运用Pro/E构建运动分析模型的几个问题

对运用PRO/E创建运动分析模型提出了几个应注意的问题。

微型球形压缩机的几何模型与运动学分析

球形压缩机是一种新的微小型结构容积式压缩机,对其进行运动学分析,建立完善的几何模型具有重要意义。基于微型球形压缩机的结构特点,以空间向量的方式表示活塞、转盘、销轴等部件的运动并进行运动学分析,通过不同坐标系下的空间坐标变换,得到不同时刻压缩机各部件的相对位置,进而建立几何学模型,在此基础上,讨论了活塞偏置角对行程容积的影响以及泄漏线长度计算等。以冰箱用微型球形压缩机为例,讨论了结构参数的选择和计算。

面向虚拟环境的CAD装配模型向运动模型的转换

探讨了在虚拟环境中进行复杂机械产品运动分析时CAD装配模型向机构模型转化的信息识别。首先在总结CAD装配系统提供的各种装配约束类型与其相对应的运动几何元素基础上,给出了平移和旋转自由度的归约规则,根据简单运动副约束与运动自由度及运动几何元素的映射关系,实现从零部件装配信息到运动分析用的构件和简单运动副信息的转换。

汽车电动侧开门系统运动分析与研究

文章主要从电动侧开门的工作原理入手,进行系统运动学分析,建立数学模型,并基于MATLAB和UG Simulation进行仿真计算,得出侧开门电动开关过程中执行器输出位移与霍尔数(或开门角度)之间的关系、执行器电机转速与侧开门角速度之间的关系、速度控制算法应用以及MATLAB/UG仿真对比和误差分析。

基于有限元的滚动汇流环疲劳寿命分析

针对滚动汇流环测试寿命实验周期长的问题,提出一种基于有限元的疲劳寿命分析方法。设计一种鼓风机滚动汇流环装置;建立运动学分析模型及接触电阻模型,明确各构件间的运动关系及接触电阻与辐条式弹性环压缩量之间的关系;对辐条式弹性环进行瞬态仿真分析,得到不同压缩量下应力随时间变化曲线,将瞬态分析结果导入疲劳分析模块,结合S-N曲线与Goodman平均应力修正方法,计算辐条式弹性环的疲劳寿命。结果表明:当辐条式弹性环压缩量为0.8 mm时,能够满足滚动汇流环疲劳寿命设计指标及电接触性能需求。

曲柄摇杆式飞剪剪刃间隙研究

首先利用闭环矢量方程建立某厂带钢连续处理机组上的曲柄摇杆式飞剪运动学分析数学模型,对剪刃端点运动坐标进行求解,在此基础上建立了上下剪刃在剪切过程中的剪刃间隙求解方程,为飞剪剪刃间隙补偿提供了理论依据。

Simulation and Analysis of Fiber Motion in Condensing Zone of Compact Spinning with Lattice Apron

To get fiber motion in condensing zone of compact spinning,velocity of this area is achieved by simulation,and then a bead-elastic rod fiber model is established.Based on simulation and dynamic analysis on this zone,governing equations are constructed and Runge-Kutta approach is used.Lastly,trajectories of fibers are calculated by specially designed Matlab procedure according to the principles mentioned above.Results show that fiber motions at different initial positions are different;X-axis velocity component makes fibers gathering on sides of suction slot;Y-axis airflow gets fibers gradually close and then stick to the surface of lattice apron.Fiber motions also reflect that the compact spinning process in condensing zone can be divided into three parts:fast convergence zone,adjustment convergence zone,and steady convergence zone.

A new linearly-combined bi-exponential model for kinetic analysis of the isometric relaxation process of Bufo gastrocnemius under electric stimulation in vitro

There was a slow-relaxing tail of skeletal muscles in vitro upon the inhibition of Ca2+-pump by cyclopiazonic acid (CPA). Herein, a new linearly-combined bi-exponential model to resolve this slow-relaxing tail from the fast-relaxing phase was investigated for kinetic analysis of the isometric relaxation process of Bufo gastrocnemius in vitro, in comparison to the single exponential model and the classical bi-exponential model. During repetitive stimulations at a 2-s interval by square pulses of a 2-ms duration at 12 V direct currency (DC), the isometric tension of Bufo gastrocnemius was recorded at 100 Hz. The relaxation curve with tensions falling from 90% of the peak to the 15th datum before next stimulation was analyzed by three exponential models using a program in MATLAB 6.5. Both the goodness of fit and the distribution of the residuals for the best fitting sup- ported the comparable validity of this new bi-exponential model for kinetic analysis of the relaxation process of the control muscles. After CPA treatment, however, this new bi-exponential model showed an obvious statistical superiority for kinetic analysis of the muscle relaxation process, and it gave the estimated rest tension consistent to that by experimentation, whereas both the classical bi-exponential model and the single exponential model gave biased rest tensions. Moreover, after the treatment of muscles by CPA, both the single exponential model and the classical bi-exponential model yielded lowered relaxation rates, nevertheless, this new bi-exponential model had relaxation rates of negligible changes except much higher rest tensions. These results suggest that this novel linearly-combined bi-exponential model is desirable for kinetic analysis of the relaxation process of muscles with altered Ca2+-pumping activity.

Comparison of wrist motion classification methods using surface electromyogram

The Gaussian mixture model (GMM), k-nearest neighbor (k-NN), quadratic discriminant analysis (QDA), and linear discriminant analysis (LDA) were compared to classify wrist motions using surface electromyogram (EMG). Effect of feature selection in EMG signal processing was also verified by comparing classification accuracy of each feature, and the enhancement of classification accuracy by normalization was confirmed. EMG signals were acquired from two electrodes placed on the forearm of twenty eight healthy subjects and used for recognition of wrist motion. Features were extracted from the obtained EMG signals in the time domain and were applied to classification methods. The difference absolute mean value (DAMV), difference absolute standard deviation value (DASDV), mean absolute value (MAV), root mean square (RMS) were used for composing 16 double features which were combined of two channels. In the classification methods, the highest accuracy of classification showed in the GMM. The most effective combination of classification method and double feature was (MAV, DAMV) of GMM and its classification accuracy was 96.85%. The results of normalization were better than those of non-normalization in GMM, k-NN, and LDA.

Novel kinetic model for the simulation analysis of the butanol productivity of Clostridium acetobutylicum ATCC 824 under different reactor configurations

Acetone–butanol–ethanol(ABE)fermentation process can be exploited for the generation of butanol as biofuel,however it does need to overcome its low volumetric solvent productivity before it can commercially compete with fossil fuel technologies.In this regard,mathematical modelling and simulation analysis are tools that can serve as the base for process engineering development of biological systems.In this work,a novel phenomenological kinetic model of Clostridium acetobutylicum ATCC 824 was considered as a benchmark system to evaluate the behaviour of an ABE fermentation under different process configurations using both free and immobilized cells:single stage batch operation,fed-batch,single stage Continuous Stirred Tank Reactor(CSTR)and multistage CSTRs with and without biomass recirculation.The proposed model achieved a linear correlation index r^2=0.9952 and r^2=0.9710 over experimental data for free and immobilized cells respectively.The predicted maximum butanol concentration and productivity obtained were 13.08 g·L^(-1)and 1.9620 g·L^(-1)·h^(-1)respectively,which represents an increase of 1.01%and 990%versus the currently developed industrial scale process reported currently into the literature.These results provide a reliable platform for the design and optimization of the ABE fermentation system and showcase the adequate predictive nature of the proposed model.

Simulation and modal analysis of the uplift device of a sugarcane harvester using virtual prototype technology

A three-dimensional model of the uplift device of a sugarcane harvester was built up in Pro/Engineer. Simulation and evaluation of its motional and dynamic performance were performed with the automatic dynamic analysis of mechanical system (ADAMS). ANSYS program was applied to the structural analysis of the model. A finite element analytic model was built up with the bottom-up methodology and was meshed. The default Block Lanczos method was used to work out the native frequency. The results indicate that the five lower modes-the transpotaion wheel, the left holding device, the right holding device, the left cutter disk, and the right cutter disk- and displacement of vibratory type only slightly affect the process of sugarcane harvester and harvesting quality. So it is advisable that the optimization of the static intensity other than the dynamic stiffness of uplift device be executed.

HELICITY ANALYSIS FOR HIGH-WIND AND UNCOMMON RAINSTORM PROCESSES OVER YUNNAN IN EARLY SUMMER

Helicity was applied to analyze several high-wind and rainstorm processes, which occurred from May to June, 2001 over Yunnan in early summer. The results of diagnostic analyses show that the rainstorm occurs in the area in which hp is positive at 700 hPa and energy is unstable. The change of helicity can reflect the movement and development of synoptic system and the position and intensity of the rainstorm. The value of hp is a negative center at the upper level and a positive at the lower level over the rainstorm position; moreover it can reflect the characteristics of vertical distribution and rotational motion.

Validation of a Marker Model for Gait Analysis with Wearable Exoskeletons

The aim of the present study was to develop and validate a new marker model for optoelectronic systems adapted to wearable devices, in order to have an analysis tool for kinematic gait evaluation of reproduced patterns by exoskeletons. The marker model has a total of 36 retro-reflective markers attached bilaterally to anatomical landmarks during the static measures （without exoskeleton） and 28 markers at the dynamics measures （with exoskeleton）. The main difference between others kinematic models and the described adapted model was the placement of the three markers in the back thigh and the other three in the back calf, what allowed removing the hip, thigh, knee, tibia and ankle markers. The proposed adapted marker model could be an effective tool to validate the joint movement and velocities of those wearable exoskeletons that at present have been developing.

滚筒式飞剪刀刃最优原始侧隙

滚筒式飞剪刀刃原始侧隙选取过大,不容易剪断带钢;选取过小,则存在刀刃干涉的可能性。因此,应合理选择刀刃原始侧隙。利用闭环矢量方程建立了滚筒式飞剪运动学分析模型,推导出上下刀刃法向侧隙求解方程,得出避免上下刀刃干涉的必要条件,在此基础上提出刀刃最优原始侧隙的计算方法。

A new LS+AR model with additional error correction for polar motion forecast

Polar motion depicts the slow changes in the locations of the poles due to the earth's internal instantaneous axis of rotation. The LS+AR model is recognized as one of the best models for polar motion prediction.Through statistical analysis of the time series of the LS+AR model's short-term prediction residuals,we found that there is a good correlation of model prediction residuals between adjacent terms.These indicate that the preceding model prediction residuals and experiential adjustment matrixes can be used to correct the next prediction results,thereby forming a new LS+AR model with additional error correction that applies to polar motion prediction.Simulated predictions using this new model revealed that the proposed method can improve the accuracy and reliability of polar motion prediction.In fact,the accuracies of ultra short-term and short-term predictions using the new model were equal to the international best level at present.