Device and method for controlling compression of tissue
A method and device for controlling the compression of tissue include 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 and, during the clamping, monitoring a parameter of the electric motor indicative of a clamping force exerted to the tissue by the clamping members. The method and device include, during the clamping, controlling the electric motor, based on the monitored parameter, to limit the clamping force to a predetermined maximum limit.
1. A surgical device comprising:
a first clamping member;
a second clamping member;
a motor configured to move at least one of the first clamp member or the second clamp member relative to each other;
a plurality of sensors coupled to the motor, each of the plurality of sensors configured to sense a corresponding operational property of the motor; and
a controller configured to:
calculate for each of the operational properties a corresponding drive signal;
select a smallest drive signal from the calculated drive signals; and
control the motor based on the selected drive signal.
2. The surgical device according to claim 1 , wherein one of the plurality of sensors is a current sensor configured to measure a current being drawn by the motor.
3. The surgical device according to claim 2 , wherein the controller is further configured to determine a current offset based on a current drawn by the motor corresponding to a frictional loss during clamping of the first and second clamping members with no tissue disposed therebetween.
4. The surgical device according to claim 3 , wherein the controller is further configured to subtract the current offset from the measured current to determine a calibrated current.
5. The surgical device according to claim 4 , wherein one of the drive signals is a current drive signal and the controller is further configured to calculate the current drive signal based on a difference between a target current and the calibrated current.
6. The surgical device according to claim 4 , wherein the controller is further configured to calculate torque applied by the motor based on the calibrated current.
7. The surgical device according to claim 6 , wherein the controller is further configured to calculate mechanical energy applied to the tissue by the first and second clamping members based on the applied torque.
8. The surgical device according to claim 1 , wherein one of the plurality of sensors is a position sensor configured to measure a position of the motor.
9. The surgical device according to claim 8 , wherein one of the drive signals is a position drive signal and the controller is further configured to calculate the position drive signal based on a difference between a target position and the measured position.
10. The surgical device according to claim 1 , wherein one of the plurality of sensors is a velocity sensor configured to measure a velocity of the motor.
11. The surgical device according to claim 10 , wherein one of the drive signals is a velocity drive signal and the controller is further configured to calculate the velocity drive signal based on a difference between a target velocity and the measured velocity.
12. A method for controlling a surgical device including a first clamp member and a second clamp member, the method comprising:
controlling a motor configured to move at least one of the first clamp member or the second clamp member relative to each other;
sensing a plurality of operational properties of the motor;
calculating a corresponding drive signal for each of the operational properties;
selecting a smallest drive signal from the calculated drive signals; and
controlling the motor based on the selected drive signal.
13. The method according to claim 12 , wherein sensing the plurality of operational properties of the motor includes measuring a current being drawn by the motor.
14. The method according to claim 12 , wherein sensing the plurality of operational properties of the motor includes measuring a position of the motor.
15. The method according to claim 14 , wherein calculating the corresponding drive signal includes calculating a position drive signal based on a difference between a target position and the measured position.
16. The method according to claim 12 , wherein sensing the plurality of operational properties of the motor includes measuring a velocity of the motor.
17. The method according to claim 16 , wherein calculating the corresponding drive signal includes calculating a velocity drive signal based on a difference between a target velocity and the measured velocity.
18. The method according to claim 12 , further comprising:
determining a current offset based on a current drawn by the motor corresponding to a frictional loss during clamping of the first and second clamping members with no tissue disposed therebetween.
19. The method according to claim 18 , further comprising:
subtracting the current offset from the measured current to determine a calibrated current.
20. The method according to claim 19 , wherein calculating the corresponding drive signal includes calculating a current drive signal based on a difference between a target current and the calibrated current.