  This work presents a computationally lightweight motion planner for
over-actuated platforms. For this purpose, a general state-space model for
mobile platforms with several kinematic chains is defined, which considers
non-linearities and constraints. The proposed motion planner is based on a
sequential multi-stage approach that takes advantage of the warm start on each
step. Firstly, a globally optimal and smooth 2D/3D trajectory is generated
using the Fast Marching Method. This trajectory is fed as a warm start to a
sequential linear quadratic regulator that is able to generate an optimal
motion plan without constraints for all the platform actuators. Finally, a
feasible motion plan is generated considering the constraints defined in the
model. In this respect, the sequential linear quadratic regulator is employed
again, taking the previously generated unconstrained motion plan as a warm
start. This novel approach has been deployed into the Exomars Testing Rover of
the European Space Agency. This rover is an Ackermann-capable planetary
exploration testbed that is equipped with a robotic arm. Several experiments
were carried out demonstrating that the proposed approach speeds up the
computation time, increasing the success ratio for a martian sample retrieval
mission, which can be considered as a representative use case of an
over-actuated mobile platform.
