Method and apparatus for video imaging of tire ground contact patch

• US 5,347,588 A
• Filed: 10/11/1991
• Issued: 09/13/1994
• Est. Priority Date: 10/11/1991
• Status: Expired due to Term

• Current Assignee: Bridgestone Corporation
• Original Assignee: Bridgestone Corporation
• Inventors: Wilson, Paul B.
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): Prikockis, Larry J.
• Application Number:
  US07/776,527
• Time in Patent Office: 1,068 Days
• Field of Search: 382/1, 382/28, 382/55, 382/41, 382/49, 358/107, 356/376, 356/379, 73/146
• US Class Current: 382/104
• CPC Class Codes: G01M 17/027 using light, e.g. infrared, ultraviolet or holographic techniques

Abstract

A method and apparatus for video imaging of a tire ground contact patch or tire footprint is presented. A digitized image of the footprint is generated as an array of pixels. Each pixel is attributed a binary value of one or zero, to present a two-valued image. Contact areas within the image are attributed a first value, while void or noncontact areas are attributed a second value. The image is then dilated and eroded in an appropriate sequence to eliminate all white pixels from the image and to eliminate surface anomalies or the like which are not of interest in the tire analysis. An image of the footprint, accurate in size and dimensions, is thereby generated and, from such footprint, total area, contact area, and void area can be determined, as well as measurements of width, center line length, and other desired lengths at various lateral width locations. This data may be used to analyze the tire construction, operation, noise generation, and performance.

Claims

1. Apparatus for video imaging the interface area between a tire and its contacting loading surface, also known as a tire footprint, comprising:

first means for generating a tire footprint upon a surface;

second means for generating a digitized video image of said footprint from said surface, said digitized video image comprising an array of pixels and having contact regions corresponding to tire tread elements, and void regions corresponding to regions between the tread elements;

third means for receiving said digitized video image and determining the area of said contact regions within said footprint image; and

fourth means for receiving said digitized video image and determining the area and boundary contour of said footprint image, said fourth means comprising a dilation filter, and an erosion filter, said dilation filter filtering said digitized video image a first number of times until all pixels within a region encompassed by the contour of the footprint are of a same value and said video image is a dilated image, said erosion filter receiving said dilated image and filtering said dilated image said first number of times plus an additional time, generating an eroded image, said dilation filter subsequently filtering said eroded image one additional time, generating a uniform footprint image wherein all pixels comprising the uniform footprint image are at equal value.

2. The apparatus according to claim 1, wherein said uniform footprint image is encompassed by a uniform footprint contour.

3. The apparatus according to claim 2, wherein said third means determines an area of said contact regions by summing all pixels within said contact regions and said fourth means determines said total area of said footprint by summing all pixels within said uniform footprint contour.

4. The apparatus according to claim 3, wherein said fourth means further determines an area of said void regions by subtracting the sum of pixels within said contact regions from the sum of pixels within said uniform footprint contour.

5. The apparatus according to claim 4, wherein said fourth means further determines a width of said uniform footprinted contour.

6. The apparatus according to claim 5, wherein said fourth means further determines a length of said uniform footprint contour along a longitudinal centerline and various lateral width locations thereof.

7. A method for video imaging the interface area between a tire and its contacting loading surface, also known as a tire footprint, comprising the steps of:

(a) generating a footprint of a tire upon a planar surface;

(b) generating a digitized video image of said footprint from said planar surface, said digitized video image comprising an array of pixels, regions in said digitized video image corresponding to tread elements being attributed a first value, and regions in said digitized video image corresponding to void areas being attributed a second value;

(c) summing the total value of all pixels having said first value, thereby determining a tread contact area;

dilating said array of pixels a first number of times until no pixels of said second value remain within the region encompassed by a contour of the footprint, thereby generating a dilated pixel array, eroding said dilated pixel array a second number of times, generating an eroded pixel array, said second number being one greater than said first number, dilating said eroded pixel array one time, generating a uniform footprint contour, and determining the area of said footprint within said uniform footprint contour; and

(e) subtracting said tread contact area from said area of said footprint, thereby determining a void area.

8. The method according to claim 7, further comprising the step of determining a width of said uniform footprint contour.

9. The method according to claim 8, further comprising the step of determining length of a longitudinal center line of said uniform footprint contour.

10. The method according to claim 9, further comprising the step of determining tire footprint lengths at various lateral width locations.

11. The method according to claim 10, wherein step (d) comprises characterization of a shape of the tire footprint.