Multiplexed Half-Bridge Load Cells for Center of Gravity Tracking
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Solution Overview
Problem
Traditional weight sensing systems in materials handling facilities are costly and unable to provide specific weight data at different locations, limiting the accuracy of inventory management by not allowing determination of the center of gravity or location of weight changes.
Innovation Solution
The use of multiplexed pairs of half-bridge load cells (HBLCs) that support a platform, providing weight data indicative of weights at different physical locations while reducing overall cost and complexity, allowing for modular configuration and accurate determination of weight changes and center of gravity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional weight sensing systems are used, then weight measurement is possible, but the cost and complexity are high and specific location weight data cannot be provided
Solution Approach 1:
The platform is divided into multiple segments with individual load cells positioned at different locations. Each load cell measures weight at its specific location, enabling the system to provide detailed weight data for different regions of the platform rather than a single aggregate measurement.
Solution Approach 2:
Multiple half-bridge load cells are combined to function as full-bridge load cells. By pairing oppositely polarized half-bridge load cells and connecting them in series, the system achieves full-bridge functionality with reduced component count and lower cost while maintaining measurement precision.
2Measurement precision
If multiple load cells are used to provide location-specific weight data, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent combines multiple half-bridge load cells to create functional equivalents of full-bridge load cells. By using oppositely polarized half-bridge load cells in series connections, the system achieves the measurement capabilities of expensive full-bridge cells while using cheaper half-bridge components, reducing overall manufacturing cost.
Solution Approach 2:
The system uses multiple copies of the same half-bridge load cell design in different locations rather than deploying different types of expensive load cells. This standardized approach simplifies manufacturing and reduces costs while still providing location-specific weight measurement capabilities.
3Measurement precision
If full-bridge load cells are used, then measurement precision is high, but power consumption and heat dissipation increase
Solution Approach 1:
The patent merges multiple low-power half-bridge load cells to achieve the measurement precision of full-bridge cells. By using half-bridge configurations with oppositely polarized elements, the system reduces the power requirements compared to traditional full-bridge cells while maintaining measurement accuracy through the combined output of multiple sensors.
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
This solution significantly reduces the cost and complexity of weight sensing systems, enabling accurate tracking of inventory movements and improving the overall accuracy of inventory management by providing detailed weight data at various locations, including the center of gravity, while minimizing power consumption and heat dissipation.
Implementation Method 1
Each HBLC includes a first strain gauge element and a second strain gauge element
Data Source
AI summary
A platform is supported at four corners by four half-bridge load cells. Adjacent load cells are oppositely polarized. During operation, analog output from a pair of oppositely polarized half-bridge load cells is provided to an instrument amplifier. Analog output from the instrument amplifier is provided to an analog to digital converter to provide digital data. The digital data is then used to determine weight data indicative of a weight as measured by the pair of half-bridge load cells at that time. A set of switching elements, such as a quad bilateral switch controlled by a microcontroller, rapidly switch between pairs of oppositely polarized load cells. The weight data may be used to determine an overall weight change on the platform, such as a pick or a place of an item. Weight data from the four pairs of load cells may be used to determine a change in center of gravity.