Estimating state of ultrasonic end effector and control system therefor
Various aspects of a generator, ultrasonic device, and method for estimating a state of an end effector of an ultrasonic device are disclosed. The ultrasonic device includes an electromechanical ultrasonic system defined by a predetermined resonant frequency, including an ultrasonic transducer coupled to an ultrasonic blade. A control circuit measures a complex impedance of an ultrasonic transducer, wherein the complex impedance is defined as Z g ( t ) = V g ( t ) I g ( t ) . The control circuit receives a complex impedance measurement data point and compares the complex impedance measurement data point to a data point in a reference complex impedance characteristic pattern. The control circuit then classifies the complex impedance measurement data point based on a result of the comparison analysis and assigns a state or condition of the end effector based on the result of the comparison analysis.
1. A method of estimating a state of an end effector of an ultrasonic device, the ultrasonic device including an electromechanical ultrasonic system defined by a predetermined resonant frequency, the electromechanical ultrasonic system including an ultrasonic transducer coupled to an ultrasonic blade, the method comprising:
applying, by a drive circuit, a drive signal to an ultrasonic transducer, wherein the drive signal is a periodic signal defined by a magnitude and a frequency;
sweeping, by a control circuit, the frequency of the drive signal from below the predetermined resonant frequency to above the predetermined resonant frequency of the electromechanical ultrasonic system;
measuring and recording, by the control circuit, impedance circle variables R e , and X e , and admittance circle variable G e , and B e ;
comparing, by the control circuit, measured impedance circle variables R e , and X e , to reference impedance circle variables R ref , and X ref , respectively;
comparing, by the control circuit, measured admittance circle variables G e , and B e to reference admittance circle variables G ref , and B ref , respectively;
and
determining, by the control circuit, a state or condition of the end effector based on the result of the comparison.
2. The method of claim 1 , wherein measuring impedance circle variables R e , and X e , and admittance circle variable G e , and B e comprises measuring impedance circle variables R e , and X e , and admittance circle variable G e , and B e around a first resonant frequency.
3. The method of claim 2 , further comprising measuring impedance circle variables R e , and X e , and admittance circle variable G e , and B e around a second resonant frequency.
4. The method of claim 1 , further comprising determining R ref , G ref , X ref , and B ref for an end effector of an ultrasonic device having empty and open jaws, an ultrasonic device having a tip bite on a tissue, or an ultrasonic device having a full bite on a tissue having a staple therein.
5. The method of claim 1 , further comprising determining R ref , G ref , X ref , and B ref for an end effector of an ultrasonic device clamping a dry chamois or clamping a wet chamois.
6. The method of claim 1 , wherein measuring impedance circle variables comprises calculating impedance circle variables R e , and X e , from a measured impedance circle radius and measured impedance circle offsets.
7. The method of claim 6 , wherein calculating impedance circle variables R e , and X e , from a measured impedance circle radius and measured impedance circle offsets comprises:
plotting, by the control circuit, real resistance values and imaginary impedance values on a two-dimensional graph; and
fitting, by the control circuit, the real resistance values and the imaginary impedance values to a circle having a radius r and offset values (a, b).
8. The method of claim 1 , wherein measuring admittance circle variables comprises calculating admittance circle variable G e , and B e from a measured admittance circle radius and measured admittance circle offsets.
9. The method of claim 8 , wherein calculating admittance circle variables G e , and B e , from a measured admittance circle radius and measured admittance circle offsets comprises:
plotting, by the control circuit, real conductance values and imaginary susceptance values on a two-dimensional graph; and
fitting, by the control circuit, the real conductance values and imaginary susceptance values to a circle having a radius r and offset values (a, b).
10. The method of claim 1 , further comprising measuring reference impedance circle variables R ref , and X ref , from a reference impedance circle radius and reference impedance circle offsets, and
measuring reference admittance circle variables G ref , and B ref from a reference admittance circle radius and reference admittance circle offsets.
11. The method of claim 10 , further comprising storing, by the control circuit, reference impedance circle variables R ref , and X ref and reference admittance circle variables G ref , and B ref in a memory circuit.