Object intrusion detection system and method

Patent metadata

Field	Value
Publication number	US-10789506-B2
Application number	US-201816139436-A
Country	US
Kind code	B2
Filing date	Sep 24, 2018
Priority date	Sep 24, 2018
Publication date	Sep 29, 2020
Grant date	Sep 29, 2020

Abstract

A three-dimensional (3D) sensor device achieves high intrusion detection probability while keeping the probability of a false intrusion detection low by capturing a set of multiple spatial or temporal samples of a measured parameter for an object detected in the sensor's field of view. When an object is detected in the field of view, the TOF sensor device defines a window of N pixels comprising a subset of the pixels corresponding to the object, and obtains N distance measurements corresponding to the N pixels of the window. If the number of the N distance values that are less than a defined threshold distance is equal to or greater than a selected threshold value M (an integer less than N), the TOF sensor device determines that the object is intruding within a protective field and generates a suitable output.

First claim

What is claimed is:

1. A sensor device, comprising:
a distance determination component configured to receive pixel data associated with respective pixels of a field of view, and to identify an object within the field of view corresponding to a first subset of the pixels; and
an intrusion detection component configured to define a pixel window comprising a second subset of the first subset of the pixels, wherein the second subset comprises N pixels, and N is an integer,
wherein
the distance determination component is further configured to determine N distance values corresponding to the N pixels of the pixel window based on a subset of the pixel data corresponding to the second subset of the first subset of the pixels,
the intrusion detection component is further configured to count a number K of the N distance values that are less than a defined distance threshold, and
the sensor device further comprises a control output component configured to, in response to determining that the number K of the N distance values that are less than the defined distance threshold is equal to or greater than a defined threshold value M, generate an output signal configured to at least one of disconnect power from an industrial machine, place an industrial automation system in safe operation mode, or send a notification to one or more client devices.

2. The sensor device of claim 1 , wherein
the distance determination component is further configured to
identify a subset of the N distance values that are outside a defined valid distance range, and
replace the subset of the N distance values with replacement distance values to yield a modified set of N distance values; and

the intrusion detection component is configured to count the number of the N distance values from the modified set of N distance values.

3. The sensor device of claim 2 , wherein the distance determination component is configured to generate a replacement distance value, of the replacement distance values, for one of the subset of the N distance values corresponding to one of the pixels based on another subset of the N distance values corresponding to pixels that are adjacent to the one of the pixels.

4. The sensor device of claim 1 , wherein
the distance determination component is further configured to:
identify a subset of the N distance values that are outside a defined valid distance range, and
remove the subset of the N distance values to yield a reduced set of distance values; and

the intrusion detection component is configured to:
reduce the defined threshold value M based on a number of the subset of the N distance values removed by the distance determination component to yield a modified threshold value M MODIFIED ,
count a number of the reduced set of distance values that are less than the defined distance threshold, and
generate the output signal in response to determining that the number of the reduced set of distance values that are less than the defined distance threshold is equal to or greater than the modified threshold value M MODIFIED .

5. The sensor device of claim 1 , wherein the intrusion detection component is configured to set the number N of pixels comprising the pixel window based on a number of the first subset of the pixels corresponding to the object.

6. The sensor device of claim 5 , wherein the intrusion detection component is further configured to select the threshold value M based on the number N.

7. The sensor device of claim 6 , wherein the intrusion detection component is configured to select the threshold value M to achieve a defined minimum intrusion detection probability according to a detection probability algorithm that defines the intrusion detection probability as a function of M and N.

8. The sensor device of claim 1 , wherein
the distance determination component is further configured to determine the N distance values at multiple different times within a measuring sequence to yield multiple sets of N distance values, and
the intrusion detection component is configured to,
for each pixel of the pixel window, average a subset of the distance values, from the multiple sets of N distance values, corresponding to the pixel, wherein averaging the subset of the distance values for each pixel yields N averaged distance values,
count the number K of the N averaged distance values that are less than the defined distance threshold, and
generate the output signal in response to determining that the number K of the N averaged distance values is equal to or greater than the defined threshold value M.

9. A method for detecting intrusion of an object within a protective field, comprising:
receiving, by a sensor device comprising a processor, pixel data for respective pixels of a field of view;
identifying, by the sensor device based on analysis of the pixel data, an object within the field of view, wherein the object corresponds to a first subset of the pixels;
defining, by the sensor device, a pixel window comprising a second subset of the first subset of the pixels, wherein the second subset comprises N pixels, and N is an integer;
determining, by the sensor device, N distance values corresponding to the N pixels of the pixel window based on the pixel data;
counting, by the sensor device, a number K of the N distance values that are less than a defined distance threshold; and
in response to determining that the number K of the N distance values that are less than the defined distance threshold is equal to or greater than a defined threshold value M, generating, by the sensor device, an output signal configured to at least one of disconnect power from an industrial machine, place an industrial automation system in safe operation mode, or send a notification to one or more client devices.

10. The method of claim 9 , wherein the determining the N distance values comprises:
identifying, based on the pixel data, a subset of the N distance values that are outside a defined valid distance range; and
replacing the subset of the N distance values with replacement distance values to yield a modified set of N distance values.

11. The method of claim 10 , wherein the replacing the subset of the N distance values comprises replacing each distance value, of the subset of the N distance values, corresponding to one of the pixels with a replacement value calculated based on another subset of the N distance values corresponding to pixels that are adjacent to the one of the pixels.

12. The method of claim 9 , wherein the counting comprises:
identifying a subset of the N distance values that are outside a defined valid distance range, wherein the subset comprises N OUTLINER distance values, and N OUTLINER is an integer;
removing the N OUTLINER distance values from the N distance values to yield a reduced set of distance values;
reducing the defined threshold value M based on a value of N OUTLINER to yield a modified threshold value M MODIFIED ;
counting a number of the reduced set of distance values that are less than the defined distance threshold; and
generating the output signal in response to determining that the number of the reduced set of distance values that are less than the defined distance threshold is equal to or greater than the modified threshold value M MODIFIED .

13. The method of claim 9 , wherein the defining the pixel window comprises setting the number N of pixels comprising the pixel window based on a number of the first subset of the pixels.

14. The method of claim 13 , further comprising setting, by the sensor device, the threshold value M based on the number N of pixels comprising the pixel window.

Assignees

• Rockwell Automation Tech Inc

Inventors

• Li Mei
• Boutaud Frederic

Classifications

• G08B13/184 Primary

  using radiation reflectors · CPC title

• G08B13/19602

  Image analysis to detect motion of the intruder, e.g. by frame subtraction · CPC title

• G06F1/3206

  Monitoring of events, devices or parameters that trigger a change in power modality · CPC title

• G01S17/04

  Systems determining the presence of a target · CPC title

• G06F16/2237

  Vectors, bitmaps or matrices · CPC title