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Article ; Online: Fe

Gao, Ming / Cheung, Chi-Fai

2024 Volume 16, Issue 3

Abstract: Particle- or fiber-reinforced polymer composites with controlled orientations are attracting interest and applications producing innovative materials, biological constructs, and energy devices. To gain the controlled orientations, filed-assisted ... ...

Abstract	Particle- or fiber-reinforced polymer composites with controlled orientations are attracting interest and applications producing innovative materials, biological constructs, and energy devices. To gain the controlled orientations, filed-assisted synthesis is widely selected for its easy operation and control. In this paper, we designed magnetic field-assisted equipment and synthesized a magnetic polymer composite Fe
Language	English
Publishing date	2024-01-28
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2527146-5
ISSN	2073-4360 ; 2073-4360
ISSN (online)	2073-4360
ISSN	2073-4360
DOI	10.3390/polym16030353
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Autostereoscopic 3D Measurement Based on Adaptive Focus Volume Aggregation.

Gao, Sanshan / Cheung, Chi Fai

Sensors (Basel, Switzerland)

2023 Volume 23, Issue 23

Abstract: Autostereoscopic three-dimensional measuring systems are a kind of portable and fast precision metrology instrument. The systems are based on integral imaging that makes use of a micro-lens array before an image sensor to observe measured parts from ... ...

Abstract	Autostereoscopic three-dimensional measuring systems are a kind of portable and fast precision metrology instrument. The systems are based on integral imaging that makes use of a micro-lens array before an image sensor to observe measured parts from multiple perspectives. Since autostereoscopic measuring systems can obtain longitudinal and lateral information within single snapshots rapidly, the three-dimensional profiles of the measured parts can be reconstructed by shape from focus. In general, the reconstruction process consists of data acquisition, pre-processing, digital refocusing, focus measures, and depth estimation. The accuracy of depth estimation is determined by the focus volume generated by focus measure operators which could be sensitive to the noise during digital refocusing. Without prior knowledge and surface information, directly estimated depth maps usually contain severe noise and incorrect representation of continuous surfaces. To eliminate the effects of refocusing noise and take advantage of traditional focus measure methods with robustness, an adaptive focus volume aggregation method based on convolutional neural networks is presented to optimize the focus volume for more accurate depth estimation. Since a large amount of data and ground truth are costly to acquire for model convergence, backpropagation is performed for every sample under an unsupervised strategy. The training strategy makes use of a smoothness constraint and an identical distribution constraint that restricts the difference between the distribution of the network output and the distribution of ideal depth estimation. Experimental results show that the proposed adaptive aggregation method significantly reduces the noise during depth estimation and retains more accurate surface profiles. As a result, the autostereoscopic measuring system can directly recover surface profiles from raw data without any prior information.
Language	English
Publishing date	2023-11-26
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2052857-7
ISSN	1424-8220 ; 1424-8220
ISSN (online)	1424-8220
ISSN	1424-8220
DOI	10.3390/s23239419
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Semi-supervised angular super-resolution method for autostereoscopic 3D surface measurement.

Gao, Sanshan / Cheung, Chi Fai / Li, Da

Optics letters

2024 Volume 49, Issue 4, Page(s) 858–861

Abstract: Autostereoscopic 3D measuring systems are an accurate, rapid, and portable method for in situ measurements. These systems use a micro-lens array to record 3D information based on the light-field theory. However, the spatial-angular-resolution trade-off ... ...

Abstract	Autostereoscopic 3D measuring systems are an accurate, rapid, and portable method for in situ measurements. These systems use a micro-lens array to record 3D information based on the light-field theory. However, the spatial-angular-resolution trade-off curtails their performance. Although learning models were developed for super-resolution, the scarcity of data hinders efficient training. To address this issue, a novel, to the best of our knowledge, semi-supervised learning paradigm for angular super-resolution is proposed for data-efficient training, benefiting both autostereoscopic and light-field devices. A convolutional neural network using motion estimation is developed for a view synthesis. Subsequently, a high-angular-resolution autostereoscopic system is presented for an accurate profile reconstruction. Experiments show that the semi-supervision enhances view reconstruction quality, while the amount of training data required is reduced by over 69%.
Language	English
Publishing date	2024-02-07
Publishing country	United States
Document type	Journal Article
ISSN	1539-4794
ISSN (online)	1539-4794
DOI	10.1364/OL.516099
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Active Compliance Smart Control Strategy of Hybrid Mechanism for Bonnet Polishing.

Li, Ze / Cheung, Chi Fai / Lam, Kin Man / Lun, Daniel Pak Kong

Sensors (Basel, Switzerland)

2024 Volume 24, Issue 2

Abstract: Compliance control strategies have been utilised for the ultraprecision polishing process for many years. Most researchers execute active compliance control strategies by employing impedance control law on a robot development platform. However, these ... ...

Abstract	Compliance control strategies have been utilised for the ultraprecision polishing process for many years. Most researchers execute active compliance control strategies by employing impedance control law on a robot development platform. However, these methods are limited by the load capacity, positioning accuracy, and repeatability of polishing mechanisms. Moreover, a sophisticated actuator mounted at the end of the end-effector of robots is difficult to maintain in the polishing scenario. In contrast, a hybrid mechanism for polishing that possesses the advantages of serial and parallel mechanisms can mitigate the above problems, especially when an active compliance control strategy is employed. In this research, a high-frequency-impedance robust force control strategy is proposed. It outputs a position adjustment value directly according to a contact pressure adjustment value. An open architecture control system with customised software is developed to respond to external interrupts during the polishing procedure, implementing the active compliance control strategy on a hybrid mechanism. Through this method, the hybrid mechanism can adapt to the external environment with a given contact pressure automatically instead of relying on estimating the environment stiffness. Experimental results show that the proposed strategy adapts the unknown freeform surface without overshooting and improves the surface quality. The average surface roughness value decreases from 0.057 um to 0.027 um.
Language	English
Publishing date	2024-01-10
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2052857-7
ISSN	1424-8220 ; 1424-8220
ISSN (online)	1424-8220
ISSN	1424-8220
DOI	10.3390/s24020421
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article: Characterization of Surface Topography Variation in the Ultra-Precision Tool Servo-Based Diamond Cutting of 3D Microstructured Surfaces.

Yuan, Wei / Cheung, Chi-Fai

Micromachines

2021 Volume 12, Issue 12

Abstract: Previous models of the relative tool-work vibration are not generalized to represent the surface generation mechanism in the ultra-precision tool servo-based diamond cutting (UTSDC) of three-dimensional (3D) microstructured surfaces. This is due to the ... ...

Abstract	Previous models of the relative tool-work vibration are not generalized to represent the surface generation mechanism in the ultra-precision tool servo-based diamond cutting (UTSDC) of three-dimensional (3D) microstructured surfaces. This is due to the fact that the tool-work vibration in UTSDC is no longer a steady harmonic vibration with a constant amplitude but is influenced by the tool motion along the thrust direction. In this paper, dynamic modeling of the cutting system is presented for the characterization of surface topography variation in UTSDC of a microlens array considering the tool-work vibration as an underdamped vibration. The natural frequency and damping ratio of the cutting system are determined by the data-dependent systems (DDS) method. Based on the analysis of the surface profile and cutting force signals, it is found that the tool-work vibration is significantly enhanced in the cut-in process when the cutting speed increases. The simulation results show that the proposed dynamic model can well-determine root-mean-squares RMS values of the surface primary profile and the dynamic force acting on the force sensor. The dynamic model provides insight into the formation of the surface topography variation in UTSDC of 3D microstructured surfaces, and the model might be applied in self-optimized machining systems in the future.
Language	English
Publishing date	2021-11-26
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2620864-7
ISSN	2072-666X
ISSN	2072-666X
DOI	10.3390/mi12121448
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Article ; Online: Theoretical and experimental investigation of the tool indentation effect in ultra-precision tool- servo-based diamond cutting of optical microstructured surfaces.

Yuan, Wei / Cheung, Chi Fai

Optics express

2021 Volume 29, Issue 24, Page(s) 39284–39303

Abstract: Ultra-precision tool-servo-based diamond cutting (UTSDC) is a promising technology for fabricating true 3-dimensional optical microstructures. The diamond tool in UTSDC moves alternatively upward and downward along the thrust direction. However, most ... ...

Abstract	Ultra-precision tool-servo-based diamond cutting (UTSDC) is a promising technology for fabricating true 3-dimensional optical microstructures. The diamond tool in UTSDC moves alternatively upward and downward along the thrust direction. However, most studies on the material removal mechanism are limited to the orthogonal cutting condition where the depth of cut is invariant. The effect caused by the tool motion in the thrust direction has been overlooked. In this paper, the indentation effect affected by the tool path, tool shape and cutting speed is systematically studied. It is found that the inclined angle between the tool path direction and the main cutting direction plays a key role in the determination of the material spring back and the formation of side burr. The characteristics of indentation force and material spring back indicates that the indentation mechanism is dominant in the cut-in process where the inclined angle is large, while the shearing mechanism is dominant in the cut-out process. A new theory is proposed to explain the tool indentation mechanism in UTSDC, and the simulation results show that the theory can well predict the indentation force under various cutting conditions.
Language	English
Publishing date	2021-11-22
Publishing country	United States
Document type	Journal Article
ZDB-ID	1491859-6
ISSN	1094-4087 ; 1094-4087
ISSN (online)	1094-4087
ISSN	1094-4087
DOI	10.1364/OE.445587
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Coating-Free Superhydrophobic Hard Surfaces by Electric Discharge Machining with a Magnetic-Assisted Self-Assembly Sheet Electrode.

Li, Kangsen / Wang, Chunjin / Gong, Feng / Cheung, Chi Fai / Chen, Zibin / Wang, Zuankai

ACS applied materials & interfaces

2024 Volume 16, Issue 12, Page(s) 15548–15557

Abstract: Artificial superhydrophobic surfaces hold significant potential in various domains, encompassing self-cleaning, droplet manipulation, microfluidics, and thermal management. Consequently, there is a burgeoning demand for cost-effective, mass-producible, ... ...

Abstract	Artificial superhydrophobic surfaces hold significant potential in various domains, encompassing self-cleaning, droplet manipulation, microfluidics, and thermal management. Consequently, there is a burgeoning demand for cost-effective, mass-producible, and easily fabricated superhydrophobic surfaces for commercial and industrial applications. This research introduces an efficient, uncomplicated method for constructing hierarchical structures on hard substrates such as binderless tungsten carbide (WC) and glass substrates. The WC substrates were processed by using electrical discharge machining (EDM) with a magnetic-assisted self-assembly sheet electrode. The resultant surfaces comprised micropillars/microgrooves and diminutive craters formed by discharge and ablation, respectively. These surfaces exhibited superior hydrophobic properties, which can be attributed to the modified surface energy and surface texture construction. Our study indicates that a superhydrophobic surface can be achieved on a textured binderless WC. The maximum contact angle and minimum roll-off angle of the hierarchical structure induced by EDM with a magnetic-assisted self-assembly sheet electrode are about 158 and 5°, respectively. The advancing and receding angles are about 161° ± 2 and 157° ± 3, respectively, when the base is tilted at 3°. Furthermore, we have successfully replicated this superhydrophobic structured surface on glass substrates utilizing glass molding technology. This innovative approach to creating superhydrophobic surfaces on hard materials paves the way for the mass production of functional structures on other materials, such as metallic glass, titanium alloy, and mold steel. Most crucially, the proposed fabrication technique offers a straightforward, cost-effective route for creating functional surfaces, rendering it attractive for large-scale industrial production due to its considerable application prospects.
Language	English
Publishing date	2024-03-15
Publishing country	United States
Document type	Journal Article
ISSN	1944-8252
ISSN (online)	1944-8252
DOI	10.1021/acsami.3c19487
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Self super-resolution autostereoscopic 3D measuring system using deep convolutional neural networks.

Gao, Sanshan / Cheung, Chi Fai / Li, Da

Optics express

2022 Volume 30, Issue 10, Page(s) 16313–16329

Abstract: Autostereoscopy technology can provide a rapid and accurate three-dimensional (3D) measurement solution for micro-structured surfaces. Elemental images (EIs) are recorded within one snapshot and the measurement accuracy can be quantified from the ... ...

Abstract	Autostereoscopy technology can provide a rapid and accurate three-dimensional (3D) measurement solution for micro-structured surfaces. Elemental images (EIs) are recorded within one snapshot and the measurement accuracy can be quantified from the disparities existing in the 3D information. However, a trade-off between the spatial and the angular resolution of the EIs is a major obstacle to the improvement on the measurement results. To address this issue, an angular super-resolution algorithm based on deep neural networks is proposed to construct a self super-resolution autostereoscopic (SSA) 3D measuring system. The proposed super-resolution algorithm can generate novel perspectives between the neighboring EIs so that the angular resolution is enhanced. The proposed SSA 3D measuring system can achieve self super-resolution on its measurement data. A comprehensive comparison experiment was conducted to verify the feasibility and technical merit of the proposed measuring system. The results show that the proposed SSA system can significantly improve the resolution of the measuring data by around 4 folds and enhance the measurement accuracy to a sub-micrometer level with lower standard deviations and biases.
Language	English
Publishing date	2022-10-12
Publishing country	United States
Document type	Journal Article
ZDB-ID	1491859-6
ISSN	1094-4087 ; 1094-4087
ISSN (online)	1094-4087
ISSN	1094-4087
DOI	10.1364/OE.454625
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article: Experimental Investigation on the Effect of Surface Shape and Orientation in Magnetic Field Assisted Mass Polishing.

Loh, Yee-Man / Cheung, Chi-Fai / Wang, Chunjin / Ho, Lai-Ting

Micromachines

2022 Volume 13, Issue 7

Abstract: Magnetic field assisted finishing (MFAF) technology has been widely used in industries such as aerospace, biomedical, and the optical field for both external and internal surface finishing due to its high conformability to complex surfaces and nanometric ...

Abstract	Magnetic field assisted finishing (MFAF) technology has been widely used in industries such as aerospace, biomedical, and the optical field for both external and internal surface finishing due to its high conformability to complex surfaces and nanometric surface finishing. However, most of the MFAF methods only allow polishing piece-by-piece, leading to high post-processing costs and long processing times with the increasing demand for high precision products. Hence, a magnetic field-assisted mass polishing (MAMP) method was recently proposed, and an experimental investigation on the effect of surface posture is presented in this paper. Two groups of experiments were conducted with different workpiece shapes, including the square bar and roller bar, to examine the effect of surface orientation and polishing performance on different regions. A simulation of magnetic field distribution and computational fluid dynamics was also performed to support the results. Experimental results show that areas near the chamber wall experience better polishing performance, and the surface parallel or inclined to polishing direction generally allows better shearing and thus higher polishing efficiency. Both types of workpieces show notable polishing performance where an 80% surface roughness improvement was achieved after 20-min of rough polishing and 20-min of fine polishing reaching approximately 20 nm.
Language	English
Publishing date	2022-06-30
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2620864-7
ISSN	2072-666X
ISSN	2072-666X
DOI	10.3390/mi13071060
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Article: Surface Roughness Prediction in Ultra-Precision Milling: An Extreme Learning Machine Method with Data Fusion.

Shang, Suiyan / Wang, Chunjin / Liang, Xiaoliang / Cheung, Chi Fai / Zheng, Pai

Micromachines

2023 Volume 14, Issue 11

Abstract: This paper pioneers the use of the extreme learning machine (ELM) approach for surface roughness prediction in ultra-precision milling, leveraging the excellent fitting ability with small datasets and the fast learning speed of the extreme learning ... ...

Abstract	This paper pioneers the use of the extreme learning machine (ELM) approach for surface roughness prediction in ultra-precision milling, leveraging the excellent fitting ability with small datasets and the fast learning speed of the extreme learning machine method. By providing abundant machining information, the machining parameters and force signal data are fused on the feature level to further improve ELM prediction accuracy. An ultra-precision milling experiment was designed and conducted to verify our proposed data-fusion-based ELM method. The results show that the ELM with data fusion outperforms other state-of-art methods in surface roughness prediction. It achieves an impressively low mean absolute percentage error of 1.6% while requiring a mere 18 s for model training.
Language	English
Publishing date	2023-10-29
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2620864-7
ISSN	2072-666X
ISSN	2072-666X
DOI	10.3390/mi14112016
Database	MEDical Literature Analysis and Retrieval System OnLINE

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