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This paper presents the design, modeling, analysis, and experimental results of a bipedal robotic system that utilizes two interconnected single degree-of-freedom leg mechanisms to produce stable forward locomotion and steering. The legs are composed of double four-bar mechanism connected in series that maintain a parallel orientation of a flat foot, relative to the biped body, that is actuated via a Reuleaux triangle cam-follower system to produce a desirable foot trajectory. The mechanical design of the leg mechanism is presented followed by kinematic analysis of the cam-follower system to select the optimal foot trajectory and synthesize the mechanism dimensions and produce a desired step height and step length. The concept of leg sequencing is then presented to maintain a constant body height above the ground and a constant forward walking velocity. Experimental results using an integrated prototype indicate that the proposed biped robot is capable of maintaining quasi-static stability during locomotion, maintaining a constant robot body height, maintaining a constant body orientation, move forward with a constant maximum velocity of 27.4 cm/s, and steer.
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Brain–body-task co-adaptation can improve autonomous learning and speed of bipedal walking
Abstract Inspired by animals that co-adapt their brain and body to interact with the environment, we present a tendon-driven and over-actuated (i.e.njoint,n+1 actuators) bipedal robot that (i) exploits its backdrivable mechanical properties to manage body-environment interactions without explicit control,and(ii) uses a simple 3-layer neural network to learn to walk after only 2 min of ‘natural’ motor babbling (i.e. an exploration strategy that is compatible with leg and task dynamics; akin to childsplay). This brain–body collaboration first learns to produce feet cyclical movements ‘in air’ and, without further tuning, can produce locomotion when the biped is lowered to be in slight contact with the ground. In contrast, training with 2 min of ‘naïve’ motor babbling (i.e. an exploration strategy that ignores leg task dynamics), does not produce consistent cyclical movements ‘in air’, and produces erratic movements and no locomotion when in slight contact with the ground. When further lowering the biped and making the desired leg trajectories reach 1 cm below ground (causing the desired-vs-obtained trajectories error to be unavoidable), cyclical movements based on either natural or naïve babbling presented almost equally persistent trends, and locomotion emerged with naïve babbling. Therefore, we show how continual learning of walking in unforeseen circumstances can be driven by continual physical adaptation rooted in the backdrivable properties of the plant and enhanced by exploration strategies that exploit plant dynamics. Our studies also demonstrate that the bio-inspired co-design and co-adaptations of limbs and control strategies can produce locomotion without explicit control of trajectory errors.
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- Award ID(s):
- 2113096
- PAR ID:
- 10565889
- Date Published:
- Journal Name:
- Bioinspiration & Biomimetics
- Volume:
- 19
- Issue:
- 6
- ISSN:
- 1748-3182
- Page Range / eLocation ID:
- 066008
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1088/1748-3190/ad8419
