1,565 research outputs found
Dynamic Walking of Bipedal Robots on Uneven Stepping Stones via Adaptive-frequency MPC
This paper presents a novel Adaptive-frequency MPC framework for bipedal
locomotion over terrain with uneven stepping stones. In detail, we intend to
achieve adaptive foot placement and gait period for bipedal periodic walking
gait with this MPC, in order to traverse terrain with discontinuities without
slowing down. We pair this adaptive-frequency MPC with a kino-dynamics
trajectory optimization for optimal gait periods, center of mass (CoM)
trajectory, and foot placements. We use whole-body control (WBC) along with
adaptive-frequency MPC to track the optimal trajectories from the offline
optimization. In numerical validations, our adaptive-frequency MPC framework
with optimization has shown advantages over fixed-frequency MPC. The proposed
framework can control the bipedal robot to traverse through uneven stepping
stone terrains with perturbed stone heights, widths, and surface shapes while
maintaining an average speed of 1.5 m/s.Comment: 6 pages, 7 figures, 1 tabl
Evolution of central pattern generators for the control of a five-link bipedal walking mechanism
Central pattern generators (CPGs), with a basis is neurophysiological
studies, are a type of neural network for the generation of rhythmic motion.
While CPGs are being increasingly used in robot control, most applications are
hand-tuned for a specific task and it is acknowledged in the field that generic
methods and design principles for creating individual networks for a given task
are lacking. This study presents an approach where the connectivity and
oscillatory parameters of a CPG network are determined by an evolutionary
algorithm with fitness evaluations in a realistic simulation with accurate
physics. We apply this technique to a five-link planar walking mechanism to
demonstrate its feasibility and performance. In addition, to see whether
results from simulation can be acceptably transferred to real robot hardware,
the best evolved CPG network is also tested on a real mechanism. Our results
also confirm that the biologically inspired CPG model is well suited for legged
locomotion, since a diverse manifestation of networks have been observed to
succeed in fitness simulations during evolution.Comment: 11 pages, 9 figures; substantial revision of content, organization,
and quantitative result
Neuro-mechanical entrainment in a bipedal robotic walking platform
In this study, we investigated the use of van der Pol oscillators in a 4-dof embodied bipedal robotic platform for the purposes of planar walking. The oscillator controlled the hip and knee joints of the robot and was capable of generating waveforms with the correct frequency and phase so as to entrain with the mechanical system. Lowering its oscillation frequency resulted in an increase to the walking pace, indicating exploitation of the global natural dynamics. This is verified by its operation in absence of entrainment, where faster limb motion results in a slower overall walking pace
Neuro-mechanical entrainment in a bipedal robotic walking platform
In this study, we investigated the use of van der Pol oscillators in a 4-dof embodied bipedal robotic platform for the purposes of planar walking. The oscillator controlled the hip and knee joints of the robot and was capable of generating waveforms with the correct frequency and phase so as to entrain with the mechanical system. Lowering its oscillation frequency resulted in an increase to the walking pace, indicating exploitation of the global natural dynamics. This is verified by its operation in absence of entrainment, where faster limb motion results in a slower overall walking pace
Infer and Adapt: Bipedal Locomotion Reward Learning from Demonstrations via Inverse Reinforcement Learning
Enabling bipedal walking robots to learn how to maneuver over highly uneven,
dynamically changing terrains is challenging due to the complexity of robot
dynamics and interacted environments. Recent advancements in learning from
demonstrations have shown promising results for robot learning in complex
environments. While imitation learning of expert policies has been
well-explored, the study of learning expert reward functions is largely
under-explored in legged locomotion. This paper brings state-of-the-art Inverse
Reinforcement Learning (IRL) techniques to solving bipedal locomotion problems
over complex terrains. We propose algorithms for learning expert reward
functions, and we subsequently analyze the learned functions. Through nonlinear
function approximation, we uncover meaningful insights into the expert's
locomotion strategies. Furthermore, we empirically demonstrate that training a
bipedal locomotion policy with the inferred reward functions enhances its
walking performance on unseen terrains, highlighting the adaptability offered
by reward learning
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