Session: MR-05/MSNDC-08-02 Motion Planning, Dynamics, and Control of Robots

Paper Number: 71976

Start Time: August 19, 11:10 AM

71976 - Reduced-Order Model With Foot Tipping Allowance for Legged Balancing 

Tipping is an instrumental aspect of multi-phase contact situations that arise during common tasks such as the locomotion of legged systems.  Despite its importance in balance recovery, tipping is often ignored in trajectory optimization due to the lack of existing methods that are able to actively plan and optimize for unspecified contacts.  Trajectory Optimization based on nonlinear programming requires a priori knowledge about anticipated contact changes, such as their order and timing, in order to generate physically feasible motions.  In this paper, a conditional optimization framework is established for direct collocation in trajectory optimization for legged balancing with foot tipping allowance.  The proposed approach can evaluate the timing of contact phases without pre-planned contact forces or sequences of events, which is not possible with conventional methods.  This conditional optimization framework is demonstrated by computing the balanced regions of two reduced-order models of a legged system, namely, inverted-pendulum-based models without and with a flywheel, and is validated with control simulations.  The contribution of tipping to balance stability is quantified in comparison to prior results obtained without tipping allowance.  The framework presented can also be generalized to other multi-phase contact scenarios, such as rolling and sliding, where unspecified discontinuous changes in contact occur with important consequences in the performance of legged systems.

Presenting Author: William Peng New York University

Authors:

William Z. Peng New York University
Hyunjong Song New York University
Joo H. Kim New York University