Knife Sharpness Monitoring via Projected Reference Line Curvature
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Solution Overview
Problem
Existing devices for monitoring the cutting edge sharpness of knives on harvesting machines, such as forage harvesters, struggle to provide a precise and reliable assessment due to the dulling of the cutting edge not affecting the shape in camera images, making it difficult to quantify sharpness effectively.
Innovation Solution
A device that projects a reference line across the cutting edge using a light source and camera, where the reference line follows the knife's contour, allowing for quantitative assessment of sharpness by evaluating its curvature, and includes features like a pulsed light source and synchronized triggering with the knife's rotation for accurate measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a camera records images of the knife from a radial direction, then the cutting edge appears as a thin line between two flanks, but the dulling of the cutting edge does not affect the shape, making it difficult to precisely assess sharpness
Solution Approach 1:
A reference line is introduced as an intermediary element that is projected onto the knife surface. This reference line serves as a mediator between the cutting edge and the camera, allowing the assessment of sharpness through the reference line's curvature rather than directly measuring the cutting edge itself. The reference line's shape changes in response to the cutting edge's condition, making the assessment possible.
Solution Approach 2:
The reference line is illuminated to create a visible contrast against the knife surface. By illuminating the reference line, it becomes visually distinguishable in the camera images, allowing for accurate detection and analysis of its curvature. The illumination creates a bright reference line that stands out against the darker background, facilitating precise measurement.
2Productivity
If the knife rotates on the drum, then continuous operation is possible, but the movement makes it difficult to capture sharp images for accurate measurement
Solution Approach 1:
The light source operates periodically by emitting light pulses that are synchronized with the knife's rotation. This periodic illumination ensures that the reference line is illuminated only during specific moments when the knife is in the correct position, creating sharp, freeze-frame images despite the continuous rotation. The pulsed light source timing is coordinated with the rotational cycle to capture optimal measurement moments.
Solution Approach 2:
A trigger device detects the position of the knife and provides feedback signals to coordinate the camera and light source operation. This feedback mechanism ensures that images are captured at the precise moment when the cutting edge is in the optimal position for measurement, maintaining image sharpness and measurement accuracy during continuous rotation.
3Illumination intensity
If a broad cone of light is used from an incandescent light source, then sufficient illumination is provided, but the light cannot be focused onto a line-shaped area
Solution Approach 1:
The cylindrical optical element creates a localized illumination pattern where the light is concentrated into a line-shaped area rather than being distributed broadly. This local concentration of light energy provides sufficient brightness along the reference line while maintaining a precise, narrow width. The optical element transforms the broad cone of light into a focused line, achieving both intensity and precision.
Solution Approach 2:
A cylindrical optical element is used to shape the light into a line form. The cylindrical geometry of the optical element naturally focuses the light into a line-shaped pattern, utilizing the curved surface properties to control the light distribution. This cylindrical optics approach efficiently transforms the broad light cone into a precise linear illumination pattern.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables a safe and reliable assessment of cutting edge sharpness by quantitatively evaluating the curvature of the reference line, reducing errors and improving the efficiency of knife maintenance by providing reproducible and predictable images for image processing.
Implementation Method 1
the reference line in the form of an illuminated line can also advantageously be obtained by arranging a cylindrical optical element such as a cylindrical lens or a cylindrical mirror or a rotating optical element on the path of the light from the light source to the knife. If the light source produces a broad cone of light, for example in the case of an incandescent light source, the cylindrical optical element can be used to focus the cone of light onto the line-shaped illuminated area.
Implementation Method 2
A laser is particularly suitable as a light source for generating a sharply bundled light beam.
Implementation Method 3
If the light source produces a sharply focused beam; then the cylindrical optical element can project the reference line by fanning out the collimated beam in one plane.
Implementation Method 4
a camera for recording images of the knife illuminated by the light source
Data Source
AI summary
A device for monitoring the edge sharpness of a knife (18) comprises a light source (36) for illuminating the knife (18) and a camera (44) for capturing images of the knife (18). The light source (36) is configured to project at least one reference line (52) onto the knife (18), the reference line intersecting the cutting edge (48) of the knife (18) within the field of view of the camera (44). The edge sharpness can be estimated based on the shape of the reference line (52) in an image captured by the camera (44).