Methods for estimating and controlling state of ultrasonic end effector
Various aspects of a generator, ultrasonic device, and method for estimating and controlling 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 as 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. The control circuit estimates the state of the end effector of the ultrasonic device and controls the state of the end effector of the ultrasonic device based on the estimated state.
1. A method for estimating and controlling a state or condition of an end effector of a modular ultrasonic device disposed in an ultrasonic system, wherein the modular ultrasonic device is defined by a predetermined resonant frequency and comprises an ultrasonic transducer coupled to an ultrasonic blade, and wherein the ultrasonic system further comprises a modular communication hub in data communication with the modular ultrasonic device and further in data communication with a distributed computer system, the method comprising:
measuring, by a control circuit, a complex impedance of the ultrasonic transducer, wherein the complex impedance is defined as
Z
g
(
t
)
=
V
g
(
t
)
I
g
(
t
)
;
receiving, by the control circuit, a complex impedance measurement data point;
comparing, by the control circuit, the complex impedance measurement data point to a data point in a reference complex impedance characteristic pattern;
classifying, by the control circuit, the complex impedance measurement data point based on a result of the comparison;
assigning, by the control circuit, the state or condition of the end effector based on the result of the comparison;
estimating, by the control circuit, an estimated state or condition of the end effector of the ultrasonic device;
controlling, by the control circuit, the state or condition of the end effector of the ultrasonic device based on the estimated state or condition of the end effector;
receiving, by the control circuit, a new impedance measurement data point;
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; and
communicating, by the control circuit, one or more impedance data with a database or a memory coupled to the distributed computer system.
2. The method of claim 1 , wherein communicating, by the control circuit, one or more impedance data with a database or memory coupled to the distributed computer system comprises receiving, by the control circuit, the reference complex impedance characteristic pattern from the database or the memory coupled to the distributed computer system.
3. The method of claim 1 , comprising:
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, an impedance of the ultrasonic transducer at each frequency;
storing, by the control circuit, a plurality of data points, wherein each of the plurality of data points corresponds to the impedance measurement at each frequency; and
curve fitting, by the control circuit, the plurality of data points to a three-dimensional curve representative of the reference complex impedance characteristic pattern, wherein the magnitude |Z| and phase φ of the reference complex impedance characteristic pattern are plotted as a function of frequency f.
4. The method of claim 3 , wherein communicating, by the control circuit, one or more impedance data with a database or memory coupled to the distributed computer system comprises storing, by the control circuit, the reference complex impedance characteristic pattern in the database or the memory coupled to the distributed computer system.
5. The method of claim 3 , wherein the curve fitting comprises a polynomial curve fitting, a Fourier series analysis, and/or a parametric equation.
6. The method of claim 1 , further comprising estimating, by the control circuit, a probability that the new impedance measurement data point is correctly classified.
7. The method of claim 6 , further comprising updating, by the control circuit, the reference complex impedance characteristic pattern with the new impedance measurement data point based on the probability of the estimated correct classification of the new impedance measurement data point.
8. The method of claim 7 , wherein communicating, by the control circuit, one or more impedance data with a database or memory coupled to the distributed computer system comprises storing, by the control circuit, the updated reference complex impedance characteristic pattern in the database or the memory coupled to the distributed computer system.
9. The method of claim 1 , comprising:
classifying, by the control circuit, data based on a set of training data S, wherein the set of training data S comprises a plurality of complex impedance measurement data {right arrow over (p)};
curve fitting, by the control circuit, the set of training data S using a parametric Fourier series for each element p of the set of training data S defined by:
=
0
+
∑
n
=
1
∞
(
n
cos
n
π
t
L
+
n
sin
n
π
t
L
)
wherein a period is defined by 2L;
wherein, for a new impedance measurement data point z, a perpendicular distance from {right arrow over (p)} to {right arrow over (z)} is found by:
D=∥{right arrow over (p)}−{right arrow over (z)}∥
when:
∂
D
∂
t
=
0
then:
D=D ⊥
wherein the probability distribution of D is used to estimate the probability of the new impedance measurement data point z belonging to the set of training data S.
10. The method of claim 1 , wherein the control circuit is located at a surgical hub in data communication with the modular ultrasonic device and the distributed computer system.
11. A system for estimating a state or condition of an end effector of a modular ultrasonic device disposed in an ultrasonic system, wherein the modular ultrasonic device is defined by a predetermined resonant frequency and comprises an ultrasonic transducer coupled to an ultrasonic blade, and wherein the ultrasonic system further comprises a modular communication hub in data communication with the modular ultrasonic device, and a distributed computer system in data communication with a generator comprising:
a control circuit coupled to a memory, the control circuit configured to:
measure a complex impedance of an ultrasonic transducer, wherein the complex impedance is defined as
Z
g
(
t
)
=
V
g
(
t
)
I
g
(
t
)
;
receive a complex impedance measurement data point;
compare the complex impedance measurement data point to a data point in a reference complex impedance characteristic pattern;
classify the complex impedance measurement data point based on a result of the comparison;
assign the state or condition of the end effector based on the result of the comparison;
estimate an estimated state or condition of the end effector of the ultrasonic device;
control the state or condition of the end effector of the ultrasonic device based on the estimated state or condition of the end effector;
receive a new impedance measurement data point;
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; and
communicate impedance data with a database or a memory coupled to the distributed computer system.
12. The system of claim 11 , wherein the control circuit is further configured to receive the reference complex impedance characteristic pattern from the database or the memory coupled to the distributed computer system.
13. The system of claim 11 , wherein the control circuit is configured to receive the reference complex impedance characteristic pattern from the memory coupled to the control circuit.
14. The system of claim 11 , further comprising:
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 impedance of the ultrasonic transducer at each frequency;
store, in the memory, a data point corresponding to each impedance measurement; and
curve fit a plurality of data points to generate a three-dimensional curve representative of the reference complex impedance characteristic pattern, wherein the magnitude |Z| and phase φ of the reference complex impedance characteristic pattern are plotted as a function of frequency f.
15. The system of claim 14 , wherein the curve fit includes a polynomial curve fit, a Fourier series, and/or a parametric equation.
16. The system of claim 11 , wherein the control circuit is further configured to estimate a probability that the new impedance measurement data point is correctly classified.
17. The system of claim 16 , wherein the control circuit is further configured to update the reference complex impedance characteristic pattern with the new impedance measurement data point based on the probability of the estimated correct classification of the new impedance measurement data point.
18. The system of claim 17 , wherein the control circuit is further configured to store the updated reference complex impedance characteristic pattern in the database or the memory coupled to the distributed computer system.
19. The system of claim 17 , wherein the control circuit is further configured to:
classify data based on a set of training data S, where the set of training data S comprises a plurality of complex impedance measurement data {right arrow over (p)};
curve fit the set of training data S using a parametric Fourier series for each element {right arrow over (p)} of the set of training data S, defined by:
=
0
+
∑
n
=
1
∞
(
n
cos
n
π
t
L
+
n
sin
n
π
t
L
)
wherein a period is defined by 2L;
wherein, for a new impedance measurement data point z, a perpendicular distance from {right arrow over (p)} to {right arrow over (z)} is found by:
D=∥{right arrow over (p)}−{right arrow over (z)}∥
when:
∂
D
∂
t
=
0
then:
D=D ⊥
wherein the probability distribution of D is used to estimate the probability of the new impedance measurement data point z belonging to the set of training data S.