L-Beam Force Sensing via Surface Wheatstone Bridge
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Solution Overview
Problem
Current strain-based measurement systems for force and location on L-beams are prone to mechanical complications, inaccuracy due to off-level conditions, fragility, and difficulty in installation or retrofitting, and lack the ability to accurately measure larger bending strains and determine load location.
Innovation Solution
A system that uses a combination of Wheatstone bridge sensors placed on the tension and compression sides of an L-beam, away from the neutral axis, to measure strain and determine the location and force of an object without physical sensors on the force-receiving portion, allowing for accurate weight measurement and off-level compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If strain gauges are placed inside an elongated hole within a beam, then the beam structure can accommodate sensors, but the beam is weakened and measurements become less accurate
Solution Approach 1:
The invention extracts the sensor from the beam interior and places it on the exterior surface. Instead of drilling holes through the beam to install strain gauges inside, the sensor is mounted on the outer surface where it can measure bending strain without compromising the beam's structural integrity. This resolves the contradiction by eliminating the hole-creation process that weakens the beam while still enabling sensor installation.
Solution Approach 2:
The invention transitions the sensor placement from the interior dimension (inside the beam cross-section) to the exterior dimension (on the beam surface). By moving the sensor to another spatial dimension - the outer surface of the beam - the system can measure strain without creating holes that would weaken the structure.
2Ease of operation
If sensors are placed closer to the neutral axis of the beam, then installation is easier, but stress measurements are less accurate because stress approaches zero near the neutral axis
Solution Approach 1:
The invention applies local quality by placing the sensor specifically on the tensile or compressive surface of the beam, away from the neutral axis. This localized placement ensures the sensor operates in a region of high stress gradient where measurement sensitivity is maximized. The sensor is positioned at a specific location (the extreme fiber) where the bending stress is greatest, rather than distributing sensors across multiple locations including near the neutral axis.
3Reliability
If vertical-shear-based systems are used, then the shear load is not affected by placement of the weight, but the systems are fragile and lack a weigh system using the strain existing in the functional structure
Solution Approach 1:
The invention enables the beam structure to serve itself as the sensing element. Instead of requiring separate fragile load cells or shear measurement devices, the beam's own bending strain - which naturally occurs during operation - is measured directly by surface-mounted sensors. The functional structure (the beam) provides both the mechanical support and the measurement medium, eliminating the need for additional fragile components.
Solution Approach 2:
The invention replaces fragile mechanical shear measurement systems with a more robust strain measurement approach. Instead of using delicate load cells that measure vertical shear forces, the system uses strain gauges or similar sensors that measure the bending strain in the beam, which is a more direct and mechanically robust measurement that leverages the primary stress state in the structure.
4Measurement precision
If bending beam systems with sensors in holes are used, then weight can be measured, but the systems lack off-level compensation and location determination capabilities
Solution Approach 1:
The invention makes the measurement system universal by enabling it to perform multiple functions: weight measurement, location determination, and off-level compensation. By placing sensors on the beam surface and using appropriate measurement techniques, the system can detect not only the magnitude of the load but also its position along the beam and the beam's orientation, providing a multi-functional measurement capability that adapts to various operating conditions.
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
The system provides enhanced accuracy and safety by minimizing mechanical complexity, reducing the risk of breakage, and enabling easier installation, while accurately measuring larger bending strains and determining load location, thus improving the reliability of force and location measurements.
Implementation Method 1
strain-based systems where a force is exerted on an L-beam
Implementation Method 2
uses a combination of Wheatstone bridge sensors placed on the tension and compression sides of an L-beam
Data Source
AI summary
Force and location sensing systems and methods are disclosed. A method comprises bending a L-beam at an initially unknown location on a force-supporting portion of the L-beam, the L-beam substantially having a tension side and a compression side, measuring a first local stress at a first location on the tension side, measuring a second local stress at a second location on the tension side, measuring a third local stress at a third location on the compression side, and measuring a fourth local stress at a fourth location on the compression side. A weight-sensing storage system capable of tracking removed items is disclosed with a product image captured via a camera, a plurality of sensors on an L-beam, a first signal from the plurality of sensors indicating a first state prior to change of the product image, and a second signal indicating lower strain on the L-beam than the first signal.