Clamp assembly including permanent magnets and coils for selectively magnetizing and demagnetizing the magnets

1. A clamp assembly for clamping a stack having a first surface and a second surface, the clamp assembly comprising:

a first clamp including a plurality of magnet devices, each magnet device including a permanent magnet and a coil surrounding the permanent magnet;

a controller for pulsing the coils to selectively magnetize and demagnetize the permanent magnets; and

a second clamp generally opposite the first clamp that forms an air gap with at least one of the permanent magnets of the first clamp, the second clamp providing a flux path between at least two of the plurality of magnet devices,

wherein the first clamp is configured to be positioned against the first surface of the stack;

wherein the second clamp is configured to be positioned against the second surface of the stack; and

wherein the air gap is configured to receive the stack.

2. The assembly of claim 1 , wherein the second clamp includes a plate for providing the flux path.

3. The assembly of claim 1 , wherein the second clamp includes a plurality of the magnet devices whose permanent magnets are aligned with corresponding permanent magnets in the first clamp.

4. The assembly of claim 1 , wherein each permanent magnet includes iron alloy.

5. The assembly of claim 1 , wherein the permanent magnets are arranged symmetrically about a process axis.

6. The assembly of claim 1 , further comprising at least one keeper for holding the permanent magnets about a process axis, the keeper also providing a flux path between the permanent magnets.

7. The assembly of claim 6 , wherein a plurality of keepers extend radially outward from the process axis.

8. The assembly of claim 6 , wherein the at least one keeper arranges the permanent magnets in a circular pattern about the process axis.

9. The assembly of claim 1 , wherein the permanent magnet of at least one magnet device is bent, and the coil is at one end of the bent permanent magnet.

10. The assembly of claim 1 , wherein the controller is configured to supply pulses to selected coils to promote and demote magnetic domain alignment of the permanent magnets.

11. The assembly of claim 10 , wherein the controller includes a closed loop control, response to an air gap sensor, for controlling control coil current duration and amplitude for each coil to achieve a target flux density of each permanent magnet.

12. The assembly of claim 1 , further comprising a capacitor system for pre-storing energy for pulsing the coils.

13. A system for clamping a stack, the system comprising:

a robot end effector including a plurality of magnet devices about a process axis, each magnet device including a permanent magnet and a coil surrounding the permanent magnet;

a controller for pulsing the coils to selectively magnetize and demagnetize the permanent magnets; and

a flux-conducting structure that forms an air gap with at least one of the magnet devices, the flux-conducting structure providing a flux path between at least two of the plurality of magnet devices,

wherein the air gap is configured to receive the stack between the plurality of magnet devices and the flux-conducting structure.

14. The system of claim 13 , wherein the end effector includes a tool assembly for performing at least one manufacturing operation along the process axis.

15. The system of claim 13 , further comprising at least one robot for positioning the plurality of magnet devices and the flux-conducting structure.