Transporting a heavy object on a frictional floor by a mobile manipulator based on adaptive MPC framework

This work tackles a task to transport an object by a mobile manipulator to the designated location. Heavy objects that the robot cannot lift up and needs to push or drag are targeted. It is assumed that the mass property of the object and the frictional characteristics between the object and the floor are unknown. In addition, a caging strategy of loosely holding the object is employed in order to reduce the required motor torques. Thus, a challenge is how to deal with uncertainties accompanied with interactions between the robot, the object and the ground. A control system that stands on a combination of an instantaneous equilibration model of a planar frictional movement and the adaptive model predictive control (MPC) to modify the model parameters during the operation is proposed and implemented on a mobile manipulator. Efficacy of the proposed method was verified through experiments, in which even objects that are equipped with casters and thus have largely different characteristics from the supposed friction model were successfully moved to the desired destination.