Controlling an ultrasonic surgical instrument according to tissue location
Various systems and methods for controlling an ultrasonic surgical instrument according to the location of tissue grasped within an end effector are disclosed. A control circuit can be configured to apply varying power levels, via a generator, to an ultrasonic transducer driving an ultrasonic electromechanical system to oscillate an ultrasonic blade. Further, the control circuit can measure impedances of the ultrasonic transducer corresponding to the varying power levels and determine a location of tissue positioned within the end effector according to a difference between the impedances of the ultrasonic transducer relative to a threshold.
1. An electrosurgical instrument comprising:
an energy source;
an end effector comprising a first jaw and a second jaw,
wherein the first jaw comprises a first plurality of electrodes disposed in a first array on an inner surface of the first jaw, and
wherein the second jaw comprises a second plurality of electrodes disposed in a second array on an inner surface of the second jaw; and
a control circuit configured to:
deliver, from the energy source, an electrical signal to each of the first plurality of electrodes of the first array;
receive a return electrical signal from the second plurality of electrodes of the second array; and
determine a position of a tissue within the end effector when the tissue is clamped between the first jaw and the second jaw,
wherein the position of the tissue is determined by the control circuit based at least in part on the electrical signals delivered to the first plurality of electrodes of the first array and the return electrical signal, and
wherein a characteristic of the electrical signal delivered to a first electrode of the first plurality of electrodes is a first frequency and a characteristic of the electrical signal delivered to a second electrode of the first plurality of electrodes is a second frequency, wherein the first frequency differs from the second frequency.
2. The electrosurgical instrument of claim 1 , wherein the first frequency and the second frequency are non-therapeutic RF frequencies.
3. The electrosurgical instrument of claim 1 , further comprises a plurality of band-pass filters, wherein each of the plurality of band-pass filters is electrically coupled to one electrode of the second plurality of electrodes.
4. The electrosurgical instrument of claim 3 , wherein a band-pass characteristic of a first band-pass filter coupled to a first electrode of the second plurality of electrodes differs from a band-pass characteristic of a second band-pass filter coupled to a second electrode of the second plurality of electrodes.
5. The electrosurgical instrument of claim 4 , wherein the band-pass characteristic of the first band-pass filter comprises a first band-pass center frequency, and the band-pass characteristic of the second band-pass filter comprises a second band-pass center frequency.
6. The electrosurgical instrument of claim 5 , wherein the first band-pass center frequency is the same as the first frequency and the second band-pass center frequency is the same as the second frequency.
7. The electrosurgical instrument of claim 3 , wherein the return electrical signal comprises a series output of the plurality of band-pass filters.
8. The electrosurgical instrument of claim 7 , wherein the position of the tissue is determined by the control circuit based at least in part on a frequency composition of the return electrical signal.