LSM Conveyor Weighing Section for Accurate In-Motion Weight Measurement
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Solution Overview
Problem
Linear synchronous motor conveyor systems pose challenges for accurate weigh-in-motion due to the weight of vehicles, power and communication cables, and track sections, which cause errors, especially when handling liquids and varying container sizes and weights.
Innovation Solution
A weigh-in-motion scale system that includes a support structure for a weigh cell, a section of linear synchronous motor conveyor track, and a vehicle, where the weigh cell is configured to weigh objects and vehicles in motion, with techniques to minimize the effect of cables, such as including their weight in tare calculations or reducing cable stiffness, and various mounting options to address the 'dead load' and track gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a weigh cell is used to measure the weight of articles on an LSM conveyor, then weight measurement is enabled, but the heavy dead load of the motor and track reduces measurement sensitivity
Solution Approach 1:
The conveyor track is divided into separate sections: motor-driven sections and a weighing section. The weighing section is isolated from the motor components, allowing the weigh cell to measure only the article weight without the heavy dead load of the motor and track. This segmentation enables precise weight measurement by physically separating the measurement zone from the propulsion zones.
Solution Approach 2:
The weighing function is extracted from the motor-driven conveyor sections and placed in a dedicated weighing section that is free from motor components. This extraction removes the interfering dead load of the motor and track from the measurement, allowing the weigh cell to focus solely on measuring the article weight with high precision.
2Ease of operation
If power and communication cables are attached to the linear synchronous motor, then motor operation is enabled, but cable weight and stiffness interfere with weight measurements
Solution Approach 1:
The cables are removed from the weighing section entirely. The vehicle is accelerated by the motor in upstream sections, then coasts through the cable-free weighing section using its momentum. This extraction of cables from the measurement zone eliminates their weight and stiffness interference, enabling accurate weight measurements while the vehicle passes through the weighing section.
Solution Approach 2:
The vehicle is accelerated to the required speed before entering the weighing section. This preliminary acceleration allows the vehicle to coast through the weighing section without requiring power or communication cables during the measurement process, thereby eliminating cable interference with the weight measurement.
3Ease of manufacture
If track sections with gaps are used in the LSM conveyor, then modular assembly is enabled, but vibrations occur when objects traverse the gaps causing measurement errors
Solution Approach 1:
The weighing section features a continuous, gapless track design to eliminate vibrations during measurement, while other sections of the conveyor maintain modular construction with gaps for ease of assembly. This local quality change ensures that the critical measurement zone has the smooth, vibration-free characteristics needed for accurate weighing, while the rest of the system retains manufacturing advantages.
4Ease of operation
If vehicles are used to transport articles on the LSM conveyor, then articles can be conveyed, but vehicle weight must be subtracted from measurements adding complexity
Solution Approach 1:
The system uses vehicle identification (such as RFID tags or optical codes) to recognize each vehicle and retrieve its pre-stored tare weight from memory. This feedback mechanism automatically provides the correct vehicle weight for subtraction, eliminating manual intervention and reducing calculation complexity. The controller automatically performs the tare weight subtraction to determine the article weight.
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 accurate weighing of objects with a wide range of weights, including liquids, at high speeds, with minimal errors, even when there are significant swings in weight, achieving accuracy of less than 0.60 g standard deviation across varying objects.
Implementation Method 1
the conveyor can be a linear synchronous motor (LSM) based system that facilitates propulsion of vehicles along the track using electromagnetic force (EMF)
Implementation Method 2
a weigh cell on the support structure on which a section of a linear synchronous motor conveyor track rests directly or indirectly
Data Source
AI summary
A weigh-in-motion scale system for a linear synchronous motor conveyor and a method for weighing objects on a linear synchronous motor conveyor are described herein. In one embodiment, the weigh-in-motion scale system includes a support structure for supporting the following: a weigh cell, a section of a linear synchronous motor conveyor track, a vehicle for transporting an object, and an object; and a weigh cell on the support structure on which a section of a linear synchronous motor conveyor track rests directly or indirectly. In one embodiment, the method includes transporting a vehicle with an object thereon along a section of a linear synchronous motor conveyor track; and at a weighing station while the vehicle with the object thereon is being transported, weighing the section of a linear synchronous motor conveyor track, vehicle, and object to determine the weight of the object.