Legged robots that balance
International Journal of Robotics Research
RHex: A Biologically Inspired Hexapod Runner
Autonomous Robots
Exploiting inherent robustness and natural dynamics in the control of bipedal walking robots
Exploiting inherent robustness and natural dynamics in the control of bipedal walking robots
IEEE Spectrum
Adaptive control strategies for open-loop dynamic hopping
IROS'09 Proceedings of the 2009 IEEE/RSJ international conference on Intelligent robots and systems
Fuzzy dynamic modeling for walking modular robot control
AEE'10 Proceedings of the 9th WSEAS international conference on Applications of electrical engineering
Modeling and hybrid position-force control of walking modular robots
AMERICAN-MATH'10 Proceedings of the 2010 American conference on Applied mathematics
Running with improved disturbance rejection by using non-linear leg springs
International Journal of Robotics Research
International Journal of Robotics Research
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Spring-like leg behavior is found in both humans and animals when running. In a spring-mass model, running proves to be self-stable in terms of external perturbations or variations in leg properties (for example, landing angle). However, biological limbs are not made of springs, rather, they consist of segments where spring-like behavior can be localized at the joint level. Here, we use a two-segment leg model to investigate the effects of leg compliance originating from the joint level on running stability. Owing to leg geometry a non-linear relationship between leg force and leg compression is found. In contrast to the linear leg spring, the segmented leg is capable of reducing the minimum speed for self-stable running from 3.5 m s-1 in the spring-mass model to 1.5 m s-1 for almost straight joint configurations, which is below the preferred transition speed from human walking to running (≈2 m s-1). At moderate speeds the tolerated range of landing angle is largely increased (17° at 5 m s-1) compare with the linear leg spring model (2°). However, for fast running an increase in joint stiffness is required to compensate for the mechanical disadvantage of larger leg compression. This could be achieved through the use of non-linear springs to enhance joint stiffness in fast running.