Robust whole-body motion control of legged robots

Abstract

We introduce a robust control architecture for the whole-body motion control of torque controlled robots with arms and legs. The method is based on the robust control of contact forces in order to track a planned Center of Mass trajectory. Its appeal lies in the ability to guarantee robust stability and performance despite rigid body model mismatch, actuator dynamics, delays, contact surface stiffness, and unobserved ground profiles. Furthermore, we introduce a task space decomposition approach which removes the coupling effects between contact force controller and the other noncontact controllers. Finally, we verify our control performance on a quadruped robot and compare its performance to a standard inverse dynamics approach on hardware.

Real-time motion planning of legged robots: A model predictive control approach

“…Here, we have chosen the direct approach. To this end, we use a robust motion control approach introduced in [22] which relies on the robust tracking of contact forces in face of rigid body model mismatch, actuator dynamics, delays, contact surface stiffness, and unobserved ground profiles. Fig.…”

“…Fig. 2 demonstrates an overview of the motion controller introduced in [22]. In order to manipulate the contact force directly, this structure uses an especial system decomposition which allows to control the swing leg trajectories and contact forces independently.…”

Passive Whole-Body Control for Quadruped Robots: Experimental Validation Over Challenging Terrain

“…Many recent contributions in locomotion control have been proposed in the literature that were successfully tested on bipeds and quadrupeds (e.g. [6,7,8,9,5,10]). Some of them are based on quasi-static assumptions or lower dimensional models [11,12,13].…”

“…WBC facilitates such decoupling between the motion planning and control in such a way that it is easy to accomplish multiple tasks while respecting the robot's behavior [9]. These tasks might include motion tasks for the robot's end effectors (legs and feet) [8,9], but also could be utilized for contacts anywhere on the robot's body [14] or for a cooperative manipulation task between robots [15]. WBC casts the locomotion controller as an optimization problem, in which, by incorporating the full dynamics of the legged robot, all of its Degrees of Freedom (DoFs) are exploited in order to spread the desired motion tasks globally to all the joints.…”

Mechanism, Actuation, Perception, and Control of Highly Dynamic Multilegged Robots: A Review

“…The WBC facilitates such decoupling because it is easy to fulfill multiple tasks while simultaneously respecting the behaviors of the legged robot. Farshidian et al [140] proposed a task space decomposition method that eliminates the coupling between contact force and non-contact controllers. The (4)…”