TECHNICAL FIELD

Various embodiments relate generally to non-contact motion detection and more specifically to a system and method of motion detection for conveyors.

BACKGROUND

Conveyor belts typically transport objects from a first location to a second desired location. Many different types of conveyor belts exist. For example, conveyor belts may consist of surfaces that include rollers, wheels, belts that may be webbed or textured, or some other surface that would easily enable the movement of materials or objects from one place to another. The objects being transported may be varied. For example, objects may be non-uniform, such as individual boxes of varying sizes and shapes, or continuous and uniform, such as a long roll of paper or paper towels.

Conveyor belt applications typically monitor the progress of objects on a conveyor belt. Specifically, conveyor belt applications may need to determine whether a flow of objects along the conveyor belt are moving freely or if the objects are stopped and no longer moving or jammed. In some cases, the determination of flow of objects on the conveyor belt involves direct human intervention by a user. For example, the user may directly observe the objects as they move along the belt from one point to another. In other cases, the monitoring of object flow may be done by a camera-based system that records the movement of the objects as they are transported along the conveyor belt.

It may be especially challenging to determine whether or not objects on a conveyor belt are moving or are jammed in cases where objects on the conveyor belt are continuous or uniform rather than discrete and non-uniform in size and/or shape. For example, it may be more difficult to detect whether a long roll of paper or paper towels are continuing to move along a conveyor belt or are stopped as opposed to individual boxes of varying sizes and shapes.

SUMMARY

Apparatus and associated methods relate to a method of non-contact motion detection. A one-dimensional optical sensor detects motion of a target or objects on a conveyor belt through a continuous measurement of targets or objects and a real-time comparison of the pixel images captured by the one-dimensional optical sensor. In an illustrative embodiment, a one-dimensional sensor may be configured to determine motion of objects based on changes to intensities of the captured pixel images over time. The sensor may continually capture photoelectric pixel images and compare a current pixel image with a previous pixel image to determine a frame differential image value. The frame differential image value is evaluated against a predetermined threshold over a predetermined time period. Based on the evaluation, a signal is output indicating whether the objects on the conveyor belt are moving or jammed.

Various embodiments may achieve one or more advantages. For example, in one exemplary aspect, a cost-competitive and economical advantage results from using a minimal amount of hardware for jam detection. For example, a single optical imaging source, such as a one-dimensional sensor, may launch a linear optical beam that illuminates a target object being transported by a conveyor system and generate a detection signal as a function of a reflection of the linear optical beam off the target object and incident on a corresponding detection surface. The detection signal may indicate whether the object is jammed or moving. The only hardware required for achieving detection results is the optical imaging source which may include both a laser and linear imager for a measurement of distance and pixel intensity and the processing engine. In some embodiments, steps of a method may advantageously provide for image processing to determine motion based on sensor measurements of a frame differential image (FDI) without regard to distance.

In some embodiments, a FDI value may indicate a measure of movement of the target object from the first detection time to the second detection time. Some embodiments may generate a jam detection signal only if a received pixel signal strength and/or distance measurement is within a predetermined qualified range. This may reduce, for example, false detections of jams.

In another exemplary aspect, a further advantage may be the easy detection of movement of uniform and/or light-colored objects, dark-colored objects or even multi-colored objects on a conveyer belt. This may be accomplished by a processor programmed with instructions to operate an algorithm that compares differences in pixel signal strength. For example, the algorithm may include operations that sum the square of the differences in pixel strength to produce a residual difference that may indicate a motion or jam state over a predetermined time period.

The details of various embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the following detailed description taken in conjunction with the accompanying drawings.

