China Mechanical Engineering

Kinematic Analysis of a Side Loading Robot for SG-Ⅲ Precision Optical Modules

SONG Daiping1;YUAN Yuejun1;GUO Zonghuan2;WANG Kang1

2018, 29(12): 1387-1392.

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In order to transport the module required for laser fusion test to the inside of main test device，a 8-DOF side loading robot was designed.Coordinate systems of joints were set up and D-H parameters were obtained by using D-H methods.Then the forward kinematic solution was derived.A virtual 6-DOF robot was constructed by using bleaching joint variable method.The inverse kinematic equations of virtual 6-DOF robot was established based on analytical method.Based on the principles of minimum space of joint and Levenberg Marquarde algorithm，the positions of joint 3 and joint 4 were solved by using the 1stOpt software.Then the inverse kinematic equation of 8-DOF side loading robot was derived.The correctness of the algorithm for inverse kinematics of side loading robot was verified by an example.The kinematic analysis may be used for precise positioning and motion planning of manipulator end effectors，which provides a theoretical reference for the realization of trajectory planning and real-time control of 8-DOF robots.

Characteristics of 2D Pressure Servo Valves with Bourdon Tube Pressure Feedbacks

ZUO Xiqing1;ZHANG Shouli1;LIU Guowen1;MENG Bin2;RUAN Jian2

2018, 29(12): 1393-1398.

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2D pressure servo valves mainly applied to aircraft brake systems were designed，whose spools had linear movements and rotary movements.Bourdon tube was used as pressure feedback unit，and the output feedback torques were linked with shift lever forks to realize the closed loop force feedback with the main valves.Pressure outputs were kept constant.Force transfer method of Bourdon tube force feedback mechanism was analyzed，mathematical model of the 2D pressure servo valves was established，static and dynamic characteristics of the main valves were simulated and analyzed.A prototype experimental program was designed，and an experimental platform was built.The experimentalal results show that the output pressures of the 2D pressure servo valves are basically linear with the input current of the rotating electromagnets，and the step response time of the output pressures is about 18ms.The experimental results are basically consistent with the simulation ones.

Study on Characteristics of Chaotic Singular Spectrum and Applications in Rolling Bearing Fault Diagnosis

ZHANG Shuqing;HE Peng;ZUO Yige;CHEN Rongfei;ZHANG Yun;LIU Wan;JIANG Wanlu

2018, 29(12): 1398-1404.

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A new metric of chaos space structure—chaotic singular spectrum was researched and an early fault recognition algorithm for rolling bearings was proposed based on chaotic singular spectral feature extraction.First，the singular spectrum discrete form was presented， and when studying the stability of singular spectrum，logarithmic function was introduced to observe the effects of the deviation on singular spectral values more sensitively.Then，it was proved from the perspective of geometric space that the singular spectrum was a description of spatial geometry based on variance maximization，which shown that the chaotic singular spectrum was a quantitative description of spatial structure of chaotic attractor and had certain anti-noise interference ability.Numerical verifications of Lorenz system prove the stability of chaotic singular spectrum and strong anti-noise performance.After experiments,the effectiveness and practicability of this method was verified.

Aerodynamics-structure Coupling Vibrations of Mistuning Blade-disk Based on Kriging Interpolation

YANG Wenjun1，2;ZHANG Kaifeng1;WANG Lei1，2;YUAN Huiqun3

2018, 29(12): 1405-1413.

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Considering the interactions of stator-rotor blade rows，flow characteristics of an aero-engine compressor were simulated with the numerical method.Stiffness mistuning was set by the test of static frequency.Load transfer of aerodynamic pressure was achieved from flow field to blade structure based on the interpolation method of Kriging model.Then distribution law of aerodynamic load was analyzed on compressor blades.In addition，the effects of stiffness mistuning and aerodynamic load on vibration characteristics of blade-disk system were discussed.The results show unsteady aerodynamic load on compressor rotor blades fluctuates periodically，and dominant frequencies are mainly at the frequency doubling of stator-rotor interaction f0.In the interaction period T，variations of aerodynamic load on pressure and suction surfaces take the contrary trend，unsteady characteristics of aerodynamic load are far greater on pressure surface than that on suction surface.By the effects of mistuning factor and aerodynamic load，the vibrations of blade-disk are enhanced seriously.The research results provide the theoretical basis for dynamics design of compressor blade-disk rotor systems.

Flow and Mass Transfer Characteristics in Random Roughness Surface Microchannels

LU Congda;XUE Hao;WU Huaping;WEN Donghui

2018, 29(12): 1414-1420.

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Abstract:In order to study the effects of random roughness on the flow and mass transfer characteristics of the microchannel walls，the random roughness of the microchannel walls with typical roughness was established using the random arrangement criterion.The effects of random roughness on velocity，pressure drop，flow resistance and mass transfer characteristics were analyzed by finite element method，and the approximate variation law of Poiseuille number and molecular diffusion in rough microchannels were given.Results show that the flow velocity of the fluid in the near-wall areas and the mainstream regions of the coarse microchannels is quite different，and the flow separation in the near-wall areas is obvious.Compared with the smooth microchannels，the pressure drop and the Poiseuille number in each positions of the microchannels increase linearly along the flow direction.The existence of the microchannel wall roughness accelerates the diffusion rate of fluid molecules mass transfer，butit is greatly affected by roughness type and relative roughness height.

Polynomial Dynamics Modeling Method of MRDs Based on PSO Algorithm

DONG Zhizhen1;FENG Zhimin1;WU Guangbin2;LIU Xiaofeng1

2018, 29(12): 1421-1427.

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In order to improve the accuracy of polynomial dynamics model of MRD，a polynomial modeling method was proposed based on PSO algorithm.MRD test platform was built.Traditional polynomial model and Chebyshev polynomial model were identified and compared by using the measured experimental data of mechanics properties.Combining PSO algorithm with Lagrange interpolation equation and measured data to optimize interpolation nodes，the polynomial dynamics model was constructed after the simplification of MATLAB Simplify function.The flow and main steps of PSO algorithm for optimizing interpolation nodes were researched，and the average cumulative relative errors between PSO algorithm and Chebyshev model were analyzed based on 12th order polynomial modeling.The results show that the relative errors of PSO polynomial modeling method is 47.0% less than that of Chebyshev polynomial model under sinusoidal excitation frequency of 1Hz，amplitude of 15mm and current of 0~1.5 A.The PSO polynomial modeling method may well reflect the dynamics characteristics of MRD and meet the needs of practical engineering applications.

Sparse Fault Diagnosis Method for Rolling Bearings of Wind Turbines Based on COMP Algorithm

LI Jimeng1;LI Ming1;WANG Hui1;ZHANG Jinfeng2;ZHANG Yungang1

2018, 29(12): 1428-1433.

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Aiming at the problems that effective impulse feature was difficult to detect because the fault signals collected from rolling bearings in wind turbines was non-stationary and submerged by strong noises，a sparse fault diagnosis method was proposed based on COMP algorithm，the correlation coefficients between atoms and residuals were calculated according to the inner product size after each iteration，the atom with the largest correlation coefficient was merged with other qualifying atoms，and the merged atom was treated as a new atom.Then，a new dictionary with strong correlation with the signals was reconstructed by these new atoms，and the signals were sparse represented by the dictionary.Finally，the accurate diagnosis of rolling bearing failures was achieved by analyzing the envelope spectrum of the results of sparse representation.Because of the strong correlations between the new atoms reconstructed by this method and the residuals，a high sparse representation precision may be obtained with only a small number of iterations.Simulations and engineering applications were performed to verify the validity and practicability of the proposed method.

Influences of Coating Performance on Longitudinal Modal Propagation Characteristics of Gas Pipelines

CAI Haichao1,2;SHANG Zhendong1,2;CHAO Hongjun3

2018, 29(12): 1434-1438.

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The propagation characteristics of the longitudinal modes in the viscoelastic coatings were analyzed theoretically，and the dispersion and attenuation characteristics of the longitudinal mode，especially the L（0，2) mode，were studied.A three-dimensional finite element model of the asphalt coating pipes was established.The influences of the excitation frequency，the coating density and the attenuation coefficient of the coating wave on the guided wave propagation was studied，and the excitation and reception of the asphalt clad steel pipe toward L（0，2) modal experiments were carried out.The results show that in the low frequency ranges，as the excitation frequency and the coating density increase，the L（0，2) mode is also affected by the asphalt coatings，and the energy attenuation is gradually increased.The attenuation curves may be used as the theoretical guidance for the modal selection of the pipelines with asphalt coatings.The low frequency longitudinal mode ultrasonic guided waves are better for the detection of the pipelines with low density coatings.

Quasi-zero-stiffness Vibration Sensor System of Equivalent Nonlinear Damping Control

YANG Pan1;DENG Zhaoxiang2，3;SHU Hongyu2，3;TUO Jiying3

2018, 29(12): 1439-1445.

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In order to accurately measure the absolute vibration displacements of mobile platform，and further expand the measurement frequency bands，a quasi-zero-stiffness sensor was designed with the equivalent nonlinear damping control method.To realize the quasi-zero-stiffness characteristics of the QZS sensors，the dynamic model of the sensors was established，and their structure and static characteristics were analyzed.The amplitude-frequency and phase-frequency characteristics of the sensors under different pre-deformations were discussed，and then the effects of the sensors on the accuracy of measured signals under different equivalent nonlinear dampings and excitations were analyzed.The results show that the range of the measurement bands may be effectively widened by equivalent nonlinear damping control of the quasi-zero-stiffness sensor systems.The system may accurately measure the absolute displacements of mobile platform to meet the requirements of engineering practice.

Parameterized Method for Personalized Oriented Welded Cinder Ladles

DONG Yude1;LI Jiucheng1;YANG Shanlai2;CHEN Minglong1;WANG Nan1

2018, 29(12): 1446-1453.

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Aiming at the problems of traditional casting cinder ladles，such as large manufacturing energy consumption，long production cycle，short service life，and high repair cost，a welded cinder ladle parameterized design approach driven by customers was put forward.This method combined techniques of model design，finite element analysis，and parameterized design.The modular design idea was adopted，the attributes of cinder ladle's parts were added in a quick and selective way by applying loop statements.Finally，a parameterized design system of welded cinder ladles was developed with SolidWorks software platform.The analysis of examples shows that the system may meet diversified and personalized customer demands，and improve design efficiency of welding cinder ladles.

A Brain Control Method for Prosthesises Based on Facial Expression

LU Zhufeng1，2;ZHANG Xiaodong1,2;LI Rui1,2;GUO Jin1

2018, 29(12): 1454-1459,1474.

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Aiming at the shortages of traditional motion imagery(MI) paradigm and steady state visual evoked potential (SSVEP) paradigm in high training difficulty of paradigm, complex equipment integration, high cost, unwearable and so on, a brain control prosthesis method was proposed based on facial expression with the help of the wide adaptability of electroencephalography, high accuracy of recognition and the convenience to integrate in portable system.A portable brain controlled prosthesis system was constructed based on facial expression，including hardware system forming，analytical algorithm design and software developing，to realize the control technique from brow-raising to hand-opening，brow-frowning to hand-closing，left-smirking to wrist-intorsion and right-smirking to wrist-extorsion and its online experiments.The online experimental results of the portable brain controlled prosthesis system indicate that the brain control method for prosthesises based on facial expression is better than SSVEP way in removing the extra inducers，and better than motor imagery way for the average online accuracy rate of recognition and control is over 85%.

Joint Trajectory Planning Algorithm for Industrial Robots Based on Mixed Interpolation

HAN Jiang;GU Taotao;XIA Lian;DONG Fangfang

2018, 29(12): 1460-1466.

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B-spline curves were widely used in trajectory planning of industrial robots in joint spaces due to the multi-order continuous derivative and local supporting characteristics.Derivative values of B-spline existed with sudden changes at the beginning and end positions，which might result in vibrations for industrial robots when starting and stopping.A new method to optimize interpolation of high order polynomials and B-splines was proposed herein，so the kinematics parameters of robot joints would be continuous and not mutational.Thus the robots may run more smoothly，the operations of the robot states are improved without increasing operating burden of the robot control systems.

Two-point Positioning and Pose Adjustment Method for Automatic Assembly of Barrel-type Cabin

JIN Herong1，2;LIU Da1，2

2018, 29(12): 1467-1474.

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In order to solve the problems of pose adjustment in digital docking assembly of spacecrafts，a two-point positioning and pose adjustment method was proposed.By adjusting the positions of the two key points in the docking bay to adjust the space posture of the cabin section，the fifth-order polynomial trajectory was used to adjust the pose of the trajectory planning，constrain cabin movement parameters，and determine the cabin section of a reasonable posture time to ensure the smooth and fast docking tasks.The method simplified the alignment algorithm，so the series mechanisms might meet the requirements of alignment algorithm，which avoided the multi-axis controls and reduced the control difficulties.The simulations of the proposed method were carried out by ADAMS.The docking cabin may reach the target position by using two-point positioning adjustment method.And the track of the displacement，velocity and acceleration are smooth and continuous，while the boundary conditions are adjusted.The maximum deviation between the pose and the target coordinate is as -0.08 mm，and the maximum acceleration during the adjustment is as 10 mm/s2.The simulation results show that the two-point positioning method may meet the requirements of accuracy，stability and high-efficiency of the digital assembly orientation of tube-type cabin，which may contribute to the automatic control of the barrel-type pose adjustments.

Meta-activity Model Driven Grain Layered Service Encapsulation and Retrieval for Multi-domain Manufacturing Resources

DONG Yuanfa1，2;WU Zhengjia1;DU Xuan1;ZHA Jing1;YUAN Qingsong1

2018, 29(12): 1475-1484.

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Polymerization and service encapsulation of multi-domain manufacturing resources were the key of sharing manufacturing capacity and directly related to the searchability and usability of cloud manufacturing services.Aiming to solve the problems of coarse-grained information and low precision ratio of cloud service，which was due to the lack of key resource informations or the characteristics of manufacturing processes and the uncertainty of service attributes，a meta-activity model of manufacturing with human，machine，material，method and environment as the core elements was constructed to realize intelligent aggregation of multi-domain resource particles firstly.Then the manufacturing capacity of resource cluster was encapsulated layer by layer based on quotient space granularity theory.A hierarchical recursive search algorithm of cloud manufacturing service level was proposed to solve the uncertainty of service attribute based on gray similarity rough set model.Finally，a set of meta-activity model driven multi-domain manufacturing resource grain layered service encapsulation and its retrieval method were established.The feasibility of the proposed method was verified by a retrieval case of cloud services for rapid prototyping of metal structures.

Effects of Typical Gaits on Paddy Soils and Parameters on Energy Consumption of Legged-robots

ZHU Peng;ZHANG Yongnian;HE Chunxia;LU wei

2018, 29(12): 1485-1491.

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The single leg of legged-robots and the soil finite element model were established by ABAQUS，and the finite element dynamics simulation was carried in order to explore the influence law of unit energy consumption of four typical gaits（rectangular，modified cycloid，elliptical，zero impact） and their parameters.The actual experiments with the same parameters were designed on the independently-developed foot-to-ground test bench in order to test the correctness of finite element dynamics simulations.The results show the performance of energy consumption of elliptical gaits is the best，and the minimum unit energy consumption decreases 12.5%，11% and 12% compared with rectangular，corrected cycloid and zero impact respectively.The simulation tests are in good agreement with the actual tests on trail of mechanical leg walking.The knee joint and hip joint torque obtained by simulation tests and actual tests are also in a good agreement.

Research on Total Fretting Fatigue Lifes of Connecting Rods under Multi-axis Variable-amplitude Stresses

WANG Lingling;HE Baiyan

2018, 29(12): 1492-1498.

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A total-life calculation model for fatigue cracks initiating and propagating under multi-axis variable-amplitude stresses was proposed.Based on the effective stress intensity factor criterion and rain-flow counting technique for multi-axis variable-amplitude stresses，the Paris formula was revised to apply to describe the fatigue cracks initiating and propagating behaviors under multi-axis variable-amplitude stresses and a short-crack correction size was introduced to obtain the total-life calculation model.Finally，a life culculation case study on mating surfaces of a obliquely split diesel connecting rod was performed.Based on the material tests and finite element analysis，the life of dangerous spots on the mating surfaces was calculated，which indicats that the total life model may calculate the fatigue life from an arbitrary initial crack size to an arbitrary critical crack size.The total life model may play a prominent role in life design and maintenance work of key components.

Effects-of-Thermal-Barrier-Coatings-on-Thermal-Loads at-Piston-Top-Surfaces

NIU Xiaoqiang1;LEI Jilin1;DENG Xiwen1;WEN Jun2;WEN Zhigao2

2018, 29(12): 1499-1506.

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TBC at the top surfaces of pistons might reduce the thermal loads and improve the service life of pistons.A non road high pressure common rail diesel engine aluminum alloy piston was used as object of the study，the temperature of 19 feature points of the common piston was measured at maximum torque conditions with hardness plug，the finite element model of piston was established by isoparametric method.The influences of TBC of piston top on piston temperature field and thermal stress field were analyzed and compared.Results show that the piston top TBC may effectively reduce the working temperature of piston head and ring groove region.The top surfaces of piston head in regional temperature decrease 20~32 [℃]，first ring and second ring groove's temperatures decrease 15~18 [℃].However，the thermal stress on the top layer of piston matrix will increase sharply when TBC is applied to piston top，especially the thermal stress concentration is obvious at the top of piston base，the throat area and the edge angle.The maximum thermal stress in the bonding zone of top throat of piston top reaches 291 MPa，which will lead to the spalling failure of TBCs.

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