This study investigated the energetics of the human ankle during the stance phase of downhill walking with the goal of modeling ankle behavior with a passive spring and damper mechanism. Kinematic and kinetic data were collected on eight male participants while walking down a ramp with inclination varying from 0° to 8°. The ankle joint moment in the sagittal plane was calculated using inverse d...

Online learning and controller adaptation will be an essential component for legged robots in the next few years as they begin to leave the laboratory setting and join our world. I present the first example of a learning system which is able to quickly and reliably acquire a robust feedback control policy for 3D dynamic bipedal walking from a blank slate using only trials implemented on the phy...

Evolving dynamically stable robots from traditional statically stable walkers has not yet been feasible due to fundamental task differences, kinematic, actuation and energetic constraints. Instead, simple solutions to the dynamic locomotion problem are available, based on "RePaC" Revolute Passive Compliance design and control. We will describe the RePaC design and control principles and show ho...

Energy expenditure considerations have been an important part of legged robotics community. A breakthrough in this was pioneered by Dr. Tad McGeer in his work on passive dynamic walking[1]. His work sparked interest among several researchers, most notably Andy Ruina’s group in Cornell University. An interesting application of this concept is the Cornell Ranger[2] that has walked 65Km on one cha...

A healthy gait pattern depends on an array of biomechanical features, orchestrated by the central nervous system for economy and stability. Injuries and other pathologies can alter these features and result in substantial gait deficits, often with detrimental consequences for energy expenditure and balance. An understanding of the role of biomechanics in the generation of healthy gait, therefor...

Painlevé paradox occurs in rigid-body dynamics of mechanical systems with frictional contacts at configurations where the instantaneous solution is either indeterminate or inconsistent. Dynamic jamming is a scenario where the solution starts with consistent slippage and then converges in finite time to a configuration of inconsistency while the contact force grows unbounded. The goal of this pa...

This paper investigates the efficiency of a 2-period gait from the kinetic energy view-point. First, we formulate a steady 2-period gait for a compass-like bipedal robot by using a simple recurrence formula for the kinetic energy of an asymmetric rimless wheel. Second, we theoretically show that, in the case that the mean value of the hip angle is constant, the generated 2-period steady gait is...