FIELD OF THE INVENTION

The present invention relates to computer-implemented methods, systems, and computer program products for monitoring wear of double roll crusher teeth by computer vision techniques.

BACKGROUND OF THE INVENTION

Double roll crushers are used to crush mined oil sand ore to a suitable size for slurry preparation as a preliminary step in hot water extraction processes. A double roll crusher includes a pair of opposed cylindrical drums having teeth that project from the drum surfaces.

Feed material placed onto the drums is crushed between the teeth as the drums rotate in opposite directions. Wear or damage to the teeth compromises crushing performance, and increases the likelihood of damage to the drum.

Manual inspection of the teeth may be carried out with a view to preventative maintenance. Manual inspection involves stopping rotation of the drums, cleaning the crusher teeth, and manually measuring the teeth. For a large-sized roller with hundreds of teeth, a manual inspection can take several hours to perform.

Over-frequent inspection results in excessive loss productivity, while under-frequent inspection allows for excessive wear and damage. As such, it would be desirable to be able to assess the degree of wear of the teeth to help decide whether a manual inspection is warranted.

The prior art includes computer vision-based technologies for detecting a damaged or missing machine part, including in particular a shovel tooth: see U.S. patent application publication no. US 2010/0142759 A1 (Ridley et al.; 2010-06-10); U.S. patent application no. US 2015/0085123 A1 (Tafazoli Bilandi et al; 2015-03-26) and U.S. patent application publication no. US2017287124 A1 (Lim et al.). These technologies involve comparing captured digital images of the shovel tooth (or digital images derived from such images) with a template or model of the expected shape of the shovel tooth. This approach requires differentiating between portions of the digital image showing the shovel tooth and its background. In some cases, this depends on detection of apparent movement between the shovel tooth and its background in time-sequenced images.

This approach is difficult to implement for monitoring wear of double roll crusher teeth. Unlike a shovel tooth that contrasts well with a background of sky or ground surface, the double roll crusher teeth and the double roll crusher drum typically have the same or similar surface finish. Further, the teeth and drum may be fouled with feed material. Further still, the teeth and the drum move in unison, which prevents use of approaches that depend on detection of apparent movement between a machine part and its background.

Accordingly, a need remains for a technological solution to monitoring wear of double roll crusher teeth. Preferably, the technology provides reliable quantitative monitoring of the sizes or shapes of the double roll crusher teeth, to assess whether a manual inspection is warranted. Preferably, the technology can be used while the drums of the double roll crusher are rotating. Preferably, the technology can be used when the drums and teeth are fouled with feed material such as mined oil sand ore. Preferably, the technology can be adapted to a variety of different configurations of teeth, without the need for predetermined models or templates of teeth configurations. Preferably, the technology is computationally efficient and practical to implement.

SUMMARY OF THE INVENTION

A method for monitoring wear of teeth of a drum of a double roll crusher, the method implemented by a processor and comprising the steps of:(a) receiving a digital video capturing rotation of the drum and the teeth;(b) for each frame of the digital video, segmenting the frame into groups of contiguous pixels, wherein each group is representative of one of the teeth;(c) determining a parameter indicative of a geometry at least one of the teeth based on at least one of the segmented groups of contiguous pixels in at least one of the frames of the digital video; and(d) generating a human-readable report based on the parameter indicative of the geometry of the at least one of the teeth.

In one embodiment of the method, the method further comprises, before the segmenting step (b), defining a region of interest in the frame by using an image processing technique, such as optical flow, to identify pixels representative of the drum and the teeth, and wherein the segmenting step (b) is performed only on the region of interest in the frame.

In one embodiment of the method, the method further comprises, before the segmenting step (b), enhancing contrast of the frame.

In one embodiment of the method:(a) the method further comprises, after the segmenting step (b) and before the determining step (c), for each group of contiguous pixels, determining pixel coordinates of a minimum bounding region of the group of contiguous pixels; and(b) inclusion of any one of the minimum bounding regions in the determining step (c) is conditional upon either one or both of:(i) the one of the minimum bounding regions having a pixel dimension equal to or greater than a pre-determined minimum pixel dimension; or(ii) the one of the minimum bounding regions being tracked through a pre-determined minimum number of successive frames of the digital video.

In embodiments of the method which include determining pixel coordinates of the minimum bounding region of the group of contiguous pixels, the method may further comprise determining an estimate of the position of the at least one of the teeth based on the pixel coordinates of one of the minimum bounding regions in at least one of the frames of the digital video, and wherein the report is further based on the estimate of the position of the at least one of the teeth. Determining the estimate of the position of the at least one of the teeth may be based on a modal pixel coordinate of the pixel coordinates of the minimum bounding regions in a plurality of the frames of the digital video.

In embodiments of the method which include determining pixel coordinates of the minimum bounding region of the group of contiguous pixels, the determining step (c) may be based on a statistical measure of a plurality of estimates of the dimension of the at least one of the teeth, determined based on the pixel coordinates of at least one of the minimum bounding regions in a plurality of the frames of the digital video. The plurality of the frames of the digital video may capture a single rotation of the drum, or a plurality of rotations of the drum.

In embodiments of the method, the parameter may be one or a combination of a pixel length, a pixel area, or a shape factor, based on at least one of the segmented groups of continuous pixels.

In another aspect, the present invention comprises a system comprising a processor operatively connected to a non-transitory tangible medium storing a set of instructions executable by the processor to implement one or a combination of the embodiments of the method of the present invention, as described above.

In another aspect, the present invention comprises a computer program product comprising a non-transitory tangible medium storing a set of instructions executable by a processor to implement one or a combination of the embodiments of the method of the present invention, as described above.

