“电工学实验”混合教学模式的探索与实践

在大类培养改革背景下,基于“电工学实验”开放式实践教学体系现状进行了“电工学实验”混合教学模式的研究,建立了“微课”资源并通过新型教学平台进行推送,确立了完备的混合教学模式应用机制并在部分专业进行了试点,通过分析试点调查数据得出混合教学模式具有在实验教学中提高学生学习效率、激发学生学习动力、促进学生个性发展、培养学生实践应用能力的优势,是落实创新应用型人才培养目标的重要举措。     

Motion control of underactuated linkage robot based on gymnastic skill

In this paper, a reproduction of a swing‐up and a giant swing motion of underactuated robots based on technique of the horizontal bar gymnast is discussed with focusing on an equivalent center of mass (ECM) of underactuated robots and the gymnast. At first, the behaviors of the ECM of the gymnast (ECMG) are analyzed by using a motion capturing technique and an efficient motion of the ECMG for the swing‐up and for the giant swing motion are identified from analysis results, respectively. Next, a partial linearization method, which can realize that the ECM of the Acrobot (ECMA) replicates this efficient motion, is designed and reproduces the underactuated robots the swing‐up and giant swing motion like the gymnast. Finally, an effectiveness of the proposed controller is shown by numerical simulations.     

Topology optimization for crashworthiness of thin-walled structures under axial crash considering nonlinear plastic buckling and locations of plastic hinges

Although topology optimization is established for linear static problems, more effort is required for solving nonlinear plastic problems. A new topology optimization approach with equivalent static loads (ESLs) is suggested to find the optimum topologies and locations of plastic hinges of thin-walled crash boxes by considering crash-induced deformation, the main crash energy-absorbing mechanism. Together with finite element method crashworthiness analyses, considering all nonlinearities with rate-dependent plasticity, the method was developed using an appropriate time-incremental scheme of ESLs without removing any high values of loads. Analyses show that the crash boxes with optimum topologies have energy-absorbing capabilities equivalent to the original structure. The proposed method is evaluated for two crashes: a crash box at low speed and a double cell subjected to high-speed collision. The results indicate that this method captures nonlinear crushing behaviours and accurate locations of plastic hinges where, if proper reinforcements are made, energy absorption can be enhanced.     

Generation-expansion planning with linearized primary frequency response constraints

As renewable energy resources increasingly penetrate the electric grid, the inertia capability of power systems has become a developmental bottleneck. Nevertheless, the importance of primary frequency response (PFR) when making generation-expansion plans has been largely ignored. In this paper, we propose an optimal generation-expansion planning framework for wind and thermal power plants that takes PFR into account. The model is based on the frequency equivalent model. It includes investment, startup/shutdown, and typical operating costs for both thermal and renewable generators. The linearization constraints of PFR are derived theoretically. Case studies based on the modified IEEE 39-bus system demonstrate the efficiency and effectiveness of the proposed method. Compared with methods that ignore PFR, the method proposed in this paper can effectively reduce the cost of the entire planning and operation cycle, improving the accommodation rate of renewable energy.     

基于一种改进逐点比较插补法的激光打标机控制加工算法

在激光打标系统中,逐点比较插补法是一种普遍使用的算法。这种算法在控制激光运动轨迹和对图像轨迹的拟合过程中,起到极其重要的作用。由于逐点比较插补法具有运算直观,脉冲输出均匀,调节方便等特点,所以是一种较为适合打标机系统应用的插补算法。但是传统的逐点比较插补算法存在精度低和速度慢等问题。为了改善该算法的性能,对传统逐点比较插补算法进行了改进,并进行了计算和模拟仿真。结果表明改进比较插补算法在精度和速度上都有明显提高。     

An energy‐dissipating approach for adjacent retrofitted structures

The approach of positioning energy dissipaters between adjacent structures can effectively prevent the collision of two adjacent buildings. For adjacent retrofitted structures, an effective strengthening approach that involves implementing energy‐dissipation measures both between and within buildings is proposed. This paper is based on the actual Shanghai ShiMao International Plaza. To avoid having to strengthen most of the structural members, the strengthening measure of energy dissipation is selected because of its construction cost and time constraints. This approach involves replacing several dampers between the adjacent structures and adding viscous damping walls in the retrofitted structure to reduce the seismic response of the retrofitted structure back to the original level. Additionally, a practical calculating method for the equivalent additional damping ratio for the adjacent structures connected by energy dissipaters is proposed. The results show that the effect of energy dissipation in the retrofitted structure is prominent and that the goal of indirect strengthening is achieved. The strengthening approach of energy dissipation and the calculating method of the equivalent additional damping ratio for adjacent structures provide a reference for similar engineering designs.     

间隙配合变轨距轮对与轨道间瞬态滚滑接触模拟研究

变轨距技术是实现不同轨距铁路联运的重要手段，我国相关研究仍在起步阶段。基于显式有限元法，建立包含渐开线花键副的三维变轨距轮对-轨道耦合瞬态分析模型，于时域内模拟速度高至400 km/h下的瞬态轮轨滚滑和花键间动态接触行为及其相互影响。模型充分考虑轮轨和花键副三维几何、系统高频结构振动等，引入时变牵引/制动转矩，采用集成库仑摩擦定律的"面-面"接触算法求解轮轨接触和花键接触。假设圆柱直齿渐开线花键，齿数取32，齿侧间隙恒0.1 mm，无激励下模拟结果表明，花键副的存在使得轮轨力波动范围大于传统轮对，例如，400 km/h下法向轮轨力波动幅值增加静载的3.7%。时速400 km/h和牵引系数0.05下，内外花键的径向和角向偏置使得花键左、右两侧各存在1个位置相对固定的承载区，各涉及5~6个键齿，承载面分别为II和I键齿工作面。瞬态法、切向接触应力极值发生在靠近一系悬挂侧的齿根或齿顶部，典型值分别为102 MPa和4.6 MPa，任一键齿的应力极值因不断有键齿进出承载区而波动上升和下降。牵引系数0.3时，左侧承载区消失，右侧承载区扩至18个键齿，相同时刻下的法、切向接触应力极值因承载齿数和总接触面积增加变为89 MPa和5.2 MPa。为变轨距机构中花键的强度和动力学分析及相关设计提供精确模拟手段。     

里必井田承压水带压开采评估

煤层底板承压水突出是发生水害事故的原因之一,要减少该类事故的发生,需对底板突水危险性进行准确评价。为保障里必井田承压水带压开采的安全进行,基于煤层底板突水研究理论分析,采用常规突水系数法和等效厚度突水系数法,分别对里必井田内3#煤和15#煤的奥灰水突水危险性进行了研究。研究发现,奥灰水对于3#煤的开采影响不大,但在局部构造及陷落柱发育地段及采区东北部区域仍存在一定的突水可能性;奥灰水对15#煤开采具有较大威胁,大部分区域具有较大突水危险性。等效岩层厚度法计算的突水系数考虑了不同性质岩层的岩石强度和阻水能力,计算更接近生产实际,结果更可靠;且在对突水系数法进一步优化后,其评价的结果可以更精确。     

Benefits of variable structure techniques for parameter estimation in stochastic systems using least squares method and instrumental variables

In this paper, we study the benefits of the equivalent control method, implemented on parameter estimation algorithms like the least squares method and instrumental variables on continuous‐time stochastic systems. Here, we show how the equivalent‐control, adapted to the stochastic case, improves the performance of these estimation algorithms in continuous‐time systems under white noise perturbations. Some numerical examples show the effectiveness of these techniques. Copyright © 2014 John Wiley & Sons, Ltd.