Techniques for adaptive control of motor velocity of a surgical stapling and cutting instrument
A surgical stapler is presented having a firing assembly, a motor, and a motor control circuit. The firing assembly is configured to translate along a longitudinal axis such that translation of the firing assembly in a distal direction is configured to deploy staples from an end effector during a firing stroke. The motor assembly includes a motor configured to drive the firing assembly along the longitudinal axis. The motor control circuit is configured to receive a firing signal indicating initiation of the firing stroke, drive the motor with a motor drive signal comprising a pulse width modulated (PWM) signal having a first constant duty cycle such that the firing assembly is translated through an initial distance, and increase a duty cycle of the PWM signal based at least in part on movement of the firing assembly through the initial distance.
1 . A surgical stapler comprising:
a firing assembly configured to translate along a longitudinal axis such that translation of the firing assembly in a distal direction is configured to deploy staples from an end effector during a firing stroke;
a motor assembly comprising a motor mechanically coupled to the firing assembly and configured to drive the firing assembly along the longitudinal axis; and
a motor control circuit configured to:
receive a firing signal indicating initiation of the firing stroke,
drive the motor, in response to receiving the firing signal, with a motor drive signal comprising a pulse width modulated (PWM) signal having a first constant duty cycle such that the firing assembly is translated through an initial distance,
detect a movement of the firing assembly; and
increase a duty cycle of the PWM signal based at least in part on the detected movement of the firing assembly through the initial distance.
2 . The surgical stapler of claim 1 , wherein the first constant duty cycle is between about 25% and about 50%.
3 . The surgical stapler of claim 2 , wherein the first constant duty cycle is about 33%.
4 . The surgical stapler of claim 1 , wherein the motor control circuit is configured to modulate the duty cycle based at least in part on translation data of the firing assembly through at least a portion of the firing stroke distal of the initial distance.
5 . The surgical stapler of claim 1 , wherein the motor control circuit is configured maintain the duty cycle at a second constant duty cycle greater than the first constant duty cycle through at least a portion of the firing stroke distal of the initial distance.
6 . The surgical stapler of claim 5 , wherein the second constant duty cycle is selected based at least in part on a velocity of the firing assembly in the initial distance.
7 . The surgical stapler of claim 5 , wherein the second constant duty cycle is between about 50% and about 80%.
8 . The surgical stapler of claim 7 , wherein the second constant duty cycle is about 66%.
9 . The surgical stapler of claim 5 , wherein the motor control circuit is configured to set the duty cycle based at least in part on position of the firing assembly being within a predetermined zone distal to the initial distance.
10 . The surgical stapler of claim 1 , wherein the duty cycle is determined based at least in part on motor current through a portion of the firing stroke distal of the initial distance.
11 . A surgical stapler comprising:
a firing assembly configured to translate along a longitudinal axis such that translation of the firing assembly in a distal direction is configured to deploy staples from an end effector during a firing stroke;
a motor assembly comprising a motor mechanically coupled to the firing assembly and configured to drive the firing assembly along the longitudinal axis; and
a motor control circuit configured to:
modulate a motor drive signal to control velocity of the firing assembly through portions of the firing stroke,
detect a position of the firing assembly,
drive the motor with the motor drive signal to linearly increase a velocity of translation of the firing assembly to a target velocity when the firing assembly is detected to be traversing a first portion of the firing stroke, and
drive the motor with the motor drive signal to maintain the target velocity when the firing assembly is detected to be traversing a second portion of the firing stroke distal of the first portion.
12 . The surgical stapler of claim 11 , wherein the motor control circuit is configured to modulate a duty cycle of the motor drive signal based on firing assembly position data to control velocity of the firing assembly through portions of the firing stroke.
13 . The surgical stapler of claim 11 , wherein the motor control circuit is configured to:
sample velocity of the firing assembly at a plurality of positions along the firing stroke, and
modulate the motor drive signal based at least in part on the sampled velocities.
14 . The surgical stapler of claim 11 , where in the motor control circuit is configured to:
sample velocity of the firing assembly at a plurality of positions within the first portion of the firing stroke, and
modulate the motor drive signal within the first portion of the firing stroke based at least in part on the sampled velocities.
15 . The surgical stapler of claim 11 , wherein the motor control circuit is configured to:
receive a firing signal indicating initiation of the firing stroke,
drive the motor, in response to receiving the firing signal, with the motor drive signal such that the firing assembly is translate through an initial distance proximal of the first portion of the firing stroke and such that the motor drive signal comprises a pulse width modulated (PWM) signal having a constant duty cycle through the initial distance.
16 . The surgical stapler of claim 11 , wherein the motor control circuit is configured to drive the motor with the motor drive signal to linearly increase the velocity of translation of the firing assembly from a starting velocity to the target velocity through the first portion of the firing stroke.
17 . The surgical instrument of claim 16 , wherein motor control circuit is configured to determine the starting velocity based at least in part on movement of the firing assembly through an initial distance of the firing stroke proximal of the first portion of the firing stroke.
18 . The surgical instrument of claim 16 , wherein the motor control circuit is configured to determine the starting velocity based at least in part on current drawn by the motor during translation of the firing assembly through an initial distance of the firing stroke proximal of the first portion of the firing stroke.