Robotic system including foldable robotic arm

1. A system for positioning an end effector inside a confined space that is accessible only through an access port, the system comprising:

a robotic arm having multiple links and a parallel-axis joint layout such that the links can be folded into a compact configuration with links stacked on top of each other;

a robotic wrist mounted to a last link of the robotic arm;

an end effector mounted to the robotic wrist; and

fine positioner modules attached to opposite sides of the end effector;

the robotic arm for positioning the end effector, the robotic wrist for orienting the end effector, the fine positioner modules for performing fine adjustment of the end effector along a surface of the confined space to correct for positional errors of the arm and wrist.

2. The system of claim 1 , wherein the robotic arm is foldable into a coextensive stack.

3. The system of claim 1 , further comprising means for positioning, lifting and tilting the robotic arm to fit through an access port.

4. The system of claim 3 , further comprising a carriage assembly for moving the system to the access port.

5. The system of claim 1 , wherein the robotic wrist mimics a spherical wrist having three degrees of freedom; and wherein all rotational axes of the wrist intersect at a common point.

6. The system of claim 1 , wherein each fine postitioner module includes:

a contact member for making contact with the surface of the confined space;

a position adjustor for causing the contact member to move the end effector along the surface; and

an actuator for relieving pressure of the end effector against the surface while the contact member is used to move the end effector along the surface.

7. A method comprising operating the robotic system of claim 1 to position the end effector within the confined space, wherein operating the robotic system includes:

folding the robotic arm such that its links are stacked on top of each other;

maneuvering the folded arm through the access port and into the confined space;

at least partially unfolding the arm within the confined space;

using the arm and the robotic wrist to position and orient the end effector over a target within the confined space; and

using the fine positioner module to correct for positional errors of the arm and wrist.

8. The method of claim 7 , further comprising stowing the robotic wrist and end effector on a last link of the folded robotic arm prior to maneuvering the folded arm through the access port.

9. The system of claim 1 , wherein the robotic wrist mimics a spherical wrist having three degrees of freedom; and wherein all rotational axes of the wrist intersect at a common point.

10. The system of claim 1 ,wherein the fine positioner modules position the end effector while the arm and wrist are pressing the end effector against the surface.