Contact-Implicit Trajectory Optimization using Orthogonal Collocation

TL;DR

This paper introduces an improved contact-implicit trajectory optimization method for dynamic robots that leverages orthogonal collocation with higher order polynomials to enhance accuracy in contact-rich scenarios.

Contribution

It combines orthogonal collocation with contact-implicit optimization, enabling more accurate trajectory generation without requiring prior contact mode scheduling.

Findings

Significantly improved trajectory accuracy with orthogonal collocation.

Effective handling of intermittent contact without mode scheduling.

Enhanced capability to generate complex robot behaviors.

Abstract

In this paper we propose a method to improve the accuracy of trajectory optimization for dynamic robots with intermittent contact by using orthogonal collocation. Until recently, most trajectory optimization methods for systems with contacts employ mode-scheduling, which requires an a priori knowledge of the contact order and thus cannot produce complex or non-intuitive behaviors. Contact-implicit trajectory optimization methods offer a solution to this by allowing the optimization to make or break contacts as needed, but thus far have suffered from poor accuracy. Here, we combine methods from direct collocation using higher order orthogonal polynomials with contact-implicit optimization to generate trajectories with significantly improved accuracy. The key insight is to increase the order of the polynomial representation while maintaining the assumption that impact occurs over the duration of one finite element.