Device and method for controlling compression of tissue

1. A method, comprising:

clamping tissue between a first clamping member and a second clamping member by driving at least one of the clamping members with an electric motor toward a predetermined tissue gap between the clamping members;

during the clamping, monitoring a parameter of the electric motor indicative of a clamping force exerted to the tissue by the clamping members; and

during the clamping, controlling the electric motor, based on the monitored parameter, to limit the clamping force to a predetermined maximum limit.

2. The method of claim 1 , wherein the predetermined maximum limit is selected based on predetermined properties of the tissue to be clamped.

3. The method of claim 2 , wherein the predetermined maximum limit is selected to limit trauma to the clamped tissue to a predetermined acceptable level.

4. The method of claim 1 , wherein the predetermined maximum limit is below a predetermined deflection limit of the at least one of the clamping members.

5. The method of claim 1 , wherein the controlling includes adjusting a voltage applied to the electric motor.

6. The method of claim 1 , wherein the controlling includes limiting the current driving the electric motor.

7. The method of claim 1 , wherein the monitoring includes measuring a current driving the electric motor.

8. The method of claim 7 , further comprising:

prior to the clamping, measuring current due to frictional losses associated with moving the clamping members; and

subtracting the frictional losses from the current measured during the clamping.

9. The method of claim 7 , further comprising, prior to the clamping, measuring a current offset.

10. The method of claim 9 , further comprising subtracting the current offset from the current measured during the clamping.

11. The method of claim 1 , wherein the predetermined maximum limit is selected to prevent the force from reaching a yield force.

12. The method of claim 1 , wherein the predetermined maximum limit is selected to prevent the clamping members from splaying.

13. The method of claim 1 , further comprising using a profile of the monitored parameter to monitor and track structural fatigue in at least one of the clamping members.

14. The method of claim 13 , wherein the profile is compared to a normal parameter signature.

15. The method of claim 1 , wherein the surgical instrument is a surgical stapler and one of the clamping members is an anvil configured to form surgical staples.

16. The method of claim 15 , further comprising using a profile of the monitored parameter to identify whether all of the staples of a staple cartridge have fired.

17. The method of claim 15 , further comprising using a profile of the monitored parameter to identify at least one of staple misfires, an absence of staples in a staple cartridge, and staple jams.

18. The method of claim 1 , wherein the controlling includes:

determining a motor velocity;

determining a motor position; and

determining a net motor current attributable to the compression by subtracting out a current offset and current due to frictional losses.

19. The method of claim 18 , wherein the controlling further comprises:

determining a velocity drive based on the determined velocity;

determining a position drive based on the determined position; and

determining a current drive based on the determined net motor current.

20. The method of claim 19 , wherein the controlling further comprises applying the smallest of the velocity drive, the position drive, and the current drive to the motor.

21. The method of claim 18 , further comprising detecting the presence of an incompressible object based on the motor velocity.

22. The method of claim 1 , wherein the controlling includes adjusting a driving speed of the motor to limit the clamping force to the predetermined maximum limit.