Variational Contact-Implicit Trajectory Optimization


Z. Manchester and S. Kuindersma, “Variational Contact-Implicit Trajectory Optimization,” in International Symposium on Robotics Research (ISRR), Puerto Varas, Chile, 2017.
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Contact constraints arise naturally in many robot planning problems. In recent years, a variety of contact-implicit trajectory optimization algorithms have been developed that avoid the pitfalls of mode pre-specification by simultaneously optimizing state, input, and contact force trajectories. However, their reliance on first-order integrators leads to a linear tradeoff between optimization problem size and plan accuracy. To address this limitation, we propose a new family of trajectory optimization algorithms that leverage ideas from discrete variational mechanics to derive higher-order generalizations of the classic time-stepping method of Stewart and Trinkle. By using these dynamics formulations as constraints in direct trajectory optimization algorithms, it is possible to perform contact-implicit trajectory optimization with significantly higher accuracy. For concreteness, we derive a second-order method and evaluate it using several simulated rigid body systems including an underactuated biped and a quadruped.

Last updated on 03/07/2018