scholarly journals Magnetic Tweezers with Magnetic Flux Density Feedback Control

2020 ◽  
Author(s):  
Waddah I. Moghram ◽  
Anton Kruger ◽  
Edward A. Sander ◽  
John C. Selby
Keyword(s):  
Feedback Control ◽  
Magnetic Flux ◽  
Flux Density ◽  
Traction Force ◽  
Magnetic Tweezers ◽  
Magnetic Flux Density ◽  
Magnetic Actuation ◽  
Superparamagnetic Beads ◽  
Control Scheme ◽  
Wide Range

ABSTRACTIn this work, we present a single-pole magnetic tweezers (MT) device designed for integration with substrate deformation tracking microscopy (DTM) and/or traction force microscopy (TFM) experiments intended to explore extracellular matrix rheology and human epidermal keratinocyte mechanobiology. Assembled from commercially available off-the-shelf electronics hardware and software, the MT device is amenable to replication in the basic biology laboratory. In contrast to conventional solenoid current-controlled MT devices, operation of this instrument is based on real-time feedback control of the magnetic flux density emanating from the blunt end of the needle core using a cascade control scheme and a digital proportional-integral-derivative (PID) controller. Algorithms that compensate for an apparent spatially non-uniform remnant magnetization of the needle core that develops during actuation are implemented into the feedback control scheme. Through optimization of PID gain scheduling, the MT device exhibits magnetization and demagnetization response times of less than 100 ms without overshoot over a wide range of magnetic flux density setpoints. Compared to current-based control, magnetic flux density-based control allows for more accurate and precise magnetic actuation forces by compensating for temperature increases within the needle core due to heat generated by the applied solenoid currents. Near field calibrations validate the ability of the MT device to actuate 4.5 μm-diameter superparamagnetic beads with forces up to 25 nN with maximum relative uncertainties of ±30% for beads positioned between 2.5 and 40 μm from the needle tip.

scholarly journals Magnetic tweezers with magnetic flux density feedback control

2021 ◽  
Vol 92 (3) ◽  
pp. 034101
Author(s):  
Waddah I. Moghram ◽  
Anton Kruger ◽  
Edward A. Sander ◽  
John C. Selby
Keyword(s):  
Feedback Control ◽  
Magnetic Flux ◽  
Flux Density ◽  
Magnetic Tweezers ◽  
Magnetic Flux Density

scholarly journals Experimental Investigation of Process Parameters of Al-SiC-B4C MMCs Finished by a Novel Magnetic Abrasive Flow Machining Setup

2021 ◽  
Vol 18 (18) ◽  
Author(s):  
Gagandeep CHAWLA ◽  
Vinod Kumar MITTAL ◽  
Sushil MITTAL
Keyword(s):  
Magnetic Flux ◽  
Flux Density ◽  
Material Removal ◽  
Permanent Magnets ◽  
Surgical Instruments ◽  
Extrusion Pressure ◽  
Magnetic Flux Density ◽  
Abrasive Flow Machining ◽  
Wide Range ◽  
Number Of Cycles

Abrasive flow machining (AFM) is one of the non-conventional finishing processes used to attain good surface quality and high material removal. However, limited attempts have been made to improve the performance of these processes. This paper presents a novel magnetic abrasive flow machining (MAFM) setup fabricated by adding a magnetization effect in which a nylon fixture and permanent magnets are replaced by a newly fabricated aluminium fixture and coil-type magnets, respectively. Inner cylindrical surfaces of hybrid Al/SiC/B4C metal matrix composites (MMCs) are finished by the MAFM process. One variable at a time (OVAT) approach is used for studying the effect of 6 input parameters, extrusion pressure (Ep), the number of cycles (N), abrasives concentration (C), workpiece material (Wp), abrasive mesh size (M), and magnetic flux density (Mf) upon response parameters, material removal rate (MRR) and change in surface roughness (ΔRa). The experimental results obtained for MRR and ΔRa show a significant improvement from 3.92 to 7.68 μg/s and 0.49 to 0.74 μm, respectively due to the increase of the extrusion pressure from 1 to 9 Mpa. The MRR and ΔRa was reduced from 6.89 to 6.78 μg/s and 0.46 to 0.22 μm, respectively with an increase in mesh number of abrasives from 80 to 400. The variation in concentration of abrasives from 40 to 60 % shows an improvement in MRR from 4.51 to 6.42 μg/s; whereas, there is a negligible effect on ΔRa which comes out from 3.82 to 3.86 μm. The MMCs, which are used for the experimentation shows a decline in MRR and ΔRa from 5.12 to 3.85 μg/s and 0.77 to 0.42 μm, respectively. This happened because there was a percentage change of reinforcement of SiC from 9 to 7 % and B4C from 1 to 3 % in Al-6063. An increase in the number of cycles from 50 to 250 shows a significant improvement in both MRR and ΔRa from 1.79 to 3.75 μg/s and 0.97 to 1.86 μm, respectively. Variation in magnetic effect also significantly improves MRR and ΔRa from 1.35 to 3.17 μg/s and 0.38 to 1.06 μm, respectively, when it is varied from 0.15 - 0.45 Tesla. The work carried out shows an overall significant improvement in MRR and ΔRa by using the MAFM process. The MAFM process finds a wide range of applications in finishing like surgical instruments, mechanical components, aerospace industry, electronics industry, etc. HIGHLIGHTS The hybrid MMCs (Al/SiC/B4C) are finished by novel MAFM setup An aluminium fixture and coil-type magnets play a significant role for finishing the workpiece surfaces An abrasive laden media acts as a cutting tool in the finishing process The OVAT approach is used for investigating the parametric effect The extrusion pressure, number of cycles and magnetic flux density are the significant parameters affecting the MRR and ΔRa GRAPHICAL ABSTRACT

Cycle-dependent and cycle-independent surface tracers of solar magnetic activity

2018 ◽  
Vol 14 (A30) ◽  
pp. 342-343
Author(s):  
D. D. Sokoloff ◽  
V. N. ◽  
Obridko ◽  
I. M. ◽  
Livshits ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Flux Density ◽  
Magnetic Activity ◽  
Solar Dynamo ◽  
Magnetic Flux Density ◽  
Small Scale ◽  
Wide Range ◽  
Background Fields ◽  
Cycle Dependent

AbstractWe consider several tracers of magnetic activity that separate cycle-dependent contributions to the background solar magnetic field from those that are independent of the cycle. The main message is that background fields include two relative separate populations. The background fields with a strength up to 100 Mx cm−2 are very poorly correlated with the sunspot numbers and vary little with the phase of the cycle. In contrast, stronger magnetic fields demonstrate pronounced cyclic behaviour. Small-scale solar magnetic fields demonstrate features of fractal intermittent behaviour, which requires quantification. We investigate how the observational estimate of the solar magnetic flux density B depends on resolution D in order to obtain the scaling In BD = −k In D + a in a reasonably wide range. The quantity k demonstrates cyclic variations typical of a solar activity cycle. k depends on the magnetic flux density, i.e. the ratio of the magnetic flux to the area over which the flux is calculated, at a given instant. The quantity a demonstrates some cyclic variation, but it is much weaker than in the case of k. The scaling is typical of fractal structures. The results obtained trace small-scale action in the solar convective zone and its coexistence with the conventional large-scale solar dynamo based on differential rotation and mirror-asymmetric convection. Here we discuss the message for solar dynamo studies hidden in the above results.

Complex transformations of hard-magnetic soft beams by designing residual magnetic flux density

Soft Matter ◽  
2020 ◽  
Vol 16 (27) ◽  
pp. 6379-6388
Author(s):  
Wei Chen ◽  
Zhi Yan ◽  
Lin Wang
Keyword(s):  
Magnetic Flux ◽  
Flux Density ◽  
Magnetic Flux Density ◽  
Magnetic Actuation

An initially straight hard-magnetic soft beam (HMSB) under magnetic actuation can deform into specific configurations by designing the distribution of residual magnetic flux density.

scholarly journals Design of a New 1D Halbach Magnet Array with Good Sinusoidal Magnetic Field by Analyzing the Curved Surface

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2522
Author(s):  
Guangdou Liu ◽  
Shiqin Hou ◽  
Xingping Xu ◽  
Wensheng Xiao
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Permanent Magnet ◽  
Flux Density ◽  
Permanent Magnets ◽  
Air Gap ◽  
Curved Surface ◽  
Magnetic Flux Density ◽  
Sinusoidal Magnetic Field ◽  
The Magnetic Field

In the linear and planar motors, the 1D Halbach magnet array is extensively used. The sinusoidal property of the magnetic field deteriorates by analyzing the magnetic field at a small air gap. Therefore, a new 1D Halbach magnet array is proposed, in which the permanent magnet with a curved surface is applied. Based on the superposition of principle and Fourier series, the magnetic flux density distribution is derived. The optimized curved surface is obtained and fitted by a polynomial. The sinusoidal magnetic field is verified by comparing it with the magnetic flux density of the finite element model. Through the analysis of different dimensions of the permanent magnet array, the optimization result has good applicability. The force ripple can be significantly reduced by the new magnet array. The effect on the mass and air gap is investigated compared with a conventional magnet array with rectangular permanent magnets. In conclusion, the new magnet array design has the scalability to be extended to various sizes of motor and is especially suitable for small air gap applications.

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