Frontiers of Mechanical Engineering

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Impact drive rotary precision actuator with piezoelectric bimorphs
ZHANG Hongzhuang, ZENG Ping, HUA Shunming, CHENG Guangming, YANG Zhigang
Front. Mech. Eng.    2008, 3 (1): 71-75.   https://doi.org/10.1007/s11465-008-0008-3
Abstract   HTML   PDF (142KB)
An impact drive rotary precision actuator with end-loaded piezoelectric cantilever bimorphs is proposed. According to finite element analysis and experiments of the dynamic characteristics of end-loaded piezoelectric cantilever bimorphs, a specific fixed-frequency and adjustable-amplitude is confirmed to control the actuator. The results show that an actuator excited by fixed-frequency and the adjustable-amplitude ramp voltage waveform works with a large travel range (180°), high resolution (1 ?rad), speed (0.2 rad/min) and heavy-load ability (0.02 Nm). With advantages of high-precision positioning ability, simple structure and only one percent the cost of traditional impact drive mechanisms, the actuator is expected to be widely used in precision industries.
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Untethered quadrupedal hopping and bounding on a trampoline
Boxing WANG, Chunlin ZHOU, Ziheng DUAN, Qichao ZHU, Jun WU, Rong XIONG
Front. Mech. Eng.    2020, 15 (2): 181-192.   https://doi.org/10.1007/s11465-019-0559-5
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For quadruped robots with springy legs, a successful jump usually requires both suitable elastic parts and well-designed control algorithms. However, these two problems are mutually restricted and hard to solve at the same time. In this study, we attempt to solve the problem of controller design with the help of a robot without any elastic mounted parts, in which the untethered robot is made to jump on a trampoline. The differences between jumping on hard surfaces with springy legs and jumping on springy surfaces with rigid legs are briefly discussed. An intuitive control law is proposed to balance foot contact forces; in this manner, excessive pitch oscillation during hopping or bounding can be avoided. Hopping height is controlled by tuning the time delay of the leg stretch. Together with other motion generators based on kinematic law, the robot can perform translational and rotational movements while hopping or bounding on the trampoline. Experiments are conducted to validate the effectiveness of the proposed control framework.

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Motion control of multi-actuator hydraulic systems for mobile machineries: Recent advancements and future trends
Bing XU, Min CHENG
Front. Mech. Eng.    2018, 13 (2): 151-166.   https://doi.org/10.1007/s11465-018-0470-5
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This paper presents a survey of recent advancements and upcoming trends in motion control technologies employed in designing multi-actuator hydraulic systems for mobile machineries. Hydraulic systems have been extensively used in mobile machineries due to their superior power density and robustness. However, motion control technologies of multi-actuator hydraulic systems have faced increasing challenges due to stringent emission regulations. In this study, an overview of the evolution of existing throttling control technologies is presented, including open-center and load sensing controls. Recent advancements in energy-saving hydraulic technologies, such as individual metering, displacement, and hybrid controls, are briefly summarized. The impact of energy-saving hydraulic technologies on dynamic performance and control solutions are also discussed. Then, the advanced operation methods of multi-actuator mobile machineries are reviewed, including coordinated and haptic controls. Finally, challenges and opportunities of advanced motion control technologies are presented by providing an overall consideration of energy efficiency, controllability, cost, reliability, and other aspects.

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Relative vibration identification of cutter and workpiece based on improved bidimensional empirical mode decomposition
Jiasheng LI, Xingzhan LI, Wei WEI, Pinkuan LIU
Front. Mech. Eng.    2020, 15 (2): 227-239.   https://doi.org/10.1007/s11465-020-0587-1
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In the process of cutting, the relative vibration between the cutter and the workpiece has an important effect on the surface topography. In this study, the bidimensional empirical mode decomposition (BEMD) method is used to identify such effect. According to Riesz transform theory, a type of isotropic monogenic signal is proposed. The boundary data is extended on the basis of a similarity principle that deals with serious boundary effect problem. The decomposition examples show that the improved BEMD can effectively solve the problem of boundary effect and decompose the original machined surface topography at multiple scales. The characteristic surface topography representing the relative vibration between the cutter and the workpiece through feature identification is selected. In addition, the spatial spectrum analysis of the extracted profile is carried out. The decimal part of the frequency ratio that has an important effect on the shape of the contour can be accurately identified through contour extraction and spatial spectrum analysis. The decomposition results of simulation and experimental surface morphology demonstrate the validity of the improved BEMD algorithm in realizing the relative vibration identification between the cutter and the workpiece.

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Recent development in low-constraint fracture toughness testing for structural integrity assessment of pipelines
Jidong KANG, James A. GIANETTO, William R. TYSON
Front. Mech. Eng.    2018, 13 (4): 546-553.   https://doi.org/10.1007/s11465-018-0501-2
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Fracture toughness measurement is an integral part of structural integrity assessment of pipelines. Traditionally, a single-edge-notched bend (SE(B)) specimen with a deep crack is recommended in many existing pipeline structural integrity assessment procedures. Such a test provides high constraint and therefore conservative fracture toughness results. However, for girth welds in service, defects are usually subjected to primarily tensile loading where the constraint is usually much lower than in the three-point bend case. Moreover, there is increasing use of strain-based design of pipelines that allows applied strains above yield. Low-constraint toughness tests represent more realistic loading conditions for girth weld defects, and the corresponding increased toughness can minimize unnecessary conservatism in assessments. In this review, we present recent developments in low-constraint fracture toughness testing, specifically using single-edge-notched tension specimens, SENT or SE(T). We focus our review on the test procedure development and automation, round-robin test results and some common concerns such as the effect of crack tip, crack size monitoring techniques, and testing at low temperatures. Examples are also given of the integration of fracture toughness data from SE(T) tests into structural integrity assessment.

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Fabrication of scaffolds in tissue engineering: A review
Peng ZHAO, Haibing GU, Haoyang MI, Chengchen RAO, Jianzhong FU, Lih-sheng TURNG
Front. Mech. Eng.    2018, 13 (1): 107-119.   https://doi.org/10.1007/s11465-018-0496-8
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Tissue engineering (TE) is an integrated discipline that involves engineering and natural science in the development of biological materials to replace, repair, and improve the function of diseased or missing tissues. Traditional medical and surgical treatments have been reported to have side effects on patients caused by organ necrosis and tissue loss. However, engineered tissues and organs provide a new way to cure specific diseases. Scaffold fabrication is an important step in the TE process. This paper summarizes and reviews the widely used scaffold fabrication methods, including conventional methods, electrospinning, three-dimensional printing, and a combination of molding techniques. Furthermore, the differences among the properties of tissues, such as pore size and distribution, porosity, structure, and mechanical properties, are elucidated and critically reviewed. Some studies that combine two or more methods are also reviewed. Finally, this paper provides some guidance and suggestions for the future of scaffold fabrication.

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Fault feature extraction of planet gear in wind turbine gearbox based on spectral kurtosis and time wavelet energy spectrum
Yun KONG, Tianyang WANG, Zheng LI, Fulei CHU
Front. Mech. Eng.    2017, 12 (3): 406-419.   https://doi.org/10.1007/s11465-017-0419-0
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Planetary transmission plays a vital role in wind turbine drivetrains, and its fault diagnosis has been an important and challenging issue. Owing to the complicated and coupled vibration source, time-variant vibration transfer path, and heavy background noise masking effect, the vibration signal of planet gear in wind turbine gearboxes exhibits several unique characteristics: Complex frequency components, low signal-to-noise ratio, and weak fault feature. In this sense, the periodic impulsive components induced by a localized defect are hard to extract, and the fault detection of planet gear in wind turbines remains to be a challenging research work. Aiming to extract the fault feature of planet gear effectively, we propose a novel feature extraction method based on spectral kurtosis and time wavelet energy spectrum (SK-TWES) in the paper. Firstly, the spectral kurtosis (SK) and kurtogram of raw vibration signals are computed and exploited to select the optimal filtering parameter for the subsequent band-pass filtering. Then, the band-pass filtering is applied to extrude periodic transient impulses using the optimal frequency band in which the corresponding SK value is maximal. Finally, the time wavelet energy spectrum analysis is performed on the filtered signal, selecting Morlet wavelet as the mother wavelet which possesses a high similarity to the impulsive components. The experimental signals collected from the wind turbine gearbox test rig demonstrate that the proposed method is effective at the feature extraction and fault diagnosis for the planet gear with a localized defect.

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A review on ductile mode cutting of brittle materials
Elijah Kwabena ANTWI, Kui LIU, Hao WANG
Front. Mech. Eng.    2018, 13 (2): 251-263.   https://doi.org/10.1007/s11465-018-0504-z
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Brittle materials have been widely employed for industrial applications due to their excellent mecha-nical, optical, physical and chemical properties. But obtaining smooth and damage-free surface on brittle materials by traditional machining methods like grinding, lapping and polishing is very costly and extremely time consuming. Ductile mode cutting is a very promising way to achieve high quality and crack-free surfaces of brittle materials. Thus the study of ductile mode cutting of brittle materials has been attracting more and more efforts. This paper provides an overview of ductile mode cutting of brittle materials including ductile nature and plasticity of brittle materials, cutting mechanism, cutting characteristics, molecular dynamic simulation, critical undeformed chip thickness, brittle-ductile transition, subsurface damage, as well as a detailed discussion of ductile mode cutting enhancement. It is believed that ductile mode cutting of brittle materials could be achieved when both crack-free and no subsurface damage are obtained simultaneously.

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Dynamic characteristics of a shrouded blade with impact and friction
Xumin GUO, Jin ZENG, Hui MA, Chenguang ZHAO, Lin QU, Bangchun WEN
Front. Mech. Eng.    2020, 15 (2): 209-226.   https://doi.org/10.1007/s11465-019-0566-6
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A simplified computational model of a twisted shrouded blade with impact and friction is established. In this model, the shrouded blade is simulated by a flexible Timoshenko beam with a tip-mass, and the effects of centrifugal stiffening, spin softening, and Coriolis force are considered. Impact force is simulated using a linear spring model, and friction force is generated by a tangential spring model under sticking state and a Coulomb friction model under sliding state. The proposed model is validated by a finite element model. Then, the effects of initial gap and normal preload, coefficient of friction, and contact stiffness ratio (the ratio of tangential contact stiffness to normal contact stiffness) on system vibration responses are analyzed. Results show that resonant peaks become inconspicuous and impact plays a dominant role when initial gaps are large between adjacent shrouds. By contrast, in small initial gaps or initial normal preloads condition, resonant speed increases sharply, and the optimal initial normal preloads that can minimize resonant amplitude becomes apparent. Coefficient of friction affects the optimal initial normal preload, but it does not affect vibration responses when the contact between shrouds is under full stick. System resonant amplitude decreases with the increase of contact stiffness ratio, but the optimal initial normal preload is unaffected.

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Remote calibration system for frequency based on in-place benchmark
Xiaobin HONG, Guixiong LIU, Zhuokui WU, Xipeng DU,
Front. Mech. Eng.    2010, 5 (3): 316-321.   https://doi.org/10.1007/s11465-010-0021-1
Abstract   PDF (248KB)
According to the deficiencies of remote calibration mode based on material object reference, a new model of a remote calibration system for frequency based on in-place benchmark is introduced, which is made of a calibration subsystem on the spot and a remote management subsystem. The key technology of some key problems for the remote calibration system is particularly discussed, including the time and frequency benchmark receiving module based on global positioning system (GPS), frequency comparison based on a phase method, frequency division based on dual high-frequency phase locked loop (PLL), and remote calibration based on the web. The results show that the system possesses some characteristics, such as high precision, good versatility, and no limitation of time and place.
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Evaluation of the power consumption of a high-speed parallel robot
Gang HAN, Fugui XIE, Xin-Jun LIU
Front. Mech. Eng.    2018, 13 (2): 167-178.   https://doi.org/10.1007/s11465-017-0456-8
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An inverse dynamic model of a high-speed parallel robot is established based on the virtual work principle. With this dynamic model, a new evaluation method is proposed to measure the power consumption of the robot during pick-and-place tasks. The power vector is extended in this method and used to represent the collinear velocity and acceleration of the moving platform. Afterward, several dynamic performance indices, which are homogenous and possess obvious physical meanings, are proposed. These indices can evaluate the power input and output transmissibility of the robot in a workspace. The distributions of the power input and output transmissibility of the high-speed parallel robot are derived with these indices and clearly illustrated in atlases. Furtherly, a low-power-consumption workspace is selected for the robot.

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Fault diagnosis of spur gearbox based on random forest and wavelet packet decomposition
Diego CABRERA,Fernando SANCHO,René-Vinicio SÁNCHEZ,Grover ZURITA,Mariela CERRADA,Chuan LI,Rafael E. VÁSQUEZ
Front. Mech. Eng.    2015, 10 (3): 277-286.   https://doi.org/10.1007/s11465-015-0348-8
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This paper addresses the development of a random forest classifier for the multi-class fault diagnosis in spur gearboxes. The vibration signal’s condition parameters are first extracted by applying the wavelet packet decomposition with multiple mother wavelets, and the coefficients’ energy content for terminal nodes is used as the input feature for the classification problem. Then, a study through the parameters’ space to find the best values for the number of trees and the number of random features is performed. In this way, the best set of mother wavelets for the application is identified and the best features are selected through the internal ranking of the random forest classifier. The results show that the proposed method reached 98.68% in classification accuracy, and high efficiency and robustness in the models.

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Sagittal SLIP-anchored task space control for a monopode robot traversing irregular terrain
Haitao YU, Haibo GAO, Liang DING, Zongquan DENG
Front. Mech. Eng.    2020, 15 (2): 193-208.   https://doi.org/10.1007/s11465-019-0569-3
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As a well-explored template that captures the essential dynamical behaviors of legged locomotion on sagittal plane, the spring-loaded inverted pendulum (SLIP) model has been extensively employed in both biomechanical study and robotics research. Aiming at fully leveraging the merits of the SLIP model to generate the adaptive trajectories of the center of mass (CoM) with maneuverability, this study presents a novel two-layered sagittal SLIP-anchored (SSA) task space control for a monopode robot to deal with terrain irregularity. This work begins with an analytical investigation of sagittal SLIP dynamics by deriving an approximate solution with satisfactory apex prediction accuracy, and a two-layered SSA task space controller is subsequently developed for the monopode robot. The higher layer employs an analytical approximate representation of the sagittal SLIP model to form a deadbeat controller, which generates an adaptive reference trajectory for the CoM. The lower layer enforces the monopode robot to reproduce a generated CoM movement by using a task space controller to transfer the reference CoM commands into joint torques of the multi-degree of freedom monopode robot. Consequently, an adaptive hopping behavior is exhibited by the robot when traversing irregular terrain. Simulation results have demonstrated the effectiveness of the proposed method.

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Exergy analysis and simulation of a 30MW cogeneration cycle
Nikhil Dev, Samsher, S. S. Kachhwaha, Rajesh Attri
Front Mech Eng    2013, 8 (2): 169-180.   https://doi.org/10.1007/s11465-013-0263-9
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Cogeneration cycle is an efficient mean to recover the waste heat from the flue gases coming out of gas turbine. With the help of computer simulation, design parameters may be selected for the best performance of cogeneration cycle. In the present work a program is executed in software EES on the basis of mathematical modelling described in paper to study cogeneration cycle performance for different parameters. Results obtained are compared with the results available in literature and are found in good agreement with them. Real gas and water properties are inbuilt in the software. Results show that enthalpy of air entering the combustion chamber is higher than that of the flue gases at combustion chamber outlet. For different operative conditions, energy and exergy efficiencies follow similar trends; although, exergy efficiency values are always lower than the corresponding energy efficiency ones. From the results it is found that turbine outlet temperature (TIT) of 524°C is uniquely suited to efficient cogeneration cycle because it enables the transfer of heat from exhaust gas to the steam cycle to take place over a minimal temperature difference. This temperature range results in the maximum thermodynamic availability while operating with highest temperature and highest efficiency cogeneration cycle. Effect of cycle pressure ratio (CR), inlet air temperature (IAT) and water pressure at heat recovery steam generator (HRSG) inlet on the 30 MW cogeneration cycle is also studied.

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Compressive behavior and energy absorption of polymeric lattice structures made by additive manufacturing
Sheng WANG, Jun WANG, Yingjie XU, Weihong ZHANG, Jihong ZHU
Front. Mech. Eng.    2020, 15 (2): 319-327.   https://doi.org/10.1007/s11465-019-0549-7
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Lattice structures have numerous outstanding characteristics, such as light weight, high strength, excellent shock resistance, and highly efficient heat dissipation. In this work, by combining experimental and numerical methods, we investigate the compressive behavior and energy absorption of lattices made through the stereolithography apparatus process. Four types of lattice structures are considered: (i) Uniform body-centered-cubic (U-BCC); (ii) graded body-centered-cubic (G-BCC); (iii) uniform body-centered-cubic with z-axis reinforcement (U-BCCz); and (iv) graded body-centered-cubic with z-axis reinforcement (G-BCCz). We conduct compressive tests on these four lattices and numerically simulate the compression process through the finite element method. Analysis results show that BCCz has higher modulus and strength than BCC. In addition, uniform lattices show better energy absorption capabilities at small compression distances, while graded lattices absorb more energy at large compression distances. The good correlation between the simulation results and the experimental phenomena demonstrates the validity and accuracy of the present investigation method.

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Modelling and diagnostics of multiple cathodes plasma torch system for plasma spraying
Kirsten BOBZIN, Nazlim BAGCIVAN, Lidong ZHAO, Ivica PETKOVIC, Jochen SCHEIN, Karsten HARTZ-BEHREND, Stefan KIRNER, José-Luis MARQUéS, Günter FORSTER
Front Mech Eng    2011, 6 (3): 324-331.   https://doi.org/10.1007/s11465-011-0125-2
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Usage of a multiple-arcs system has significantly improved process stability and coating properties in air plasma spraying. However, there are still demands on understanding and controlling the physical process to determine process conditions for reproducible coating quality and homogeneity of coating microstructure. The main goal of this work is the application of numerical simulation for the prediction of the temperature profiles at the torch outlet for real process conditions. Behaviour of the gas flow and electric arcs were described in a three-dimensional numerical model. The calculated results showed the characteristic triangular temperature distribution at the torch nozzle outlet caused by three electric arcs. These results were compared with experimentally determined temperature distributions, which were obtained with specially developed computed tomography equipment for reconstructing the emissivity and temperature distribution of the plasma jet close to the torch exit. The calculated results related to temperature values and contours were verified for the most process parameters with experimental ones.

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Synthesis of spherical parallel manipulator for dexterous medical task
Abdelbadia CHAKER, Abdelfattah MLIKA, Med Amine LARIBI, Lotfi ROMDHANE, Sa?d ZEGHLOUL
Front Mech Eng    2012, 7 (2): 150-162.   https://doi.org/10.1007/s11465-012-0325-4
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This paper deals with the design and the analysis of a spherical parallel manipulator (SPM) for a haptic minimally invasive surgery application. First the medical task was characterized with the help of a surgeon who performed a suture technique called anastomosis. A Vicon system was used to capture the motion of the surgeon, which yielded the volume swept by the tool during the anastomosis operation. The identified workspace can be represented by a cone with a half vertex angle of 26°. A multi objective optimization procedure based on genetic algorithms was then carried out to find the optimal SPM. Two criteria were considered, i.e., task workspace and mechanism dexterity. The optimized SPM was then analyzed to determine the error on the orientation of the end effector as a function of the manufacturing errors of the different links of the mechanism.

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Conceptual design and kinematic analysis of a novel parallel robot for high-speed pick-and-place operations
Qizhi MENG, Fugui XIE, Xin-Jun LIU
Front. Mech. Eng.    2018, 13 (2): 211-224.   https://doi.org/10.1007/s11465-018-0471-4
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This paper deals with the conceptual design, kinematic analysis and workspace identification of a novel four degrees-of-freedom (DOFs) high-speed spatial parallel robot for pick-and-place operations. The proposed spatial parallel robot consists of a base, four arms and a 1½ mobile platform. The mobile platform is a major innovation that avoids output singularity and offers the advantages of both single and double platforms. To investigate the characteristics of the robot’s DOFs, a line graph method based on Grassmann line geometry is adopted in mobility analysis. In addition, the inverse kinematics is derived, and the constraint conditions to identify the correct solution are also provided. On the basis of the proposed concept, the workspace of the robot is identified using a set of presupposed parameters by taking input and output transmission index as the performance evaluation criteria.

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Self-propelled automatic chassis of Lunokhod-1: History of creation in episodes
Mikhail MALENKOV
Front. Mech. Eng.    2016, 11 (1): 60-86.   https://doi.org/10.1007/s11465-016-0370-5
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This report reviews the most important episodes in the history of designing the self-propelled automatic chassis of the first mobile extraterrestrial vehicle in the world, Lunokhod-1. The review considers the issues in designing moon rovers, their essential features, and the particular construction properties of their systems, mechanisms, units, and assemblies. It presents the results of exploiting the chassis of Lunokhod-1 and Lunokhod-2. Analysis of the approaches utilized and engineering solutions reveals their value as well as the consequences of certain defects.

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Review on the progress of ultra-precision machining technologies
Julong YUAN, Binghai LYU, Wei HANG, Qianfa DENG
Front. Mech. Eng.    2017, 12 (2): 158-180.   https://doi.org/10.1007/s11465-017-0455-9
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Ultra-precision machining technologies are the essential methods, to obtain the highest form accuracy and surface quality. As more research findings are published, such technologies now involve complicated systems engineering and been widely used in the production of components in various aerospace, national defense, optics, mechanics, electronics, and other high-tech applications. The conception, applications and history of ultra-precision machining are introduced in this article, and the developments of ultra-precision machining technologies, especially ultra-precision grinding, ultra-precision cutting and polishing are also reviewed. The current state and problems of this field in China are analyzed. Finally, the development trends of this field and the coping strategies employed in China to keep up with the trends are discussed.

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EEG controlled neuromuscular electrical stimulation of the upper limb for stroke patients
Hock Guan TAN, Cheng Yap SHEE, Keng He KONG, Cuntai GUAN, Wei Tech ANG
Front Mech Eng    2011, 6 (1): 71-81.   https://doi.org/10.1007/s11465-011-0207-1
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This paper describes the Brain Computer Interface (BCI) system and the experiments to allow post-acute (<3 months) stroke patients to use electroencephalogram (EEG) to trigger neuromuscular electrical stimulation (NMES)-assisted extension of the wrist/fingers, which are essential pre-requisites for useful hand function. EEG was recorded while subjects performed motor imagery of their paretic limb, and then analyzed to determine the optimal frequency range within the mu-rhythm, with the greatest attenuation. Aided by visual feedback, subjects then trained to regulate their mu-rhythm EEG to operate the BCI to trigger NMES of the wrist/finger. 6 post-acute stroke patients successfully completed the training, with 4 able to learn to control and use the BCI to initiate NMES. This result is consistent with the reported BCI literacy rate of healthy subjects. Thereafter, without the loss of generality, the controller of the NMES is developed and is based on a model of the upper limb muscle (biceps/triceps) groups to determine the intensity of NMES required to flex or extend the forearm by a specific angle. The muscle model is based on a phenomenological approach, with parameters that are easily measured and conveniently implemented.

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Additive manufacturing: technology, applications and research needs
Nannan GUO, Ming C. LEU
Front Mech Eng    2013, 8 (3): 215-243.   https://doi.org/10.1007/s11465-013-0248-8
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Additive manufacturing (AM) technology has been researched and developed for more than 20 years. Rather than removing materials, AM processes make three-dimensional parts directly from CAD models by adding materials layer by layer, offering the beneficial ability to build parts with geometric and material complexities that could not be produced by subtractive manufacturing processes. Through intensive research over the past two decades, significant progress has been made in the development and commercialization of new and innovative AM processes, as well as numerous practical applications in aerospace, automotive, biomedical, energy and other fields. This paper reviews the main processes, materials and applications of the current AM technology and presents future research needs for this technology.

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Dynamic modulation performance of ferroelectric liquid crystal polarization rotators and Mueller matrix polarimeter optimization
Song ZHANG, Lelun WANG, Anze YI, Honggang GU, Xiuguo CHEN, Hao JIANG, Shiyuan LIU
Front. Mech. Eng.    2020, 15 (2): 256-264.   https://doi.org/10.1007/s11465-019-0573-7
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A ferroelectric liquid crystal polarization rotator (FLCPR) has been widely used in polarization measurement due to its fast and stable modulation characteristics. The accurate characterization of the modulation performance of FLCPR directly affects the measurement accuracy of the instrument based on liquid crystal modulation. In this study, FLCPR is accurately characterized using a self-developed high-speed Stokes polarimeter. Strong linear and weak circular birefringence are observed during modulation processes, and all the optical parameters of FLCPR are dependent on driving voltage. A dual FLCPR-based Mueller matrix polarimeter is designed on the basis of the Stokes polarimeter. The designed polarimeter combines the advantages of the high modulation frequency of FLCPR and the ultrahigh temporal resolution of the fast polarization measurement system in the Stokes polarimeter. The optimal configuration of the designed polarizer is predicted in accordance with singular value decomposition. A simulated thickness measurement of a 24 nm standard SiO2 thin film is performed using the optimal configuration. Results show that the relative error in thickness measurement caused by using the unsatisfactory modulation characteristics of FLCPR reaches up to −4.34%. This finding demonstrates the importance of the accurate characterization of FLCPR in developing a Mueller matrix polarizer.

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Motion/force transmission indices of parallel manipulators
Xinjun LIU, Chao WU, Fugui XIE
Front Mech Eng    2011, 6 (1): 89-91.   https://doi.org/10.1007/s11465-011-0215-1
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A dynamic model of mobile concrete pump boom based on discrete time transfer matrix method
Wu REN, Yunxin WU, Zhaowei ZHANG
Front Mech Eng    2013, 8 (4): 360-366.   https://doi.org/10.1007/s11465-013-0280-8
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Mobile concrete pump boom is typical multi-body large-scale motion manipulator. Due to posture constantly change in working process, kinematic rule and dynamic characteristic are difficult to solve. A dynamics model of a mobile concrete pump boom is established based on discrete time transfer matrix method (DTTMM). The boom system is divided into sub-structure A and sub-structure B. Sub-structure A is composed by the 1st boom and hydraulic actuator as well as the support. And sub-structure B is consists of the other three booms and corresponding hydraulic actuators. In the model, the booms and links are regarded as rigid elements and the hydraulic cylinders are equivalent to spring-damper. The booms are driven by the controllable hydraulic actuators. The overall dynamic equation and transfer matrix of the model can be assembled by sub-structures A and B. To get a precise result, step size and integration parameters are studied then. Next the tip displacement is calculated and compared with the result of ADAMS software. The displacement and rotation angle curves of the proposed method fit well with the ADAMS model. Besides it is convenient in modeling and saves time. So it is suitable for mobile concrete pump boom real-time monitoring and dynamic analysis. All of these provide reference to boom optimize and engineering application of such mechanisms.

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A comprehensive analysis of a 3-P (Pa) S spatial parallel manipulator
Yuzhe LIU,Liping WANG,Jun WU,Jinsong WANG
Front. Mech. Eng.    2015, 10 (1): 7-19.   https://doi.org/10.1007/s11465-015-0324-3
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In this paper, a novel 3-degree of freedom (3-DOF) spatial parallel kinematic machine (PKM) is analyzed. The manipulator owns three main motions (two rotations and one translation) and three concomitant motions (one rotation and two translations). At first, the structure of this spatial PKM is simplified according to the characteristic of each limb. Secondly, the kinematics model of this spatial PKM is set up. In addition, the relationship between the main motions and concomitant motions is studied. The workspaces respectively based on the outputs and inputs are derived and analyzed. Furthermore, the velocity model is put forward. Two indexes based on the velocity model are employed to investigate the performance of this spatial PKM. At last, the output error model can be obtained and simulated. The comprehensive kinematics analysis in this paper is greatly useful for the future applications of this spatial PKM.

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Response surface regression analysis on FeCrBSi particle in-flight properties by plasma spray
Runbo MA,Lihong DONG,Haidou WANG,Shuying CHEN,Zhiguo XING
Front. Mech. Eng.    2016, 11 (3): 250-257.   https://doi.org/10.1007/s11465-016-0401-2
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This work discusses the interactive effects between every two of argon flow rate, voltage, and spray distance on in-flight particles by plasma spray and constructs models that can be used in predicting and analyzing average velocity and temperature. Results of the response surface methodology show that the interactive effects between voltage and spray distance on particle in-flight properties are significant. For a given argon flow rate, particle velocity and temperature response surface are obviously bending, and a saddle point exists. With an increase in spray distance, the interactive effects between voltage and argon flow rate on particle in-flight properties appear gradually and then weaken. With an increase in voltage, the interactive effects between spray distance and argon flow rate on particle in-flight properties change from appearing to strengthening and then to weakening.

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A carbon efficiency upgrading method for mechanical machining based on scheduling optimization strategy
Shuo ZHU, Hua ZHANG, Zhigang JIANG, Bernard HON
Front. Mech. Eng.    2020, 15 (2): 338-350.   https://doi.org/10.1007/s11465-019-0572-8
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Low-carbon manufacturing (LCM) is increasingly being regarded as a new sustainable manufacturing model of carbon emission reduction in the manufacturing industry. In this paper, a two-stage low-carbon scheduling optimization method of job shop is presented as part of the efforts to implement LCM, which also aims to reduce the processing cost and improve the efficiency of a mechanical machining process. In the first stage, a task assignment optimization model is proposed to optimize carbon emissions without jeopardizing the processing efficiency and the profit of a machining process. Non-dominated sorting genetic algorithm II and technique for order preference by similarity to an ideal solution are then adopted to assign the most suitable batch task of different parts to each machine. In the second stage, a processing route optimization model is established to plan the processing sequence of different parts for each machine. Finally, niche genetic algorithm is utilized to minimize the makespan. A case study on the fabrication of four typical parts of a machine tool is demonstrated to validate the proposed method.

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Digital high-efficiency print forming method and device for multi-material casting molds
Zhongde SHAN, Zhi GUO, Dong DU, Feng LIU, Wenjiang LI
Front. Mech. Eng.    2020, 15 (2): 328-337.   https://doi.org/10.1007/s11465-019-0574-6
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Sand mold 3D printing technology based on the principle of droplet ejection has undergone rapid development in recent years and has elicited increasing attention from engineers and technicians. However, current sand mold 3D printing technology exhibits several problems, such as single-material printing molds, low manufacturing efficiency, and necessary post-process drying and heating for the manufacture of sand molds. This study proposes a novel high-efficiency print forming method and device for multi-material casting molds. The proposed method is specifically related to the integrated forming of two-way coating and printing and the short-flow manufacture of roller compaction and layered heating. These processes can realize the high-efficiency print forming of high-performance sand molds. Experimental results demonstrate that the efficiency of sand mold fabrication can be increased by 200% using the proposed two-way coating and printing method. The integrated forming method for layered heating and roller compaction presented in this study effectively shortens the manufacturing process for 3D-printed sand molds, increases sand mold strength by 63.8%, and reduces resin usage by approximately 30%. The manufacture of multi-material casting molds is demonstrated on typical wheeled cast-iron parts. This research provides theoretical guidance for the engineering application of sand mold 3D printing.

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Smart manufacturing systems for Industry 4.0: Conceptual framework, scenarios, and future perspectives
Pai ZHENG, Honghui WANG, Zhiqian SANG, Ray Y. ZHONG, Yongkui LIU, Chao LIU, Khamdi MUBAROK, Shiqiang YU, Xun XU
Front. Mech. Eng.    2018, 13 (2): 137-150.   https://doi.org/10.1007/s11465-018-0499-5
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Information and communication technology is undergoing rapid development, and many disruptive technologies, such as cloud computing, Internet of Things, big data, and artificial intelligence, have emerged. These technologies are permeating the manufacturing industry and enable the fusion of physical and virtual worlds through cyber-physical systems (CPS), which mark the advent of the fourth stage of industrial production (i.e., Industry 4.0). The widespread application of CPS in manufacturing environments renders manufacturing systems increasingly smart. To advance research on the implementation of Industry 4.0, this study examines smart manufacturing systems for Industry 4.0. First, a conceptual framework of smart manufacturing systems for Industry 4.0 is presented. Second, demonstrative scenarios that pertain to smart design, smart machining, smart control, smart monitoring, and smart scheduling, are presented. Key technologies and their possible applications to Industry 4.0 smart manufacturing systems are reviewed based on these demonstrative scenarios. Finally, challenges and future perspectives are identified and discussed.

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