三控制型核心筒悬挂结构振动台试验研究

提出了三控制型核心筒悬挂结构体系．进行了1:10的三控制型核心筒悬挂结构模型的模拟地震振动台试验研究．通过试验分析了该结构在3种地震波激励作用下的结构动力特性和地震反应,并利用结构分析软件SAP2000进行了结构的线性和非线性时程分析,计算结果与试验结果吻合较好,该结构具有良好的减震性能．

基于三次S型速度控制算法的移动机械臂末端振动研究

移动机械臂在实际工作环境中,受其自身柔性特征和外部因素的影响而引起机械臂末端的振动,而速度控制是实现机械臂末端抑振的有效手段之一。以UR10机械臂和Husky移动平台组成的移动机械臂为研究对象,针对梯形和S型速度控制算法的不足,提出一种三次S型速度控制算法,通过建立移动机械臂刚柔耦合动力学的理论和仿真模型得到移动机械臂末端的振动位移曲线和加速度变化曲线,验证了三次S型速度控制算法的正确性和抑振效果的有效性。

四管Buck-Boost变换器的改进型三模式变频软开关控制策略

四管Buck-Boost变换器(FSBB)具有无源元件少、开关管电压应力低、输入输出电压同极性、控制自由度多等优势,非常适用于宽输入电压的预调节器。该文对传统三模式控制的中间模式进行优化,提出一种改进型三模式控制策略,降低了导通损耗,提升了变换器工作效率。为进一步提高功率密度、降低高频硬开关带来的开关损耗和电磁干扰,该文提出变频控制策略,能够在全电压范围内实现软开关。分析表明,改进型三模式控制可优化变频范围,与变频软开关控制具有很好的契合度。在实验室研制了一台输入80~160V,输出125V/300W的原理样机,验证了所提控制策略的正确性,并通过效率对比和损耗分析证明所提控制策略有利于FSBB实现高效率和高功率密度。

三位两挡控制型多路开关阀的研制及应用

三位两挡控制型多路开关阀是一种新型多路开关阀,可通过同一联控制回路输出两种不同的工作流量,从而实现油缸的两种速度切换。此多路开关阀对控制不同油缸的速度具有更好的灵活性,可以满足不同油缸作业工况差异的需要;对控制同一油缸具有更好的调速性能,能够实现同一油缸作业过程中采用不同速度,如慢速启动、快速工作等;巧妙嵌入了进油旁路节流功能,在提升液压系统调速性能和灵活性的同时,减少了发热,提高了效率。

浅析静态三型控制系统

静态三型控制系统是美国通用电气公司电动轮驱动系统。该系统在矿山重型卡车中普遍应用。对安太堡矿685E&730E重型卡车的静态三型控制系统进行分析,并对一些特殊故障的原因及处理方法作简要论述。

Horizontal roof gap of backfill hydraulic support

For the backfill hydraulic support as the key equipment for achieving integration of backfilling and coal mining simultaneously in the practical process, its characteristics will directly influence the backfill body's compression ratio. Horizontal roof gap, as a key parameter of backfilling characteristics, may impact the backfilling effect from the aspects of control of roof subsidence in advance, support stress, backfilling process and the support design. Firstly, the reason why horizontal roof gap exists was analyzed and its definition, causes and connotation were introduced, then adopting the Pro/E 3D simulation software, three typical 3D entity models of backfill hydraulic supports were built, based on the influence of horizontal roof gap on backfilling effect, and influence rules of four factors, i.e. support height, suspension height, suspension angle and tamping angle, were emphatically analyzed on horizontal roof gap. The results indicate that, the four factors all have significant impacts on horizontal roof gap, but show differences in influence trend and degree, showing negative linear correlation, positive linear correlation, positive semi-parabolic correlation and negative semi-parabolic correlation, respectively. Four legs type is the most adaptive to the four factors, while six legs(II) type has the poorest adaptability, and the horizontal roof gap is small under large support height, small suspension height, small suspension angle and large tamping angle situation. By means of optimizing structure components and their positional relation and suspension height of backfill scrape conveyor in the process of support design and through controlling working face deployment, roof subsidence in advance, mining height and backfilling during engineering application, the horizontal roof gap is optimized. The research results can be served as theoretical basis for support design and guidance for backfill support to have better performance in backfilling.

FCS-MPC for four-switch three-phase AC-DC converters with DC-link capacitor voltage balancing

Due to the decrease in the number of switches for the four-switch three-phase alternating current-direct current(FSTP AC-DC)converter,it can easily lead to DC-link capacitor voltage imbalance and the system stability reduction.In order to solve these problems,a finite control set model predictive control(FCS-MPC)for FSTP AC-DC converters with DC-link capacitor voltage balancing is proposed.In this strategy,in order to facilitate calculation,theαβcoordinate system model is established and all voltage vectors are evaluated by establishing a cost function.During the whole process,phase locked loop(PLL)and complex modulation strategy are not required.In the new established cost function,the additional objective term of suppressing capacitor voltage fluctuation is to eliminate effectively the capacitor voltages oscillations and deviations and improve the system reliability.The simulation results show that the proposed strategy can keep the capacitor voltage balancing and has good dynamic and static performance.

Model predictive control of three-level active front-end converter with low switching frequency

In medium voltage-high power(MV-HP)applications,the high switching frequency of power converter will result in unnecessary energy losses,which directly affect efficiency.To resolve this issue,a novel finite control set-model predictive control(FCS-MPC)with low switching frequency for three-level neutral point clamped-active front-end converters(NPC-AFEs)is proposed.With this approach,the prediction model of three-level NPC-AFEs is established inα-βreference frame,and the control objective of low average switching frequency is introduced into a cost function.The proposed method not only achieves the desired control performance under low switching frequency,but also performs the efficient operation for the three-level NPC-AFEs.The simulation results are provided to verify the effectiveness of proposed control scheme.

Role based access control design using Triadic concept analysis

Role based access control is one of the widely used access control models.There are investigations in the literature that use knowledge representation mechanisms such as formal concept analysis(FCA),description logics,and Ontology for representing access control mechanism.However,while using FCA,investigations reported in the literature so far work on the logic that transforms the three dimensional access control matrix into dyadic formal contexts.This transformation is mainly to derive the formal concepts,lattice structure and implications to represent role hierarchy and constraints of RBAC.In this work,we propose a methodology that models RBAC using triadic FCA without transforming the triadic access control matrix into dyadic formal contexts.Our discussion is on two lines of inquiry.We present how triadic FCA can provide a suitable representation of RBAC policy and we demonstrate how this representation follows role hierarchy and constraints of RBAC on sample healthcare network available in the literature.

Virtual Dressing Room Application with Virtual Human Using Kinect Sensor

This study proposes a real time 3D virtual model controll and a virtual dressing room application to enable users to try virtual garments and shoes on in front of a virtual mirror. A virtual representation of the user appears in a virtual changing room and the user＇s hand motions select the clothes from a list on the screen. Afterwards, the selected virtual clothes appear on a humanoid model in the virtual mirror. For the purpose of aligning the 3D garments and shoes with the model, 3D locations of the joints are used for positioning, scaling and rotating. By using our developed algorithm, small, medium, large or xlarge garment size is selected automatically and this information is shown on the screen. Then, we apply skin color detection to handle the unwanted occlusions between the user and the model. To create a more realistic effect, the system takes into account different images of the clothes according to different human poses and movements. Optional mirror selection buttons make it possible to have multiple viewing angles on the model. Additionally, we developed an algorithm for matching up all motions between the model and garments. In this study, we benefit from the Microsoft Kinect SDK （software development kit） in order to follow the user＇s movements, coordinate the suitable clothe try-ons and provide depth sort effect to the human body and clothes. In order to use the rapid calculation attributes of game engines, we used unity 3D game engine.

Parametric Body Model Development

This study shows a novel three-dimensional （3D） parametric body model development using cross-section control and control algorithm retrieved from anthropometric survey. The 3D parametric body model was shaped into the most common body shape of the young Hong Kong female and be able to automatically change its critical body shape according to the user＇s critical body dimension inputs. The control algorithm controls the profile of the parametric model is retrieved from an anthropometric survey using 3D scanner to study the profile change of body and the relation between some critical body dimensions. Compared to the traditional anthropometric surveys, the 3D body scanner provides more accurate body dimension and information as well as new body shape measurements.

A modified predictive control strategy of three-phase grid-connected converters with optimized action time sequence

Due to the excellent dynamic performance,the Finite Control Set Model Predictive Control has been widely used in various types of converters.However,when Finite Control Set Model Predictive Control is adopted,the switching frequency of converters varies significantly with system operating conditions.Consequently,constant-frequency predictive control strategy has been proposed.Two active voltage vectors and a zero voltage vector are selected within each sampling period.The action time sequence is then calculated.Due to the unsymmetrical distribution of current variation rates around zero,the calculated value of the voltage-vector action time will turn up negative.According to common sense,the voltage-vector action time is greater than or equal to zero.The action time is normally forced to zero whenever a negative value is predicted,resulting in the control failure and performance deterioration.To solve this problem,this paper proposes modified strategy.The modified strategy examines the action time calculated out.When negative action time comes out,the modified strategy reselects the active voltage vector accordingly,instead of forcing the action time to be zero.Optimized action time sequence is further determined by minimizing the cost function.The effectiveness of the modified strategy is clearly verified by experimental tests,and analytical remarks are all founded in practical results.