Trunk pitch oscillations for energy trade-offs in bipedal running birds and robots

Drama, Özge; Badri-Spröwitz, Alexander

doi:10.1088/1748-3190/ab7570

Cited by 16 publications

(16 citation statements)

References 47 publications

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“…with D _ xj i À1 being the difference in apex velocity _ x between time steps -1 and i. The VP angle is defined with respect to a CoM-centred, stationary coordinate frame that is aligned with the global vertical axis, if the VP is set below the CoM (figure 2b,d) [25]. It is adjusted based on the difference between the desired mean body angle u Des C , and the mean body angle observed in the last step Δθ C as,…”

Section: Simulation Methodsmentioning

confidence: 99%

“…In the simulation model, the selection of the VP position influences the energetics of the system by distributing the work performed by the leg and the hip [23,25]. A VP B in the human TSLIP model reduces the leg loading at the cost of increased peak hip torques for steady-state gaits.…”

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confidence: 99%

“…In human gait, the trunk moves forward during the single stance phase of walking and running, which is reversed by a backward trunk motion in the double stance phase of walking [27] and flight phase of running [10,27]. In TSLIP model simulations of human running, the trunk moves forward during the stance phase if a VP B is used, whereas it moves backward for a VP A [12,23,25,28].…”

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confidence: 99%

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Postural stability in human running with step-down perturbations: an experimental and numerical study

et al. 2020

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Postural stability is one of the most crucial elements in bipedal locomotion. Bipeds are dynamically unstable and need to maintain their trunk upright against the rotations induced by the ground reaction forces (GRFs), especially when running. Gait studies report that the GRF vectors focus around a virtual point above the centre of mass (VP A ), while the trunk moves forward in pitch axis during the stance phase of human running. However, a recent simulation study suggests that a virtual point below the centre of mass (VP B ) might be present in human running, because a VP A yields backward trunk rotation during the stance phase. In this work, we perform a gait analysis to investigate the existence and location of the VP in human running at 5 m s −1 , and support our findings numerically using the spring-loaded inverted pendulum model with a trunk. We extend our analysis to include perturbations in terrain height (visible and camouflaged), and investigate the response of the VP mechanism to step-down perturbations both experimentally and numerically. Our experimental results show that the human running gait displays a VP B of ≈−30 cm and a forward trunk motion during the stance phase. The camouflaged step-down perturbations affect the location of the VP B . Our simulation results suggest that the VP B is able to encounter the step-down perturbations and bring the system back to its initial equilibrium state.

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Section: Simulation Methodsmentioning

confidence: 99%

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Postural stability in human running with step-down perturbations: an experimental and numerical study

et al. 2020

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“…Daley and Biewener (2006, p. 185). In virtual point-based control strategies for bipedal running, positive work is inserted into hip joints, and negative work is then dissipated in equal amounts in the spring-damper leg (Drama and Spröwitz, 2020). In sum, either physical damping or virtual damping allows removing energy from a legged locomotion system.…”

Section: Figure 1 | (A-c)mentioning

confidence: 99%

Effective Viscous Damping Enables Morphological Computation in Legged Locomotion

Izzi

Haeufle

et al. 2020

Front. Robot. AI

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Muscle models and animal observations suggest that physical damping is beneficial for stabilization. Still, only a few implementations of physical damping exist in compliant robotic legged locomotion. It remains unclear how physical damping can be exploited for locomotion tasks, while its advantages as sensor-free, adaptive force-and negative work-producing actuators are promising. In a simplified numerical leg model, we studied the energy dissipation from viscous and Coulomb damping during vertical drops with ground-level perturbations. A parallel spring-damper is engaged between touchdown and mid-stance, and its damper auto-decouples from mid-stance to takeoff. Our simulations indicate that an adjustable and viscous damper is desired. In hardware we explored effective viscous damping and adjustability, and quantified the dissipated energy. We tested two mechanical, leg-mounted damping mechanisms: a commercial hydraulic damper, and a custom-made pneumatic damper. The pneumatic damper exploits a rolling diaphragm with an adjustable orifice, minimizing Coulomb damping effects while permitting adjustable resistance. Experimental results show that the leg-mounted, hydraulic damper exhibits the most effective viscous damping. Adjusting the orifice setting did not result in substantial changes of dissipated energy per drop, unlike adjusting the damping parameters in the numerical model. Consequently, we also emphasize the importance of characterizing physical dampers during real legged impacts to evaluate their effectiveness for compliant legged locomotion.

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“…Damping elements are sometimes added to SLIP-based models to study energy-injecting controllers [ 11 – 13 ]. These studies, however, focus on the stabilizing effects of the presented controllers and their potential applications in robotics.…”

Section: Introductionmentioning

confidence: 99%

A little damping goes a long way: a simulation study of how damping influences task-level stability in running

et al. 2020

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It is currently unclear if damping plays a functional role in legged locomotion, and simple models often do not include damping terms. We present a new model with a damping term that is isolated from other parameters: that is, the damping term can be adjusted without retuning other model parameters for nominal motion. We systematically compare how increased damping affects stability in the face of unexpected ground-height perturbations. Unlike most studies, we focus on task-level stability: instead of observing whether trajectories converge towards a nominal limit-cycle, we quantify the ability to avoid falls using a recently developed mathematical measure. This measure allows trajectories to be compared quantitatively instead of only being separated into a binary classification of ‘stable' or ‘unstable'. Our simulation study shows that increased damping contributes significantly to task-level stability; however, this benefit quickly plateaus after only a small amount of damping. These results suggest that the low intrinsic damping values observed experimentally may have stability benefits and are not simply minimized for energetic reasons. All Python code and data needed to generate our results are available open source.

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Trunk pitch oscillations for energy trade-offs in bipedal running birds and robots

Cited by 16 publications

References 47 publications

Postural stability in human running with step-down perturbations: an experimental and numerical study

Postural stability in human running with step-down perturbations: an experimental and numerical study

Effective Viscous Damping Enables Morphological Computation in Legged Locomotion

A little damping goes a long way: a simulation study of how damping influences task-level stability in running

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