Devices and techniques for cutting and coagulating tissue
Various embodiments are directed to a method of driving an end effector coupled to an ultrasonic drive system of a surgical instrument. In accordance with the method, a generator is configured to generate at least one time varying electrical signal having a resonant frequency, monitor the resonant frequency of the at least one electrical signal, calculate a frequency slope between frequency data points of the time varying electrical signal, where the frequency slope is the change in resonant frequency over time, compare the frequency slope to a threshold frequency slope, and trigger a first response of the generator when the frequency slope crosses the threshold frequency slope.
1. A method of driving an end effector coupled to an ultrasonic drive system of a surgical instrument, the method comprising:
generating, by a generator, at least one time-varying electrical signal having a resonant frequency;
monitoring, by the generator, the resonant frequency of the at least one time-varying electrical signal;
calculating, by the generator, a frequency slope between frequency data points of the time varying electrical signal, where the frequency slope is a change in resonant frequency over time;
comparing, by the generator, the frequency slope to a frequency slope threshold; and
triggering, by the generator, a first response of the generator when the frequency slope crosses the frequency slope threshold.
2. The method of claim 1 , comprising:
comparing, by the generator, the frequency slope to the frequency slope threshold; and
triggering, by the generator, a second response of the generator when the frequency slope crosses the frequency slope threshold.
3. The method of claim 2 , comprising:
determining, by the generator, when the frequency slope is less than the frequency slope threshold;
incrementing, by the generator, a timer when the frequency slope is less than the frequency slope threshold;
determining, by the generator, when the timer is greater than a required trigger time; and
setting a logic condition when the timer is greater than the required trigger time.
4. The method of claim 3 , comprising:
incrementing, by the generator, the timer when the resonant frequency is less than a resonant frequency threshold and the frequency slope is less than the frequency slope threshold.
5. The method of claim 2 , comprising:
comparing, by the generator, the frequency slope to a cross-back frequency slope threshold, wherein the cross-back frequency slope threshold is the frequency slope threshold above which a triggered response stops.
6. A method of driving an end effector coupled to an ultrasonic drive system of a surgical instrument, the method comprising:
receiving, by a generator, a frequency slope threshold;
monitoring, by the generator, a frequency slope of the ultrasonic drive system;
comparing, by the generator, the frequency slope of the ultrasonic drive system with the frequency slope threshold; and
incrementing, by the generator, a timer when the frequency slope is less than the frequency slope threshold.
7. The method of claim 6 , further comprising:
receiving, by the generator, a required time before trigger parameter;
receiving, by the generator, a timer value from the timer;
comparing, by the generator, the required time before trigger parameter and the timer value;
setting, by the generator, a condition set latch when the timer value is greater than the required time before trigger parameter and indicating that a predetermined condition has set been met; or
resetting, by the generator, the condition set latch when the timer value is less than or equal to the required time before trigger parameter.
8. The method of claim 6 further comprising:
resetting, by the generator, the timer when the frequency slope is greater than the frequency slope threshold.
9. The method of claim 8 , further comprising:
determining, by the generator, when a cross-back frequency slope latch is set; and
indicating that a predetermined condition set has not been met when the cross-back frequency slope latch is not set.
10. The method of claim 9 , further comprising:
receiving, by the generator, a minimum latch time parameter for a condition set latch;
receiving, by the generator, a cross-back frequency slope threshold parameter;
receiving, by the generator, an indication that at least one of the condition set latch or the cross-back frequency slope latch is set;
comparing, by the generator, a latched time of the condition set latch with the minimum latch time parameter for the condition set latch;
comparing, by the generator, the frequency slope with the cross-back frequency slope threshold parameter; and
indicating, by the generator, that a predetermined condition set has been met when the frequency slope is less than the cross-back frequency slope threshold parameter.
11. The method of claim 10 , further comprising:
resetting, by the generator, a timer latch; and
indicating, by the generator, that a predetermined condition set has not been met when the frequency slope is greater than the cross-back frequency slope threshold parameter.
12. A generator configured to drive an end effector coupled to an ultrasonic drive system of a surgical instrument, the generator comprising:
a processor;
a timer circuit coupled to the processor;
a timer latch coupled to the processor;
a condition set latch coupled to the processor; and
a memory coupled to the processor, wherein the memory includes machine executable instructions that when executed by the processor cause the processor to:
receive a frequency slope threshold;
monitor a frequency slope of the ultrasonic drive system;
compare the frequency slope of the ultrasonic drive system with the frequency slope threshold; and
increment the timer circuit when the frequency slope is less than the frequency slope threshold.
13. The generator of claim 12 , wherein the machine executable instructions, when executed by the processor, cause the processor to:
receive a required time before trigger parameter;
receive a timer value from the timer circuit;
compare the required time before trigger parameter and the timer value;
set the condition set latch when the timer value is greater than the required time before trigger parameter and indicate that a predetermined condition has not been met; or
reset the condition set latch when the timer value is less than or equal to the required time before trigger parameter.
14. The generator of claim 12 , wherein the machine executable instructions, when executed by the processor, cause the processor to:
reset the timer circuit when the frequency slope is greater than the frequency slope threshold.
15. The generator of claim 14 , wherein the machine executable instructions, when executed by the processor, cause the processor to:
indicate a cross-back frequency slope latch is set; and
indicate that a predetermined condition set has not been met when the cross-back frequency slope latch is not set.
16. The generator of claim 15 , wherein the machine executable instructions, when executed by the processor, cause the processor to:
receive a minimum latch time parameter for the condition set latch;
receive a cross-back frequency slope threshold parameter;
receive an indication that the cross-back frequency slope latch is set;
compare the frequency slope with the cross-back frequency slope threshold parameter; and
indicate that a predetermined condition set has been met when the frequency slope is less than the cross-back frequency slope threshold parameter.
17. The generator of claim 15 , wherein the machine executable instructions, when executed by the processor, cause the processor to:
reset the timer latch; and
indicate that the predetermined condition set has not been met when the frequency slope is greater than the cross-back frequency slope threshold parameter.