A virtual pivot point approach to the control of quadrupedal robot running
Date
2020
Authors
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Journal ISSN
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Publisher
University of Delaware
Abstract
Despite significant progress on wheeled vehicles, a large portion of earth landmass is limited to the wheeled robots. Legged robots provide an attractive alternative to address mobility limitations in extreme terrain environments. Much of the effort on legged robots has been concentrated on quadrupeds due to their inherent stability characteristics. ☐ In this thesis, we focus on running quadrupeds with a bounding gait. We propose a discrete-time control approach that stabilizes periodic bounding gaits that take advantage of the passive dynamics of the system. The proposed controller uses the concept of a Virtual Pivot Point (VPP) within a discrete Linear Quadratic Regulator (LQR) to enhance bounding stability. In our approach, stability is evaluated by computing eigenvalues of linearized Poincare return map. By computing estimates of the basin of attraction (BoA) around fixed points corresponding to passive bounding gaits, it is shown that the proposed VPP controller enhances locomotion stability. The approach was tested in simulations with different perturbations including ground height variations up to 4.1 cm (20% of the nominal leg length). Finally, taking advantage of symmetries in the passively generated bounding gait leg motions on quadruped robots, the number of parameter variables of the controller was reduced. The methods and control laws proposed in this thesis are implemented in simulation models of the quadruped robot Minitaur.
Description
Keywords
Active walking, Basin of attraction, Periodic orbit, Quadruped robot control, Quadrupedal bounding gait, Virtual Pivot Point