291,401 research outputs found
On the Embodiment That Enables Passive Dynamic Bipedal Running
2008 IEEE International Conference on Robotics and Automation, Pasadena, CA, USA, May 19-23, 200
Quantifying foot placement variability and dynamic stability of movement to assess control mechanisms during forward and lateral running
Research has indicated that human walking is more unstable in the secondary, rather than primary plane of progression. However, the mechanisms of controlling dynamic stability in different planes of progression during running remain unknown. The aim of this study was to compare variability (standard deviation and coefficient of variation) and dynamic stability (sample entropy and local divergence exponent) in anteriorâposterior and medio-lateral directions in forward and lateral running patterns. For this purpose, fifteen healthy, male participants ran in a forward and lateral direction on a treadmill at their preferred running speeds. Coordinate data of passive reflective markers attached to body segments were recorded using a motion capture system. Results indicated that: (1) there is lower dynamic stability in the primary plane of progression during both forward and lateral running suggesting that, unlike walking, greater control might be required to regulate dynamic stability in the primary plane of progression during running, (2) as in walking, the control of stability in anteriorâposterior and medio-lateral directions of running is dependent on the direction of progression, and (3), quantifying magnitude of variability might not be sufficient to understand control mechanisms in human movement and directly measuring dynamic stability could be an appropriate alternative
Constraints on dynamic stability during forward, backward and lateral locomotion in skilled football players
Abstract The aim of this study was to investigate effects of speed and plane of motion on stability during locomotion in skilled football players. Ten male national-level football players participated in this study to run forward, backward and in lateral directions on a treadmill at 80%, 100% and 120% of their preferred running speeds. The coordinate data of passive reflective markers attached to body segments were recorded using motion capture systems. Time series data obtained from the ankle marker were used for further analyses. The largest finite-time Lyapunov exponent and maximum Floquet multiplier were adopted to quantify local and orbital dynamic stabilities, respectively. Results showed that speed did not significantly change local and orbital dynamic stabilities in any of running patterns. However, both local and orbital dynamic stability were significantly higher in the secondary plane of progression. Data revealed that in running, unlike walking, stability in the direction perpendicular to the direction of running is significantly higher, implying that less active control is required in the secondary plane of progression. The results of this study could be useful in sports training and rehabilitation programmes where development of fundamental exercise programmes that challenge both speed and the ability to maintain stability might produce a tangible enhancement of athletic skill level
Bipedal Robot Running: Human-like Actuation Timing Using Fast and Slow Adaptations
We have been developing human-sized biped robots based on passive dynamic
mechanisms. In human locomotion, the muscles activate at the same rate relative
to the gait cycle during running. To achieve adaptive running for robots, such
characteristics should be reproduced to yield the desired effect. In this
study, we designed a central pattern generator (CPG) involving fast and slow
adaptation to achieve human-like running using a simple spring-mass model and
our developed bipedal robot, which is equipped with actuators that imitate the
human musculoskeletal system. Our results demonstrate that fast and slow
adaptations can reproduce human-like running with a constant rate of muscle
firing relative to the gait cycle. Furthermore, the results suggest that the
CPG contributes to the adjustment of the muscle activation timing in human
running.Comment: 15 pages, 12 figures, submitted to Advanced Robotic
Design of a Tunable Stiffness Composite Leg for Dynamic Locomotion
Passively compliant legs have been instrumental in the development of dynamically running legged robots. Having properly tuned leg springs is essential for stable, robust and energetically efficient running at high speeds. Recent simulation studies indicate that having variable stiffness legs, as animals do, can significantly improve the speed and stability of these robots in changing environmental conditions. However, to date, the mechanical complexities of designing usefully robust tunable passive compliance into legs has precluded their implementation on practical running robots. This paper describes a new design of a âstructurally controlled variable stiffnessâ leg for a hexapedal running robot. This new leg improves on previous designsâ performance and enables runtime modification of leg stiffness in a small, lightweight, and rugged package. Modeling and leg test experiments are presented that characterize the improvement in stiffness range, energy storage, and dynamic coupling properties of these legs. We conclude that this variable stiffness leg design is now ready for implementation and testing on a dynamical running robot
Passive Variable Compliance for Dynamic Legged Robots
Recent developments in legged robotics have found that constant stiffness passive compliant legs are an effective mechanism for enabling dynamic locomotion. In spite of its success, one of the limitations of this approach is reduced adaptability. The final leg mechanism usually performs optimally for a small range of conditions such as the desired speed, payload, and terrain. For many situations in which a small locomotion system experiences a change in any of these conditions, it is desirable to have a tunable stiffness leg for effective gait control.
To date, the mechanical complexities of designing usefully robust tunable passive compliance into legs has precluded their implementation on practical running robots. In this thesis we present an overview of tunable stiffness legs, and introduce a simple leg model that captures the spatial compliance of our tunable leg. We present experimental evidence supporting the advantages of tunable stiffness legs, and implement what we believe is the first autonomous dynamic legged robot capable of automatic leg stiffness adjustment. Finally we discuss design objectives, material considerations, and manufacturing methods that lead to robust passive compliant legs
Experimental Investigations into the Role of Passive Variable Compliant Legs for Dynamic Robot Locomotion
Biomechanical studies suggest that animalsâ abilities to tune their effective leg compliance in response to changing terrain conditions plays an important role in their agile, robust locomotion. However, despite growing interest in leg compliance within the robotics literature, little experimental work has been reported on tunable passive leg compliance in running machines. In this paper we present an empirical study into the role of leg compliance using a composite tunable leg design implemented on our dynamic hexapod, EduBot, with gaits optimized for running speed using a range of leg stiffnesses, on two different surface stiffnesses, and with two different payload configurations (0 kg and 0.91 kg). We found that leg stiffness, surface compliance, and payload had a significant impact on the robotâs final optimized speed and efficiency. These results document the value and efficacy of what we believe is the first autonomous dynamic legged robot capable of runtime leg stiffness adjustment.
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