Of the clamps of the hanger inserting the lifted part

of the clamps of the hanger, inserting the lifted part into the clamps at the desired picking points
locations and commanding their closure, releasing the body of the hanger once moved back to
the conveyor. The large handling maneuvers like reaching the free hanger and orienting the
grasping device so that it can dock to it and the reverse procedure will be executed by the robot
carrying the reconfigurable grasping device. The reconfigurable grasping device, complying
with these remarks comprises three articulated fingers, two lateral 2 d of and one central 1 d of,
with serial architecture and actuators distributed along the chain. Each finger carries at its end a
grasping picking module. The central finger comprises one prismatic joint and the
corresponding picking module translates in a fixed direction. Each lateral finger contains three
revolute joints, two active and one passive at fingertip, with parallel axes. A suitable mechanical
architecture constrains the picking modules to translate in a plane orthogonal to the revolute
joints of the fingers. Kinematic, dynamic analysis and computational simulations were
performed in order to assess the grasping device parameters. The docking of the grasping
device to the hanger body is made by a groove and a pneumatic lock guarantees for accurate
self-positioning and blockage of the hanger. Three dedicated pneumatic cylinders are used to
release the friction joints of the hanger fingers.
12

Working cycle and system control
As first, the gripper docks to one hanger at a known location, when this operation has been
completed, the grasping device blocks to the hanger through a locking mechanism including a
cylinder and a conic peg. The first operation done is the hanger reset. The robot rotates the
grasping device with the central gripper finger vertical downwards. The three unlocking
cylinders in the gripper are activated and they press and release the joints of the hanger; the
fingers of the hanger fall down on their stops. Then the unlocking cylinders of the grasping
device are deactivated and the fingers locked. Now the secondary docking step starts. The
cylinders on the picking module are activated; then the gripper fingers move the picking
modules to the prescribed locations. The hollow pipes of the picking modules envelope the
docking tips.
The third step is the setting of the hanger. The hanger joints are released. The gripper fingers
move the clamps to the desired grasping points on the part. The gripper deactivates again the
releasing cylinders and the hanger joints block. The fourth step is the grasping of the part. The
service robot moves the grasping device on the part with the mouths of the vacuum pipes close
to the desired grasping points. The cylinders of the picking module are still deactivated. When
the mouths touch the part, vacuum is activated and the grasping forces generated. The cylinders
in the picking module are activated and they move up together with the grasped part. The
clamps are activated and clamps opened. The hollow pipes of the picking modules move up.