Methods and systems for data smoothing stress data

• US 8,234,082 B1
• Filed: 08/18/2009
• Issued: 07/31/2012
• Est. Priority Date: 08/18/2009
• Status: Expired due to Fees

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Bridge, Ralph J., Biggs, Gary L.
• Primary Examiner(s): Bui, Bryan
• Application Number:
  US12/583,570
• Time in Patent Office: 1,078 Days
• Field of Search: 702/42, 702/189, 73/543.7, 73/544.1
• US Class Current: 702/42
• CPC Class Codes: G01M 5/0033 by determining damage, crack or wear
• CPC Class Codes: G06F 17/17 Function evaluation by approximation methods, e.g. inter- or extrapolation, smoothing, least mean square method G06F17/18 takes precedence ; interpolation for numerical control G05B19/18

Abstract

Methods and systems for data smoothing raw data such as stress data. The present invention may utilize various techniques to smooth data such as dropping data using a stress threshold, dropping data by resample (or decimation), and smoothing by dynamic binning. Additionally, the present invention may utilize a transform function to estimate stress from a stress sensor to areas of peak stress. In an exemplary application, the present invention can be utilized to reduce stress data collected by a plurality of embedded stress sensors in a rocket motor for purposes of computing service life of the motor.

Claims

1. A data smoothing method for reducing raw stress data, comprising:

receiving a data set at a processor,

wherein said data set comprises raw stress data from at least one sensor;

transforming the data set responsive to a transform function using said processor; and

smoothing the raw stress data to reduce the quantity of the data set while retaining significant stress events for yielding a reduced data set,

wherein said smoothing comprises dynamic binning is applied to the raw stress data,

wherein the dynamic binning is controlled by a minimum and maximum allowable bin size, and

wherein the dynamic binning comprises fewer bins in a low stress region relative to a high stress region.

2. The data smoothing method of claim 1, further comprising calculating a service life prediction from the reduced data set.

3. The data smoothing method of claim 1, further comprising measuring the raw stress data with said at least one sensor being embedded in a rocket motor.

4. The data smoothing method of claim 3, wherein the transform function is configured to estimate peak stress from the raw stress data set at a peak stress point in the rocket motor.

5. The data smoothing method of claim 3, further comprising determining a transform coefficient responsive to a geometry of the rocket motor.

6. The data smoothing method of claim 1, wherein the dynamic binning is controlled by a dynamic stress bin trigger where a change in stress prompts a new bin, and wherein the dynamic binning is controlled by a minimum and maximum allowable bin size.

7. The data smoothing method of claim 1, wherein the smoothing further comprises the raw stress data is re-sampled responsive to a predetermined frequency.

8. The data smoothing method of claim 1 wherein the smoothing further comprises the raw stress data is dropped responsive to a stress threshold.

9. The data smoothing method of claim 1, wherein the smoothing comprises dynamic binning is applied to the raw stress data,

wherein the dynamic binning is controlled by a dynamic stress bin trigger where a change in stress prompts a new bin,

wherein the dynamic binning is controlled by a minimum and maximum allowable bin size,

wherein the dynamic binning comprises fewer bins in a low stress region relative to a high stress region,

wherein the raw stress data is re-sampled responsive to a predetermined frequency in the low stress region;

and

wherein the raw stress data is dropped responsive to a stress threshold in the low stress region.

10. A method of computing a service life prediction of a device being based on measured stress, comprising:

receiving stress measurements from at least one embedded stress sensors yielding a data set comprising raw stress data;

smoothing the raw stress data for reducing a quantity of the data set while retaining significant stress events using a processor for producing a reduced data set;

calculating a service life prediction from the reduced data set; and

removing the device from service responsive to the service life prediction,

wherein smoothing comprises dynamic binning is applied to the raw stress data

wherein the dynamic binning is controlled by a dynamic stress bin trigger comprising a change in stress that prompts a new bin and a minimum and maximum allowable bin size,

wherein the dynamic binning is controlled by a minimum and maximum allowable bin size, and

wherein the dynamic binning comprises fewer bins in a low stress region relative to a high stress region.

11. The method of claim 10, further comprising applying a transform function to the raw stress data for estimating peak stress from the raw stress data set at a peak stress point in the device.

12. The method of claim 10, wherein the smoothing further comprises the raw stress data is re-sampled responsive to a predetermined frequency;

and the raw stress data is dropped responsive to a stress threshold.

13. The method of claim 10, wherein smoothing comprises dynamic binning is applied to the raw stress data,

wherein the dynamic binning is controlled by a dynamic stress bin trigger where a change in stress prompts anew bin,

wherein the dynamic binning is controlled by a minimum and maximum allowable bin size,

wherein the dynamic binning comprises fewer bins in a low stress region relative to a high stress region,

wherein the raw stress data is re-sampled responsive to a predetermined frequency in the low stress region;

and

wherein the raw stress data is dropped responsive to a stress threshold in the low stress region.

14. A data smoothing system, comprising:

a structure for data input and output;

at least one processor being coupled to a memory and said structure for said data input and output,

wherein said at least one processor is configured to receive a data set, which comprises raw stress data, transform the data set responsive to a transform function, smooth the raw stress data to reduce the quantity of the data set while retaining significant stress events, and calculate a service life prediction from the reduced data set, and

a plurality of embedded sensors in a rocket motor,

wherein the plurality of embedded sensors are configured to measure the raw stress data

wherein said smooth comprises

dynamic binning is applied to the raw stress data

wherein the dynamic binning is controlled by a dynamic stress bin trigger where a change in stress prompts a new bin,

wherein the dynamic binning is controlled by a minimum and maximum allowable bin size,

wherein the dynamic binning comprises fewer bins in a low stress region relative to a high stress region,

wherein the raw stress data is re-sampled responsive to a pre-determined frequency in the low stress region; and

wherein the raw stress data is dropped responsive to a stress threshold in the low stress region.

15. The data smoothing system of claim 14 wherein the transform function is configured to estimate peak stress from the raw stress data set at a peak stress point in the rocket motor.