2018年, 第31卷, 第2期　
刊出日期：2018-04-16

  

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Intelligent Manufacturing Technology
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  Leakage and Stifness Characteristics of Bionic Cluster Spiral Groove Dry Gas Seal

  Jin-Bo Jiang, Xu-Dong Peng, Ji-Yun Li, Yuan Chen

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 21-21. https://doi.org/10.1186/s10033-018-0227-4

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  Spiral groove dry gas seal (S-DGS), the most widely used DGS in the world, encounters the problem of high leakage rate and inferior film stability when used in high-speed machinery equipment, which could not be well solved by optimization of geometrical parameters and molded line of spiral groove. A new type of bionic cluster spiral groove DGS (CS-DGS) is proved to have superior film stability than S-DGS at the condition of high-speed and low-pressure numerically. A bionic CS-DGS is experimentally investigated and compared with common S-DGS in order to provide evidence for theoretical study. The film thickness and leakage rate of both bionic spiral groove and common spiral groove DGS are measured and compared with each other and with theoretical values under different closing force at the condition of static pressure, high-speed and low-pressure, and the film stiffness and stiffness-leakage ratio of these two face seals are derived by the relationship between closing force and film thickness at the steady state. Experimental results agree well with the theory that the leakage and stiffness of bionic CS-DGS are superior to that of common S-DGS under the condition of high-speed and low-pressure, with the decreasing amplitude of 20% to 40% and the growth amplitude of 20%, respectively. The opening performance and stiffness characteristics of bionic CS-DGS are inferior to that of common S-DGS when rotation speed equals to 0 r/min. The proposed research provides a new method to measure the axis film stiffness of DGS, and validates the superior performance of bionic CS-DGS at the condition of high-speed and low-pressure experimentally.
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  New Immersed Boundary Method on the Adaptive Cartesian Grid Applied to the Local Discontinuous Galerkin Method

  Xu-Jiu Zhang, Yong-Sheng Zhu, Ke Yan, You-Yun Zhang

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 22-22. https://doi.org/10.1186/s10033-018-0222-9

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  Currently, many studies on the local discontinuous Galerkin method focus on the Cartesian grid with low computational efficiency and poor adaptability to complex shapes. A new immersed boundary method is presented, and this method employs the adaptive Cartesian grid to improve the adaptability to complex shapes and the immersed boundary to increase computational efficiency. The new immersed boundary method employs different boundary cells (the physical cell and ghost cell) to impose the boundary condition and the reconstruction algorithm of the ghost cell is the key for this method. The classical model elliptic equation is used to test the method. This method is tested and analyzed from the viewpoints of boundary cell type, error distribution and accuracy. The numerical result shows that the presented method has low error and a good rate of the convergence and works well in complex geometries. The method has good prospect for practical application research of the numerical calculation research.
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  Numerical Simulation and Experimental Verifcation of the Stifness and Stability of Thrust Pad Aerostatic Bearings

  Hai-Long Cui, Yang Wang, Bao-Rui Wang, Hong Yang, Huan Xia

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 23-23. https://doi.org/10.1186/s10033-018-0228-3

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  Many researchers concentrate on improving the stiffness and stability of aerostatic bearings, however the contradiction between stiffness and stability is still existed. Therefore, orifice, multiple, and porous restrictors are designed to illustrate the influence of restrictor characteristics on the stability and stiffness of the aerostatic circular pad bearings. Because both the stiffness and stability of aerostatic bearings are determined by the internal pressure distribution, the full Navier-Stokes (N-S) equations are applied to solve internal pressure distribution in bearing film by using computational fluid dynamics (CFD) method. Simulation results present that the stiffness and stability of aerostatic circular pad bearings are influenced significantly by geometrical and material parameters, such as film thickness, orifice diameters, and viscous resistance coefficient. Verified by the experimental data, the micro vibration of orifice restrictor is almost the same as multiple restrictors with amplitude of 0.02 m/s², but it is much stronger than the porous restrictors with acceleration of 0.006 m/s². The optimal stiffness of multiple restrictors increased by 46%, compared to only 30.2 N/μm of orifice restrictor, and the porous restrictors had obvious advantage in the small film thickness less than 6 μm where the optimal stiffness increased to 38.3 N/μm. The numerical and experimental results provide guidance for improving the stiffness and stability of aerostatic bearings.
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  Life Distribution Transformation Model of Planetary Gear System

  Ming Li, Li-Yang Xie, Hai-Yang Li, Jun-Gang Ren

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 24-24. https://doi.org/10.1186/s10033-018-0221-x

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  Planetary gear systems have been widely used in transportation, construction, metallurgy, petroleum, aviation and other industrial fields. Under the same condition of power transmission, they have a more compact structure than ordinary gear train. However, some critical parts, such as sun gear, planet gear and ring gear often suffer from fatigue and wear under the conditions of high speed and heavy load. For reliability research, in order to predict the fatigue probability life of planetary gear system, detailed kinematic and mechanical analysis for a planetary gear system is firstly completed. Meanwhile, a gear bending fatigue test is carried out at a stress level to obtain the strength information of specific gears. Then, a life distribution transformation model is established according to the order statistics theory. Transformation process is that, the life distribution of test gear is transformed to that of single tooth, and then the life distribution of single tooth can be effectively transformed to that of the planetary gear system. In addition, the effectiveness of the transformation model is finally verified by a processing method with random censoring data.
Advanced Transportation Equipment
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  Fuzzy Sliding Mode Control for the Vehicle Height and Leveling Adjustment System of an Electronic Air Suspension

  Xiao-Qiang Sun, Ying-Feng Cai, Chao-Chun Yuan, Shao-Hua Wang, Long Chen

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 25-25. https://doi.org/10.1186/s10033-018-0223-8

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  The accurate control for the vehicle height and leveling adjustment system of an electronic air suspension (EAS) still is a challenging problem that has not been effectively solved in prior researches. This paper proposes a new adaptive controller to control the vehicle height and to adjust the roll and pitch angles of the vehicle body (leveling control) during the vehicle height adjustment procedures by an EAS system. A nonlinear mechanism model of the full-car vehicle height adjustment system is established to reflect the system dynamic behaviors and to derive the system optimal control law. To deal with the nonlinear characters in the vehicle height and leveling adjustment processes, the nonlinear system model is globally linearized through the state feedback method. On this basis, a fuzzy sliding mode controller (FSMC) is designed to improve the control accuracy of the vehicle height adjustment and to reduce the peak values of the roll and pitch angles of the vehicle body. To verify the effectiveness of the proposed control method more accurately, the full-car EAS system model programmed using AMESim is also given. Then, the co-simulation study of the FSMC performance can be conducted. Finally, actual vehicle tests are performed with a city bus, and the test results illustrate that the vehicle height adjustment performance is effectively guaranteed by the FSMC, and the peak values of the roll and pitch angles of the vehicle body during the vehicle height adjustment procedures are also reduced significantly. This research proposes an effective control methodology for the vehicle height and leveling adjustment system of an EAS, which provides a favorable control performance for the system.
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  Analysis of the Load-Stress Response Characteristics of the Bogie Frame in Intercity Electric Multiple Unit

  Hua Zou, Shou-Guang Sun, Qiang Li, Zun-Song Ren

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 26-26. https://doi.org/10.1186/s10033-018-0226-5

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  Load spectra research for bogie frame requires establishing the load-stress relationship on working condition, which has been omitted by the researchers. With the load-stress of the bogie frame of an intercity Electric Multiple Unit (Hereinafter referred to as EMU) as the research object, an optimization model of the load-stress transfer relationship is established. The load-stress coefficient for EMU bogie frame was calibrated in the laboratory bench and online test was arranged on Dazhou-Chengdu line. Comparison of nonlinear and linear neural networks proves that the linear transitive relation between the load and stress of the bogie frame in the operating process is highly suitable. An optimization model of the load-stress transfer coefficient is obtained. The data calculated with the modified coefficient are closer to the dynamic stress results in the actual operating process than the data calculated with the calibration coefficient. The coefficient of the modified transitive relation is unaffected by operating area, empty load, heavy load, or other conditions in the operating process of the intercity EMU. The real loads in actual situations are obtained. The model of online load-stress relationship that is highly suitable for line stress calculation is finally established. The research is helpful for further damage calculation and inferring the time history signal of the load in load spectra research.
Intelligent Manufacturing Technology
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  Application of Fractal Contact Model in Dynamic Performance Analysis of Gas Face Seals

  Song-Tao Hu, Wei-Feng Huang, Xiang-Feng Liu, Yu-Ming Wang

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 27-27. https://doi.org/10.1186/s10033-018-0224-7

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  Fractal theory provides scale-independent asperity contact loads and assumes variable curvature radii in the contact analyses of rough surfaces, the current research for which mainly focuses on the mechanism study. The present study introduces the fractal theory into the dynamic research of gas face seals under face-contacting conditions. Structure-Function method is adopted to handle the surface profiles of typical carbon-graphite rings, proving the fractal contact model can be used in the field of gas face seals. Using a numerical model established for the dynamic analyses of a spiral groove gas face seal with a flexibly mounted stator, a comparison of dynamic performance between the Majumdar-Bhushan (MB) fractal model and the Chang-Etsion-Bogy (CEB) statistical model is performed. The result shows that the two approaches induce differences in terms of the occurrence and the level of face contact. Although the approach distinctions in film thickness and leakage rate can be tiny, the distinctions in contact mechanism and end face damage are obvious. An investigation of fractal parameters D and G shows that a proper D (nearly 1.5) and a small G are helpful in raising the proportion of elastic deformation to weaken the adhesive wear in the sealing dynamic performance. The proposed research provides a fractal approach to design gas face seals.
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  Active Profling and Polishing Model and Validation Based on Rotor Spiral Groove

  Guo Yu, Feng Li, Yong-Min Yu, Shou-Xiang Zai

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 28-28. https://doi.org/10.1186/s10033-018-0225-6

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  When a spiral groove is formed using superplastic molding, precision casting, additive manufacturing, or other non-mechanical processing technology, it is difficult to meet the molding precision required for direct use, and the surface quality and accuracy of the shape need to be improved through a finishing process. In view of the poor reachability of the current tool-based polishing process, a tool-less polishing method using free-abrasive grains for complex spiral grooves is proposed. With this method, by controlling the movement of the workpiece, the design basis and relative motion of the abrasive particles along a helical path remain consistent, resulting in a better polishing profile. A spiral groove of a revolving body is taken as the research object; the influence of the installation method and the position of the parts, as well as the effect of the rotational speed of the abrasive ball on its relative motion along a helical trajectory, are studied, and the polishing cutting process of an abrasive ball is reasonably simplified. A consistent mathematical model of the trajectory of an abrasive ball relative to the design helix is constructed. The grooved drum parts are verified through a polishing experiment. The spiral groove of the revolving body is modified and polished. Experiments show that the process not only corrects the shape a spiral groove error, but also reduces the surface roughness of a spiral groove. This study provides a theoretical basis for achieving free-abrasive, tool-free polishing.
Innovative Design of Complex Products
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  Efect of Degree-of-Symmetry on Kinetostatic Characteristics of Flexure Mechanisms: A Comparative Case Study

  Xiao-Bing He, Jing-Jun Yu, Wan-Wan Zhang, Guang-Bo Hao

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 29-29. https://doi.org/10.1186/s10033-018-0235-4

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  The current research of kinetostatic characteristics in fexure mechanisms mainly focus on the improvement of accuracy. To reduce or eliminate the parasitic motion is considered as an approach by using the common knowledge of symmetry. However, there is no study on designing the fexure mechanisms with symmetrical features as many as possible for better kinetostatic performance, when considering the resulting cost by the symmetry. In this paper, the concept of degree of symmetry (DoS) is proposed for the frst time, which is committed to symmetry design in the phase of conceptual design. A class of fexure mechanisms with 0-DoS, 1-DoS, 2-DoS and 3-DoS are synthesized respectively based on the Freedom and Constraint Topology method. Their overall compliance matrices in an analytical form formulated within the framework of the screw theory are used to analyze and compare the efect of diferent number of DoS on the kinetostatic characteristics for fexure mechanisms. The fnite element analysis (FEA) simulations are implemented to verify the analytical results. These results show that the higher the DoS is, the smaller the parasitic motion error will be. The fexure model with 3-DoS is optimized according to the overall compliance matrix and then tested by using the FEA simulation. The testing result shows that with the best combination parameters, the parasitic motion error for 3-DoS mechanism is almost eliminated. This research introduces a design principle which can alleviate the unwanted parasitic motion for better accuracy.
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  Quasi-Static and Dynamic Behaviors of Helical Gear System with Manufacturing Errors

  Bing Yuan, Shan Chang, Geng Liu, Li-Yan Wu

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 30-30. https://doi.org/10.1186/s10033-018-0238-1

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  Time-varying mesh stiffness (TVMS) and gear errors include short-term and long-term components are the two main internal dynamic excitations for gear transmission. The coupling relationship between the two factors is usually neglected in the traditional quasi-static and dynamic behaviors analysis of gear system. This paper investigates the influence of short-term and long-term components of manufacturing errors on quasi-static and dynamic behaviors of helical gear system considering the coupling relationship between TVMS and gear errors. The TVMS, loaded static transmission error (LSTE) and loaded composite mesh error (LCMS) are determined using an improved loaded tooth contact analysis (LTCA) model. Considering the structure of shaft, as well as the direction of power flow and bearing location, a precise generalized finite element dynamic model of helical gear system is developed, and the dynamic responses of the system are obtained by numerical integration method. The results suggest that lighter loading conditions result in smaller mesh stiffness and stronger vibration, and the corresponding resonance speeds of the system become lower. Long-term components of manufacturing errors lead to the appearance of sideband frequency components in frequency spectrum of dynamic responses. The sideband frequency components are predominant under light loading conditions. With the increase of output torque, the mesh frequency and its harmonics components tend to be enhanced relative to sideband frequency components. This study can provide effective reference for low noise design of gear transmission.
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  Optimization Design and Performance Analysis of Vehicle Powertrain Mounting System

  Han Zhou, Hui Liu, Pu Gao, Chang-Le Xiang

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 31-31. https://doi.org/10.1186/s10033-018-0237-2

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  The design strategies for powertrain mounting systems play an important role in the reduction of vehicular vibration and noise. As stiffness and damping elements connecting the transmission system and vehicle body, the rubber mount exhibits better vibration isolation performance than the rigid connection. This paper presents a complete design process of the mounting system, including the vibration decoupling, vibration simulation analysis, topology optimization, and experimental verification. Based on the 6-degrees-of-freedom vibration coupling model of the powertrain mounting system, an optimization algorithm is used to extract the best design parameters of each mount, thus rendering the mounting system fully decoupled and the natural frequency well configured, and the optimal parameters are used to design the mounting system. Subsequently, vibration simulation analysis is applied to the mounting system, considering both transmission and road excitations. According to the results of finite element analysis, the topological structure of the metal frame of the front mount is optimized to improve the strength and dynamic characteristics of the mounting system. Finally, the vibration bench test is used to verify the availability of the optimization design with the analysis of acceleration response and vibration transmissibility of the mounting system. The results show that the vibration isolation performance of the mounting system can be improved effectively using the vibration optimal decoupling method, and the structural modification of the metal frame can well promote the dynamic characteristics of the mounting system.
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  Vibration Response and Stress Analysis of Planar Elastic Tube Bundle Induced by Fluid Flow

  De-Rong Duan, Pei-Qi Ge, Wen-Bo Bi, Yan-Ying Dong

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 32-32. https://doi.org/10.1186/s10033-018-0240-7

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  Flow-induced vibration plays a positive role on heat transfer enhancement. Meanwhile, it is also a negative factor for fatigue strength. Satisfying the fatigue strength is the primary prerequisite for heat transfer enhancement. This paper numerically studied the flow-induced vibration of planar elastic tube bundle based on a two-way fluid–structure interaction (FSI) calculation. The numerical calculation involved the unsteady, three-dimensional incompressible governing equations solved with finite volume approach and the dynamic balance equation of planar elastic tube bundle solved with finite element method combined with dynamic mesh scheme. The numerical approach was verified by comparing with the published experimental results. Then the vibration trajectory, deformation and stress contour of planar elastic tube bundle were all studied. Results show that the combined movement of planar elastic tube bundle represents the agitation from inside to outside. The vibration of out-of-plane is the main vibration form with the typically sinusoidal behavior because the magnitude of displacement along the out-of-plane direction is the 100 times than the value of in-plane direction. The dangerous point locates in the innermost tube where the equivalent stress can be utilized to study the multiaxial fatigue of planar elastic tube bundle due to the alternating stress concentration. In the velocity range of 0.2?3 m/s, it is inferred that the vibration amplitude plays a role on the stress response and the stress amplitude is susceptible to the fluid velocity. This research paves a way for studying the fatigue strength of planar elastic tube bundle by flow-induced vibration.
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  Design and Experiment of Triangular Prism Mast with Tape-Spring Hyperelastic Hinges

  Hui Yang, Hong-Wei Guo, Yan Wang, Rong-Qiang Liu, Meng Li

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 33-33. https://doi.org/10.1186/s10033-018-0242-5

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  Because of the limited space of the launch rockets, deployable mechanisms are always used to solve the phenomenon. One dimensional deployable mast can deploy and support antenna, solar sail and space optical camera. Tape-spring hyperelastic hinges can be folded and extended into a rod like confguration. It utilizes the strain energy to realize self-deploying and drive the other structures. One kind of triangular prism mast with tape-spring hyperelastic hinges is proposed and developed. Stretching and compression stifness theoretical model are established with considering the tape-spring hyperelastic hinges based on static theory. The fnite element model of ten-module triangular prism mast is set up by ABAQUS with the tape-spring hyperelastic hinge and parameter study is performed to investigate the infuence of thickness, section angle and radius. Two-module TPM is processed and tested the compression stifness by the laser displacement sensor, deploying repeat accuracy by the high speed camera, modal shape and fundamental frequency at cantilever position by LMS multi-channel vibration test and analysis system, which are used to verify precision of the theoretical and fnite element models of ten-module triangular prism mast with the tape-spring hyperelastic hinges. This research proposes an innovative one dimensional triangular prism with tape-spring hyperelastic hinge which has great application value to the space deployable mechanisms.
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  Personalization for Massive Product Innovation Using Open Architecture

  Qing-Jin Peng, Yun-Hui Liu, Jian Zhang, Pei-Hua Gu

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 34-34. https://doi.org/10.1186/s10033-018-0239-0

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  Product innovation is creation of new concepts to plan and realize technological and functional details in the product to satisfy market and customer needs. One of the key drivers to product innovation is reactions of the product to users' needs. Product innovation needs a cognitive design method based on needs of variant users for the product personalization. In this paper, an open concept is introduced to provide ways to meet user's individual need in product lifespan. It is for industries to propose product concepts based on open sources, develop and support the product on the public capability. Using the open concept in the product architecture, called open-architecture product (OAP), can improve the product personalization leading to massive product innovation. To promote this promise of the OAP, efective methods are discussed for the OAP development. This paper introduces research on OAPs using adaptable design methods to meet product personalization. Adaptable design is based on the modular structure for product adaptability using function modules and adaptable interfaces. The proposed method provides solutions for planning modules and implementation of OAPs. Methods of OAP module planning, detail and interface design are described for transformation of product concepts into physical structures. A multiple-purpose electrical car is developed in a case study to show efectiveness of the proposed method.
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  Configuration Design of an Under-Actuated Robotic Hand Based on Maximum Grasping Space

  Shang-Ling Qiao, Rong-Qiang Liu, Hong-Wei Guo, Yu-Xuan Liu, Zong-Quan Deng

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 35-35. https://doi.org/10.1186/s10033-018-0243-4

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  Capture is a key component for on-orbit service and space debris clean. The current research of capture on-orbit focuses on using special capture devices or full-actuated space arms to capture cooperative targets. However, the structures of current capture devices are complex, and both space debris and abandoned spacecraft are noncooperative targets. To capture non-cooperative targets in space, a lightweight, less driven under-actuated robotic hand is proposed in this paper, which composed by tendon-pulley transmission and double-stage mechanisms, and always driven by only one motor in process of closing fnger. Because of the expandability, general grasping model is constructed. The equivalent joint driving forces and general grasping force are analyzed based on the model and the principle of virtual work. Which reveal the relationship among tendon driving force, joint driving forces and grasping force. In order to confgure the number of knuckles of fnger, a new analysis method which takes the maximum grasping space into account, is proposed. Supposing the maximum grasped object is an envelope circle with diameter of 2.5 m. In the condition, a fnger grasping maximum envelope circle with diferent knuckles is modeled. And the fnger lengths with corresponding knuckles are calculated out. The fnger length which consists of three knuckles is the shortest among under-actuated fngers consists of not more than fve knuckles. Finally, the principle prototype and prototype robotic hand which consists of two dingers are designed and assembled. Experiments indicate that the under-actuated robotic hand can satisfy the grasp requirements.
Editorial
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  Special Issue on Innovative Design of Complex Products

  Jian-Rong Tan

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 36-36. https://doi.org/10.1186/s10033-018-0232-7

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Innovative Design of Complex Products
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  Design by Analogy: Achieving More Patentable Ideas from One Creative Design

  Zhen-Li Jia, Chun-Long Wu, Xue-Hong Zhu, Run-Hua Tan

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 37-37. https://doi.org/10.1186/s10033-018-0234-5

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  A patent is a kind of technical document to protect intellectual property for individuals or enterprises. Patentable idea generation is a crucial step for patent application and analogy is confrmed to be an efective technique to inspire creative ideas. Analogy-based design usually starts from representation of an analogy source and is followed by the retrieval of appropriate analogs, mapping of design knowledge and adaptation of target solution. To difuse one core idea into other new contexts and achieve more patentable ideas, this paper mainly centered on the frst two stages of analogy-based design and proposed a patentable ideation framework. The analogical information of the source system, including source design problems and solution, was mined comprehensively through International Patent Classifcation analysis and represented in the form of function, behavior and structure. Three heuristics were suggested for searching the set of candidate target systems with a similar design problem, where the source design could be transferred. To systematize the process of source representation, analogs retrieval, idea transfer, and solution generation, an ideation model was put forward. Finally, the bladeless fan was selected as a source design to illustrate the application of this work. The design output shows that the representation and heuristics are benefcial, and this systematic ideation method can help the engineer or designer enhance creativity and discover more patentable opportunities.
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  Optimization of Uncertain Structures with Interval Parameters Considering Objective and Feasibility Robustness

  Jin Cheng, Zhen-Yu Liu, Jian-Rong Tan, Yang-Yan Zhang, Ming-Yang Tang, Gui-Fang Duan

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 38-38. https://doi.org/10.1186/s10033-018-0244-3

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  For the purpose of improving the mechanical performance indices of uncertain structures with interval parameters and ensure their robustness when fluctuating under interval parameters, a constrained interval robust optimization model is constructed with both the center and halfwidth of the most important mechanical performance index described as objective functions and the other requirements on the mechanical performance indices described as constraint functions. To locate the optimal solution of objective and feasibility robustness, a new concept of interval violation vector and its calculation formulae corresponding to different constraint functions are proposed. The mathematical formulae for calculating the feasibility and objective robustness indices and the robustness-based preferential guidelines are proposed for directly ranking various design vectors, which is realized by an algorithm integrating Kriging and nested genetic algorithm. The validity of the proposed method and its superiority to present interval optimization approaches are demonstrated by a numerical example. The robust optimization of the upper beam in a high-speed press with interval material properties demonstrated the applicability and effectiveness of the proposed method in engineering.
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  An Error Equivalent Model of Revolute Joints with Clearances for Antenna Pointing Mechanisms

  Quan Liu, Sheng-Nan Lu, Xi-Lun Ding

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 39-39. https://doi.org/10.1186/s10033-018-0233-6

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  Joint clearances in antenna pointing mechanisms lead to uncertainty in function deviation. Current studies mainly focus on radial clearance of revolute joints, while axial clearance has rarely been taken into consideration. In fact, owning to errors from machining and assembly, thermal deformation and so forth, practically, axial clearance is inevitable in the joint. In this study, an error equivalent model (EEM) of revolute joints is proposed with considering both radial and axial clearances. Compared to the planar model of revolute joints only considering radial clearance, the journal motion inside the bearing is more abundant and matches the reality better in the EEM. The model is also extended for analyzing the error distribution of a spatial dual-axis ("X-Y" type) antenna pointing mechanism of Spot-beam antennas which especially demand a high pointing accuracy. Three case studies are performed which illustrates the internal relation between radial clearance and axial clearance. It is found that when the axial clearance is big enough, the physical journal can freely realize both translational motion and rotational motion. While if the axial clearance is limited, the motion of the physical journal will be restricted. Analysis results indicate that the consideration of both radial and axial clearances in the revolute joint describes the journal motion inside the bearing more precise. To further validate the proposed model, a model of the EEM is designed and fabricated. Some suggestions on the design of revolute joints are also provided.
Intelligent Manufacturing Technology
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  Fault Feature Extraction of Diesel Engine Based on Bispectrum Image Fractal Dimension

  Jian Zhang, Chang-Wen Liu, Feng-Rong Bi, Xiao-Bo Bi, Xiao Yang

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 40-40. https://doi.org/10.1186/s10033-018-0230-9

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  Fault feature extraction has a positive effect on accurate diagnosis of diesel engine. Currently, studies of fault feature extraction have focused on the time domain or the frequency domain of signals. However, early fault signals are mostly weak energy signals, and time domain or frequency domain features will be overwhelmed by strong background noise. In order consistent features to be extracted that accurately represent the state of the engine, bispectrum estimation is used to analyze the nonlinearity, non-Gaussianity and quadratic phase coupling (QPC) information of the engine vibration signals under different conditions. Digital image processing and fractal theory is used to extract the fractal features of the bispectrum pictures. The outcomes demonstrate that the diesel engine vibration signal bispectrum under different working conditions shows an obvious differences and the most complicated bispectrum is in the normal state. The fractal dimension of various invalid signs is novel and diverse fractal parameters were utilized to separate and characterize them. The value of the fractal dimension is consistent with the non-Gaussian intensity of the signal, so it can be used as an eigenvalue of fault diagnosis, and also be used as a non-Gaussian signal strength indicator. Consequently, a symptomatic approach in view of the hypothetical outcome is inferred and checked by the examination of vibration signals from the diesel motor. The proposed research provides the basis for on-line monitoring and diagnosis of valve train faults.
Innovative Design of Complex Products
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  Light-Weight Design Method for Force-Performance-Structure of Complex Structural Part Based Co-operative Optimization

  Ya-Li Ma, Jian-Rong Tan, De-Lun Wang, Zi-Zhe Liu

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 42-42. https://doi.org/10.1186/s10033-018-0236-3

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  A light-weight design method of integrated structural topology and size co-optimization for the force-performance-structure of complex structural parts is presented in this paper. Firstly, the supporting function of a complex structural part is built to map the force transmission, where the force exerted areas and constraints are considered as connecting structure and the structural configuration, to determine the part performance as well as the force routines. Then the connecting structure design model, aiming to optimize the static and dynamic performances on connection configuration, is developed, and the optimum design of the characteristic parameters is carried out by means of the collaborative optimization method, namely, the integrated structural topology optimization and size optimization. In this design model, the objective is to maximize the connecting stiffness. Based on the relationship between the force and the structural configuration of a part, the optimal force transmission routine that can meet the performance requirements is obtained using the structural topology optimization technology. Accordingly, the light-weight design of conceptual configuration for complex parts under multi-objective and multi-condition can be realized. Finally, based on the proposed collaborative optimization design method, the optimal performance and optimal structure of the complex parts with light weight are realized, and the reasonable structural unit configuration and size characteristic parameters are obtained. A bed structure of gantry-type machining center is designed by using the proposed light-weight structure design method in this paper, as an illustrative example. The bed after the design optimization is lighter 8% than original one, and the rail deformation is reduced by 5%. Moreover, the lightweight design of the bed is achieved with enhanced performance to show the effectiveness of the proposed method.
Intelligent Manufacturing Technology
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  Parameters Sensitivity Characteristics of Highly Integrated Valve-Controlled Cylinder Force Control System

  Kai-Xian Ba, Bin Yu, Xiang-Dong Kong, Chun-He Li, Qi-Xin Zhu, Hua-Long Zhao, Ling-Jian Kong

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 43-43. https://doi.org/10.1186/s10033-018-0231-8

  摘要 ( ) PDF全文 ( )   可视化   收藏

  Nowadays, a highly integrated valve-controlled cylinder (HIVC) is applied to drive the joints of legged robots. Although the adoption of HIVC has resulted in high-performance robot control, the hydraulic force system still has problems, such as strong nonlinearity, and time-varying parameters. This makes HIVC force control very difficult and complex. How to improve the control performance of the HIVC force control system and find the influence rule of the system parameters on the control performance is very significant. Firstly, the mathematical model of HIVC force control system is established. Then the mathematical expression for parameter sensitivity matrix is obtained by applying matrix sensitivity analysis (PSM). Then, aimed at the sinusoidal response under (three factors and three levels) working conditions, the simulation and the experiment are conducted. While the error between the simulation and experiment canot be avoided. Therefore, combined with the range analysis, the error in the two performance indexes of sinusoidal response under the whole working condition is analyzed. Besides, the sensitivity variation pattern for each system parameter under the whole working condition is figured out. Then the two sensitivity indexes for the three system parameters, which are supply pressure, proportional gain and initial displacement of piston, are proved experimentally. The proposed method significantly reveals the sensitivity characteristics of HIVC force control system, which can make the contribution to improve the control performance.
Innovative Design of Complex Products
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  A Finite and Instantaneous Screw Based Approach for Topology Design and Kinematic Analysis of 5-Axis Parallel Kinematic Machines

  Tao Sun, Shuo-Fei Yang, Tian Huang, Jian S. Dai

  Chinese Journal of Mechanical Engineering. 2018, 31(2): 44-44. https://doi.org/10.1186/s10033-018-0241-6

  摘要 ( ) PDF全文 ( )   可视化   收藏

  Unifying the models for topology design and kinematic analysis has long been a desire for the research of parallel kinematic machines (PKMs). This requires that analytical description, formulation and operation for both finite and instantaneous motions are performed by the same mathematical tool. Based upon finite and instantaneous screw theory, a unified and systematic approach for topology design and kinematic analysis of PKMs is proposed in this paper. Using the derivative mapping between finite and instantaneous screws built in the authors' previous work, the finite and instantaneous motions of PKMs are analytically described by the simple and non-redundant screws in quasi-vector and vector forms. And topological and parametric models of PKMs are algebraically formulated and related. These related topological and parametric models are ready to do type synthesis and kinematic analysis of PKMs under the unified framework of screw theory. In order to show the validity of the proposed approach, a kind of two-translational and three-rotational (2T3R) 5-axis PKMs is taken as example. Numerous new structures of the 2T3R PKMs are synthesized as the results of topology design, and their Jacobian matrix is obtained easily for parameter optimization and performance evaluation. Some of the synthesized PKMs have outstanding capabilities in terms of large workspaces and flexible orientations, and have great potential for industrial applications of machining and manufacture. Among them, METROM PKM is a typical example which has attracted a lot of attention from global companies and already been developed as commercial products. The approach is a general and unified approach that can be used in the innovative design of different kinds of PKMs.