Table of Content

28 June 2020, Volume 54 Issue 6 Previous Issue    Next Issue

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Modeling and Simulation of Pneumatic Soft Actuator with Multiple Chambers XU Qiping, LIU Jinyang 2020, 54 (6):  551-561.  doi: 10.16183/j.cnki.jsjtu.2019.041 Abstract ( 1119 )   PDF (11543KB) ( 621 )   Save Pneumatic soft actuators have broad application prospects in engineering fields. The whole deformation investigation on soft actuators used to be carried out mainly by adopting simple models such as beams and rods, which is different from hard contact of rigid materials. Therefore, the establishment of accurate mechanical models and analysis of the overall configuration and stress distribution for soft contact of soft actuators are still challenging conundrums. Aimed at the soft contact problem between two adjacent air chambers of a pneumatic soft actuator with multiple chambers, a novel modeling approach is proposed in this paper by combining the complexity of the air chamber structure with geometric and material nonlinearities, and employing the segment-to-segment contact method for multiple-point contact. It has solved the interpenetration problem between two adjacent air chambers without considering the contact interaction, which is suitable for analyzing soft structures with large deformation. Compared with traditional models like beams and rods, this model can not only improve the accuracy in simulating the overall deformation, but also accurately describe the stress distribution law inside the air chamber structure. The simulation results for the pneumatic soft actuator with multiple chambers demonstrate that the soft contact between adjacent air chambers has a remarkable effect on large deflection of the actuator. Finally, the quasi-static research on the whole process of grasping a cylinder by a soft four-claw mechanism is implemented, and the overall configuration variations and Mises stress distribution are elaborated in detail. The results show that the stress in the contact area reaches a maximum value. This paper is of theoretical guiding significance for the mechanical property analysis and optimal design of soft actuators. References | Related Articles | Metrics

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Design and Characteristic Analysis of a Bio-Inspired Delay Magnification System ZHANG Yaqiong, YU Fengning, TA Na, RAO Zhushi 2020, 54 (6):  562-568.  doi: 10.16183/j.cnki.jsjtu.2019.085 Abstract ( 924 )   PDF (1486KB) ( 516 )   Save In order to magnify time delays between received signals of small aperture arrays and improve the localization performance of such arrays, a multiple-input-multiple-output (MIMO) delay magnification system is presented. The mechanical model of the coupled ears is extended to be n-dimensional. Besides, the relationship between coupling parameters and magnification is investigated. Based on the mechanical model, a MIMO delay magnification system is proposed and realized by algorithm. System parameters can be adjusted flexibly according to sound frequency, and the magnification factor can be precisely controlled. Experimental results show that the delay magnification system can be applied to small aperture arrays to magnify the time delay of received signals and improve the sound source localization accuracy. References | Related Articles | Metrics

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Force Identification Based on Measuring Point Selection and Improved L-Curve Method LI Xiaowang, ZHAO Haitao, CHEN Ji’an 2020, 54 (6):  569-576.  doi: 10.16183/j.cnki.jsjtu.2019.016 Abstract ( 926 )   PDF (1550KB) ( 497 )   Save To solve the ill-posed problem, a two-step ideology is proposed to reduce the ill condition of transmissibility function and weaken the influence of noise in force identification research. First, the optimal combination of measurement points is calculated based on the conditional number theory of transfer function, and a transfer function matrix with the lowest degree of ill condition is obtained. Then, Tikhonov regularization is adopted to identify input excitation. In the procedure mentioned above, B-spline function is introduced to interpolate L-curve to acquire more exact regularization parameters. Simulation results show that the method proposed is able to effectively reduce force identification error and achieve a more accurate force time history. References | Related Articles | Metrics

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Effect of Circular Non-Smooth Surface Blades on Cavitation Characteristics of Centrifugal Pump MOU Jiegang, ZHANG Zicheng, GU Yunqing, SHI Zhengzan, ZHENG Shuihua 2020, 54 (6):  577-583.  doi: 10.16183/j.cnki.jsjtu.2019.070 Abstract ( 1080 )   PDF (6552KB) ( 417 )   Save In order to improve the anti-cavitation characteristics of centrifugal pumps, based on the bionics principle, the circular bionic non-smooth surface structure was arranged at the suction surface where the centrifugal pump blade was most prone to cavitation. The numerical simulation method was used to analyze the external characteristics, bubble volume, turbulent kinetic energy and pressure distribution characteristics of centrifugal pumps with different diameters of circular non-smooth surface blades under different cavitation allowances. The effects of circular non-smooth surface blades on the cavitation performance of centrifugal pumps were studied. The results show that centrifugal pumps with circular protrusion diameter of 0.5 mm and 1.0 mm have high heads and great efficiency, which are close to the values of centrifugal pumps with smooth surface blades. In severe cavitation, the centrifugal pump with circular protrusion diameter of 1.0 mm has the smallest bubble volume. The low pressure section of the impeller is small, the pressure gradient is large, and the turbulent energy near the wall surface of the suction surface of the blade is increased, with the result that the pressure drag caused by the separation is reduced, which has a good inhibitory effect on cavitation. References | Related Articles | Metrics

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Uncertainty Quantification for CFD Simulation of Stochastic Drag Flow Based on Non-Intrusive Polynomial Chaos Method XIA Li, ZOU Zaojian, YUAN Shuai, ZENG Zhihua 2020, 54 (6):  584-591.  doi: 10.16183/j.cnki.jsjtu.2019.062 Abstract ( 1036 )   PDF (2668KB) ( 407 )   Save In this paper, verification & validation and uncertainty quantification in uncertainty analysis for computational fluid dynamics (CFD) simulation are compared. A state-of-the-art method for uncertainty quantification problems, i.e., the non-intrusive polynomial chaos (NIPC) method, is introduced and applied to quantifying the uncertainty of two-dimensional stochastic drag flow, together with the Monte-Carlo (MC) method. For the MC method, the random sampling (RS) method and the Latin hypercube sampling (LHS) method are adopted. The uncertainty of the stochastic drag flow induced by the inlet and outlet pressure boundaries is studied, with the boundaries treated as stochastic variables with uniform distribution. It is shown that there is no big difference between LHS and RS, and the NIPC method can simulate the uncertainty propagation better. References | Related Articles | Metrics

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Energy Efficiency Optimization Based on Time Reversal in SWIPT CHEN Shanxue, LIU Zuoliang, LI Fangwei 2020, 54 (6):  592-598.  doi: 10.16183/j.cnki.jsjtu.2018.080 Abstract ( 907 )   PDF (760KB) ( 376 )   Save Targeted at the problem of energy efficiency (EE) optimization in simultaneous wireless information and power transfer (SWIPT), this paper considers using an optimization algorithm based on time reversal (TR) to maximize the energy efficiency of the system under the condition of satisfying certain communication service quality and collecting energy. First, the time reversal is introduced into simultaneous wireless information and power transfer to construct a new transmission scheme, and the closed expression of energy efficiency is analyzed. Next, through analyzing and planning the problem, it is found that the optimization problem is a two-element fractional non-convex programming problem which needs to be transformed into a convex optimization problem by mathematical transformation. Finally, the solution of the problem is obtained by using the Dinkelbach algorithm and CVX. The simulation results show that the optimized energy efficiency will increase when the decoding noise power, the maximum transmission power, and the signal-to-noise ratio increase. The optimization algorithm based on time reversal can significantly increase the energy efficiency when the constraints are satisfied. References | Related Articles | Metrics

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A Hybrid Genetic Algorithm for Computing the k-Error Linear Complexity of Periodic Sequences NIU Zhihua, YUAN Can, KONG Deyu 2020, 54 (6):  599-606.  doi: 10.16183/j.cnki.jsjtu.2020.99.006 Abstract ( 866 )   PDF (832KB) ( 253 )   Save The linear complexity of periodic sequences and its stability are important metrics for the evaluation in stream cipher. The k-error linear complexity is an important evaluation index for the stability of linear complexity. However, at present, it is difficult to compute the k-error linear complexity of the period sequences (except for 2n、pn、2pn). Therefore, a hybrid genetic algorithm is proposed to approximate the k-error linear complexity of arbitrary periodic sequences by adopting the roulette wheel and elitist reserved strategy, the two-point crossover and simple random mutation, and by introducing adaptive operators to adjust the crossover and mutation probabilities to ensure the convergence of the genetic algorithm. The efficiency of the algorithm is improved by using the parallel computing fitness function. Simultaneously, by combining with the simulated annealing algorithm, it increases the convergence speed and avoids the premature convergence. The results show that the experiment value of k-error linear complexity is only 8% higher than the exact value when k<8 and the period is less than 256. References | Related Articles | Metrics

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High-Accuracy Calibration of Hand-Eye Matrix of Line-Structured Laser Sensor: Multiple Coordinates Transformation JING Xiaolong, HU Yuan, GUO Weizhong 2020, 54 (6):  607-614.  doi: 10.16183/j.cnki.jsjtu.2019.033 Abstract ( 1315 )   PDF (4878KB) ( 599 )   Save Aimed at the calibration of line-structured laser mounted on manipulator, this paper presents a novel method, i.e., multiple coordinates transformation (MCT) for calibrating the hand-eye matrix. With the help of a laser tracker and reference object, the coordinates of end-effector and line-structured laser are measured with respect to laser tracker coordinate. Thus, the hand-eye matrix of laser coordinate with respect to the end-effector coordinate can be calculated indirectly and quickly. This method is easy to operate. It has the advantages of small errors, high precision, and low requirements for the experimental equipment. Experiments on the prismatic-rotational-prismatic (PRP) 3 degree-of-freedom robot arm mounted with line-structured laser are conducted. The results show that the rotational axis error is within 0.001, the rotational angle error is within 0.07°, and the translational matrix error is within 0.25mm. The method proposed can be used to calibrate the hand-eye matrix of any two or more degree-of-freedom manipulator mounted with two- or three-dimensional laser sensors. References | Related Articles | Metrics

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Bilateral Adaptive Impedance Control Scheme in Master-Slave Manipulator Teleoperation System ZHANG Jianjun, WU Zhonghua, LIU Qunpo, WANG Hongqi, LIU Weidong 2020, 54 (6):  615-623.  doi: 10.16183/j.cnki.jsjtu.2018.184 Abstract ( 1483 )   PDF (1067KB) ( 566 )   Save In the process of force-displacement tracking control in the bilateral teleoperation system, there are uncertainties caused by the joint friction and external uncertainty disturbance in the manipulator model. Therefore, a bilateral adaptive impedance control strategy is proposed for the problems in the teleoperation system. A robust adaptive control law based on sliding mode function is designed to compensate the uncertain errors of the manipulator model, and two kinds of non-linear model reference adaptive controller are designed. The adaptive law is employed to estimate the upper bound of the external disturbance, which ensures that the closed-loop dynamic equations of the master and slave robots are consistent with the dynamic equations of the reference impedance model, and realizes that the expected position error of the reference impedance model output and the end-effector position of the master and slave robots asymptotically converge to zero. The Lyapunov function is employed to prove the tracking performance and global stability. A 2 degree of freedom (DOF) teleoperation simulation is achieved on the MATLAB/Simulink platform, and the force-position tracking asymptotic convergence ability is verified. The results show that the overall controller has a good force-position tracking ability under the conditions of model uncertainty and external disturbances. The overall system has stability and a high transparency, and it has robustness and small steady-state error with adaptive control capability. References | Related Articles | Metrics

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Modeling and Optimization of Resource Constrained Project Scheduling Problem Considering Employee-Timetabling ZHU Hongwei, LU Zhiqiang 2020, 54 (6):  624-635.  doi: 10.16183/j.cnki.jsjtu.2018.134 Abstract ( 1189 )   PDF (1555KB) ( 433 )   Save Aimed at the practical situation where human resources conduct production activities in the form of shifts in production systems, this paper addresses the resource constrained project scheduling problem considering employee-timetabling and establishes a mathematical model with the objective of minimizing project makespan. Since the serial schedule generation scheme has difficulty in generating a good solution under the solution space delivered by traditional activity list, an improved activity list coding method based on the concept of disjunctive arc in job shop scheduling problem is designed to expand the search extent. Moreover, to improve the local search capability of the genetic algorithm, a branch-and-bound-based search framework based on the improved activity list coding method is designed to sectionally and deeply search the chromosome obtained by the genetic algorithm, and dominant rules are designed to reduce the computational time. The results show that the genetic algorithm with the branch-and-bound-based search framework could improve the solution quality, and the dominant rules could reduce the computing time efficiently and effectively. References | Related Articles | Metrics

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Design and Realization of a Versatile Simulation Platform for Telecontrol Multi-Rotor Unmanned Aerial Vehicle with a Robotic Arm MA Zhonghang, ZHANG Zhinan 2020, 54 (6):  636-642.  doi: 10.16183/j.cnki.jsjtu.2018.374 Abstract ( 1482 )   PDF (5480KB) ( 571 )   Save In order to improve the stability of aerial grasping, it is necessary to design and validate the telecontrol algorithm of unmanned aerial vehicle (UAV). After establishing the whole dynamic model of an aerial telecontrol manipulator, based on the secondary development of virtual robot experimentation platform (V-REP), the precise description and the visual simulation of the robot system are realized. Moreover, a stabilization-grasping algorithm for UAV based on centroid acquisition and inverse kinematics is proposed, and a versatile simulation platform is developed. The results show that the simulation experimental platform provides a new solution for UAV telecontrol grasping. References | Related Articles | Metrics

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Stress and Deformation Performance of Deep Excavation with Asymmetrical Retaining Structures in Adjacent Surcharge GAO Yiwen, LI Mingguang, CHEN Jinjian 2020, 54 (6):  643-651.  doi: 10.16183/j.cnki.jsjtu.2018.293 Abstract ( 942 )   PDF (2788KB) ( 371 )   Save In this paper, the influence of surcharge on the stress and deformation of retaining structures with different embedded lengths at each side is investigated through numerical analysis and field measurement relying on a foundation pit project in Xiamen. Fast Lagrangian Analysis of Continua in 3 Dimensions (FLAC3D) software is used to establish the typical section analysis model of the deep excavation. Soil behaviors are modeled by a constitutive that considers degradation of stiffness with shear strain. Excavations with different embedding depths and surcharges are simulated. Structure deformation, as well as adjacent soil stress distribution, is analyzed in association with field measurement. It is found that surcharge not only increases the stress and deformation of the retaining structure near the surcharge, but also forces the top of other retaining structure to move away from deep excavation. This further results in the passive earth pressure outside the pit and increases the deflection of the retaining structure on both sides. When the embedded depth of that retaining structure is insufficient, the surcharge further increases the inclination of retaining structure, which may cause significant kicking deformation. However, the deformation and tilt of the far-surcharge side retaining structure can be limited by increasing the embedded depth of retaining structure near the surcharge. When the distance between the surcharge and the foundation pit is greater than half of excavation depth, the effect of surcharge on the side overload of far-side can be ignored. The numerical results are consistent with the field measurement and can provide reference for related projects. References | Related Articles | Metrics

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A Hybrid Evolutionary Algorithm for Identifying Multiple Alternatives in Model Updating KANG Juntao, ZHANG Yazhou, QIN Shiqiang 2020, 54 (6):  652-660.  doi: 10.16183/j.cnki.jsjtu.2018.270 Abstract ( 899 )   PDF (4599KB) ( 298 )   Save To make the result of finite element model updating more accord with the real structure, this paper converts to provide multiple alternatives, instead of offering just a single result. With those options, the policy makers can apply their working experience and consider field condition, which leads to more suitable decision. This paper proposes a hyper algorithm which combines the steady-state genetic algorithm and the gradient descent algorithm. A numerical simulation and an ASCE-Benchmark problem are employed to verify the ability to find multiple alternatives and optimization accuracy of the proposed method. The results show that the algorithm can optimize all the minimums and show a better accuracy compared to the steady-state genetic algorithm. After updating the frequency, error between the finite element model and real structure is significantly reduced. References | Related Articles | Metrics