# When to make a step? Tackling the timing problem in multi-contact locomotion by TOPP-MPC

Stéphane Caron and Quang-Cuong Pham. Humanoids 2017, Birmingham, United Kingdom, November 2017.

## Abstract¶

We present a model predictive controller (MPC) for multi-contact locomotion where predictive optimizations are realized by time-optimal path parameterization (TOPP). A key feature of this solution is that, contrary to existing planners where step timings are provided as inputs, here the timing between contact switches is computed as output of a fast nonlinear optimization. This is appealing to multi-contact locomotion, where proper timings depend on terrain topology and suitable heuristics are unknown. We show how to formulate legged locomotion as a TOPP problem and demonstrate the behavior of the resulting TOPP-MPC controller in simulations with a model of the HRP-4 humanoid robot.

## Presentation¶

 Poster 1 — Linear MPC for Multi-contact Walking (recap of previous work) Poster 2 — MPC by Time-optimal Retiming (this paper) Poster 3 — Nonlinear MPC for Dynamic Walking (later work, better behavior) Poster 4 — Boundedness MPC in 3D (latest works, still ongoing!)

## BibTeX¶

@inproceedings{caron2017humanoids,
title = {When to make a step? Tackling the timing problem in multi-contact locomotion by TOPP-MPC},
author = {Caron, St{\'e}phane and Pham, Quang-Cuong},
booktitle = {IEEE-RAS International Conference on Humanoid Robots},
year = {2017},
month = nov,
url = {https://hal.archives-ouvertes.fr/hal-01363757},
doi = {10.1109/HUMANOIDS.2017.8246922},
}


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