Advanced Materials Research Vols. 479-481

Abstract: Compared with a traditional single-container overhead crane, the double-container overhead crane is a type of new efficient container stevedoring machinery, however, it is actually a complicated nonlinear system. In this brief, both the kinematic and dynamic characteristics concerning the double-container crane are investigated, and then an accurate dynamic model of the underactuated double-container overhead crane is established by utilizing Euler-Lagrange's method. Not only is the variation of the rope and payloads, but also some uncertainties such as mechanical frictions and air-resistance in the environment are taken into account in modeling. Simulation results show the validity of the established double-container overhead crane model.

Abstract: In this paper a new time varying multivariate Prony (TVM-Prony) method is put forward to identify modal parameters of time varying (TV) multiple-degree-of-freedom systems from measured vibration responses. The proposed method is based on the classical Prony method that is often used to identify modal parameters of linear time invariant systems. The main advantage of the propose approach is that it can analyze multi-dimensional nonstationary signals simultaneously. A modified recursive least square method based on the traditional one is presented to determine the TV coefficient matrices of the multivariate parametric model established in the proposed method. The efficiency and accuracy of the identification approach is demonstrated by a numerical example, in which a TV mass-string system with three-degree-of-freedom is investigated. Satisfied results are obtained.

Abstract: Beam double-well pump unit as a new generation of pumping unit is currently used in mechanical oil production. However, due to a number of pumping system parameters, the conventional design can not achieve the optimal pumping system parameters Using MATLAB simulation optimization algorithms, simulates the structural parameters, rod speed, rod acceleration, rod load, crank torque factors and gear’s crank shaft net torque of the double horse head double-well pumping unit, achieving optimal design of double horse head double-well pumping system, with the existing conventional design of double horse head double-well pumping unit, double horse head double-well pumping unit has a great improving than conventional pumping unit in motion and power dynamic characteristics.

Abstract: In this paper, we present the modeling and kinematics simulation of a six-DOF segment erector for tunnel boring machine (TBM), which is performed in the virtual prototype platform. The 3D virtual assembling model of a tunnel segment erector is built based on Pro/E software according to its design parameters such as structure and size. After the interference inspection, the model is imported into ADAMS through the interface module of Mech/Pro. The model is simplified and optimized reasonably and various constraints are applied under variety working conditions. The results of simulation show that the design has six degrees of freedom movement capacity which meets the design requirements. At the same time the kinematics characteristics of each part along three different directions are obtained and they will provide some references for the further optimal design.

Abstract: Inertial device is an important part of the fuze system. It is a key mechanism to keep safety at ordinary times and period after launch. Therefore, the dynamic characteristics of the inertial device during falling or launching environments are very important. The paper make a study of the dynamic characteristics of the MEMS inertial device used in the fuze of the ammunition under the two kind of inertial acceleration by simulation. The simulation result shows that the MEMS inertial device can ensure the safety of fuze and ammunition.

Abstract: On the basis of flexible multi-body system dynamics theory, we built flexible multi-body system dynamics models which include a backlash, and to a slider-crank mechanism as the research object, we made a preliminary study on the effect on the flexible components and the backlash of the kinematic pair on mechanical system dynamics characteristics. To consider the backlash of the kinematic pair and component of flexible space can show a preliminary research on the dynamic simulation, and focus on the backlash, friction and gravity field to influence in the dynamic characteristics of the system. The simulation results show that, due to the existence of backlash made the two components frequent collision in the process of the stretching, clearance, flexible and friction are closed, make the system nonlinear characteristics increased.

Abstract: In this paper, we investigate first integrals of discrete dynamical systems with the variational principle of Jourdain. The operators of discrete transformation are introduced for the system. Based on the Jourdainian generalized variational formula, we derive the discrete analog of Noether-type identity, and then we obtain the first integrals of discrete dynamical system. We discuss an example to illustrate these results.

Abstract: According to engineering requirements, structure of multibody systems would change and lead to obvious modifications in dynamics model obtained by traditional methods. In this paper, an existing method for rigid body systems with changing structures is extended to systems with flexible appendages, which is more common in engineering. Application of the new generalized approach to a typical 4-body system is actualized. Numerical simulation is carried out and results are the same as theoretical analysis, which indicate the availability and applicability of the new approach.

Abstract: According to the characteristics of the low efficiency of drainage equipment for coal bed methane wells, we analyzed and calculated the coefficient of fullness, plunger stroke loss, leakage and volume factor, which affect pump efficiency. After analyzing the displacement loss caused by various factors, we obtained coefficient of fullness of the most influential factor on the pump efficiency. By analyzing the change relationship among the coefficient of fullness and clearance space, gas fluid ratio, compression ratio and pumping speed, we found shrinking clearance space and reducing gas fluid ratio, compression ratio and pumping speed can increase coefficient of fullness, and we presented several improvement measures to improve pump efficiency. These measures will enable coal bed methane wells production more stable and efficient.

Abstract: Based on a palletizing robot, its kineto-static model is created via d'alembert's principle and dynamic statics method. The force of key components with its posture change will be obtained by use of the Matlab. This model is applicable to dynamic analysis on the robots with similar configuration and the results based on the parameter variation is also applicable to this kind of robot’s design, checking and kinetic control.