End effector control and calibration

An apparatus for controlling an end effector comprising a clamp arm and an ultrasonic blade, the apparatus comprising:

• a sensor configured to generate signals in response to movement of a first tube relative to a second tube, the first tube driving movement of the clamp arm of the end effector;
• and
• a control circuit configured to:
• receive a first signal, a second signal, and a third signal from the sensor, wherein the first signal, the second signal, and the third signal are associated with positions of the clamp arm of the end effector as it moves;
• generate a fit curve based on the first signal, the second signal, and the third signal;
• receive a fourth signal from the sensor, wherein the fourth signal is associated with a current position of the clamp arm of the end effector as it moves;
• generate a conclusion associated with a relative position of the clamp arm based on the fourth signal and the generated fit curve;
• determine an impedance of the ultrasonic blade in contact with tissue;
• and
• determine a type of the tissue based on the impedance.

A computer-implemented method of controlling an end effector comprising a clamp arm and an ultrasonic blade, the method comprising:

• receiving, via a control circuit, a first signal, a second signal, and a third signal from a sensor configured to generate signals in response to movement of a first tube of the end effector relative to a second tube of the end effector, the first tube driving movement of the clamp arm of the end effector, wherein the first signal, the second signal, and the third signal are associated with positions of the clamp arm of the end effector as it moves;
• generating, via the control circuit, a fit curve based on the first signal, the second signal, and the third signal;
• receiving, via the control circuit, a fourth signal from the sensor, wherein the fourth signal is associated with a current position of the clamp arm of the end effector as it moves;
• generating, via the control circuit, a conclusion associated with a relative position of the clamp arm based on the fourth signal and the generated fit curve;
• determining, via the control circuit, a thickness of a tissue based on the generated conclusion;
• determining, via the control circuit, an impedance of the ultrasonic blade in contact with the tissue;
• and
• determining, via the control circuit, a type of the tissue based on the impedance.