Free-encoder positioning system using acoustic features and IMU

1. A method of estimating a position of a probe assembly of a non-destructive inspection system, the probe assembly positioned on a material and in communication with an inertial measurement unit (IMU) sensor, the method comprising:

acquiring, at a first position of the probe assembly, a first acoustic data signal of the material using the probe assembly;

acquiring, at a second position of the probe assembly, a second acoustic data signal of the material using the probe assembly;

determining a first estimate of a displacement of the probe assembly between the first and second positions using the first and second acoustic data signals;

determining a second estimate of the displacement of the probe assembly between the first and second positions using a signal from the IMU sensor;

combining the first and second estimates of displacements;

estimating, using the combination, a motion of the probe assembly;

generating, using the estimated motion, the second position of the probe assembly; and

displaying an image that represents the acquired acoustic data signals.

2. The method of claim 1 , wherein determining the first estimate of the displacement of the probe assembly includes determining a first probability density function of a first displacement probability, and

wherein determining the second estimate of the displacement of the probe assembly includes determining a second probability density function of a second displacement probability.

3. The method of claim 1 , further comprising:

generating a first acoustic image using the first acoustic data signal; and

generating a second acoustic image using the second acoustic data signal,

wherein determining the first estimate of the displacement of the probe assembly between the first and second positions using the first and second acoustic data signals includes:

determining the first estimate of the displacement of the probe assembly between the first and second positions using at least one feature common to both the first and second acoustic images.

4. The method of claim 3 , wherein the material is a pipe, and wherein the feature includes corrosion.

5. The method of claim 1 , comprising:

determining, at the first position, a first time-of-flight (TOF) to a feature in the material using the first acoustic data signal; and

determining, at the second position, a second TOF to the feature in the material using the second acoustic data signal, and

wherein determining the first estimate of the displacement of the probe assembly between the first and second positions using the first and second acoustic data signals includes:

determining the first estimate of the displacement of the probe assembly between the first and second positions using the first TOF and the second TOF.

6. The method of claim 1 , further comprising:

determining, at the first position and using the first acoustic data signal, a plurality of first time-of-flights that each correspond to a plurality of first features in the material; and

determining, at the second position and using the second acoustic data signal, a plurality of second time-of-flights that each correspond to a plurality of second features in the material,

wherein the second features are the same as the first features, and

wherein determining the first estimate of the displacement of the probe assembly between the first and second positions using the first and second acoustic data signals includes:

determining the first estimate of the displacement of the probe assembly using a difference between the plurality of first time-of-flights and the second time-of-flights.

7. The method of claim 1 , further comprising:

predicting the second position,

wherein combining the first and second estimates of displacements includes combining the first and second estimates of displacement and the predicted second position.

8. The method of claim 7 , wherein predicting the second position includes:

predicting the second position using a previous system state and a physical model of system motion.

9. The method of claim 8 , wherein predicting the second position using the physical model of system motion includes:

predicting the second position using a previously determined speed, a previously determined direction, and a sampling rate.

10. An ultrasound inspection system for estimating a position of an ultrasonic probe assembly of a non-destructive inspection system, the system comprising:

the ultrasonic probe assembly to be positioned on a material and in communication with an inertial measurement unit (IMU) sensor; and

a processor configured to:

acquire, at a first position of the probe assembly, a first acoustic data signal of the material using the probe assembly;

acquire, at a second position of the probe assembly, a second acoustic data signal of the material using the probe assembly;

determine a first estimate of a displacement of the probe assembly between the first and second positions using the first and second acoustic data signals;

determine a second estimate of the displacement of the probe assembly between the first and second positions using a signal from the IMU sensor;

combine the first and second estimates of displacements;

estimate, using the combination, a motion of the probe assembly;

generate, using the estimated motion, the second position of the probe assembly; and

display an image that represents the acquired acoustic data signals.

11. The system of claim 10 , wherein the processor configured to determine the first estimate of the displacement of the probe assembly is configured to determine a first probability density function of a first displacement probability, and

wherein the processor configured to determine the second estimate of the displacement of the probe assembly is configured to determine a second probability density function of a second displacement probability.

12. The system of claim 10 , wherein the processor is configured to:

generate a first acoustic image using the first acoustic data signal; and

generate a second acoustic image using the second acoustic data signal,

wherein the processor configured to determine the first estimate of the displacement of the probe assembly between the first and second positions using the first and second acoustic data signals is configured to:

determine the first estimate of the displacement of the probe assembly between the first and second positions using at least one feature common to both the first and second acoustic images.

13. The system of claim 12 , wherein the material is a pipe, and wherein the feature includes corrosion.

14. The system of claim 10 , the processor configured to:

determine, at the first position, a first time-of-flight (TOF) to a feature in the material using the first acoustic data signal; and

determine, at the second position, a second TOF to the feature in the material using the second acoustic data signal,

wherein the processor configured to determine the first estimate of the displacement of the probe assembly between the first and second positions using the first and second acoustic data signals is configured to:

determine the first estimate of the displacement of the probe assembly between the first and second positions using the first TOF and the second TOF.

15. The system of claim 10 , the processor configured to:

determine, at the first position and using the first acoustic data signal, a plurality of first time-of-flights that each correspond to a plurality of first features in the material; and

determine, at the second position and using the second acoustic data signal, a plurality of second time-of-flights that each correspond to a plurality of second features in the material, wherein the second features are the same as the first features,

wherein the processor configured to determine the first estimate of the displacement of the probe assembly between the first and second positions using the first and second acoustic data signals is configured to:

determine the first estimate of the displacement of the probe assembly using a difference between the plurality of first time-of-flights and the second time-of-flights.

16. The system of claim 10 , the processor configured to:

predict the second position,

wherein the processor configured to combine the first and second estimates of displacements is configured to combine the first and second estimates of displacement and the predicted second position.

17. The system of claim 16 , wherein the processor configured to predict the second position is configured to:

predict the second position using a previous system state and a physical model of system motion.

18. The system of claim 17 , wherein the processor configured to predict the second position using the physical model of system motion is configured to:

predict the second position using a previously determined speed, a previously determined direction, and a sampling rate.