The modelling and design of a mechanism for micro-force measurement

Choi, In-Mook; Choi, Daeseon; Kim, Soo Hyun

doi:10.1088/0957-0233/12/8/339

Cited by 9 publications

(5 citation statements)

References 8 publications

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“…The settling time with the 15 g disturbance was 57 ms, and the repeatability with the 10 g standard weight was 2.35 mg. Compared with previous studies of conventional EMFC weighing cells [7][8][9], further improvements are required in terms of resolution and repeatability.…”

Section: Discussionmentioning

confidence: 99%

“…Finally, the mass of the unknown weight is calculated by multiplying the electric current applied to an electromagnetic actuator and the force constant of the actuator. Due to the high sensitivity of the lever mechanism and high resolution of the displacement sensor, the EMFC weighing cell achieves a high weighing resolution of 0.01−0.1 mg and a repeatability of 0.1 mg in static weighing with a typical load capacity of 200 g [7][8][9]. Also, a settling time of about 100 ms was acquired through feedback control [7,10,11].…”

Section: Introductionmentioning

confidence: 99%

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Electromagnetic force compensation weighing cell with magnetic springs and air bearings

Yoon

Park

Choi

2020

Meas. Sci. Technol.

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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.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electromagnetic force compensation weighing cell with magnetic springs and air bearings

Yoon

Park

Choi

2020

Meas. Sci. Technol.

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“…The lever mechanism connected to the parallel spring is designed to increase the resolution and to be used as a counter-mass. The design schemes of the parallel spring and the lever mechanism were proposed in a previous paper in detail [7]. In the previous work, various design specifications could be achieved through the use of a two-stage amplification mechanism and a modified parallel spring.…”

Section: System Design and Analysismentioning

confidence: 99%

“…In equation (7), angle displacement, θ T , caused by additional torsion does not affect the vertical displacement of the sixth rigid body, δ T , theoretically. However, since the alignment error of the displacement sensor and the assembling error can affect the vertical displacement, the angle displacement should be minimized during design.…”

Section: System Design and Analysismentioning

confidence: 99%

Parallelism error analysis and compensation for micro-force measurement

Choi

Kim

Woo

et al. 2003

Meas. Sci. Technol.

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The null balance method for micro-and nano-force measurement is widely used in various precision industries. A parallel spring and a lever mechanism are designed and analysed for an electrostatic force balance by the null balance method. Various design parameters are required to obtain high resolution, a large measurement range, and fast response. The corner loading error is one of the most dominant error sources that should be removed. A parallel spring known as the Roberval mechanism, used in the micro-weighing device, can be used for one-axis force measurement since it is very sensitive to the vertical direction force, but insensitive to other force components. However, precise control of parallelism to below a micrometre is required not only to compensate for but also to remove the corner loading error. In this paper, the effects of the parallelism error have been analysed using the Lagrange method and verified by the FEA method. It was found that parallelism control by the proposed precise compensation mechanism enables the simultaneous elimination of and compensation for the corner loading error.

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“…The more compliant the lever, the higher the measurement sensitivity of the weighing cell. The static weight measurement of these EMFC weighing cells has a high resolution of up to 0.02 mg and a repeatability of 0.1 mg [16,17]. Therefore, EMFC weighing cell is more favorable in the high precision inspection process with dynamic weighing.…”

Section: Introductionmentioning

confidence: 99%

Metrology and Measurement Systems

Lee,

Yoon,

Choi

2021

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A dynamic weighing system or a checkweigher is an automated inspection system that measures the weight of objects while transferring them between processes. In our previous study, we developed a new electromagnetic force compensation (EMFC) weighing cell using magnetic springs and air bearings. This weighing cell is free from flexure hinges which are vulnerable to shock and fatigue and also eliminates the resonance characteristics and implements a very low stiffness of only a few N/m due to the nature of the Halbach array magnetic spring. In this study, we implemented a checkweigher with the weighing cell including a loading and unloading conveyor to evaluate its dynamic weighing performances. The magnetic springs are optimized and re-designed to compensate for the weight of a weighing conveyor on the weighing cell. The checkweigher has a weighing repeatability of 23 mg (1σ) in static situation. Since there is no lowfrequency resonance in our checkweigher that influences the dynamic weighing signal, we could measure the weight by using only a notch filter at high conveyor speeds. To determine the effective measurement time, a dynamic weighing process model is used. Finally, the proposed checkweigher meets Class XIII of OIML R51-1 of verification scale e 0.5 g at a conveyor speed of up to 2.7 m/s.

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The modelling and design of a mechanism for micro-force measurement

Cited by 9 publications

References 8 publications

Electromagnetic force compensation weighing cell with magnetic springs and air bearings

Electromagnetic force compensation weighing cell with magnetic springs and air bearings

Parallelism error analysis and compensation for micro-force measurement

Metrology and Measurement Systems

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