Robotic acquisition of objects by means including histogram techniques
First Claim
1. A robot system for acquiring randomly-arranged workpieces, comprisinga robot assembly including a hand, and a controller for controlling the movement of the hand to positions to successively grasp workpieces of given size and transfer them to a predetermined site,a video imaging device to provide a video signal representing a brightness image of the randomly-arranged workpieces, anda computer programmed to be responsive to the video signal from the imaging device and operative to modify the image, to compute a holdsite on a workpiece in the image, and to command the robot assembly to grasp the workpiece and transfer it to said predetermined site,said video imaging device including a video range expander for selecting and amplifying a range of video signal amplitudes between a gray threshold level and a white clipping level,said computer including program means to quantize the selected video signal having said range of amplitudes into digital pixels within a plurality of windows all having a size proportional to the size of the workpieces, said means to quantize the selected video signal including means to generate the same number of digital pixels of the image within the window regardless of the size of the window, and to enhance the quantized image by making all pixels having a brightness intensity less than a threshold intensity T equal to zero, and retaining the brightness intensities of all pixels above the threshold T, said threshold intensity T being computed by program from an intensity histogram so that T exceeds the intensity of the most numerous dark pixels by a predetermined fraction of the difference between the intensity of the most numerous dark pixels and the intensity of the most numerous bright pixels.
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Accused Products
Abstract
A robotic apparatus and method of acquiring jumbled objects or workpieces from a bin, and transferring them to a final site, or to an intermediate site for quality inspection. A video camera system produces a video signal representing a brightness image of the jumbled objects. An intermediate amplitude range of the video signal is selected, expanded, stored, and quantized into digital pixels. A computer enhances the image using histogram techniques, performs edge suppression, performs repeated shrinking with progressively-increased pixel thresholds until an area limit is reached, performs clustering of closely-spaced pixels, and commands movement of the robot gripper to a computed grip site on a recognized object. The gripper may limit its gripping pressure as a function of the deformation of the object gripped.
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Citations
30 Claims
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1. A robot system for acquiring randomly-arranged workpieces, comprising
a robot assembly including a hand, and a controller for controlling the movement of the hand to positions to successively grasp workpieces of given size and transfer them to a predetermined site, a video imaging device to provide a video signal representing a brightness image of the randomly-arranged workpieces, and a computer programmed to be responsive to the video signal from the imaging device and operative to modify the image, to compute a holdsite on a workpiece in the image, and to command the robot assembly to grasp the workpiece and transfer it to said predetermined site, said video imaging device including a video range expander for selecting and amplifying a range of video signal amplitudes between a gray threshold level and a white clipping level, said computer including program means to quantize the selected video signal having said range of amplitudes into digital pixels within a plurality of windows all having a size proportional to the size of the workpieces, said means to quantize the selected video signal including means to generate the same number of digital pixels of the image within the window regardless of the size of the window, and to enhance the quantized image by making all pixels having a brightness intensity less than a threshold intensity T equal to zero, and retaining the brightness intensities of all pixels above the threshold T, said threshold intensity T being computed by program from an intensity histogram so that T exceeds the intensity of the most numerous dark pixels by a predetermined fraction of the difference between the intensity of the most numerous dark pixels and the intensity of the most numerous bright pixels.
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17. A robot system for acquiring non-touching randomly-arranged workpieces, comprising
a robot assembly including a hand, and a controller for controlling the movement of the hand to positions to successively grasp workpieces of given size and transfer them to a predetermined site, a video imaging device to provide a video signal representing a brightness image of the randomly-arranged workpieces, and a computer programmed to be responsive to said video signal from the imaging device and operative to modify the image, to compute a holdsite on a workpiece in the image, and to command the robot assembly to grasp the workpiece and transfer it to said predetermined site, said video imaging device including a video range expander for selecting and amplifying a range of video signal amplitudes between a gray threshold level and a white coupling level, said computer including program means to quantize the selected video signal having said range of amplitudes into digital pixels within a plurality of windows all having a size proportioned to the size of the workpieces, program means to enhance the quantized image by making all pixels having a brightness intensity less than a threshold T equal to zero, and retaining the brightness intensities of all pixels above the threshold T, wherein said threshold intensity T is computed from an intensity histogram by program means which selects the threshold intensity T at a value intermediate that of the most numerous dark pixels and that of the most numerous bright pixels, and program means to determine whether the bright pixel area in a given window is greater than an area, computed during a training phase, which is in the range of 1/2 a standard deviation, to three standard deviations less than, the average of the areas found in all of said plurality of windows.
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23. The processing of a video image of randomly-arranged and touching workpiece of given size, comprising the steps of
selecting and amplifying a range of video signal amplitudes between a gray threshold level and a white clipping level, quantizing the selected video signal, having said range of amplitudes, within a window having a size proportional to the size of the workpieces, enhancing the digitized video image by making all pixels having a brightness intensity less than a threshold T equal to zero, where the threshold T is computed from an intensity histogram by means of a computer program which selects the threshold intensity T at a value intermediate that of the most numerous dark pixels and that of the most numerous bright pixels, suppressing the edges in the enhanced video image by reducing to zero all pixels whose brightness compared with the brightness of any adjacent pixel is greater than a predetermined ratio R, shrinking the edge-suppressed image having an area A to an image having an area An by making equal to zero each pixel which has an intensity less than a predetermined initial threshold, or which is adjacent to a pixel having an intensity less that the predetermined threshold, repeating said shrinking with progressively higher thresholds until the ratio of the area A to the area An is larger than a predetermined limit ratio, or until a predetermined number of iterations is exceeded, identifying clusters each consisting of adjacent bright pixel in a earlier than the last one of the progressively shrunk images, merging clusters of bright pixels by adding bright pixels in spaces which are less than a predetermined minimum distance between existing bright pixels, identifying merged clusters having areas greater than a predetermined minimum, and having a length-width ratio greater than a predetermined minimum, and computing a grasp location and orientation of an identified cluster.
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24. The processing of a video image of randomly-arranged non-touching workpieces of given size, comprising the steps of
selecting and amplifying a range of video signal amplitudes between a gray threshold level and a white clipping level, quantizing the selected video signal, having said range of amplitudes, within a window having a size proportional to the size of the workpieces, enhancing the digitized video image by making all pixels having a brightness intensity less than a threshold T equal to zero, where the threshold T is computed from an intensity histogram by means of a computer program which selects the threshold intensity T at a value intermediate that of the most numerous dark pixels and that of the most numerous bright pixels, identifying clusters each consisting of adjacent bright pixels, merging clusters of bright pixels adding bright pixels in spaces which are less than a predetermined minimum distance between existing bright pixels, identifying merged clusters having areas greater than a predetermined minimum, and having a length-width ratio greater than a predetermined minimum, and computing a grasp location and orientation of an identified cluster.
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25. A robot system for acquiring randomly-arranged workpieces of given size, comprising
a robot assembly including a hand, and a controller for controlling the movement of the hand to positions to successively grasp workpieces and transfer them to a predetermined site, a video imaging device to provide a video signal representing a brightness image of the randomly-arranged workpieces, and a computer programmed to be responsive to the video signal from the imaging device and operative to modify the image, to compute a holdsite on a workpiece in the image, and to command the robot assembly to grasp the workpiece and transfer it to said predetermined site, said video imaging device including a video range expander for selecting and amplifying a range of video signal amplitudes between a gray threshold level and a white clipping level, said computer including program means to quantize the selected video signal having said range of amplitudes into digital pixels within a plurality of windows all having a size proportioned to the size of the workpieces, program means to enhance the quantized image by making all pixels having a brightness intensity less than a threshold T equal to zero, and retaining the brightness intensities of all pixels above the threshold T, program means to form clusters of bright pixels by adding bright pixels in spaces less than a predetermined minimum distance between existing bright pixels, program means to identify said clusters having an area greater than a predetermined minimum area, program means to identify said large clusters which also have a length-width ratio greater than a predetermined minimum, program means to compute the location and orientation of a grasp site on a workpiece represented by an identified large elongated cluster of pixels, and to command the robot assembly to grasp the workpiece and transfer it to a predetermined site, and program means to compute the center of area of the cluster of pixels to determine the location of the grasp site, and to compute the axis of least moment of inertia of the cluster of pixels to determine the orientation of the grasp site.
Specification