CASE STUDY
Revolutionizing Precision Weighing: The Integration of Magnetic Levitation and OAV Air Bearings
Ajou University researchers integrated OAV Air Bushings with magnetic levitation to develop a faster, more rugged, and highly precise electromagnetic force compensation weighing system.
CUSTOMER
Ajou University
INDUSTRY
Research & Academics
APPLICATION
Magnetic Levitation
PRODUCT USED
Air Bushings
BENEFIT
Precision Measurement
THE CHALLENGE
Precision mass measurement is important in industries such as semiconductor manufacturing, food production, and medicine, where accurate weighing is used for quality control and product inspection. Two common technologies are strain gauge load cells and electromagnetic force compensation (EMFC) weighing cells. However, both have limitations when high accuracy, fast response, and mechanical durability are required.
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Strain gauge load cells are rugged and relatively inexpensive, but their accuracy and weighing speed can be limited by weak damping and resonant behavior. EMFC weighing cells offer high repeatability and resolution, but conventional flexure-based mechanisms can result in longer settling times and limited load capacity. Repeated or excessive loading can also increase the risk of fatigue failure.
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To address these limitations, researchers developed an EMFC weighing cell that replaced the conventional flexure mechanism with magnetic springs and OAV Air Bushings. The magnetic springs provided near-zero negative stiffness to increase system bandwidth and compensated for gravitational forces from deadweight. The OAV Air Bushings provided frictionless guidance while increasing stiffness in parasitic directions, which improved the system ruggedness and reduced measurement errors caused by external forces.
THE SOLUTION
The proposed design used magnetic springs to compensate for deadweight while providing near-zero stiffness, helping increase system bandwidth and measurement sensitivity. OAV Air Bushings replaced the conventional flexure-based guide mechanism, providing greater stiffness in parasitic directions and increased mechanical ruggedness. High-precision optical encoders were used for position sensing, while voice coil motors (VCMs) provided the force required for electromagnetic compensation.
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The magnetic springs were designed around the required static force, dimensional constraints, and target stiffness. Through analytical modeling and optimization, the researchers developed a configuration that provided gravity compensation while maintaining near-zero negative stiffness within the required operating range.
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Together, the magnetic springs and OAV Air Bushings addressed several limitations of conventional flexure-based EMFC weighing cells. The design combined the high sensitivity required for precision mass measurement with greater mechanical stiffness and a faster dynamic response.
Figure 1. Experimental setup of the EMFC precision weighing system.
Figure 2. EMFC weighing cell architecture showing the magnetic spring, air bearing guidance system, and key components.
THE RESULTS
The integration of magnetic springs and OAV Air Bushings improved the performance of the EMFC weighing system by addressing key limitations of conventional flexure-based designs. The resulting system achieved faster settling, increased ruggedness, and high measurement precision while maintaining the sensitivity required for precision mass measurement.
Reduced settling time for faster precision measurements
Increased load capacity and system ruggedness
Minimized measurement errors caused by external forces
Achieved high-precision, repeatable mass measurement
The research demonstrated how OAV Air Bearing technology can complement magnetic levitation in advanced precision weighing systems where accuracy, response time, and mechanical robustness are critical.
REFERENCES
Yoon, K.-T., Park, S.-R., & Choi, Y.-M. (2021). Electromagnetic force compensation weighing cell with magnetic springs and air bearings. Measurement Science and Technology, 32(1), 015905. DOI: 10.1088/1361-6501/abae8e