Inertial sensor apparatus and method for creating an NDI image with hand scanning

摘要

A free-hand inspection apparatus for non-destructively inspecting a structure includes an array and an inertial sensor. The array includes a plurality of elements for transmitting and receiving inspection signals to/from a structure being inspected. The inertial sensor measures acceleration and angular rotation rate in three dimensions. A frame with a unique physical pattern on its edges, which are detectable by the system, is provided. In one embodiment, the frame comprises a special appliqué including a plastic sheet that has periodic edge features, or markings. The markings are detectable by the sensor and allow the system to correct the measurement distortions caused by the inertial sensors used for positioning while making scans. A computer-based process is provided to correct for drift when the sensor encounters one of these markings, thereby solving the problem of error accumulation and the resulting position inaccuracy.

主权项

1. A system for performing free-hand non-destructive inspection (NDI) of a surface, comprising:
a probe comprising an array of sensor elements for transmitting and receiving inspection signals towards and from a surface under inspection, and an inertial sensor for measuring acceleration and angular rotation of the array; an appliqué comprising edge markings detectable by the array of sensor elements; and a computer operatively coupled to the probe, wherein the computer is configured to receive signals from the array of sensor elements and the inertial sensor and to generate an NDI image of the surface, and wherein the computer includes a software-based process for removing distortions in the NDI image using image data corresponding to the edge markings, wherein the software-based process for removing distortions in the NDI image comprises:
processing an uncorrected image to produce a temporary image showing the edge markings;detecting peak points in the temporary image;selecting a first peak on each side of the temporary image as an anchor point in an image grid, and using a calculated inertial distance for these two points as a baseline to establish two absolute points on the image grid;determining a best fit of two straight parallel lines for all peak points using the anchor points as a reference;computing an offset for each peak point that will move each peak point to the straight line;computing an offset for each of a plurality of points to move the point into the correct position to un-distort the image points corresponding to the edge markings;determining a coordinate correction for a plurality of image data points; andusing a corrected coordinate for a first and last data point in each scan line, adjusting the spacing of intermediated data points to match the end points of the intermediated data points and un-distort the image.