Increased Mobility in Presence of Multiple Contacts - Identifying Contact Configurations that Enable Arbitrary Acceleration of CoM

TL;DR

This paper identifies contact configurations that allow a humanoid robot's CoM to have arbitrary acceleration, providing an efficient method to determine feasible motions and constraints based on contact arrangements.

Contribution

It introduces a low-complexity algorithm to identify contact configurations enabling arbitrary CoM acceleration and efficiently update constraints as the CoM moves.

Findings

Certain contact configurations allow unrestricted CoM acceleration.

The proposed method can quickly determine and update motion constraints.

Simulation results demonstrate the effectiveness of the approach.

Abstract

Planning of any motion starts by planning the trajectory of the CoM. It is of the highest importance to ensure that the robot will be able to perform planned trajectory. With increasing capabilities of the humanoid robots, the case when contacts are spatially distributed should be considered. In this paper, it is shown that there are some contact configurations in which any acceleration of the center of mass (CoM) is feasible. The procedure for identifying such a configurations is presented, as well as its physical meaning. On the other hand, for the configurations in which the constraint on CoM movement exists, it will be shown how to find that linear constraint, which defines the space of feasible motion. The proposed algorithm has a low complexity and to speed up the procedure even further, it will be shown that the whole procedure needs to be run only once when contact configuration changes. As the CoM moves, the new constraints can be calculated from the initial one, thus yielding significant computation speedup. The methods are illustrated in two simulated scenarios.