Faculty Advisor or Committee Member

Michael A. Gennert, Advisor

Faculty Advisor or Committee Member

Michael A Gennert, Committee Chair

Faculty Advisor or Committee Member

Gregory Fischer, Committee Member

Faculty Advisor or Committee Member

Taskin Padir, Committee Member

Faculty Advisor or Committee Member

Mahdi Agheli, Committee Member

Identifier

etd-3006

Abstract

Current state-of-the-art walking controllers for humanoid robots use simple models, such as Linear Inverted Pendulum Mode (LIPM), to approximate Center of Mass(CoM) dynamics of a robot. These models are then used to generate CoM trajectories that keep the robot balanced while walking. Such controllers need prior information of foot placements, which is generated by a walking pattern generator. While the robot is walking, any change in the goal position leads to aborting the existing foot placement plan and re-planning footsteps, followed by CoM trajectory generation. This thesis proposes a tightly coupled walking pattern generator and a reactive balancing controller to plan and execute one step at a time. Walking is an emergent behavior from such a controller which is achieved by applying a virtual force in the direction of the goal. This virtual force, along with external forces acting on the robot, is used to compute desired CoM acceleration and the footstep parameters for only the next step. Step location is selected based on the capture point, which is a point on the ground at which the robot should step to stay balanced. Because each footstep location is derived as needed based on the capture point, it is not necessary to compute a complete set of footsteps. Experiments show that this approach allows for simpler inputs, results in faster operation, and is inherently immune to external perturbing and other reaction forces from the environment. Experiments are performed on Boston Dynamic's Atlas robot and NASA's Valkyrie R5 robot in simulation, and on Atlas hardware.

Publisher

Worcester Polytechnic Institute

Degree Name

PhD

Department

Robotics Engineering

Project Type

Dissertation

Date Accepted

2019-09-13

Accessibility

Unrestricted

Subjects

humanoid robots, biped walking, dynamic walking, humanoid balancing

Available for download on Thursday, December 03, 2020

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