Methods for closed loop control of motor velocity of a surgical stapling and cutting instrument

1. A method of adjusting velocity in a motorized surgical instrument, the motorized surgical instrument comprising a displacement member configured to translate within the motorized surgical instrument over a plurality of predefined zones, a motor coupled to the displacement member to translate the displacement member, a control circuit coupled to the motor, a position sensor coupled to the control circuit, wherein the position sensor is configured to measure a position of the displacement member, and a timer circuit coupled to the control circuit, wherein the timer circuit is configured to measure elapsed time, the method comprising:

determining, by the control circuit, a position of the displacement member;

determining, by the control circuit, a zone in which the displacement member is located; and

setting, by the control circuit, a directed velocity of the displacement member based on the zone in which the displacement member is located.

2. The method of claim 1 , further comprising:

receiving, by the position sensor, the position of the displacement member;

receiving, by the timer circuit, elapsed time; and

setting, by the control circuit, duty cycle of the motor based on the zone in which the displacement member is located.

3. The method of claim 2 , further comprising:

determining, by the control circuit, an actual velocity of the displacement member.

4. The method of claim 3 , further comprising:

determining, by the control circuit, an error between the directed velocity of the displacement member and the actual velocity of the displacement member.

5. The method of claim 4 , further comprising:

setting, by the control circuit, a new directed velocity of the displacement member based on the error.

6. The method of claim 4 , wherein the error is based on at least one of a short term error (S), cumulative error (C), rate of change error (R), and number of overshoots error (N).

7. The method of claim 1 , wherein the surgical instrument further comprises an end effector, wherein the displacement member is configured to translate within the end effector.

8. A method of adjusting velocity in a surgical instrument, the surgical instrument comprising a displacement member configured to translate within the surgical instrument, a motor coupled to the displacement member to translate the displacement member, a control circuit coupled to the motor, a position sensor coupled to the control circuit, wherein the position sensor is configured to measure a position of the displacement member, and a timer circuit coupled to the control circuit, wherein the timer circuit is configured to measure elapsed time, the method comprising:

setting, by the control circuit, a directed velocity of the displacement member;

determining, by the control circuit, a position of the displacement member;

determining, by the control circuit, actual velocity of the displacement member;

comparing, by the control circuit, the directed velocity of the displacement member to the actual velocity of the displacement member;

determining, by the control circuit, an error between the directed velocity of the displacement member to the actual velocity of the displacement member; and

adjusting, by the control circuit, the directed velocity of the displacement member based on the error.

9. The surgical instrument of claim 8 , further comprising:

comparing, by the control circuit, the error to an error threshold.

10. The method of claim 9 , further comprising:

maintaining, by the control circuit, the directed velocity of the displacement member when the error is within the error threshold.

11. The method of claim 9 , further comprising:

adjusting, by the control circuit, the directed velocity of the displacement member to change the directed velocity when the error exceeds the error threshold.

12. The method of claim 8 , wherein the actual velocity of the displacement member is given by the following expression:

V

DM

=

A

·

S

+

B

·

∑

C

+

D

·

Δ

⁢

⁢

R

Δ

⁢

⁢

t

,

where:

A, B, and D are coefficients;

S is a short term error;

C is a cumulative error; and

R is a rate of change error.

13. The method of claim 8 , wherein the surgical instrument comprises an end effector, wherein the displacement member is configured to translate within the end effector.

14. A method of adjusting velocity in a surgical instrument, the surgical instrument comprising a displacement member configured to translate within the surgical instrument, a motor coupled to the displacement member to translate the displacement member, a control circuit coupled to the motor, a position sensor coupled to the control circuit, wherein the position sensor is configured to measure a position of the displacement member, and a timer circuit coupled to the control circuit, wherein the timer circuit is configured to measure elapsed time, the method comprising:

setting, by the control circuit, a directed velocity of the displacement member;

determining, by the control circuit, a position of the displacement member;

determining, by the control circuit, actual velocity of the displacement member;

comparing, by the control circuit, the directed velocity of the displacement member to the actual velocity of the displacement member;

determining, by the control circuit, an error between the directed velocity of the displacement member to the actual velocity of the displacement member; and

adjusting, by the control circuit, the directed velocity of the displacement member at a rate of change based on the error.

15. The method of claim 14 , further comprising:

comparing, by the control circuit, the error to multiple error thresholds.

16. The method of claim 15 , further comprising:

adjusting, by the control circuit, the directed velocity of the displacement member at multiple rates of change based on the error.

17. The method of claim 15 , further comprising:

comparing, by the control circuit, the error to a first error threshold; and

maintaining, by the control circuit, the directed velocity of the displacement member when the error is within the first error threshold.

18. The method of claim 17 , further comprising:

comparing, by the control circuit, the error to a second error threshold;

adjusting, by the control circuit, the directed velocity of the displacement member at a first rate of change when the error exceeds the first error threshold and is within the second error threshold.

19. The method of claim 17 , further comprising:

comparing, by the control circuit, the error to a second error threshold;

adjusting, by the control circuit, the directed velocity of the displacement member at a second rate of change when the error exceeds both the first error threshold and the second error threshold.

20. The method of claim 14 , wherein the error is based on a PID error.