Gait development in African elephant calves

Most descriptions of elephant locomotion recognize only one gait: the lateral sequence walk. In contrast, several studies on African elephants (Loxodonta africana) have indicated that elephants use at least two other gaits: an amble and a trot. Other animals modify their gaits over the lifespan, but there is no published research on the gaits of elephant calves. The present study examines gait development in African elephant calves born at the Indianapolis Zoo between 2000 and 2015. I conducted frame-by-frame analysis on the gait samples of six calves across two time periods: Early (zero to six months of age) and Late (two to three years). I analyzed 90 gait samples and combined them with archived data on the same calves in order to have sample sizes sufficient for meaningful comparison. Gait diagrams, on which the variables “Duty Factor” and “Phase Lag” are plotted, showed that the calves exhibited two gaits: Lateral sequence walks and walking trots. Comparisons between the two time periods indicated 1) the relative frequency of trotting was similar at both ages, 2) the mean lateral sequence Phase Lag was similar at both ages, 3) a decrease in the Phase Lag variability of lateral sequence gaits, and 4) consistent with the increase in body size, the mean stride duration was longer in the Late period. Since the frequency of trotting was similar in the Early and Late periods, the reduction in trotting typical in adults must occur at a later age

Robustness: a new SLIP model based criterion for gait transitions in bipedal locomotion

Bipedal locomotion is a phenomenon that still eludes a fundamental and concise mathematical understanding. Conceptual models that capture some relevant aspects of the process exist but their full explanatory power is not yet exhausted. In the current study, we introduce the robustness criterion which defines the conditions for stable locomotion when steps are taken with imprecise angle of attack. Intuitively, the necessity of a higher precision indicates the difficulty to continue moving with a given gait. We show that the spring-loaded inverted pendulum model, under the robustness criterion, is consistent with previously reported findings on attentional demand during human locomotion. This criterion allows transitions between running and walking, many of which conserve forward speed. Simulations of transitions predict Froude numbers below the ones observed in humans, nevertheless the model satisfactorily reproduces several biomechanical indicators such as hip excursion, gait duty factor and vertical ground reaction force profiles. Furthermore, we identify reversible robust walk-run transitions, which allow the system to execute a robust version of the hopping gait. These findings foster the spring-loaded inverted pendulum model as the unifying framework for the understanding of bipedal locomotion.Comment: unpublished, in preparatio

Autonomous Locomotion Mode Transition Simulation of a Track-legged Quadruped Robot Step Negotiation

Multi-modal locomotion (e.g. terrestrial, aerial, and aquatic) is gaining increasing interest in robotics research as it improves the robots environmental adaptability, locomotion versatility, and operational flexibility. Within the terrestrial multiple locomotion robots, the advantage of hybrid robots stems from their multiple (two or more) locomotion modes, among which robots can select from depending on the encountering terrain conditions. However, there are many challenges in improving the autonomy of the locomotion mode transition between their multiple locomotion modes. This work proposed a method to realize an autonomous locomotion mode transition of a track-legged quadruped robot steps negotiation. The autonomy of the decision-making process was realized by the proposed criterion to comparing energy performances of the rolling and walking locomotion modes. Two climbing gaits were proposed to achieve smooth steps negotiation behaviours for energy evaluation purposes. Simulations showed autonomous locomotion mode transitions were realized for negotiations of steps with different height. The proposed method is generic enough to be utilized to other hybrid robots after some pre-studies of their locomotion energy performances