evolution of locomotion. We explored the mechanisms of energy supply during swimming and tail-flipping locomotion modes in the whiteleg shrimp Litopenaeus vannamei (Boone, 1931). We studied the metabolic pathways of glycogen and triglycerides and the regulation of glycolytic enzyme on glycolysis, and analyzed their relationship with the behavior modes of locomotion. Swimming includes sustained and prolonged modes, where the shrimp were forced to swim at a speed of 10 cm s−1 for 200 min (sustained), and at 20 cm s−1 until fatigue (prolonged). In tail-flipping locomotion, shrimp were forced to tail-flip by tapping the animal until fatigue. The results showed that the hydrolysis of glycogen in pleopod muscle increased with the rate of pleopod strokes due to increased energy demand during fast swimming. Similarly, glycogen breakdown in abdominal muscles was increased during tail-flipping. Glycogen and triglycerides were utilized in aerobic metabolism pathway as a result of the lower rate of pleopod strokes during sustained swimming. Prolonged and tail-flipping modes of locomotion were powered by anaerobic glycolysis because oxygen supply probably was not sufficient to meet the requirements of glycogen and triglyceride oxidation. Lactate accumulation due to increased glycolysis consequently resulted in locomotion fatigue. These findings highlight our understanding of physiology and behavior of locomotion in shrimps, essential during migration, foraging, and escape from predators.

The grain size distribution of four sandy beaches, three in the Baltic Sea and one at the Swedish West Coast, is described. A core sampler of new construction and giving successive subsamples of 10 or 20 cm3 is used to establish the horisontal, vertical and lateral distribution of grain size and grade of sorting for the four types of beaches. In a core with the total mean diameter of the grains of 500 jp the corresponding values of the subsamples may vary from 100 to 800 p. The lateral distribution in the beach is less heterogenous. Layers of quite different grain size may have the same grade of sorting just as well as a stratum of homogenous sand may contain adjacent subsamples of quite different sorting. The significance of these differences for the interstitial fauna is shown in choice experiments with the turbellarian Coelogynopora schulzii and the tubificid Aktedrilus monospermatecus. Representing two different modes of locomotion - creeping by means of cilia and burrowing by means of peristaltic movements of the whole body - they show no significant preference for graded sand fractions in the range

Lamprey (a lower vertebrate) can employ different modes of locomotion, i.e. swimming in open water and crawling in tight places. Swimming is due to the periodic waves of lateral undulations with reciprocal activity of right and left muscles. In contrast, crawling (forward and backward) is based on single waves with coactivation of muscles on two sides. Basic mechanisms of swimming and, most likely, crawling reside in the spinal cord, and are activated by supraspinal commands. The main source of these commands is the reticulospinal (RS) system. The goal of the present experiments was to characterize the activity of individual RS neurons during swimming and during crawling in a U-shaped tunnel. The activity was recorded by means of chronically implanted electrodes in freely behaving animals. All recorded RS neurons were active during swimming but silent in quiescent animals. Many of them (61%) showed phasic modulation of their firing rate approximately in phase with the activity of ipsilateral rostral muscles. The majority of the neurons (80%) were also active during crawling. Many of them either increased or decreased their activity during crawling as compared to the background activity. These changes were better correlated with the direction of progression (forward or backward) than with the direction of turning in the tunnel (right or left). No correlation of the activity of RS neurons during locomotion and their sensory inputs was found. The results of this study suggest that different modes of locomotion in lampreys can be caused by considerably overlapping groups of RS neurons.

In this paper, we develop an approach to inverse optimal control for a class of hybrid dynamical system with impacts. As it is usually posed, the problem of inverse optimal control is to find a cost function that is consistent with an observed sequence of decisions, under the assumption that these decisions are optimal. We assume instead that observed decisions are only approximately optimal and find a cost function that minimizes the extent to which these decisions violate first-order necessary conditions for optimality. For the hybrid dynamical system that we consider with a cost function that is a linear combination of known basis functions, this minimization is a convex program. In fact, it reduces to a simple least-squares computation that - unlike most other forms of inverse optimal control - can be solved very efficiently. We apply our approach to a dynamic bipedal climbing robot in simulation, showing that we can recover cost functions from observed trajectories that are consistent with two different modes of locomotion.

Age-related declines in sport performance are characteristic of all endurance and sprinting disciplines. However, it is not known if the mode of locomotion (ie, swimming, cycling or running) influences the age-related decline in sport performance in sprinting and endurance events. To examine the age-related decline in 3 different modes of locomotion (ie, swimming, cycling, and running) for endurance and sprint events, the world-best performances achieved for men in the age groups 18-39, 40-44, 45-49, 50-54, 55-59, 60-64, 65-69, 70-74, 75-79, and 80-84y were compared in swimming (1500 and 50m), cycling (1h and 200m), and running (10 and 100m). Each performance was considered as an average speed (throughout the distance), and the age-related decline in performance was expressed as a percentage of the world record (regardless of age group) for that discipline. The age-related decline in 1-h track cycling is less pronounced than in 1500-m swimming and 10-km running after 60y. In contrast, the age-related decline was similar among the 3 locomotion modes for the sprinting events. The data show that the maintenance of high performance in cycling persists longer into old age than in running and swimming.

Locomotion is one of the major physiological functions for most animals. Previous studies have described aging mechanisms linked to locomotor performance among different species. However, the precise dynamics of these age-related changes, and their interactions with development and senescence, are largely unknown. Here, we use the same conceptual framework to describe locomotor performances in Caenorhabditis elegans, Mus domesticus, Canis familiaris, Equus caballus, and Homo sapiens. We show that locomotion is a consistent biomarker of age-related changes, with an asymmetrical pattern throughout life, regardless of the type of effort or its duration. However, there is variation (i) among species for the same mode of locomotion, (ii) within species for different modes of locomotion, and (iii) among individuals of the same species for the same mode of locomotion. Age-related patterns are modulated by genetic (such as selective breeding) as well as environmental conditions (such as temperature). However, in all cases, the intersection of the rising developmental phase and the declining senescent phase reveals neither a sharp transition nor a plateau, but a smooth transition, emphasizing a crucial moment: the age at peak performance. This transition may define a specific target for future investigations on the dynamics of such biological interactions.

Previous research on the locomotion of the Nematalycidae has only been undertaken on Gordialycus, which is by far the most elongated genus of the family. Gordialycus is dependent on an unusual form of peristalsis to move around. It was not known whether the genera of Nematalycidae with shorter bodies also used this mode of locomotion. Our videographic recordings of Osperalycus did not reveal peristalsis. Instead, this mite appears to move around the mineral regolith via the expansion and constriction of the metapodosomal and genital region, allowing greater versatility in the way that the annular regions contract and extend. This type of locomotion would enable relatively short bodied nematalycids to anchor themselves into secure positions before extending their anterior regions through tight spaces. Low-temperature scanning electron micrographs show that the short bodied genera have integumental features that appear to be associated with this mode of locomotion. Peristalsis is almost certainly a more derived form of locomotion that is an adaptation to the unusually long body form of Gordialycus.Electronic supplementary materialThe online version of this article (doi:10.1007/s10493-014-9857-0) contains supplementary material, which is available to authorized users.

Multi-material Additive Manufacturing of Functional Soft Robot

Hybrid mobile robots are able to function in a number of different modes of locomotion, which increases their capacity to overcome challenges and makes them appropriate for a wide range of applications. To be able to develop navigation techniques that make use of these improved capabilities, one must first have a solid grasp of the constraints imposed by each of those different modalities of locomotion. In this paper, we present a data-driven approach for evaluating the robots’ locomotion modes. To do this, we formalize the problem as a reinforcement learning task that is applied to a digital twin simulation of the mobile robot. The proposed method is demonstrated through the use of a case study that examines the capabilities of hybrid wheel-on-leg robot locomotion modes in terms of speed, slope ascent, and step obstacle climbing. First, a comprehensive explanation of the process of creating the digital twin of the mobile robot through the use of the Unity gaming engine is presented. Second, a description of the construction of three test environments is provided so that the aforementioned capabilities of the robot can be evaluated. In the end, Reinforcement Learning is used to evaluate the two types of locomotion that the mobile robot can utilize in each of these different environments. Corresponding simulations are conducted in the virtual environment and the results are analyzed.

The common guillemot, Uria aalge, a member of the auk family of seabirds exhibits locomotive capabilities in both aerial and aquatic substrates. Simplistic forms of this ability have yet to be achieved by robotic vehicle designs and offer significant potential as inspiration for future concept designs. In this investigation, we initially investigate the power requirements of the guillemot associated with different modes of locomotion, empirically determining the saving associated with the retraction of the wing during aquatic operations. A numerical model of a morphing wing is then created to allow power requirements to be determined for different wing orientations, taking into account the complex kinematic and inertial dynamics associated with the motion. Validation of the numerical model is achieved by comparisons with the actual behaviour of the guillemot, which is done by considering specific mission tasks, where by the optimal solutions are found utilizing an evolutionary algorithm, which are found to be in close agreement with the biological case.

Long bones are subjected to mechanical loads during locomotion that will influence their biomechanical properties through a feedback mechanism (the bone mechanostat). This mechanism adapts the spatial distribution of the mineralized tissue to resist compression, bending and torsion. Among vertebrates, anurans represent an excellent group to study long bone properties because they vary widely in locomotor modes and habitat use, which enforce different skeletal loadings. In this study, we hypothesized that (a) the cortical bone mass, density and design of anuran femur and tibiofibula would reflect the mechanical influences of the different locomotor modes and habitat use, and (b) the relationships between the architectural efficiency of cortical design (cross-sectional moments of inertia) and the intrinsic stiffness of cortical tissue [cortical mineral density; the 'distribution/quality' (d/q) relationship] would describe some inter-specific differences in the efficiency of the bone mechanostat to improve bone design under different mechanical loads. To test this hypothesis, we determined tomographic (peripheral quantitative computed tomography) indicators of bone mass, mineralization, and design along the femur and tibiofibula of four anuran species with different modes of locomotion and use of habitat. We found inter-specific differences in all measures between the distal and proximal ends and mid-diaphysis of the bones. In general, terrestrial-hopper species had the highest values. Arboreal-walker species had the lowest values for all variables except for cortical bone mineral density, which was lowest in aquatic-swimmer species. The d/q relationships showed similar responses of bone modeling as a function of cortical stiffness for aquatic and arboreal species, whereas terrestrial-hoppers had higher values for moments of inertia regardless of the tissue compliance to be deformed. These results provide new evidence regarding the significant role of movement and habitat use in addition to the biomechanical properties of long bones within a morpho-functional and comparative context in anuran species.

The magnitude of change in sex differences across age groups in triathlon performance for the Ironman distance has been established. However, the influence of age on sex differences at shorter-distance triathlons is yet to be determined. The aim of this study was to compare sex differences across age groups for the different modes of locomotion among varying triathlon distances (Sprint, Olympic, and Ironman 70.3) in amateur triathletes from the 2009-2011 triathlon World Championship. Data for the top 10 male and female amateur triathletes for the age groups between 18 and 64 yr were collected from the 2009-2011 World Championships for Sprint, Olympic, and Ironman 70.3 triathlons. Sex differences across age groups were compared using time performances for swimming, cycling, running, transition time, overall race time, and estimated power output. Total time differences between sexes were largest in 55-59 yr age groups for Sprint (18.7%, P < 0.05) and in 60-64 yr age groups for Olympic and Ironman 70.3 (14.8% and 21.7%, P < 0.05). Mean sex difference in performance time was smallest for cycling in Sprint (11.8% ± 0.41%) and in Ironman 70.3 (11.2% ± 0.41%), whereas running showed the smallest sex difference in Olympic (7.5% ± 0.33%, P < 0.05). Mean sex differences in estimated power output were significantly greater for swimming in Sprint (41.0% ± 1.47%), Olympic (39.8% ± 1.24%), and Ironman 70.3 (37.%5 ± 1.67%, P < 0.05). Sex differences for total performance time were greatest in the youngest age groups and older age groups for Sprint, Olympic, and Ironman 70.3 distances. Sex differences varied among the modes of locomotion for the three distances of triathlons; however, for short- to mid-distance triathlons, both performance time and estimated power output seem to indicate that the largest sex differences exist for swimming.