Event-triggered-based finite-time cooperative path following control for underactuated multiple marine surface vehicles

This paper develops an event-triggered-based finite-time cooperative path following (CPF) control scheme for underactuated marine surface vehicles (MSVs) with model parameter uncertainties and unknown ocean disturbances. First, a finite-time extended state observer (FTESO) is proposed, in which the FTESO can estimate the velocities and compound disturbances in finite time. Then, the finite-time LOS guidance law based on velocity estimation values is designed to obtain the desired surge velocity and the desired yaw rate. In order to realize the cooperative control of multiple paths in finite time, the cooperative control law for the path variable is designed. In addition, the relative threshold event-triggered control (ETC) mechanism is incorporated into the formation control algorithm, and an event-triggered-based finite-time CPF controller is designed, which not only effectively reduces the update frequency of controller and the mechanical loss of actuator but also improves the control performance of system. Furthermore, by using homogeneous method, Lyapunov theory, and finite-time stability theory, it is proved that under the proposed finite-time CPF control scheme, the formation errors can converge to a small neighborhood around origin in finite time. Finally, numerical simulation results illustrate the effectiveness of the proposed control scheme.     

电渗结合透水模板成型混凝土表观质量试验

基于电渗均匀快速的排水特性,建立了电渗滤水试验模型,阐述电压加载初始时点、电压值、电渗历时及电极间距对混凝土成型效果的影响,并研究了结合透水模板垫层来改善电渗混凝土成型外观的方法.结果表明:电渗结合透水模板工艺排水可形成致密无孔洞混凝土表面,显著降低混凝土渗水透气性能,且可提高混凝土表面强度.     

透水模板性能对比研究

通过对几种透水模板及胶合板模板进行了对比试验,由对比试验和数据分析得出:透水模板能够有效地改善混凝土的表面状况,提高混凝土强度及耐久性,并且得出透水模板性能与相关数据的规律.     

基于容积粒子滤波的配电网动态状态估计

配电网中分布式电源的渗透率逐渐升高,为确保配电网安全稳定的运行,需要对配电网运行状态进行准确的感知。针对容积卡尔曼滤波(Cubature Kalman Filter, CKF)算法对强非线性非高斯系统滤波精度有限、标准粒子滤波(Particle Filter, PF)选取重要性密度函数不准确的问题,提出了基于容积粒子滤波(Cubature Particle Filter, CPF)的配电网动态状态估计模型：利用CKF算法设计PF的重要性密度函数。既克服了CKF算法要求噪声为高斯分布的限制又保留了PF算法的强抗干扰能力。仿真结果表明,在高斯噪声和非高斯噪声下,CPF算法比CKF算法滤波精度更高、更灵活。     

基于知识的部分匹配方法研究

针对Super提出的基于知识的部分匹配方法中,直接以坐标值描述部分轮廓的方法容易受形变或扭曲等干扰因素的影响,基于SIFT描述思想提出了一种新的BSIFT轮廓描述子,用于改进Super的坐标值描述方法。首先介绍了基于知识的部分匹配方法的基本思想、特点及实现过程;然后详细阐述了BSIFT描述子的构建方法;最后,通过实验验证了该方法具有更好的鲁棒性,部分匹配的准确度更高,匹配的部分轮廓更有意义。     

Evaluation of concrete mixes and mineral additions when used with controlled permeable formwork (CPF)

The influence of concrete mixes and commonly used mineral additions and their effects on the near surface performance of vertically cast concrete against controlled permeable formwork (CPF) are the focus of this study. Three grades of concrete (C25, C30 and C45) and mineral additives including GGBS and PFA have been tested for surface performance in situ with CPF. The various loadings were chosen to represent the minimum and maximum levels seen in standard industry practice. The range of tests used to characterise the near surface performance include subjective assessment of surface quality, surface hardness and surface tensile strength. Permeability studies of the liners after casting indicate that no excessive embedding of fine particles occurred irrespective of constituents used. Surface quality was dramatically improved in each case and changes to surface colour through densification were quantified. Near surface performance studies indicated a significant improvement for all systems studied.     

An Investigation into the critical factors affecting the performance of composite controlled permeable formwork liners: Part I – Drainage medium

The critical elements associated with a CPF drainage medium and their associated effects on the near surface performance of vertically cast concrete slabs are the focus of this study. A range of board absorption levels, textured features and texture depth are investigated using a Taguchi orthogonal array approach. A permeable polypropylene filter layer was used in conjunction with the various drainage mediums. Statistical software was utilised to determine significant variables as a function of the near surface performance. The range of tests used to characterise the surface performance of the various drainage mediums include surface roughness, surface hardness, surface tensile strength and water absorption. Results are compared to a control sample which was cast against impermeable plywood formwork. All drainage medium permutations showed similar evidence of water/cement ratio reduction at the near surface region of the concrete slab. Surface quality was analysed using quantitative methods and showed significant improvements for all systems over the control. The results for the systems studied indicate that the features of a drainage medium are not critical to the functionality of a CPF liner to reduce the near surface w/c ratio. In fact, it is indicated that the absence of a drainage medium has the same enhancement in near surface concrete slab properties as that of a complex structure when compared to the control sample.     

可控制渗透性模板内衬对提高混凝土表层性能的研究

可控制渗透性模板内衬(CPF)是一种通过改变混凝土自身的表层性能而提高混凝土耐久性的技术,尽管在欧美和中东地区广泛使用,但由于其价格昂贵,其在国内的推广受到阻碍.通过对国内研发的一种可控制渗透性内衬模板(CPF)进行的空气渗透性与表层水吸附、抗压强度回弹法检测,从表层渗透性和表层强度两个方面对普通混凝土面和采用CPF的混凝土面进行了对比分析,同时从经济角度对可控制混凝土内衬模板(CPF)的重复性使用进行了研究.     

失稳故障支路拟裕度评估及控制的虚拟支路法

为评估失稳故障支路的严重程度及解决故障后系统失去潮流可行解的问题,提出了失稳故障支路拟裕度评估及控制的虚拟支路法。该方法将待切除的故障支路用一条含参数的虚拟支路置换,使虚拟支路开断问题转换为故障支路两端点注入功率增长的裕度问题,并用拟裕度大小评估故障支路的严重程度。算法利用最小控制代价的过程控制法,使虚拟支路完全切除后系统获得可行潮流解;故障后优化控制是在可行解上优化系统,以满足稳定裕度要求。通过IEEE算例验证了方法的可行性和有效性。     

缓解电压紧张的出力调整策略及算法

通过分析负荷节点和发电机节点参与因子的物理涵义,提出将参与因子应用于发电机出力调整方案以缓解电压紧张。该方法通过对未化简的雅可比矩阵进行模态分析求得参与因子,用参与因子指导发电机有功功率再调整;采用连续潮流法计算调整过程中系统运行状态的变化,以无功网损为间接指示指标来监视系统电压态势的改善情况。IEEE 39节点系统的仿真结果验证了所提出的考虑机组参与因子的发电再调度方法可以一定程度地改善系统的电压态势,提高电压稳定裕度。