China Mechanical Engineering

Prescribed Performance Tracking Control of Electro-hydraulic Servo Systems with Hysteresis Compensation

Dong Zhenle, Ma Dawei, Yao Jianyong, Wang Xiaofeng

2016, 27(08): 995-1000.

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For the common parametric uncertainties and uncertain nonlinearities(hysteresis, nonlinear friction, external disturbances, et al) existing in electro-hydraulic servo systems, a novel method was proposed, which was based on adaptive robust control, and named prescribed performance tracking control with hysteresis compensation. First, taking valve controller single-rod hydraulic cylinder position servo system for instance, a mathematic model consisting of hysteresis nonlinearity was constructed. And then, a prescribed performance function was utilized to characterize the convergence rate, maximum over-shoot, and steady-state errors. At last, an adaptive robust controller was design based on the planned tracking errors to guarantee the excellent steady-state performance and transient performance. Extensive simulations show that the proposed controller can attenuate the hysteresis effects on the tracking accuracy, improve the convergence rate, reduce the over-shoot, and eventually achieve an excellent tracking.

Type Synthesis of Two-translational and Three-rotational Hybrid Mechanisms

Qin Youlei, Cao Yi , Chen Hai,

2016, 27(08): 1001-1006.

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A systematic and effective type synthesis method which was suit for serial and parallel as well as hybrid mechanism was proposed based on GF set. The basic concept of GF set, algorithms and the type synthesis principles, requirements for rotation were introduced based on GF set firstly. Secondly, an approach to synthesize of hybrid mechanism was presented by analyzing the characteristics of structure composition. The topological arrangements of hybrid mechanisms might be developed by the elements of GF set combination and rotation axis transfer theorem. According to the relationships among dimensions of end-effector characteristics and structural parameters of mechanisms the number synthesis formulas was set up. Specific process for structural synthesis of HMs was finished. Simultaneously, a lot of new mechanisms were attained. According to the proposed approach, 2T3R 5-DOF hybrid mechanism with determined kinematic characteristic was enumerated. Meanwhile, a method was proposed to analyze kinematic characteristic of hybrid mechanisms synthesized above. Finally, a novel hybrid mechanism was synthesized to demonstrate the applicability of the novel method of structural synthesis for hybrid mechanisms.

A Constitutive Law Based on Transverse Isotropic Hypothesis and Finite Element Model of Fixed Joints

Zhao Jinjuan, Wang Shijun, Yang Chao, Wang Shiyi, Yang Huixin

2016, 27(08): 1007-1011.

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A finite element method modeling fixed joints was presented. In the method, the contact layers of the fixed joints were regarded as a homogenous virtual transverse isotropic material. According to the relations among deformations and loads of joints, the nonlinear relations among 5 independent variables and normal stress in constitutive matrix were deduced, and then the relations were introduced into finite element analysis to model fixed joints. The analytical results and experimental results of the joints were compared and the validity of the method was confirmed.

Dynamics Control of a Novel Hybrid Mechanism for Automobile Electro-coating Conveying

Gao Guoqin, Fan Dujuan, Fang Zhiming

2016, 27(08): 1012-1018.

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As a novel hybrid mechanism used for automobile electro-coating conveying possessed high nonlinearity and coupling, it was difficult to achieve the high-performance control. To solve this problem, a dynamic model of the hybrid mechanism was established by Lagrange method. Then, a PD sliding mode neural network dynamics controller was designed in the task space and the stability of the controller was proved. Finally, the controller was simulated and compared with the PD sliding mode controller. The results show that the dynamics controller, by the action of feed-forward control of neural network, may solve the severe chattering problem existed in the PD sliding mode controller effectively, and may make the automobile electro-coating conveying system achieve the high control performance.

Modular Design of Mechanical Noumenon for Industrial Robots

Xiao Chao, Zhou Yulin, Sheng Haiyong, Hou Yulei

2016, 27(08): 1018-1025.

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Based on the idea of mechanical noumenon modular design method as well as decomposition principles of structure functions, a standard mechanical structure module library was established and the self-assembling function was achieved. The human arm parameters were used as built-in parameters of the standard mechanical structure module library, which might establish a extended structure module library with different sizes and similar functions. The workspace was reclassified based on the geometric characteristics of boundary curves. The solving process of workspace was modularized according to the key point position analysis method and improved CAD variable geometric method. The D-H parameters generated by the module library of coordinate system were used as share data among each module library, which might realize automatic solution of kinematics and workspace. The forward kinematics and workspace modular automatic solution of KUKA KR6-2 were taken as an example, the software running results and theoretical calculation results were compared and analyzed, and the results show that this method can meet the robot's flexible and autonomous design requirements.

Design of Piezoelectric Rotary Actuator Based on Asymmetric Clamping Mechanism

Wen Jianming, Cheng Guangming, Ma Jijie, Zeng Ping, Kan Junwu

2016, 27(08): 1026-1031.

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A novel piezoelectric inertial rotary actuator was presented herein based on asymmetric clamping mechanism. The actuator can achieve unidirectional rotation movement by the reciprocating swing of the masses to produce asymmetric inertial impact force when the piezoelectric bimorph pasted on the substrate was applied to the symmetric electrical signals. A prototype was fabricated and a series of experiments were conducted to evaluate its performance in terms of angular displacement, friction torque, and load characteristics. The results show that the angular displacement resolution of 1.82μrad is obtained by applied square wave of 15V, frequency of 10Hz under the clamping difference of 3mm and maximum output load is 0.122N under the friction torque of 2.475N·mm.

Oil Hydraulic Press Control Characteristics with Open Variable Pump-controlled System

Song Yu, Kong Xiangdong, Yao Jing, Wang Zhuo

2016, 27(08): 1031-1038.

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In order to solve the problems of high energy consumption for huge free forging hydraulic press, an open variable pump-controlled hydraulic system for oil hydraulic press was proposed. Firstly, combined with ADAMS and AMESim, a co-simulation platform of open variable pump-controlled hydraulic press system was built, and aiming at typical work modes, regular forging and fast forging, the control characteristics were studied by simulations. Secondly, based on 600kN forging hydraulic press experimental platform, control characteristics for the open variable pump-controlled hydraulic press with regular forging and fast forging was verified respectively by experiments, and compared with the simulation results. The simulation and experimental results approve that the open variable pump-controlled hydraulic press system can meet the technical requirements. For regular forging, it has a good performance about manipulation, low impact and stability. For fast forging, when the forging frequency is up to 80 times per minute, the position control accuracy is less than 1mm.

Motion System Analysis of Small Heterogeneous Parts Polishing Machine

Liu Jianchun, Chen Xiongfeng, Liao Nilan

2016, 27(08): 1039-1042,1052.

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In a small heterogeneous parts automatic polishing machine(SHPAPM), it was significant to precisely control the relative motion between a clamp and a cloth wheel, especially for polishing of complex surface parts. Based on the structure of SHPAPM, the motion system with 3 linear axes and 3 rotational axes was analyzed, and the DH machines coordinate system was established. In the coordinate system, pose's equations were deduced from kinematics forward and reverse operations, then their inverse solutions were obtained. Those solutions determined mapping relationship between clamp poses and robot's joints. For verification, a faucet 3D surface model was applied to justify the new method in a MATLAB/ADAMS based simulator. In the simulation, the new method successfully solves unknown variables for joints. Besides simulation, field polishing experiments were also conducted, which results in low roughness(Rz=0.36μm) and high accuracy.

Study on Electrochemical-mechanical Characteristics of Conductive Polymer Actuator

Tian Sukun, Wang Xiangjiang

2016, 27(08): 1043-1046.

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The bend characteristics testing experimental system was set up by actuator to study the electrochemical-mechanical characteristics. The bending deformation was measured by applying low voltage(0 ~ 1V) to the actuator with different lengths. The relationship among the bending displacement, the voltage and the voltage frequency was analyzed. The electric-mechanical transfer model was established based on the experimental results. The results show that the voltage and the bending force are in a linear relationship. When the voltage is 0.8V and sampling period is 0.02s, the bending displacement of the actuator decreases gradually with the increase of the frequency. Furthermore, it is verified by lifting the weights of the drive of different sizes，the larger the width of the drive, the larger the bending force, and the longer the length, the smaller the bending force.

Light Weight Design of Automobile Rear Axle Housing Based on Typical Conditions

Ding Xiaoming, Lü Juncheng, Wang Wei

2016, 27(08): 1047-1052.

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Lightweight design was done for the rear axle housing of multi-link rear suspension, based on typical conditions and the method of inertia release. According to the analyses, the maximal stress of the rear axle housing appeared on unilateral pothole condition. It indicated that the thickness of axle shaft sleeve and rear axle housing had an effect on maximal stress value as thickness changed,the maximum stress position would also shift. Finally, the optimized rear axle housing weight loss is of 11.6% compared to the original one, and no durability problems after fatigue tests and durability tests, the optimized rear axle housing can meet the design requirements.

Impact Dynamics Modeling and Simulation Analyses of Pneumatic Cylinders

Du Qungui, Sun Zhiquan, Huang Chongxi, Zhai Xiaochen

2016, 27(08): 1053-1058.

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Impact of pneumatic cylinder at the stroke terminal was considered to be an integrated system of vibrations, including slender piston rod, mass load, piston and end cover.Based on one-dimensional wave equation, a mathematical model of longitudinal vibration of slender piston rod was established firstly. Impact force,contact displacement and contact time were analyzed by means of mode superposition method.Then impact process of pneumatic cylinder was numerically simulated by nonlinear FEM software LS-DYNA.The variation of impact interface force and contact time were studied in detail under different masses of driven load and impact velocities. Compared with numerical solution of LS-DYNA,the accuracy of analytical solution was verified, and how impact force varies as velocity and load was concluded. Vibration frequencies of impact response were furtherly analyzed, and reasons for the changes of impact forces were studied. Research conclusions provide reference for design and applications of pneumatic cylinders.

Flexible Job Shop Scheduling Based on Modified Artificial Fish Swarm Algorithm

Zhao Min, Yin Huan, Sun Dihua, Zheng Linjiang, He Wei, Yuan Chuan

2016, 27(08): 1059-1065.

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An improved algorithm for solving flexible job shop scheduling was proposed based on the artificial fish swarm algorithm. In view of the blindness and low precision of the basic artificial fish swarm algorithm in its late stage search, the new algorithm presented some strategies like separating the step into the random moving step and target moving step, adopting flexible parameter setting, and infusing local traversal search in the late period of the algorithm based on the analyses of parameter influences of the algorithm, which enhanced the search ability and search precision of the modified algorithm. Finally, the effectiveness of the improved artificial fish swarm algorithm in solving flexible job shop scheduling problem was verified by the standard MK sample and comparison experiments.

Experimental Research of Surface Integrity for Precision Hard Turning Finished Bearing Rings

Ding Honghan, Hang Lubin, Chen Youguang

2016, 27(08): 1066-1071.

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In order to avoid the shortcomings appeared in grinding and to explore new processing technology of hard turning finished bearing rings, the surface integrity of hard turning rings was studied by experimental method, and the relationship among the flatness of datum surface, the tool wear of cutting edge and the precision of hard turning was investigated. Based on the researches of surface roughness, roundness of raceway, micro-hardness, heat damage, microstructure, residual stress distribution and processing efficiency of the samples, it is found that the processing accuracy of hard turning is as high as that of grinding, while the micro-structure of hard turning remains stable, heat damage does not generate easily, the residual stress distribution is controllable and the processing efficiency is higher. These results are conducive to the industrialization of high precision bearing production. Furthermore, the influences of flatness of datum surface on the roundness of raceway were analyzed while the ring was clamped by magnetic chuck on hard turning machine tools. The results show that better flatness will produce better roundness of hard turning raceway. At last, the influences of tool wear on the processing accuracy of hard turning were analyzed, which reveals that the tool wear is an important cutting parameter to be controlled strictly in finish stage to get better roundness of raceway.

Xu Xinsheng, Wang Cheng, Xiao Ying

2016, 27(08): 1072-1077.

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In order to find reusable product structure promptly, an approach of measuring the similarity among product structures was proposed based on non-negative matrix factorization. A comprehensive matrix which containsed all structures was constructed on the basic of adjacent vectors that were transformed from the adjacent matrices of product structures. The non-negative matrix factorization for the comprehensive matrix was implemented based on Multiplicative Updates(MU) algorithm. Then all product structures might be described in low dimensional space. On the basis of these, the similarity between two product structures could be measured by calculating the Euclidean distance among these low dimensional vectors. Finally, an example was presented to verify the principles and methods mentioned above. The results show that the proposed methodologies are more effective than those of the existing methods.

Grey Target Model for Parameter Design of Multi-quality-characteristic Products

Li Yaping, Liu Sifeng, Fang Zhigeng, Chen Hongzhuan, Xu Lan

2016, 27(08): 1078-1083.

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A grey target model for parameter choice of multi-quality-characteristic products was proposed to aid engineering designers to make decisions. Based on orthogonal experimental design, elements and relationships among them of the grey target model were studied for the parameter choice of multi-quality-characteristic products. A group of improved Taguchi quality loss functions were developed, and their values were thought to be the basic measures for the effects in the grey model. The internal and external factors were considered simultaneously in the design process. According to the effect value, acceptable parameter combinations were distinguished from unacceptable ones to get a satisfactory domain for design. Moreover, based on the effect value, the optimal parameter combination for multi-quality-characteristic products can be obtained.

Pneumatic Wheel Precession Finishing Trajectory Optimization in Neighborhood of Mould Boundaries

Cai Donghai, Ji Shiming, Zhang Heteng, Jin Mingsheng

2016, 27(08): 1084-1089.

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For the vibration intensified and excessive removal of material in finishing the neighborhood of mould boundaries by pneumatic wheel precession finishing technology, the direction constraint of relative cutting speed was applied in precession finishing trajectory planning process and the boundary constraint conditions were derived. Then the precession finishing trajectory generation program with boundary constraint conditions was compiled. The optimized precession finishing trajectory means used the normal precession to finish the continuous surface and used constraint precession to finish the boundary. It provided with disordered cutting directions and avoided vibration intensified and excessive removal of material. Precession finishing trajectory with boundary constraint conditions had even smaller vibration and more intact boundary line, compared to unconstrained precession finishing trajectory. This boundary constraint conditions improve both of the process and the outcome of pneumatic wheel precession finishing method, and has been verified at the actual processing.

Fuzzy Evaluation of Assembly Sequence Quality Based on Relative Entropy Method

Zhang Genbao, Luo Dongmei, Ran Yan, She Lin

2016, 27(08): 1089-1095.

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Based on the definition of assembly sequence quality, an evaluation system was firstly established to present comprehensive quality of assembly sequences by interpretative structure model, and the index attribute values were calculated quantitatively. Then in order to get index weights, the Vague set was used to concentrate experts' opinions. Finaly, a new decision-making method was founded based on entropy theory, which was supported for alternative assessments with large difference, to evaluate comprehensive quality of all feasible assembly sequences. Case study indicates the rationality and effectiveness of this method.

Dynamics Analysis of 6-DOF Manipulators with Flexible Joints

Wang Hai, Fu Bangchen, Xue Bin, Yang Chunlai

2016, 27(08): 1096-1101.

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Most robots were hypothetical designed and controlled in rigid body dynamics. Hence, the accuracy and efficiency of these robots were limited in working. However, the flexible joint manipulators provided a good point of these problems. The 6-DOF manipulator with flexible joints was studied herein. Firstly, a simplified model was given, and the kinetic model of this manipulator was built by Lagrange equations. Then, the control law was created by neural network backstepping method in the case of 6-DOF manipulator with flexible joints. Finally, the rationality of the controller was proven by Simulink.

Automatic Ultrasonic Evaluation of Vehicle Spot Welding Quality Based on Time-frequency Characteristics

Nie Xin, Guo Zhifu, He Zhicheng

2016, 27(08): 1102-1106.

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A spot welding quality automatic evaluation methodology was proposed by defining the time-frequency characteristics of ultrasonic echo, and a spot welding quality evaluation criterion was built, which was convenient for online automatic detection by data statistical analysis. Finally, vehicle spot welding quality was evaluated automatically. Practical test results indicate the detecting system based on the proposed method can automatically identify eight types of spot welding quality quickly and effectively, so this system may preliminarily apply to online automatic detection of spot welding quality.

Generation of Branching Support Structures Based on Critical Angle Constraint

Shen Zhenhong, Dai Ning, Li Dawei, Wu Changyou

2016, 27(08): 1107-1112.

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In order to optimize support structures' volume, and save the material and printing time, an automatic generation algorithm was proposed based on critical angle constraint. Firstly, the algorithm detected areas that required support, and the support points were obtained by adaptive sampling based on the area. Secondly, through critical angle constraint, the nodes in branching support structures were calculated, and all nodes information in a tree were saved. Finally, the resulting structure was obtained by the sweep surface after Poisson reconstruction. The algorithm was evaluated by experiments, and the experimental results demonstrate that the algorithm provides a reliable method to ensure the printing stability as well as reducing the printing material and time.

Calculation and Experimental Analysis of Stretch-bend Straightening Elongation

Qi Xiangdong, Lian Jiachuang, Dong Zhikui

2016, 27(08): 1113-1116.

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At present, there was a lack of complete mathematical model in process of stretch-bend straightening. According to the calculation models of the neutral layer offset and the elongation of the strip in the process of stretch-bend straightening, the calculating methods of the tension, straightening force and elongation were given. Through calculations and industrial tests, the effects of the straightening procedure on the residual elongation were analyzed, and the accuracy of the models was verified.

Effects of Strain-strengthening on Microstructure and Mechanics Behavior of 022Cr17Ni12Mo2 Austenitic Stainless Steel

Kong Weihai, Chen Xuedong, Yan Yongchao, Hu Pan

2016, 27(08): 1117-1122.

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The effects of strain-strengthening on microstructure and mechanics behavior of 022Cr17Ni12Mo2 austenitic stainless steel were investigated by universal testing machine, X-ray diffraction, optical microscopy, and transmission electron microscopy. The results show that there is no phase transformation during the early stage of pre-strain strengthening. With the increase of deformation twins, the cold deformation can enhance the strength and hardness significantly, whereas the ductility of the steel is decreased. The deformation twinning induced strength effects are occurred. Meanwhile, the strain-strengthening ability of the strengthened steel and the transient strain are weakened with increase of the pre-strain. The appearance of deformation twins makes the change of dislocation slip mode, which transforms from single-slip and planar-slip to multiple-slip and cross-slip.

Research on Driving Dynamics for Vehicles Equipped With a Single Loop Systems

Wang Zhen, Cui Yahui, Liu Kai, Xu Lin

2016, 27(08): 1123-1129.

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Power split structure scheme of the single loop system was given, bond graph model of the vehicle which equipped with XP and PX type power split continuously variable transmission was established, and the state equation of the system was deduced. Taking MATLAB/Simulink as a platform, the simulation model of the vehicle was established. Given UDDS driving cycles, using the best fuel economy control strategy for the economics selection of the XP type and PX type power split single loop system, the XP type single loop system has better economy. When the driving cycle acceleration rapidly changing,the engine torque and the single loop system transmission ratio has abrupt variation, which leads to the vibration of the basic component of the differential gear train.

Lightweight Design of a Truck Frame Based on Intervals

Hu Zhaohui, Zhang Jian, Li Guangyao, Yuan Zhijun

2016, 27(08): 1130-1135.

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Topology optimization was the main method for the model conceptual design of a lightweight design. But the calculation results of the direct topology was usually chaotic for large models. So the topology space should be divided into several small areas in accordance with the operating requirements to make the results more clear. Based on topology calculation, the optimal placement method of the high strength bolts used bar elements to simulate bolts to calculate their relative densities. Then according to results, the position of high strength bolts in parts could be accurately determined. It is conducive for the rational use of high strength bolts. In the lightweight design process of a certain truck frame, the premise was to ensure the stiffness and strength performance to meet the demands of the typical working conditions from beginning to end. At the same time according to different design goals the design variables and constraints should be constantly adjusted and refined for the comprehensive applictions of topology optimization and size optimization. The final results show that after the optimization design the total mass reduces 60.4 kg. The effectiveness of weight loss is more than 10%.

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