Chinese Journal of Mechanical Engineering
Chinese Journal of Mechanical Engineering
ISSN 1000-9345
CN 11-2737/TH
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1. Intelligent Manufacturing Systems in COVID-19 Pandemic and Beyond: Framework and Impact Assessment
Xingyu Li, Baicun Wang, Chao Liu, Theodor Freiheit, Bogdan I. Epureanu
Chinese Journal of Mechanical Engineering    2020, 33 (4): 58-58.   DOI: 10.1186/s10033-020-00476-w
摘要132)      PDF(pc) (1034KB)(0)    收藏
Pandemics like COVID-19 have created a spreading and ever-higher healthy threat to the humans in the manufacturing system which incurs severe disruptions and complex issues to industrial networks. The intelligent manufacturing (IM) systems are promising to create a safe working environment by using the automated manufacturing assets which are monitored by the networked sensors and controlled by the intelligent decision-making algorithms. The relief of the production disruption by IM technologies facilitates the reconnection of the good and service flows in the network, which mitigates the severity of industrial chain disruption. In this study, we create a novel intelligent manufacturing framework for the production recovery under the pandemic and build an assessment model to evaluate the impacts of the IM technologies on industrial networks. Considering the constraints of the IM resources, we formulate an optimization model to schedule the allocation of IM resources according to the mutual market demands and the severity of the pandemic.
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2. A Comparative Study of Fractional Order Models on State of Charge Estimation for Lithium Ion Batteries
Jinpeng Tian, Rui Xiong, Weixiang Shen, Ju Wang
Chinese Journal of Mechanical Engineering    2020, 33 (4): 51-51.   DOI: 10.1186/s10033-020-00467-x
摘要48)      PDF(pc) (3908KB)(0)    收藏
State of charge (SOC) estimation for lithium ion batteries plays a critical role in battery management systems for electric vehicles. Battery fractional order models (FOMs) which come from frequency-domain modelling have provided a distinct insight into SOC estimation. In this article, we compare fve state-of-the-art FOMs in terms of SOC estimation. To this end, frstly, characterisation tests on lithium ion batteries are conducted, and the experimental results are used to identify FOM parameters. Parameter identifcation results show that increasing the complexity of FOMs cannot always improve accuracy. The model R(RQ)W shows superior identifcation accuracy than the other four FOMs. Secondly, the SOC estimation based on a fractional order unscented Kalman flter is conducted to compare model accuracy and computational burden under diferent profles, memory lengths, ambient temperatures, cells and voltage/current drifts. The evaluation results reveal that the SOC estimation accuracy does not necessarily positively correlate to the complexity of FOMs. Although more complex models can have better robustness against temperature variation, R(RQ), the simplest FOM, can overall provide satisfactory accuracy. Validation results on diferent cells demonstrate the generalisation ability of FOMs, and R(RQ) outperforms other models. Moreover, R(RQ) shows better robustness against truncation error and can maintain high accuracy even under the occurrence of current or voltage sensor drift.
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3. Hot Extrusion Processing of Al–Li Alloy Profiles and Related Issues: A Review
Yongxiao Wang, Guoqun Zhao
Chinese Journal of Mechanical Engineering    2020, 33 (4): 64-64.   DOI: 10.1186/s10033-020-00479-7
摘要37)      PDF(pc) (5973KB)(0)    收藏
Al–Li alloy is a new structural material with the advantages of lightweight and high strength. The extrusion profiles of Al–Li alloy are widely used in aerospace and other fields, which can significantly reduce the weight of the aerospace equipment and improve their carrying capacity and service performance. Particular service conditions of structural components in aeronautical and space areas put forward strict requirements on microstructure, mechanical properties, and dimensional precision of Al–Li alloy profiles. Therefore, it places higher requirements on the shape forming and microstructure controlling of the Al–Li alloy profiles. The manufacturing process of the profiles involves billet homogenization, hot extrusion, solution and quenching treatments, artificial aging, and others. The parameters of each process as well as the die structure have important effects on the final performance of the profiles. This article summarizes the main applications and key mechanical properties of Al–Li alloy extrusion profiles. The technologies related to the manufacturing process of the extrusion profiles are summarized and analyzed. The related studies about the evolutions of the microstructure and mechanical properties during homogenization and extrusion processes are reviewed. The developments of the solid solution and quenching treatments as well as the aging strengthening technology for extruded Al–Li alloy profiles are also introduced. The scientific problems and key technologies that need to be solved in the manufacturing of Al–Li alloy extrusion profiles are presented, and the prospect for future development trends in these fields is given.
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4. Compound Impedance Control of a Hydraulic Driven Parallel 3UPS/S Manipulator
Wang Lihang, Cui Shaofei, Ma Chong, Zhang Lijie
Chinese Journal of Mechanical Engineering    2020, 33 (4): 56-56.   DOI: 10.1186/s10033-020-00470-2
摘要37)      PDF(pc) (3164KB)(0)    收藏
The hydraulic parallel manipulator combines the high-power density of the hydraulic system and high rigidity of the parallel mechanism with excellent load-carrying capacity. However, the high-precision trajectory tracking control of the hydraulic parallel manipulator is challenged by the coupling dynamics of the parallel mechanism and the high nonlinearities of the hydraulic system. In this study, the trajectory control of a 3-DOF symmetric spherical parallel 3UPS/S manipulator is evaluated. Focusing on the highly coupling and nonlinear system dynamics, a compound impedance control method for a hydraulic driven parallel manipulator is proposed, which combines impedance control with the spatial motion characteristics of a parallel manipulator. The control strategy is divided into the inner and outer loops. The inner loop controls the impedance of the actuator in the joint space, and the outer loop controls the impedance of the entire platform in the task space to compensate the coupling of the actuators and improve the tracking accuracy of the moving platform. Compound impedance control does not require force or pressure sensors and is less dependent on modeling precision. The experimental results show that the compound impedance control effectively improves the tracking accuracy of the moving platform. This research proposes a compound impedance control strategy for a 3-DOF hydraulic parallel manipulator, which has high tracking precision with a simple and cheap system configuration.
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5. Formability of Materials with Small Tools in Incremental Forming
Hongyu Wei, G. Hussain, X. Shi, B. B. L Isidore, Mohammed Alkahtani, Mustufa Haider Abidi
Chinese Journal of Mechanical Engineering    2020, 33 (4): 55-55.   DOI: 10.1186/s10033-020-00474-y
摘要37)      PDF(pc) (2602KB)(0)    收藏
Single point incremental forming (SPIF) is an innovative sheet forming process with a high economic pay-off. The formability in this process can be maximized by executing forming with a tool of specific small radius, regarded as threshold critical radius. Its value has been reported as 2.2 mm for 1 mm thick sheet materials. However, with a change in the forming conditions specifically in the sheet thickness and step size, the critical radius is likely to alter due to a change in the bending condition. The main aim of the present study is to undertake this point into account and develop a relatively generic condition. The study is composed of experimental and numerical investigations. The maximum wall angle (θmax) without sheet fracturing is regarded as sheet formability. A number of sheet materials are formed to fracture and the trends correlating formability with normalized radius (i.e., R/To where R is the tool-radius and To is the sheet thickness) are drawn. These trends confirm that there is a critical tool-radius (Rc) that maximizes the formability in SPIF. Furthermore, it is found that the critical radius is not fixed rather it shows dependence on the sheet thickness such that Rc = βTo, where β varies from 2.2 to 3.3 as the thickness increases from 1 mm to 3 mm. The critical radius, however, remains insensitive to variation in step size ranging from 0.3 mm to 0.7 mm. This is also observed that the selection of tool with R < Rc narrows down the formability window not only on the higher side but also on the lower side. The higher limit, as revealed by the experimental and FEA results, diminishes due to excessive shearing because of in-plane biaxial compression, and the lower limit reduces due to pillowing in the bottom of part. The new tool-radius condition proposed herein study would be helpful in maximizing the formability of materials in SPIF without performing experimental trials.
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6. Study on Cutting Force, Cutting Temperature and Machining Residual Stress in Precision Turning of Pure Iron with Different Grain Sizes
Yinfei Yang, Lu Jin, Jinpeng Zhu, Jinxing Kong, Liang Li
Chinese Journal of Mechanical Engineering    2020, 33 (4): 53-53.   DOI: 10.1186/s10033-020-00471-1
摘要34)      PDF(pc) (1651KB)(0)    收藏
Pure iron is one of the difficult-to-machine materials due to its large chip deformation, adhesion, work-hardening, and built-up edges formation during machining. This leads to a large workpiece deformation and challenge to meet the required technical indicators. Therefore, under varying the grain size of pure iron, the influence of cutting speed, feed, and depth of cut on the cutting force, heat generation, and machining residual stresses were explored in the turning process to improve the machinability without compromising the mechanical properties of the material. The experimental findings have depicted that the influence of grain size on cutting force in the precision turning process is not apparent. However, the cutting temperature and residual stress of machining fine-grain iron were much smaller than the coarse grain at all levels of cutting parameters.
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7. A Survey of Mathematical Tools in Topology and Performance Integrated Modeling and Design of Robotic Mechanism
Xinming Huo, Shuofei Yang, Binbin Lian, Tao Sun, Yimin Song
Chinese Journal of Mechanical Engineering    2020, 33 (4): 62-62.   DOI: 10.1186/s10033-020-00481-z
摘要34)      PDF(pc) (1339KB)(0)    收藏
Topology and performance are the two main topics dealt in the development of robotic mechanisms. However, it is still a challenge to connect them by integrating the modeling and design process of both parts in a unified frame. As the properties associated with topology and performance, finite motion and instantaneous motion of the robot play key roles in the procedure. On the purpose of providing a fundamental preparation for integrated modeling and design, this paper carries out a review on the existing unified mathematic frameworks for motion description and computation, involving matrix Lie group and Lie algebra, dual quaternion and pure dual quaternion, finite screw and instantaneous screw. Besides the application in robotics, the review of the work from these mathematicians concentrates on the description, composition and intersection operations of the finite and instantaneous motions, especially on the exponential-differential maps which connect the two sides. Furthermore, an in-depth discussion is worked out by investigating the algebraical relationship among these methods and their further progress in integrated robotic development. The presented review offers insightful investigation to the motion description and computation, and therefore would help designers to choose appropriate mathematical tool in the integrated design and modeling and design of mechanisms and robots.
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8. Preparation of Nickel-Cobalt/Carborundum Carbide Composite Coatings by Supergravity Field-Enhanced Electrodeposition
Xiaoyun Hu, Ningsong Qu
Chinese Journal of Mechanical Engineering    2020, 33 (4): 57-57.   DOI: 10.1186/s10033-020-00478-8
摘要31)      PDF(pc) (1742KB)(0)    收藏
Nickel-cobalt/silicon carbide (Ni-Co/SiC) composite coatings were fabricated by supergravity field-enhanced electrodeposition. The surface morphology and the distribution of the SiC particles in the coatings were examined by scanning electron microscope and energy dispersive X-ray spectrometry. The preferred orientations of the coatings were measured by X-ray diffractometry. The wear resistance and microhardness were measured by a reciprocating tribometer and a microhardness instrument, respectively. The results revealed that the use of the supergravity field enhanced the smoothness of the as-deposited Ni-Co/SiC coatings, and the SiC nanoparticles were uniformly distributed in comparison with that for conventional electrodeposition. When the rotation speed of the cathode, which provided the supergravity field, was 800 r/min, the SiC content in the coating reached a maximum of 8.1 wt%, which was a much higher content than the 2.2 wt% value obtained under conventional electrodeposition. The highest coating microhardness of 680 HV was also observed at this rotation speed. In addition, the wear resistance of the as-prepared Ni-Co/SiC coatings exhibited improved performance relative to that prepared under normal gravity. A minimum wear weight loss of 1.4 mg together with an average friction coefficient of 0.13 were also realized at a rotation speed of 800 r/min, values which were much lower than those for normal gravity.
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9. Combined Prediction for Vehicle Speed with Fixed Route
Lipeng Zhang, Liu Wei, Bingnan Qi
Chinese Journal of Mechanical Engineering    2020, 33 (4): 60-60.   DOI: 10.1186/s10033-020-00472-0
摘要27)      PDF(pc) (4990KB)(0)    收藏
Achieving accurate speed prediction provides the most critical support parameter for high-level energy management of plug-in hybrid electric vehicles. Nowadays, people often drive a vehicle on fixed routes in their daily travels and accurate speed predictions of these routes are possible with random prediction and machine learning, but the prediction accuracy still needs to be improved. The prediction accuracy of traditional prediction algorithms is difficult to further improve after reaching a certain accuracy; problems, such as over fitting, occur in the process of improving prediction accuracy. The combined prediction model proposed in this paper can abandon the transitional dependence on a single prediction. By combining the two prediction algorithms, the fusion of prediction performance is achieved, the limit of the single prediction performance is crossed, and the goal of improving vehicle speed prediction performance is achieved. In this paper, an extraction method suitable for fixed route vehicle speed is designed. The application of Markov and back propagation (BP) neural network in predictions is introduced. Three new combined prediction methods, all named Markov and BP Neural Network (MBNN) combined prediction algorithm, are proposed, which make full use of the advantages of Markov and BP neural network algorithms. Finally, the comparison among the prediction methods has been carried out. The results show that the three MBNN models have improved by about 19%, 28%, and 29% compared with the Markov prediction model, which has better performance in the single prediction models. Overall, the MBNN combined prediction models can improve the prediction accuracy by 25.3% on average, which provides important support for the possible optimization of plug-in hybrid electric vehicle energy consumption.
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10. Temperature Field Simulation and Experimental Study of Anti-backlash Single-Roller Enveloping Hourglass Worm Gear
Shisong Wang, Shike Wang, Jie Wang, Xingqiao Deng
Chinese Journal of Mechanical Engineering    2020, 33 (4): 59-59.   DOI: 10.1186/s10033-020-00475-x
摘要27)      PDF(pc) (2862KB)(0)    收藏
In gear transmission, temperature rise has a non-negligible impact on the accuracy, noise and transmission efficiency. However, there is no relevant research on the temperature rise of the anti-backlash single-roller enveloping hourglass worm (ASEHW) gear. To solve this problem, based on tribology principle and Hertz contact theory, the thermal power calculation method of the ASEHW gear was proposed for the first time and thermal analysis was carried out by Ansys software. The bulk temperature of the ASEHW gear under four different rotating speed (300 r/min, 600 r/min, 900 r/min, 1200 r/min) is calculated. The main factors causing temperature rise of the ASEHW gear are analyzed theoretically. Meanwhile, an experimental study is performed to verify the simulation results and validate the theory methods. The theory presented in this paper provides a solution for the thermal power calculation of ASEHW gear. This research provides a theoretical basis for further optimization of ASEHW gear.
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11. Algebraic Method-Based Point-to-Point Trajectory Planning of an Under-Constrained Cable-Suspended Parallel Robot with Variable Angle and Height Cable Mast
Tao Zhao, Bin Zi, Sen Qian, Jiahao Zhao
Chinese Journal of Mechanical Engineering    2020, 33 (4): 54-54.   DOI: 10.1186/s10033-020-00473-z
摘要27)      PDF(pc) (3996KB)(0)    收藏
To avoid impacts and vibrations during the processes of acceleration and deceleration while possessing flexible working ways for cable-suspended parallel robots (CSPRs), point-to-point trajectory planning demands an under-constrained cable-suspended parallel robot (UCPR) with variable angle and height cable mast as described in this paper. The end-effector of the UCPR with three cables can achieve three translational degrees of freedom (DOFs). The inverse kinematic and dynamic modeling of the UCPR considering the angle and height of cable mast are completed. The motion trajectory of the end-effector comprising six segments is given. The connection points of the trajectory segments (except for point P3 in the X direction) are devised to have zero instantaneous velocities, which ensure that the acceleration has continuity and the planned acceleration curve achieves smooth transition. The trajectory is respectively planned using three algebraic methods, including fifth degree polynomial, cycloid trajectory, and double-S velocity curve. The results indicate that the trajectory planned by fifth degree polynomial method is much closer to the given trajectory of the end-effector. Numerical simulation and experiments are accomplished for the given trajectory based on fifth degree polynomial planning. At the points where the velocity suddenly changes, the length and tension variation curves of the planned and unplanned three cables are compared and analyzed. The OptiTrack motion capture system is adopted to track the end-effector of the UCPR during the experiment. The effectiveness and feasibility of fifth degree polynomial planning are validated.
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12. A Comprehensive Review of Isogeometric Topology Optimization: Methods, Applications and Prospects
Jie Gao, Mi Xiao, Yan Zhang, Liang Gao
Chinese Journal of Mechanical Engineering    2020, 33 (6): 87-87.   DOI: 10.1186/s10033-020-00503-w
摘要27)      PDF(pc) (2638KB)(0)    收藏
Topology Optimization (TO) is a powerful numerical technique to determine the optimal material layout in a design domain, which has accepted considerable developments in recent years. The classic Finite Element Method (FEM) is applied to compute the unknown structural responses in TO. However, several numerical deficiencies of the FEM significantly influence the effectiveness and efficiency of TO. In order to eliminate the negative influence of the FEM on TO, IsoGeometric Analysis (IGA) has become a promising alternative due to its unique feature that the Computer-Aided Design (CAD) model and Computer-Aided Engineering (CAE) model can be unified into a same mathematical model. In the paper, the main intention is to provide a comprehensive overview for the developments of Isogeometric Topology Optimization (ITO) in methods and applications. Finally, some prospects for the developments of ITO in the future are also presented.
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13. A Review on Self-Recovery Regulation (SR) Technique for Unbalance Vibration of High-End Equipment
Xin Pan, Jiaqiao Lu, Jiaji Huo, Jinji Gao, Haiqi Wu
Chinese Journal of Mechanical Engineering    2020, 33 (6): 89-89.   DOI: 10.1186/s10033-020-00514-7
摘要26)      PDF(pc) (4735KB)(0)    收藏
The high-end equipment represented by high-end machine tools and aero-engines is the core component of the national intelligent manufacturing plan, and the mass unbalance is the main reason for its excessive vibration, that seriously impacts the operation efficiency and running life of the equipment. In order to change the traditional way that the fault of equipment can only be repaired by human, the self-recovery mechanism of human and animal are given to the equipment in this paper, which forms the self-recovery regulation (SR) system for unbalance vibration of high-end equipment. The system can online generate the self-recovery force to restrain the unbalance vibration of the equipment in operation, which is an important direction for the development of the equipment to the advanced intelligent stage. Based on the basic principles of SR technique, the typical engineering application cases of this technique in the field of aeroengine and high-end machine tools are introduced, and four related studies promoting the development of this technique are summarized and analyzed in turn. It includes feature extraction, imbalance location, regulation method and balancing actuator. Self-recovery Regulation (SR) Technique is an important way to realize intelligent manufacturing and intelligent maintenance. Relevant research can lay a technical foundation for the development of high-end equipment with self-health function.
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14. Dynamic Stiffness Analysis and Experimental Verification of Axial Magnetic Bearing Based on Air Gap Flux Variation in Magnetically Suspended Molecular Pump
Jinji Sun, Wanting Wei, Jiqiang Tang, Chun-E Wang
Chinese Journal of Mechanical Engineering    2020, 33 (4): 52-52.   DOI: 10.1186/s10033-020-00469-9
摘要26)      PDF(pc) (2134KB)(0)    收藏
Current and displacement stiffness are important parameters of axial magnetic bearing (AMB) and are usually considered as constants for the control system. However, in actual dynamic work situations, time-varying force leads to time-varying currents and air gap with a specific frequency, which makes the stiffness of appear decrease and even worsens control performance for the whole system. In this paper, an AMB dynamic stiffness model considering the flux variation across the air gap due to frequency is established to obtain the accurate dynamic stiffness. The dynamic stiffness characteristics are analyzed by means of the dynamic equivalent magnetic circuit method. The analytical results show that the amplitude of current and displacement stiffness decreases with frequency increasing. Moreover, compared with the stiffness model without considering the variation of flux density across the air gap, the improved dynamic stiffness results are closer to the actual results. Through the dynamic stiffness measurement method of AMB, experiments of AMB in magnetically suspended molecular pump (MSMP) are carried out and the experimental results are consistent with theoretical analysis results. This paper proposes the dynamic stiffness model of axial magnetic bearing considering the variation of flux density across the air gap, which improves the accuracy of the AMB stiffness analysis.
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15. Parallel Distributed Compensation / H Control of Lane-keeping System Based on the Takagi-Sugeno Fuzzy Model
Wuwei Chen, Linfeng Zhao, Huiran Wang, Yangcheng Huang
Chinese Journal of Mechanical Engineering    2020, 33 (4): 61-61.   DOI: 10.1186/s10033-020-00477-9
摘要24)      PDF(pc) (1981KB)(0)    收藏
Current research on lane-keeping systems ignores the effect of the driver and external resistance on the accuracy of tracking the lane centerline. To reduce the lateral deviation of the vehicle, a lane-keeping control method based on the fuzzy Takagi-Sugeno (T-S) model is proposed. The method adopts a driver model based on near and far visual angles, and a driver-road-vehicle closed-loop model based on longitudinal nonlinear velocity variation, obtaining the expected assist torque with a robust H controller which is designed based on parallel distributed compensation and linear matrix inequality. Considering the external influences of tire adhesion and aligning torque when the vehicle is steering, a feedforward compensation control is designed. The electric power steering system is adopted as the actuator for lane-keeping, and active steering redressing is realized by a control motor. Simulation results based on Carsim/Simulink and real vehicle test results demonstrate that the method helps to maintain the vehicle in the lane centerline and ensures driving safety.
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16. A Novel Ni-Free Zr-Based Bulk Metallic Glass with High Glass Forming Ability, Corrosion Resistance and Thermal Stability
Yu Luo, Yidong Jiang, Pei Zhang, Xin Wang, Haibo Ke, Pengcheng Zhang
Chinese Journal of Mechanical Engineering    2020, 33 (4): 65-65.   DOI: 10.1186/s10033-020-00482-y
摘要23)      PDF(pc) (1872KB)(0)    收藏
Zr-based Bulk metallic glasses exhibit incredible corrosion resistance and glass forming ability, however, these properties need further enhancement to meet the practical use. In this study, Zr63Fe2.5Cu23Al11.5, a new type of Zr-based bulk metallic glass was fabricated. Potentiodynamic polarization techniques were used to measure the corrosion resistance of this alloy. Furthermore, crystallization behavior and kinetics of Zr63Fe2.5Cu23Al11.5 bulk metallic glass were investigated by using differential scanning calorimetry of non-isothermal model. Kissinger and Ozawa methods were used for calculating activation energies of crystallization and the mechanism of crystallization was analyzed by Johnson-Mehl-Avrami-Kolmogorow methods. The results suggest that this specified metallic glass system possesses a relatively high thermal stability and glass forming ability. Moreover, the crystallization procedure is mainly dominated by nucleation with an increasing rate. The study demonstrates that the slight composition adjustment of Zr–Fe–Cu–Al system bulk metallic glass can make a considerable contribution to higher glass forming and thermal stability as well as corrosion resistance.
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17. Mechanism, Actuation, Perception, and Control of Highly Dynamic Multilegged Robots: A Review
Jun He, Feng Gao
Chinese Journal of Mechanical Engineering    2020, 33 (5): 79-79.   DOI: 10.1186/s10033-020-00485-9
摘要21)      PDF(pc) (5693KB)(0)    收藏
Multilegged robots have the potential to serve as assistants for humans, replacing them in performing dangerous, dull, or unclean tasks. However, they are still far from being sufficiently versatile and robust for many applications. This paper addresses key points that might yield breakthroughs for highly dynamic multilegged robots with the abilities of running (or jumping and hopping) and self-balancing. First, 21 typical multilegged robots from the last five years are surveyed, and the most impressive performances of these robots are presented. Second, current developments regarding key technologies of highly dynamic multilegged robots are reviewed in detail. The latest leg mechanisms with serial-parallel hybrid topologies and rigid-flexible coupling configurations are analyzed. Then, the development trends of three typical actuators, namely hydraulic, quasi-direct drive, and serial elastic actuators, are discussed. After that, the sensors and modeling methods used for perception are surveyed. Furthermore, this paper pays special attention to the review of control approaches since control is a great challenge for highly dynamic multilegged robots. Four dynamics-based control methods and two model-free control methods are described in detail. Third, key open topics of future research concerning the mechanism, actuation, perception, and control of highly dynamic multilegged robots are proposed. This paper reviews the state of the art development for multilegged robots, and discusses the future trend of multilegged robots.
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18. Blade Segment with a 3D Lattice of Diamond Grits Fabricated via an Additive Manufacturing Process
Bin Chen, Peng Chen, Yongjun Huang, Xiangxi Xu, Yibo Liu, Shuangxi Wang
Chinese Journal of Mechanical Engineering    2020, 33 (5): 73-73.   DOI: 10.1186/s10033-020-00496-6
摘要21)      PDF(pc) (4639KB)(0)    收藏
Diamond tools with orderly arrangements of diamond grits have drawn considerable attention in the machining field owing to their outstanding advantages of high sharpness and long service life. This diamond super tool, as well as the manufacturing equipment, has been unavailable to Chinese enterprises for a long time due to patents. In this paper, a diamond blade segment with a 3D lattice of diamond grits was additively manufactured using a new type of cold pressing equipment (AME100). The equipment, designed with a rotary working platform and 16 molding stations, can be used to additively manufacture segments with diamond grits arranged in an orderly fashion, layer by layer; under this additive manufacturing process, at least 216000 pcs of diamond green segments with five orderly arranged grit layers can be produced per month. The microstructure of the segment was observed via SEM and the diamond blade fabricated using these segments was compared to other commercial cutting tools. The experimental results showed that the 3D lattice of diamond grits was formed in the green segment. The filling rate of diamond grits in the lattice could be guaranteed to be above 95%; this is much higher than the 90% filling rate of the automatic array system (ARIX). When used to cut stone, the cutting amount of the blade with segments made by AME100 is two times that of ordinary tools, with the same diamond concentration. When used to dry cut reinforced concrete, its cutting speed is 10% faster than that of ARIX. Under wet cutting conditions, its service life is twice that of ARIX. By applying the machine vision online inspection system and a special needle jig with a negative pressure system, this study developed a piece of additive manufacturing equipment for efficiently fabricating blade segments with a 3D lattice of diamond grits.
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19. Development and Analysis of a Closed-Chain Wheel-Leg Mobile Platform
Chaoran Wei, Yanan Yao, Jianxu Wu, Ran Liu
Chinese Journal of Mechanical Engineering    2020, 33 (5): 80-80.   DOI: 10.1186/s10033-020-00493-9
摘要20)      PDF(pc) (2543KB)(0)    收藏
Current research concerning legged platforms and wheeled platforms primarily focuses on terrain adaptive capability and speed capability, respectively. Compared with wheeled platforms, legged platforms with a closed-chain mechanism still present deficiencies regarding speed ability. To integrate the advantages of these two types of platforms, a wheel-leg mobile platform with two modes based on a closed-chain mechanism is proposed. First, a closed-chain mechanism that generates a high-knee trajectory in legged mode is designed and analyzed based on kinematic analysis. To improve the platformos obstacle-surmounting performance, the dimensional parameters of the closed-chain mechanism are optimized and the design requirements for the platformos frame are analyzed. In addition, the particular structure of the leg group is designed to realize transformation between legged mode and wheeled mode. The mobility of the constructed platform is calculated through an obstacle-surmounting probability analysis. The performances of the two motion modes are analyzed and compared by conducting dynamic simulations. Finally, experiments are carried out to verify both the theoretical analyses and the prototype performance. This study proposes a new approach to designing wheel-leg platforms with prominent speed ability and mobility based on a closed-chain mechanism.
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20. Novel Surface Design of Deployable Reflector Antenna Based on Polar Scissor Structures
Pengyuan Zhao, Jinguo Liu, Chenchen Wu, Yangmin Li, Keli Chen
Chinese Journal of Mechanical Engineering    2020, 33 (5): 68-68.   DOI: 10.1186/s10033-020-00488-6
摘要20)      PDF(pc) (3294KB)(0)    收藏
Space-deployable mechanisms can be used as supporting structures for large-diameter antennas in space engineering. This study proposes a novel method for constructing the surface design of space reflector antennas based on polar scissor units. The concurrency and deployability equations of the space scissor unit with definite surface constraints are derived using the rod and vector methods. Constraint equations of the spatial transformation for space n-edge polar scissor units are summarized. A new closed-loop deployable structure, called the polar scissor deployable antenna (PSDA), is designed by combining planar polar scissor units with spatial polar scissor units. The over-constrained problem is solved by releasing the curve constraint that locates at the end-point of the planar scissor mechanism. Kinematics simulation and error analysis are performed. The results show that the PSDA can effectively fit the paraboloid of revolution. Finally, deployment experiments verify the validity and feasibility of the proposed design method, which provides a new idea for the construction of large space-reflector antennas.
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21. Design of Vegetable Pot Seedling Pick-up Mechanism with Planetary Gear Train
Tong Zhipeng, Yu Gaohong, Zhao Xiong, Liu Pengfei, Ye Bingliang
Chinese Journal of Mechanical Engineering    2020, 33 (4): 63-63.   DOI: 10.1186/s10033-020-00484-w
摘要18)      PDF(pc) (2499KB)(0)    收藏
It has been challenging to design seedling pick-up mechanism based on given key points and trajectories, because it involves dimensional synthesis and rod length optimization. In this paper, the dimensional synthesis of seedling pick-up mechanism with planetary gear train was studied based on the data of given key points and the trajectory of the endpoint of seedling pick-up mechanism. Given the positions and orientations requirements of the five key points, the study first conducted a dimensional synthesis of the linkage size and center of rotation. The next steps were to select a reasonable solution and optimize the data values based on the ideal seedling trajectory. The link motion was driven by the planetary gear train of the two-stage gear. Four pitch curves of noncircular gears were obtained by calculating and distributing the transmission ratio according to the data. For the pitch curve with two convex points, the tooth profile design method of incomplete noncircular gear was applied. The seedling pick-up mechanism was tested by a virtual prototype and a physical prototype designed with the obtained parameter values. The results were consistent with the theoretical design requirements, confirming that the mechanism meets the expected requirements for picking seedlings up. This paper presents a new design method of vegetable pot seedling pick-up mechanism for an automatic vegetable transplanter.
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22. Effect of Mechanical Surface Treatment on the Bonding Mechanism and Properties of Cold-Rolled Cu/Al Clad Plate
Jianchao Han, Hui Niu, Sha Li, Zhongkai Ren, Yi Jia, Tao Wang, A. I. Plokhikh, Qingxue Huang
Chinese Journal of Mechanical Engineering    2020, 33 (5): 69-69.   DOI: 10.1186/s10033-020-00483-x
摘要16)      PDF(pc) (4747KB)(0)    收藏
In the case of valuable cold-rolled Cu/Al clad plates, billet surface treatment before rolling is a significant process that can affect the bonding efficiency and quality. While the current studies primarily focus on the influence of rolling parameters, insufficient attention has been paid to surface treatment. In this study, the effects of mechanical surface treatment on the bonding mechanism and bonding properties of cold-rolled Cu/Al clad plates were investigated. The results showed that different mechanical surface treatments have significant effects on the surface morphology, roughness, and residual stress. In addition, the effect of surface mechanical treatment on bonding quality was also observed to be critical. When the grinding direction was consistent with the rolling direction (RD), the bonding quality of the Cu/Al clad plates was significantly improved. After surface treatment along the RD for 20 s, the Cu/Al clad plates showed the highest shear strength (78 MPa), approximately four times as high as that of the unpolished samples. Simultaneously, the peel strength of this process was also significantly higher than that achieved via the other processes. Finally, on the basis of the surface morphology, roughness, and residual stress, the effect of surface treatment on the bonding mechanism and bonding properties of Cu/Al clad plates was analyzed. This study proposes a deeper understanding of the bonding behavior and bonding mechanism for cold rolled clad plates processed via mechanical surface treatment.
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23. Review and Analysis of Key Techniques in Marine Sediment Sampling
Shudong He, Youduo Peng, Yongping Jin, Buyan Wan, Guangping Liu
Chinese Journal of Mechanical Engineering    2020, 33 (5): 66-66.   DOI: 10.1186/s10033-020-00480-0
摘要16)      PDF(pc) (2264KB)(0)    收藏
Deep-sea sediment is extremely important in marine scientific research, such as that concerning marine geology and microbial communities. The research findings are closely related to the in-situ information of the sediment. One prerequisite for investigations of deep-sea sediment is providing sampling techniques capable of preventing distortion during recovery. As the fruit of such sampling techniques, samplers designed for obtaining sediment have become indispensable equipment, owing to their low cost, light weight, compactness, easy operation, and high adaptability to sea conditions. This paper introduces the research and application of typical deep-sea sediment samplers. Then, a representative sampler recently developed in China is analyzed. On this basis, a review and analysis is conducted regarding the key techniques of various deep-sea sediment samplers, including sealing, pressure and temperature retaining, low-disturbance sampling, and no-pressure drop transfer. Then, the shortcomings in the key techniques for deep-sea sediment sampling are identified. Finally, prospects for the future development of key techniques for deep-sea sediment sampling are proposed, from the perspectives of structural diversification, functional integration, intelligent operation, and high-fidelity samples. This paper summarizes the existing samplers in the context of the key techniques mentioned above, and can provide reference for the optimized design of samplers and development of key sampling techniques.
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24. Investigation on Yield Behavior of 7075-T6 Aluminum Alloy at Elevated Temperatures
Jianping Lin, Xingyu Bao, Yong Hou, Junying Min, Xinlei Qu, Zhimin Tao, Jiajie Chen
Chinese Journal of Mechanical Engineering    2020, 33 (5): 76-76.   DOI: 10.1186/s10033-020-00494-8
摘要16)      PDF(pc) (3095KB)(0)    收藏
Aluminum alloys have drawn considerable attention in the area of automotive lightweight. High strength aluminum alloys are usually deformed at elevated temperatures due to their poor formability at room temperature. In this work, the yield behavior of 7075 aluminum alloy in T6 temper (AA7075-T6) within the temperature ranging from 25 ℃ to 230 ℃ was investigated. Uniaxial and biaxial tensile tests with the aid of induction heating system were performed to determine the stress vs. strain curves and the yield loci of AA7075-T6 at elevated temperatures, respectively. Von Mises, Hill48 and Yld2000-2d yield criteria were applied to predicting yield loci which were compared with experimentally measured yield loci of the AA7075-T6. Results show that yield stress corresponding to the same equivalent plastic strain decreases with increasing temperature within the investigated temperature range and the shape of yield loci evolves nearly negligibly. The experimental yield locus expands with an increase of equivalent plastic strain at the same temperature and the work hardening rate of AA7075-T6 exhibits obvious stress-state-dependency. The non-quadratic Yld2000-2d yield criterion describes the yield surfaces of AA7075-T6 more accurately than the quadratic von Mises and Hill48 yield criteria, and an exponent of 14 in the Yld2000-2d yield function gives the optimal predictions for the AA7075-T6 at all investigated temperatures.
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25. Intelligent Modularized Reconfigurable Mechanisms for Robots: Development and Experiment
Wenfu Xu, Liang Han, Xin Wang, Han Yuan, Bin Liang
Chinese Journal of Mechanical Engineering    2020, 33 (5): 74-74.   DOI: 10.1186/s10033-020-00497-5
摘要16)      PDF(pc) (2522KB)(0)    收藏
With the development of intelligent flexible manufacturing, traditional industrial manipulators with a single configuration are difficult to meet a variety of tasks. Reconfigurable robots have developed rapidly which could change their configurations and end effectors for different tasks. The reconfigurable connecting mechanism (RCM) is a core component of reconfigurable robots. In this paper, two types of intelligent modularized RCMs with light weight, high payload, and large pose (position and attitude) error tolerance are developed. One is driven by shape memory alloy (SMA) and recovery spring. It is locked by steel balls and key. The other is driven by electromagnetic coil and locked by permanent magnet and key. The locking principle, mechanical system and control system of the two RCMs are detailed introduced. Both of them meet the requirements of high precision and high payload in the industrial field. Finally, the developed RCMs are respectively integrated to a practical robot and experimented. The experiment results verified the performance of the two RCMs.
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26. A New Method to Calculate Water Film Stiffness and Damping for Water Lubricated Bearing with Multiple Axial Grooves
Guojun Ren
Chinese Journal of Mechanical Engineering    2020, 33 (5): 72-72.   DOI: 10.1186/s10033-020-00492-w
摘要15)      PDF(pc) (3628KB)(0)    收藏
Water lubricated guide bearings for hydro turbines and pumps are conventionally designed with multiple axial grooves to provide effectively cooling and flushing away abrasives. Due to the variety of groove configuration in terms of number and size, a predication of their performance is difficult. This paper deals with an analytical procedure to investigate groove effect on load capacity, stiffness and damping for this type of bearing where it is considered as an assembly of many inclined slide bearings. The result can be applied to bearings made of hard materials combined with low bearing pressure.
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27. Design of Self-Reconfigurable Multiarm Robot Mechanism Based on Deployable Kinematic Chains
Fu-Qun Zhao, Sheng Guo, Hai-Jun Su, Hai-Bo Qu, Ya-Qiong Chen
Chinese Journal of Mechanical Engineering    2020, 33 (5): 70-70.   DOI: 10.1186/s10033-020-00489-5
摘要15)      PDF(pc) (2667KB)(0)    收藏
As the structures of multiarm robots are serially arranged, the packaging and transportation of these robots are often inconvenient. The ability of these robots to operate objects must also be improved. Addressing this issue, this paper presents a type of multiarm robot that can be adequately folded into a designed area. The robot can achieve different operation modes by combining different arms and objects. First, deployable kinematic chains (DKCs) are designed, which can be folded into a designated area and be used as an arm structure in the multiarm robot mechanism. The strategy of a platform for storing DKCs is proposed. Based on the restrictions in the storage area and the characteristics of parallel mechanisms, a class of DKCs, called base assembly library, is obtained. Subsequently, an assembly method for the synthesis of the multiarm robot mechanism is proposed, which can be formed by the connection of a multiarm robot mechanism with an operation object based on a parallel mechanism structure. The formed parallel mechanism can achieve a reconfigurable characteristic when different DKCs connect to the operation object. Using this method, two types of multiarm robot mechanisms with four DKCs that can switch operation modes to perform different tasks through autonomous combination and release operation is proposed. The obtained mechanisms have observable advantages when compared with the traditional mechanisms, including optimizing the occupied volume during transportation and using parallel mechanism theory to analyze the switching of operation modes.
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28. A Sensitivity Mapping Technique for Tensile Force and Case Depth Characterization Based on Magnetic Minor Hysteresis Loops
Cunfu He, Wenqiao Dou, Xiucheng Liu, Meng Yang, Ruifang Zhang
Chinese Journal of Mechanical Engineering    2020, 33 (6): 84-84.   DOI: 10.1186/s10033-020-00508-5
摘要14)      PDF(pc) (2271KB)(0)    收藏
In the nondestructive testing and evaluation area, magnetic major hysteresis loop measurement technology are widely applied for ferromagnetic material evaluation. However the characterization ability of major hysteresis loop measurement technology greatly varies as the evaluated target properties. To solve this limitation, magnetic minor hysteresis loops, which reflect the responses of ferromagnetic material magnetization in a systematic way, is recommend. Inspired by plenty of information carried by the minor loops, the sensitivity mapping technique was developed to achieve the highest sensitivity of minor-loop parameters to the nondestructively evaluated targets. In this study, for the first time, the sensitivity mapping technique is used to measure the tensile force in a steel strand and evaluate the effective case depth in induction-hardened steel rods. The method and procedures for the sensitivity mapping technique are given before experimental detection. The obtained experimental results indicate that the linear correlation between the induced voltage (or the magnetic induction intensity) and the tensile force (or effective case depth) exists at most of the locations in the cluster of minor loops. The obtained sensitivity maps can be used to optimize the applied magnetic field (or excitation current) and the analyzed locations at the minor loops for achieving the highest sensitivity. For the purpose of tensile force measurement, it is suggested that the strand should be firstly magnetized to the near-saturation state and then restored to the remanent state. In this way, the highest sensitivity is obtained as about 15.26 mV/kN. As for the induction-hardened steel rods, the highest sensitivity of magnetic induction intensity to the effective case depth occurs under low magnetic field conditions and the absolute value of the highest sensitivity is about 0.1110 T/mm. This indicates that if the highest sensitivity is required in the case depth evaluation, the induction-hardened steel rods are only required to be weakly magnetized. The proposed sensitivity mapping technique shows the good performance in the high-sensitivity evaluation of tensile force and case depth in ferromagnetic materials and its application scope can be extended to other nondestructive detection fields.
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29. Sensitivity of Influential Factors on Needle Insertion Experiments: A Quantitative Analysis on Phantom Deformations and Needle Deflections
Murong Li, Yong Lei, Tian Xu
Chinese Journal of Mechanical Engineering    2020, 33 (6): 97-97.   DOI: 10.1186/s10033-020-00515-6
摘要14)      PDF(pc) (2356KB)(0)    收藏
High repeatability of needle insertion experiments is essential to the needle-phantom interaction model validation. However, the influential factors governing the accuracy of the phantom and needle deformations have not been systematically studied. In this paper, the impact of influential factors, including phantom characteristic represented by the ratio of DMSO and thawing time (TT), needle properties represented by needle external diameter (NED) and operating factors such as needle insertion velocity (Ⅳ), insertion positions (IP) and repeated insertion times (RITs) are analyzed by orthogonal experiment design. The range calculation shows the most sensitive parameters to phantom deformations are RITs, Ⅳ and DMSO while the most sensitive parameters to needle deflection are DMSO, TT and NED. By variance analysis, the significant factors on maximum tissue deformation (MTD) are Ⅳ, followed by RITs, DMSO and IP. And NED and TT have nearly no significant impact on MTD. The significant sequence on maximum needle deflection (MND) is as follows: DMSO, TT and NED. Results show that, among all impacting factors, phantom deformation is susceptible to both material properties and operative factors while the needle deflection is more susceptible to material properties of the phantom, which can help researchers in related fields to conduct experiments in a more precise manner and better understand the needle-phantom interaction mechanism.
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30. Practical Structural Design Approach of Multiconfiguration Planar Single-Loop Metamorphic Mechanism with a Single Actuator
Qiang Yang, Guangbo Hao, Shujun Li, Hongguang Wang, Haiyang Li
Chinese Journal of Mechanical Engineering    2020, 33 (5): 77-77.   DOI: 10.1186/s10033-020-00498-4
摘要14)      PDF(pc) (1950KB)(0)    收藏
As a type of multiconfiguration mechanism that can operate in an under-actuated state, metamorphic mechanisms were proposed more than two decades ago and attracted significant interest. Studies on structural synthesis of metamorphic mechanisms tend to focus more on metamorphic techniques and the structural synthesis of source mechanisms for metamorphic mechanisms. By designing different constraint architectures of metamorphic joints, multistructures can be obtained from the same source metamorphic mechanism. To determine the constraint architectures of metamorphic joints and their different assembly combinations, a kinematic status matrix and a corresponding constraint status matrix are constructed based on the metamorphic cyclogram of a source mechanism. According to the equivalent resistance gradient model and the constraint status matrix, an equivalent resistance matrix for the metamorphic joints is proposed. A structural synthesis matrix of the metamorphic mechanism is then obtained from the equivalent resistance matrix by deducing the constraint form vectors of the metamorphic joints. Furthermore, a kinematic diagram synthesis of the source metamorphic mechanism of a planar single-loop metamorphic mechanism is proposed, which is based on only the 14 one- or zero-degrees-of-freedom linkage groups. The entire structural design method of a metamorphic mechanism is based on the structural synthesis matrix and is presented as a systematic process. Finally, the proposed structural design approach is illustrated by two examples to verify its feasibility and practicality. This study provides an effective method for designing a practical multi-mobility and multiconfiguration planar single-loop metamorphic mechanism with a single actuator.
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31. Obstacle Avoidance and Multitarget Tracking of a Super Redundant Modular Manipulator Based on Bezier Curve and Particle Swarm Optimization
Li Chen, Ying Ma, Yu Zhang, Jinguo Liu
Chinese Journal of Mechanical Engineering    2020, 33 (5): 71-71.   DOI: 10.1186/s10033-020-00491-x
摘要14)      PDF(pc) (2992KB)(0)    收藏
A super redundant serpentine manipulator has slender structure and multiple degrees of freedom. It can travel through narrow spaces and move in complex spaces. This manipulator is composed of many modules that can form different lengths of robot arms for different application sites. The increase in degrees of freedom causes the inverse kinematics of redundant manipulator to be typical and immensely increases the calculation load in the joint space. This paper presents an integrated optimization method to solve the path planning for obstacle avoidance and discrete trajectory tracking of a super redundant manipulator. In this integrated optimization, path planning is established on a Bezier curve, and particle swarm optimization is adopted to adjust the control points of the Bezier curve with the kinematic constraints of manipulator. A feasible obstacle avoidance path is obtained along with a discrete trajectory tracking by using a follow-the-leader strategy. The relative distance between each two discrete path points is limited to reduce the fitting error of the connecting rigid links to the smooth curve. Simulation results show that this integrated optimization method can rapidly search for the appropriate trajectory to guide the manipulator in obtaining the target while achieving obstacle avoidance and meeting joint constraints. The proposed algorithm is suitable for 3D space obstacle avoidance and multitarget path tracking.
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32. Special Issue on Reconfigurable Robots
Jinguo Liu, Yuwang Liu, Guangbo Hao
Chinese Journal of Mechanical Engineering    2020, 33 (5): 82-82.   DOI: 10.1186/s10033-020-00501-y
摘要13)      PDF(pc) (766KB)(0)    收藏
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33. A Stiffness Variable Passive Compliance Device with Reconfigurable Elastic Inner Skeleton and Origami Shell
Zhuang Zhang, Genliang Chen, Weicheng Fan, Wei Yan, Lingyu Kong, Hao Wang
Chinese Journal of Mechanical Engineering    2020, 33 (5): 75-75.   DOI: 10.1186/s10033-020-00490-y
摘要13)      PDF(pc) (2263KB)(0)    收藏
Devices with variable stiffness are drawing more and more attention with the growing interests of human-robot interaction, wearable robotics, rehabilitation robotics, etc. In this paper, the authors report on the design, analysis and experiments of a stiffness variable passive compliant device whose structure is a combination of a reconfigurable elastic inner skeleton and an origami shell. The main concept of the reconfigurable skeleton is to have two elastic trapezoid four-bar linkages arranged in orthogonal. The stiffness variation generates from the passive deflection of the elastic limbs and is realized by actively switching the arrangement of the leaf springs and the passive joints in a fast, simple and straightforward manner. The kinetostatics and the compliance of the device are analyzed based on an efficient approach to the large deflection problem of the elastic links. A prototype is fabricated to conduct experiments for the assessment of the proposed concept. The results show that the prototype possesses relatively low stiffness under the compliant status and high stiffness under the stiff status with a status switching speed around 80 ms.
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34. Constraint and Mobility Change Analysis of Rubik's Cube-inspired Reconfigurable Joints and Corresponding Parallel Mechanisms
Duanling Li, Pu Jia, Jiazhou Li, Dan Zhang, Xianwen Kong
Chinese Journal of Mechanical Engineering    2020, 33 (5): 81-81.   DOI: 10.1186/s10033-020-00500-z
摘要13)      PDF(pc) (2638KB)(0)    收藏
The current research of reconfigurable parallel mechanism mainly focuses on the construction of reconfigurable joints. Compared with the method of changing the mobility by physical locking joints, the geometric constraint has good controllability, and the constructed parallel mechanism has more configurations and wider application range. This paper presents a reconfigurable axis (rA) joint inspired and evolved from Rubik's Cubes, which have a unique feature of geometric and physical constraint of axes of joint. The effectiveness of the rA joint in the construction of the limb is analyzed, resulting in a change in mobility and topology of the parallel mechanism. The rA joint makes the angle among the three axes inside the groove changed arbitrarily. This change in mobility is completed by the case illustrated by a 3(rA)P(rA) reconfigurable parallel mechanism having variable mobility from 1 to 6 and having various special configurations including pure translations, pure rotations. The underlying principle of the metamorphosis of this rA joint is shown by investigating the dependence of the corresponding screw system comprising of line vectors, leading to evolution of the rA joint from two types of spherical joints to three types of variable Hooke joints and one revolute joint. The reconfigurable parallel mechanism alters its topology by rotating or locking the axis of rA joint to turn all limbs into different phases. The prototype of reconfigurable parallel mechanism is manufactured and all configurations are enumerated to verify the validity of the theoretical method by physical experiments.
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35. Flow Control for a Two-Stage Proportional Valve with Hydraulic Position Feedback
He Wang, Xiaohu Wang, Jiahai Huang, Long Quan
Chinese Journal of Mechanical Engineering    2020, 33 (6): 93-93.   DOI: 10.1186/s10033-020-00517-4
摘要12)      PDF(pc) (2272KB)(0)    收藏
The current research mainly focuses on the flow control for the two-stage proportional valve with hydraulic position feedback which is named as Valvistor valve. Essentially, the Valvistor valve is a proportional throttle valve and the flow fluctuates with the change of load pressure. The flow fluctuation severely restricts the application of the Valvistor valve. In this paper, a novel flow control method the Valvistor valve is provided to suppress the flow fluctuation and develop a high performance proportional flow valve. The mathematical model of this valve is established and linearized. Fuzzy proportional-integral-derivative (PID) controller is adopted in the closed-loop flow control system. The feedback is obtained by the flow inference with back-propagation neural network (BPNN) based on the spool displacement in the pilot stage and the pressure differential across the main orifice. The results show that inference with BPNN can obtain the flow data fast and accurately. With the flow control method, the flow can keep at the set point when the pressure differential across the main orifice changes. The flow control method is effective and the Valvistor valve changes from proportional throttle valve to proportional flow valve. For the developed proportional flow valve, the settling time of the flow is very short when the load pressure changes abruptly. The performances of hysteresis, linearity and bandwidth are in a high range. The linear mathematical model can be verified and the assumptions in the system modeling is reasonable.
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36. Tire Dynamics Modeling Method Based on Rapid Test Method
Dang Lu, Lei Lu, Haidong Wu, Wei Wang, Manyi Lv
Chinese Journal of Mechanical Engineering    2020, 33 (6): 85-85.   DOI: 10.1186/s10033-020-00513-8
摘要12)      PDF(pc) (1332KB)(0)    收藏
Combined with the tire dynamics theoretical model, a rapid test method to obtain tire lateral and longitudinal both steady-state and transient characteristics only based on the tire quasi-steady-state test results is proposed. For steady state data extraction, the test time of the rapid test method is half that of the conventional test method. For transient tire characteristics the rapid test method omits the traditional tire test totally. At the mean time the accuracy of the two method is much closed. The rapid test method is explained theoretically and the test process is designed. The key parameters of tire are extracted and the comparison is made between rapid test and traditional test method. The result show that the identification accuracy based on the rapid test method is almost equal to the accuracy of the conventional one. Then, the heat generated during the rapid test method and that generated during the conventional test are calculated separately. The comparison shows that the heat generated during the rapid test is much smaller than the heat generated during the conventional test process. This benefits to the reduction of tire wear and the consistency of test results. Finally, it can be concluded that the fast test method can efficiently, accurately and energy-efficiently measure the steady-state and transient characteristics of the tire.
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37. Cavitation of a Submerged Jet at the Spherical Valve Plate/Cylinder Block Interface for Axial Piston Pump
Bin Zhao, Weiwei Guo, Long Quan
Chinese Journal of Mechanical Engineering    2020, 33 (5): 67-67.   DOI: 10.1186/s10033-020-00486-8
摘要10)      PDF(pc) (4900KB)(0)    收藏
The spherical valve plate/cylinder block pair has the advantages of strong overturning resistance and large bearing area. However, the configurations of the unloading and pre-boosting triangular grooves on the spherical valve plate are different from those in the planar valve plate, resulting in special cavitation phenomenon on the spherical port plate pair. In order to study cavitation characteristics of spherical port plate pair, a dynamic CFD model of the piston pump including turbulence model, cavitation model and fluid compressibility is established. A detailed UDF compilation scheme is provided for modelling of the micron-sized spherical oil film mesh, which makes up for the lack of research on the meshing of the spherical oil film. In this paper, using CFD simulation tools, from the perspectives of pressure field, velocity field and gas volume fraction change, a detailed analysis of the transient evolution of the submerged cavitation jet in a axial piston pump with spherical valve plate is carried out. The study indicates the movement direction of the cavitation cloud cluster through the cloud image and the velocity vector direction of the observation point. The sharp decrease of velocity and gas volume fraction indicates the collapse phenomenon of bubbles on the part wall surface. These discoveries verify the special erosion effect in case of the spherical valve plate/cylinder block pair. The submerged cavitation jet generated by the unloading triangular grooves distributed on the spherical valve plate not only cause denudation of the inner wall surface of the valve plate, but also cause strong impact and denudation on the lower surface of the cylinder body. Finally, the direction of the unloading triangular groove was modified to extend the distance between it and the wall surface which can effectively alleviate the erosion effect.
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38. Amending Research on the Expression of the Contact Force of the Spindle Barrel Finishing Based on EDEM Simulation
Na Wang, Shengqiang Yang, Tingting Zhao, Bo Cao, Chengwei Wang
Chinese Journal of Mechanical Engineering    2020, 33 (6): 83-83.   DOI: 10.1186/s10033-020-00502-x
摘要10)      PDF(pc) (3093KB)(0)    收藏
The spindle barrel finishing is commonly used to improve the surface integrity of the important parts of the high-end equipment while it is difficult to provide enough test artifacts for the traditional trial and error experiment to obtain the desirable processing technology. The EDEM simulation of the spindle barrel finishing can provide effective help for the process design, however, the difference between the simulation and experiment is closely related to the selection of the contact model during simulation. In this paper, simulations and experiments are conducted based on the identical apparatus and conditions to facilitate the comparison and validation between each other. Based on the Hertz contact theory, the effect of the material properties of contact objects and the relative position of the workpiece on the contact force is qualified. The expression of the correlation coefficient of the contact model is deduced. Then the formula for calculating the contact force between the barrel finishing abrasive and the workpiece that includes influence coefficient of the material properties and the relative positions is established. Finally, the contact force calculation formula is verified by changing the rotating speed. The result shows that the material correction coefficient ranges from 1.41 to 2.38, which is inversely related to the equivalent modulus E. The position correction coefficient ranges from 2.0 to 2.3. The relative error value between the calculation result and the experimental test result is from 0.58% to 14.07%. This research lay a theoretical foundation for the correction theory of the core elements of the spindle barrel finishing process.
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39. A New Method for Type Synthesis of 2R1T and 2T1R 3-DOF Redundant Actuated Parallel Mechanisms with Closed Loop Units
Yongquan Li, Yang Zhang, Lijie Zhang
Chinese Journal of Mechanical Engineering    2020, 33 (6): 78-78.   DOI: 10.1186/s10033-020-00487-7
摘要9)      PDF(pc) (6958KB)(0)    收藏
The current type synthesis of the redundant actuated parallel mechanisms is adding active-actuated kinematic branches on the basis of the traditional parallel mechanisms, or using screw theory to perform multiple getting intersection and union to complete type synthesis. The number of redundant parallel mechanisms obtained by these two methods is limited. In this paper, based on Grassmann line geometry and Atlas method, a novel and effective method for type synthesis of redundant actuated parallel mechanisms (PMs) with closed-loop units is proposed. Firstly, the degree of freedom (DOF) and constraint line graph of the moving platform are determined successively, and redundant lines are added in constraint line graph to obtain the redundant constraint line graph and their equivalent line graph, and a branch constraint allocation scheme is formulated based on the allocation criteria. Secondly, a scheme is selected and redundant lines are added in the branch chains DOF graph to construct the redundant actuated branch chains with closed-loop units. Finally, the branch chains that meet the requirements of branch chains configuration criteria and F & C (degree of freedom & constraint) line graph are assembled. In this paper, two types of 2 rotational and 1 translational (2R1T) redundant actuated parallel mechanisms and one type of 2 translational and 1 rotational (2T1R) redundant actuated parallel mechanisms with few branches and closed-loop units were taken as examples, and 238, 92 and 15 new configurations were synthesized. All the mechanisms contain closed-loop units, and the mechanisms and the actuators both have good symmetry. Therefore, all the mechanisms have excellent comprehensive performance, in which the two rotational DOFs of the moving platform of 2R1T redundant actuated parallel mechanism can be independently controlled. The instantaneous analysis shows that all mechanisms are not instantaneous, which proves the feasibility and practicability of the method.
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40. A Robust and Efficient Compressed Sensing Algorithm for Wideband Acoustic Imaging
Fangli Ning, Zhe Liu, Jiahao Song, Feng Pan, Pengcheng Han, Juan Wei
Chinese Journal of Mechanical Engineering    2020, 33 (6): 95-95.   DOI: 10.1186/s10033-020-00504-9
摘要8)      PDF(pc) (3366KB)(0)    收藏
Wideband acoustic imaging, which combines compressed sensing (CS) and microphone arrays, is widely used for locating acoustic sources. However, the location results of this method are unstable, and the computational efficiency is low. In this work, in order to improve the robustness and reduce the computational cost, a DCS-SOMP-SVD compressed sensing method, which combines the distributed compressed sensing using simultaneously orthogonal matching pursuit (DCS-SOMP) and singular value decomposition (SVD) is proposed. The performance of the DCS-SOMP-SVD is studied through both simulation and experiment. In the simulation, the locating results of the DCS-SOMP-SVD method are compared with the wideband BP method and the DCS-SOMP method. In terms of computational efficiency, the proposed method is as efficient as the DCS-SOMP method and more efficient than the wideband BP method. In terms of locating accuracy, the proposed method can still locate all sources when the signal to noise ratio (SNR) is - 20 dB, while the wideband BP method and the DCS-SOMP method can only locate all sources when the SNR is higher than 0 dB. The performance of the proposed method can be improved by expanding the frequency range. Moreover, there is no extra source in the maps of the proposed method, even though the target sparsity is overestimated. Finally, a gas leak experiment is conducted to verify the feasibility of the DCS-SOMP-SVD method in the practical engineering environment. The experimental results show that the proposed method can locate both two leak sources in different frequency ranges. This research proposes a DCS-SOMP-SVD method which has sufficient robustness and low computational cost for wideband acoustic imaging.
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