  Manipulation of objects by exploiting their contact with the environment can
enhance both the dexterity and payload capability of robotic manipulators. A
common way to manipulate heavy objects beyond the payload capability of a robot
is to use a sequence of pivoting motions, wherein, an object is moved while
some contact points between the object and a support surface are kept fixed.
The goal of this paper is to develop an algorithmic approach for automated plan
generation for object manipulation with a sequence of pivoting motions. A plan
for manipulating a heavy object consists of a sequence of joint angles of the
manipulator, the corresponding object poses, as well as the joint torques
required to move the object. The constraint of maintaining object contact with
the ground during manipulation results in nonlinear constraints in the
configuration space of the robot, which is challenging for motion planning
algorithms. Exploiting the fact that pivoting motion corresponds to movements
in a subgroup of the group of rigid body motions, SE(3), we present a novel
task-space based planning approach for computing a motion plan for both the
manipulator and the object while satisfying contact constraints. We also
combine our motion planning algorithm with a grasping force synthesis algorithm
to ensure that friction constraints at the contacts and actuator torque
constraints are satisfied. We present simulation results with a dual-armed
Baxter robot to demonstrate our approach.
