Feasible Region: an Actuation-Aware Extension of the Support Region

In legged locomotion the support region is defined as the 2D horizontal convex area where the robot is able to support its own body weight in static conditions. Despite this definition, when the joint-torque limits (actuation limits) are hit, the robot can be unable to carry its own body weight, even when the projection of its Center of Mass (CoM) lies inside the support region. In this manuscript we overcome this inconsistency by defining the Feasible Region, a revisited support region that guarantees both global static stability of the robot and the existence of a set of joint torques that are able to sustain the body weight. Thanks to the usage of an Iterative Projection (IP) algorithm, we show that the Feasible Region can be efficiently employed for online motion planning of loco-manipulation tasks for both humanoids and quadrupeds. Unlike the classical support region, the Feasible Region represents a local measure of the robots robustness to external disturbances and it must be recomputed at every configuration change. For this, we also propose a global extension of the Feasible Region that is configuration independent and only needs to be recomputed at every stance change.