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:
measuring, by a control circuit, a complex impedance of an ultrasonic transducer, wherein the complex impedance is defined as
Z
g
(
t
)
=
V
g
(
t
)
I
g
(
t
)
;
receiving, by the control circuit, a reference complex impedance characteristic pattern comprising a plurality of data points from a database or memory coupled to the control circuit, wherein each of the plurality of data points is defined by an ultrasonic transducer impedance magnitude |Z|, an ultrasonic transducer impedance phase φ, and a frequency f at which the complex impedance of the ultrasonic transducer is measured;
generating, by the control circuit, the reference complex impedance characteristic pattern, wherein generating the reference complex impedance characteristic pattern comprises:
applying, by a drive circuit coupled to the control circuit, a nontherapeutic drive signal to the ultrasonic transducer starting at an initial frequency, ending at a final frequency, and at a plurality of frequencies therebetween;
measuring, by the control circuit, the complex impedance of the ultrasonic transducer at each frequency of the plurality of the frequencies;
storing, by the control circuit, a data point corresponding to each complex impedance measurement; and
curve fitting, by the control circuit, a plurality of data points comprising each data point corresponding to each complex impedance measurement to generate a three-dimensional curve representative of the reference complex impedance characteristic pattern, wherein the magnitude |Z| and the phase φ are plotted as a function of the frequency f,
receiving, by the control circuit, a complex impedance measurement data point;
comparing, by the control circuit, the complex impedance measurement data point to one of the plurality of data points of the reference complex impedance characteristic pattern;
classifying, by the control circuit, the complex impedance measurement data point based on a result of a comparison with the three-dimensional curve representative of the reference complex impedance characteristic pattern, wherein the three-dimensional curve representative of the reference complex impedance characteristic pattern includes a polynomial curve fit, a Fourier series, and/or a parametric equation; and
assigning, by the control circuit, a state of the end effector based on the result of the comparison.
2. The method of claim 1 , comprising:
receiving, by the control circuit, a new impedance measurement data point ; and
classifying, by the control circuit, the new impedance measurement data point using a Euclidean perpendicular distance from the new impedance measurement data point to a trajectory which has been fitted to the reference complex impedance characteristic pattern.
3. The method of claim 2 , comprising estimating, by the control circuit, a probability that the new impedance measurement data point is correctly classified.
4. The method of claim 3 , comprising adding, by the control circuit, the new impedance measurement data point to the reference complex impedance characteristic pattern based on the probability of the estimated correct classification of the new impedance measurement data point .
5. The method of claim 4 , comprising:
classifying, by the control circuit, data based on a set of training data S, wherein a plurality of elements of the set of training data S comprise a plurality of complex impedance measurement data ;
curve fitting, by the control circuit, the set of training data S using a parametric Fourier series for each of the plurality of elements of training data set S defined by:
p
⇀
=
a
⇀
0
+
∑
n
=
1
∞
(
a
⇀
n
cos
n
π
t
L
+
b
⇀
n
sin
n
π
t
L
)
wherein a period is defined by 2L;
wherein, for the new impedance measurement data point , the Euclidean perpendicular distance from to is found by:
D
=
p
⇀
-
z
⇀
when
:
∂
D
∂
t
=
0
then
:
D
=
D
⊥
wherein a probability distribution of D is used to estimate a probability of the new impedance measurement data point belonging to the set of training data S.
6. The method of claim 1 , wherein the control circuit is located at a surgical hub in communication with the electromechanical ultrasonic system.
7. A generator for 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 generator comprising:
a control circuit coupled to a memory, the control circuit configured to:
measure a complex impedance of the ultrasonic transducer, wherein the complex impedance is defined as
Z
g
(
t
)
=
V
g
(
t
)
I
g
(
t
)
;
receive a reference complex impedance characteristic pattern comprising a plurality of data points, wherein each of the plurality of data points is defined by an ultrasonic transducer impedance magnitude |Z|, an ultrasonic transducer impedance phase φ, and a frequency f at which the complex impedance of the ultrasonic transducer is measured;
receive a complex impedance measurement data point;
compare the complex impedance measurement data point to one of the plurality of data points of the reference complex impedance characteristic pattern;
classify the complex impedance measurement data point based on a result of a comparison with a three-dimensional curve representative of the reference complex impedance characteristic pattern, wherein the three-dimensional curve representative of the reference complex impedance characteristic pattern includes a polynomial curve fit, a Fourier series, and/or a parametric equation; and
assign a state of the end effector based on a result of the comparison; and
a drive circuit coupled to the control circuit, the drive circuit configured to apply a nontherapeutic drive signal to the ultrasonic transducer starting at an initial frequency, ending at a final frequency, and at a plurality of frequencies therebetween;
wherein the control circuit is further configured to generate the reference complex impedance characteristic pattern;
wherein the control circuit is configured to:
receive the reference complex impedance characteristic pattern from a database or the memory coupled to the control circuit;
measure the complex impedance of the ultrasonic transducer at each frequency of the plurality of frequencies;
store, in the memory, a data point corresponding to each complex impedance measurement; and
curve fit a plurality of data points to generate the three-dimensional curve representative of the reference complex impedance characteristic pattern, wherein the magnitude |Z| and the phase φ are plotted as a function of the frequency f.
8. The generator of claim 7 , wherein the control circuit is further configured to:
receive a new impedance measurement data point ; and
classify the new impedance measurement data point using a Euclidean perpendicular distance from the new impedance measurement data point to a trajectory which has been fitted to the reference complex impedance characteristic pattern.
9. The generator of claim 8 , wherein the control circuit is further configured to estimate a probability that the new impedance measurement data point is correctly classified.
10. The generator of claim 9 , wherein the control circuit is further configured to add the new impedance measurement data point to the reference complex impedance characteristic pattern based on the probability of the estimated correct classification of the new impedance measurement data point .
11. The generator of claim 9 , wherein the control circuit is further configured to:
classify data based on a set of training data S, wherein a plurality of elements of the set of training data S comprise a plurality of complex impedance measurement data ;
curve fit the set of training data S using a parametric Fourier series for each of the plurality of elements of training data set S, defined by:
p
⇀
=
a
⇀
0
+
∑
n
=
1
∞
(
a
⇀
n
cos
n
π
t
L
+
b
⇀
n
sin
n
π
t
L
)
wherein a period is defined by 2L;
wherein, for the new impedance measurement data point , the Euclidean perpendicular distance from to is found by:
D
=
p
⇀
-
z
⇀
when
:
∂
D
∂
t
=
0
then
:
D
=
D
⊥
wherein a probability distribution of D is used to estimate a probability of the new impedance measurement data point belonging to the set of training data S.
12. The generator of claim 7 , wherein the control circuit and the memory are located at a surgical hub in communication with the electromechanical ultrasonic system.
13. An ultrasonic device for estimating a state of an end effector thereof, the ultrasonic device comprising:
an electromechanical ultrasonic system defined by a predetermined resonant frequency, the electromechanical ultrasonic system comprising an ultrasonic transducer coupled to an ultrasonic blade;
a control circuit coupled to a memory, the control circuit configured to:
measure a complex impedance of the ultrasonic transducer, wherein the complex impedance is defined as
Z
g
(
t
)
=
V
g
(
t
)
I
g
(
t
)
;
receive a reference complex impedance characteristic pattern comprising a plurality of data points, wherein each of the plurality of data points is defined by an ultrasonic transducer impedance magnitude |Z|, an ultrasonic transducer impedance phase φ, and a frequency f at which the complex impedance of the ultrasonic transducer is measured;
receive a complex impedance measurement data point;
compare the complex impedance measurement data point to one of the plurality of data points of the reference complex impedance characteristic pattern;
classify the complex impedance measurement data point based on a result of a comparison with a three-dimensional curve representative of the reference complex impedance characteristic pattern, wherein the three-dimensional curve representative of the reference complex impedance characteristic pattern includes a polynomial curve fit, a Fourier series, and/or a parametric equation; and
assign a state of the end effector based on the result of the comparison; and
a drive circuit coupled to the control circuit, the drive circuit configured to apply a nontherapeutic drive signal to the ultrasonic transducer starting at an initial frequency, ending at a final frequency, and at a plurality of frequencies therebetween;
wherein the control circuit is further configured to generate the reference complex impedance characteristic pattern;
wherein the control circuit is configured to:
receive the reference complex impedance characteristic pattern from a database or the memory coupled to the control circuit;
measure the complex impedance of the ultrasonic transducer at each frequency of the plurality of frequencies;
store, in the memory, a data point corresponding to each complex impedance measurement; and
curve fit a plurality of data points to generate the three-dimensional curve representative of the reference complex impedance characteristic pattern, wherein the magnitude |Z| and the phase φ are plotted as a function of the frequency f.
14. The ultrasonic device of claim 13 , wherein the control circuit is further configured to:
receive a new impedance measurement data point ; and
classify the new impedance measurement data point using a Euclidean perpendicular distance from the new impedance measurement data point to a trajectory which has been fitted to the reference complex impedance characteristic pattern.
15. The ultrasonic device of claim 14 , wherein the control circuit is further configured to estimate a probability that the new impedance measurement data point is correctly classified.
16. The ultrasonic device of claim 15 , wherein the control circuit is further configured to add the new impedance measurement data point to the reference complex impedance characteristic pattern based on the probability of the estimated correct classification of the new impedance measurement data point .
17. The ultrasonic device of claim 15 , wherein the control circuit is further configured to:
classify data based on a set of training data S, wherein a plurality of elements of the set of training data S comprise a plurality of complex impedance measurement data ;
curve fit the set of training data S using a parametric Fourier series for each of the plurality of elements of training data set S, defined by:
p
⇀
=
a
⇀
0
+
∑
n
=
1
∞
(
a
⇀
n
cos
n
π
t
L
+
b
⇀
n
sin
n
π
t
L
)
wherein a period is defined by 2L;
wherein, for the new impedance measurement data point , the Euclidean perpendicular distance from to is found by:
D
=
p
⇀
-
z
⇀
when
:
∂
D
∂
t
=
0
then
:
D
=
D
⊥
wherein a probability distribution of D is used to estimate a probability of the new impedance measurement data point belonging to the set of training data S.
18. The ultrasonic device of claim 13 , wherein the control circuit and the memory are located at a surgical hub in communication with the electromechanical ultrasonic system.