Techniques for cutting and coagulating tissue for ultrasonic surgical instruments

A method of driving an end effector coupled to an ultrasonic drive system of an ultrasonic surgical instrument, the method comprising:

• receiving a trigger signal;
• in response to the trigger signal, providing a first drive signal to the ultrasonic drive system to drive the end effector, wherein the first drive signal is at a first power level;
• maintaining the first drive signal at the first power level for a first period;
• providing a second drive signal to the ultrasonic drive system to drive the end effector, wherein the second drive signal is at a second power level lower than the first power level;
• applying a plurality of input variables to a multi-variable model to generate a multi-variable model output, wherein the multi-variable model output corresponds to an effect of the ultrasonic surgical instrument on tissue, and wherein the plurality of input variables comprises at least one variable describing the drive signal and at least one variable describing a property of the ultrasonic surgical instrument;
• after the multi-variable model output exceeds a threshold value for a first threshold time period, triggering a first response that is a feedback;
• and
• after the multi-variable model output has exceeded the threshold value for a second threshold time period greater than the first threshold time period, providing a third drive signal for the ultrasonic drive system to drive the end effector, wherein the third drive signal is at a third power level less than the first power level.

A method of driving an end effector coupled to an ultrasonic drive system of an ultrasonic surgical instrument, the method comprising:

• receiving a trigger signal;
• in response to the trigger signal, providing a first drive signal to the ultrasonic drive system to drive the end effector, wherein the first drive signal is at a first power level;
• maintaining the first drive signal at the first power level for a first period;
• providing a second drive signal to the ultrasonic drive system to drive the end effector, wherein the second drive signal is at a second power level lower than the first power level;
• applying a plurality of input variables to a multi-variable model to generate a multi-variable model output, wherein the multi-variable model output corresponds to an effect of the ultrasonic surgical instrument on tissue, and wherein the plurality of input variables comprises at least one variable describing the drive signal and at least one variable describing a property of the ultrasonic surgical instrument;
• after the multi-variable model output exceeds a threshold value for a threshold time period, triggering a first response that is a feedback, wherein the multi-variable model output exceeds the threshold value within a second period from modifying the drive signal to the second power level;
• and
• upon expiration of the second period, providing a third drive signal for the ultrasonic drive system to drive the end effector, wherein the third drive signal is at a third power level less than the first power level.