Key Engineering Materials Vol. 620

Abstract: In the study of the dynamic characteristics of the system, should pay attention to the influence on the dynamic performance of the system mode change. Mode change is closely related with mutation phenomena of mode localization process, in the natural frequency with the change of parameters, with a large curvature are quickly turned to separate the two natural frequency curve in the close position. Mode change will lead to the drastic changes in the natural frequency and modal energy, the variation of system parameters is also the location of the influence degree mutation position. Based on the modal characteristics of unique two stage power branch double wide helical planetary composite transmission system, studied the mode change phenomena, reveal the modal system changes.

Abstract: In this paper, dynamic model of two stage power branch double wide helical gear planetary drive system based on complex, in-depth study of the natural vibration characteristic. Starting from the first star and second planetary gear around the sun wheel non equidistant arrangement in the respective gear train, calculating modal analysis of characteristics of the system, so as to understand the mechanism of the system vibration, to provide theoretical guidance for the design of underwater device two power branch double wide helical planetary composite transmission system. At the same time to improve the dynamic characteristics of the device structure of underwater engineering significance.

Abstract: Rough set has been applied into the conceptual design of products in order to choose the structure correct project rapidly according to the users’ demand. First of all, using rough set, the relation between features has been found out to set up the simple decision-making table and get the regulations of the project decision-making. According to the decision table, the redundant project is deleted to choose the correct project rapidly in the stage of conceptual design. The example of the rapid design of an astronomical doom shows this method is more objective and concise than those conventional methods and the processing speed is much faster.

Abstract: Focusing on the On-Orbit Servicing technology, a novel automatic autonomous probe-cone docking mechanism used for microsatellite docking is proposed. The structure of this mini docking mechanism is provided, and a virtual prototype model of the mini-type universal docking system is established by using MATLAB software. The simplified dynamic analysis model during the capture process is established. The dynamic characteristic analysis of the capturing process is completed to research the influence of the key parameter, and the simulation results meet the designs demand of mini-type universal autonomous docking mechanism.

Abstract: A finite element model of high-strength rectangular section steel tube in rotary-draw bending is established to study the stress and strain in the bending process. Based on control variate method, this paper analyzes the influence laws of three geometric parameters on rotary-draw bending. The results show that bending radius is the most important factor, forming property increases significantly with the increase of bending radius, the trends of cracking and wrinkling are all decreased. The thickness of wall has influence on the strain of inwall, thinner tube may cause crack and wrinkle. Fillet radius has no effect on ektexine, the strain of inwall decreases slightly with the increase of fillet radius.

Abstract: In the design process of lightweight harmonic drive system, low-frequency resonance generally affects controller design, and restricts system servo performance. In the design stage of system, it has great significance that the resonant frequencies and dynamic performances could be predicted. This paper presents a modeling method of harmonic drive system which has low-frequency resonance. Takes an uniaxial harmonic drive system as example to describe the implementation process of the modeling method. The dynamics model of harmonic drive system has been built. Using Ansys, Recurdyn and Matlab, the rigid-flexible coupling dynamics simulation model of system has been established. The simulation model analysis and the actual system experiment have been done respectively. Comparing the simulation and experiment results, it shows that: the open-loop time-frequency domain characteristics and the structural modals of simulation and experiment results are basically consistent. Using this method, the resonant frequency and dynamic performance of harmonic drive system can be predicted in the system design stage, and improve design efficiency.

Abstract: In this paper, Based on the original operating parameters of the Coke tower which works in the PetroChina Dushanzi Petrochemical Corp, and the skirt - tower body support section as the research object, using stochastic finite element method and Monte Carlo method, 60 groups of pressure, temperature are extracted randomly as variables in the original operating parameters curve, the change of the distribution function of temperature and pressure are analysed and established, and 200 groups of random pressure, temperature variable array is produced based on this; The maximum stress in dangerous section corresponding to each array is obtained by using the finite element method, the stress distribution of the probability density function is obtained; The strength reliability analysis of dangerous section is completed by using stress strength interference model and combining with the material intensity distribution function. The analysis results provide the basis for the tower life prediction and predicting repair, and provide a method for reliability analysis of the equipment whose large size is hard to measure and the working environment is hard.

Abstract: Large size hydrostatic bearing is the core component of heavy CNC equipment. The influence of pressure, heating and running time can reduce film thickness during operation. This will directly affect machining accuracy and operation reliability of the entire machine. Aiming at the problem of influence of rotational velocity on carrying capacity of heavy hydrostatic bearing, use finite volume method (FVM) to simulate gap film pressure field of heavy hydrostatic bearing with Constant Flow and study pressure field distribution law on the conditions of the different rotational velocity and same cavity depth, oil cavity area, then optimize oil cavity structure. Results show that, pressure field distribution law of the different rotational velocity is basically identical, but its carrying capacity is different. From the relation curve of the pressure and rotational velocity can be seen, because of the dynamic pressure of existence, along with the increase of rotational velocity, carrying capacity gradually. The study is of vital theoretical significance for the improvement of machining accuracy of numerical control machine and the entire CNC equipment and provides valuable theoretical basis for the design of hydrostatic guide rail in engineering practice.

Abstract: According to the poor tracking accuracy of periodic signals for continuous rotary electro-hydraulic servo motor, the mathematic model of the electro-hydraulic position servo system of the continuous rotary motor was established, a composite control strategy combining with proportion controller and adaptive zero phase error tracking controller was designed. The working principle of composite strategy was given, and the composite strategy was verified on Co-simulation of MATLAB and AMESim platform. The simulation result shows that the amplitude attenuation and phase delay of the tracking curve which excitated by the sinusoidal signal 0.5degree and 10Hz for continuous rotary motor is less than 1.2% and 1.08°respectively, and the efficiency of the composite controller is verified through simulation.

Abstract: Aiming at the overshoot problem of electro-hydraulic position servo system used in the process of railway rescue crane hydraulic automatic leveling, and based on its characteristics such as big output power, high control accuracy, quick response speed, et al, this paper established the linear mathematical model of railway rescue crane electro-hydraulic automatic leveling system, besides, the fractional order PID control method was proposed based on the oustaloup digital filter algorithm and the working principle of fractional order PID control method was given, and then the fractional order PID controller was designed. In order to verify the effectiveness of the proposed control strategy, the MATLAB/Simulink simulation software was used. The simulation results show that the fractional order PID controller improved the speed of electro-hydraulic servo system unit step response and the capacity of resisting disturbance compared to traditional integer order PID controller, besides it can ensure the response without overshoot at the same time, so it meets the requirements for rapidity and no overshoot of railway rescue crane hydraulic automatic leveling system very well.