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Chen H.,Jiangnan University | Cao Y.,Jiangnan University | Cao Y.,Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology | Cao Y.,Shanghai JiaoTong University | Qin Y.,Jiangnan University
Zhongguo Jixie Gongcheng/China Mechanical Engineering

Based on the screw theory, a method of structural synthesis of fully-decoupled and fully-isotropic one-translational and one-rotational (1T1R) parallel mechanisms was proposed, the parallel mechanism adopted with driven-chain whose output link was provided by independent motors. Firstly, according to the prescribed characteristics of each mechanism limb, a methodology was proposed that made use of the screw theory to synthesize desired forms for both of the direct and the inverse Jacobian matrices. Secondly, according to the features both of the direct and the inverse Jacobian matrices, the actuation screws, actuated screws and mobile un-actuated screws of every limb were confirmed at first based on the reciprocal screw theory, and the leg structure was obtained. Then the structural synthesis of each kinematic chain for fully-isotropic 1T1R parallel robotic manipulators was performed in the light of different connectivities of the limbs. Finally, the anticipant manipulators were synthesized by using the rules and regulations of fully-isotropic parallel mechanisms and a lot of parallel mechanisms were obtained. Many of fully-decoupled and fully-isotropic 1T1R parallel mechanisms were synthesized by using the above method. Kinematical analysis about one of manipulators designed here show that the method is reasonable and correct. © 2016, China Mechanical Engineering Magazine Office. All right reserved. Source

Li H.-W.,Jiangnan University | Wang J.,Jiangnan University | Wang J.,Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology
Journal of Vibroengineering

A novel method combining max-min approach (MMA) with energy method is proposed for the derivation of the approximate analytical solution for shock response of the strong nonlinear system. MMA is used to evaluate the governing differential equation with nonlinearity terms and to obtain the approximate solution. The maximum shock response displacement of the system is obtained by energy method, and then the approximation solution by MMA is corrected. Three examples are given to illustrate the validity of the method. It is shown that the corrected MMA method always lead to a better approximate solution for different kinds of nonlinear problems. The results provides a new simple but effective method for the analysis of shock response of strong nonlinear problems. © 2015, JVE INTERNATIONAL LTD. Source

Sun H.,Jiangnan University | Sun H.,Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology | Li K.,Jiangnan University | Li K.,Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology | And 4 more authors.
Mathematical Problems in Engineering

The condition diagnosis of rotating machinery depends largely on the feature analysis of vibration signals measured for the condition diagnosis. However, the signals measured from rotating machinery usually are nonstationary and nonlinear and contain noise. The useful fault features are hidden in the heavy background noise. In this paper, a novel fault diagnosis method for rotating machinery based on multiwavelet adaptive threshold denoising and mutation particle swarm optimization (MPSO) is proposed. Geronimo, Hardin, and Massopust (GHM) multiwavelet is employed for extracting weak fault features under background noise, and the method of adaptively selecting appropriate threshold for multiwavelet with energy ratio of multiwavelet coefficient is presented. The six nondimensional symptom parameters (SPs) in the frequency domain are defined to reflect the features of the vibration signals measured in each state. Detection index (DI) using statistical theory has been also defined to evaluate the sensitiveness of SP for condition diagnosis. MPSO algorithm with adaptive inertia weight adjustment and particle mutation is proposed for condition identification. MPSO algorithm effectively solves local optimum and premature convergence problems of conventional particle swarm optimization (PSO) algorithm. It can provide a more accurate estimate on fault diagnosis. Practical examples of fault diagnosis for rolling element bearings are given to verify the effectiveness of the proposed method. © 2014 Hao Sun et al. Source

Chen H.-W.,Jiangnan University | Chen H.-W.,Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology | Zhang Q.-J.,Jiangnan University | Zhang Q.-J.,Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology
Shock and Vibration

This paper studies dynamics of a three-column centrifuge and tries to design a ball balancer to suppress its vibration and increase its operating speed. At first, two vibration models with and without the balancer are introduced. Then modal analysis of the centrifuge itself is carried out with two isolated natural frequency groups identified. Centrifugal forces acting on the system at the steady state are analyzed and a tip-over phenomenon is discovered and validated through simulations. A ball balancer is adopted in the centrifuge and several potential tip-over phenomena related to the balancer are studied. At last, a comparison between dynamics of the centrifuge before and after the balancer is installed is made with benefits and side effects of the balancer presented. © 2016 Hai-Wei Chen and Qiu-Ju Zhang. Source

Lu L.-X.,Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology | Lu L.-X.,Jiangnan University | Chen X.-Q.,Jiangnan University | Wang J.,Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology | Wang J.,Jiangnan University
Packaging Technology and Science

Ventilated packaging is widely used in the forced-air precooling practice for horticultural produce. Fresh fruits are living organisms which are sensitive to temperature in turn related to airflow and heat transfer inside package. In this study, a transient mathematical model considering heat of respiration and evaporation is developed to predict the thermal response of tray-layered fruits in ventilated packages during forced-air precooling. Specifically, the heat source is combined with the energy conservation equation and loaded into numerical solution by User Defined Function (UDF). Temperature profiles of three variously distributed circular and oblong vents in three different patterns (spaced, paralleled and crossed stacking) are simulated, separately. The results show that the heat source affects fruit cooling process, and the layered fruit in paralleled stacking pattern tends to be cooled better than others. Furthermore, the results indicate that vertical oblong vent could improve the longitudinal and lateral airflow, while non-central vent design could greatly improve the overall cooling performance. Definitely a triangular distribution of three circular vents was superior to laterally distributed centre vents with 66.5% higher uniformity and 2.5C lower of the highest temperature. Compared with the three identical vertical oblong vent conditions, vent design with one hand hole and two side vertical oblong vents can be cooled more uniformly with an increase of 6.5%. It is revealed that vents with large major-to-minor axis ratio could be applied to balance airflow and ease cooling differences for a rapid but uniform cooling. Experimental validations were performed for Sim2, Sim4 and Sim6, Sim8, Sim9, and good agreement was obtained considering the five vent conditions with the error less than 3.5C but coordinated later (within the limits of the experimental uncertainty).Thus the numerical model can be used to predict and optimize temperature distribution within precooling packages. © 2016 John Wiley & Sons, Ltd. Source

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