Electromagnetic force compensation weighing cell with magnetic springs and air bearings

Abstract

The electromagnetic force compensation (EMFC) principle is a state-of-the-art weighing method for precision mass measurement. In this method, the low stiffness of the flexure-based Roberval guide mechanism and high lever ratio of force transmission contribute to achieving extremely high weighing sensitivity. However, weak damping and the parasitic resonant frequencies of the flexure mechanism lead to a slow settling time after loading a weight. Moreover, the low ruggedness of the flexure mechanism limits the load capacity of the EMFC weighing cell and may result in fatigue failure under repeated loading. In this paper, we propose a novel precision weighing cell with Halbach array magnetic springs and air bearings instead of the flexure mechanism. The magnetic spring is designed for near-zero negative stiffness to increase the system bandwidth, as well as for gravity force compensation ability against deadweights. The air bearings ensure high ruggedness toward parasitic directions with high stiffness in the parasitic direction and a damping effect from the pressurized air film. The stiffness of the fabricated prototype weighing cell is −27.3 N m−1, which is tens of times lower than that of conventional EMFC weighing cells. The weighing repeatability of the weighing cell is 2.35 mg, as measured with a 10 g E2 class test mass, and the settling time within ±2% of its final value is 57 ms in air.

Micro-force sensing techniques and traceable reference forces: a review

“…Comparing the force to be measured with the standard force is the basic principle of a force-balanced sensor. One of the most commonly used forcebalanced sensors is the electromagnetic balance [15].…”

“…35CrMnSiA alloy steel is suitable for Review content from six types of sensors, mainly including resistive force sensors, inductive force sensors, capacitive force sensors, magnetoelastic force sensors, piezoelectric force sensors, and optical force sensors. Summary of the gravity of standard mass (Reprinted from [14], Copyright (2021), with permission from Elsevier), electromagnetic force (Reproduced from [15]. © IOP Publishing Ltd. All rights reserved), electrostatic force (Reproduced from [16].…”

“…Therefore, considerable efforts have been made in developing novel principles of measurement, sensing materials, and the creative structure of force sensors [12]. In addition, to ensure the traceability of micro-force metrology, a number of national metrology institutes worldwide have built different small-force facilities based on individual designs and operating principles to extend the range of traceable force measurement down to the nanonewton level [13][14][15][16][17].…”

Research on attitude compensated algorithm for shipborne dynamic weighing

“…The Electromagnetic Force Compensation (EMFC) principle stands as a cutting-edge weighing method for precise mass measurements. This method leverages the low stiffness and high leverage of the flexure-based Roberval guidance mechanism for force transfer, resulting in an exceptionally high weighing sensitivity [21]. Vimalesh et al introduced a balanced-type checkweigher scheme comprising a lever mechanism, VCA, laser displacement sensor, conveyor, and balancing compensation controller.…”

Multi-objective optimization design of novel differential permanent magnet spring based on analytical modeling

“…4 These characteristics are of great significance in improving vibration and noise, reducing energy consumption, and increasing service life and durability. 5 Therefore, PMS are widely used for motors, 6,7 robots, 8 vibration isolators, 9 static load compensation, 10 pumps, 11 valves, 12 energy harvesting, 13,14 and many other apparatuses.…”