一种单信标测距辅助INS的导航方法

传统基于地球物理场的匹配辅助惯性导航方法在基础数据变化特征不明显或数据缺乏等苛刻条件下,难以实现有效匹配定位。为解决这一问题,提出了一种单信标测距辅助惯性导航系统(INS)的方法。首先,在单信标测距解析基准图上引入相关极值匹配辅助导航算法并进行重新建模。然后,采用差分进化寻优算法对该模型进行解算,并设计了一种固定匹配序列长度的建模方法以解决相关极值匹配算法实时性差的缺点。所提方法在缺乏地球物理基础数据条件下,仅需在海底布放单只声信标即可实现局部海域水下高精度实时定位。同时,由于采用的测距基准图为解析形式,所提方法也能较好地解决离散匹配算法定位精度受限于基准图分辨率等问题。最后,设计了相关实测实验,实验结果表明当惯导定位误差累积为1529.4 m时,采用所提方法与单信标匹配,定位误差减小为111.8 m,算法的有效性得到了验证。

板壳结构在声振联合试验下的振动响应耦合分析

目的研究具有工程实践意义的板壳组合结构在声振联合作用下的响应预测方法。方法在噪声试验、振动试验和声振联合试验响应曲线的基础上,分析板壳组合结构在噪声和振动同时激励下的响应耦合规律,并根据噪声试验和振动试验的响应极值包络法,来预测在声振联合试验作用下板壳结构的响应分布。结果声振联合试验响应曲线近似于噪声试验和振动试验的最大值包络线,噪声的面激励和随机振动的基础激励在不同的频率范围内对结构响应起着主要影响。试验件的噪声试验和振动试验响应曲线在给定的频率点出现相交,小于交越频率的声振联合试验响应与振动试验高度吻合,高于交越频率的响应则以噪声试验为主。结论在工程实际中,可以直接利用振动试验和噪声试验的响应数据对声振联合试验的响应进行预测。由于交越频率难以事先获得,因此响应叠加法在实践中更易于实现。

基于扰动补偿的高速列车自适应滑模黏着控制

列车安全和平稳运行依赖于牵引力的有效发挥,而牵引力的有效发挥受限于轮轨间的黏着状态。为了解决高速列车行驶在低黏着轨面时牵引力不足的问题,考虑到车重、阻力、坡度等参数不易精确获取,设计一种基于扰动补偿的自适应滑模黏着控制算法。根据黏着计算模型和简化列车模型,建立高速列车轮轨动力学模型。通过设计动态观测精度更高的鲁棒黏着观测器,以精确获取当前轨面提供的黏着力。在此基础上,针对列车工作在最优黏着点附近时能够获得较大牵引力这一特性,采用梯度观测极值搜索算法获取该点附近的蠕滑速度。同时,设计基于扰动补偿的自适应滑模控制器控制电机输出转矩,使高速列车能够在部分系统参数未知的情况下跟踪极值搜索算法输出的蠕滑速度,从而提高列车牵引力。基于扰动补偿的自适应滑模控制,通过观测补偿系统不确定部分和自适应调节开关增益,减少滑模控制律抖振对黏着控制性能的影响。研究结果表明,基于扰动补偿的自适应滑模黏着控制算法在系统中存在未知参数时,能够控制列车在10 s内到达冰雪轨面最优黏着工作点附近,在1 s内到达潮湿轨面最优黏着工作点附近。此外,相比于传统滑模黏着控制和自适应滑模黏着控制,所提算法控制律抖振更低,并且能够更精确地搜寻和跟踪最优黏着工作点。所提算法可以为实际列车黏着控制算法设计提供参考。

基于视野和速度引导的无人机集群避障算法

在未来的多无人机(unmanned aerial vehicle,UAV)空中作战中,无人机集群在未知空域中安全飞行是集群研究中的重要内容。针对无人机集群避障以及集群形态保持问题,提出了一种基于视野和速度引导(visual field and velocity guidance,VFVG)的集群避撞算法。基于视野法设计集群自适应通讯拓扑机制,结合远吸近斥势力原则及一致性方法,在保持集群形态的同时,加速了集群无人机个体间的避障信息的传递。在此基础上,提出将极限环与人工势场法相结合构造避障速度引导项,解决了集群遇障分群困难、避障徘徊停滞等问题。引入避障时间指标,验证了算法的避障效率。仿真结果表明,该方法能够使多无人机以良好的集群形态安全快速平稳地通过复杂障碍区域,有效提高了集群避障成功率和避障效率。

法兰螺栓紧固力超声测量研究

针对法兰螺栓安装过程中紧固力难以测量和控制的问题,建立法兰螺栓超声测量模型并设计了法兰螺栓紧固力超声测试系统。系统首先基于FPGA和以太网技术设计了周期脉冲激励、数据采集、高速通讯传输、信号处理模块实现超声信号的发射和接收,并采用阈值法和极值法相结合来提高对超声渡越时间的测量精度,然后根据法兰螺栓超声测量模型计算得出螺栓紧固力大小。螺栓标定实验表明:法兰超声模型可靠,且标定系数的重复准确度达±2.4%;超声法—应变片法对比试验表明:所设计的测试系统能够实现螺栓紧固力的测量,与应变片法的相对误差不超过5%。

机构动作可靠性估计的自适应极值响应面法

针对存在随机-区间混合不确定性的机构动作可靠性估计问题,本文提出了一种基于自适应极值响应面的高效计算方法,将其转化为随机不确定性下的动作可靠度上下界求解问题。使用麻雀搜索算法优化的混合核极限学习机构建从混合不确定性变量到极限状态函数响应值的初始响应面和从随机变量到极限状态函数响应极值的极值响应面;利用结合主动学习与反向学习的自适应加点策略选取极限状态曲面附近的样本点更新极值响应面以提高其精度与效率;最后结合极值响应面和蒙特卡罗仿真算得到动作可靠度上下界的近似解。通过数值案例和回转链式输送机的工程案例对所提自适应极值响应面方法的高效性与准确性进行了验证,为随机-区间混合不确定性下的机构动作可靠性估计提供了一种参考。

基于自适应极值的白光干涉信号解调算法研究

针对传统时域解调算法等光程点定位稳定性差、抗干扰能力弱,而频域解调算法效率低且部分方法受扫描采样步长限制等问题,课题组提出一种基于自适应极值的白光干涉解调算法。从干涉信号统计学规律出发,通过对干涉信号包络曲线加权平均,将它修正为高斯型包络曲线;然后,通过对包络曲线高斯拟合插值得到等光程点,进而得到测量方向的深度信息以及三维形貌;最后,以高度为20μm标准台阶样块为测量对象进行多次实验。结果表明:与传统算法相比,课题组所提出算法的测量重复性和精度均有显著提升。该算法为白光干涉中信号解调提供了一种重复性更好、误差更小的方法。

Extremum of second-order directional derivatives

In this paper, the extremum of second-order directional derivatives, i.e. the gradient of first-order derivatives is discussed. Given second-order directional derivatives in three nonparallel directions, or given second-order directional derivatives and mixed directional derivatives in two nonparallel directions, the formulae for the extremum of second-order directional derivatives are derived, and the directions corresponding to maximum and minimum are perpendicular to each other.

“三全育人”理念下“数学分析”教学案例——以《条件极值》为例

本文以“数学分析”中的条件极值为例,在课堂教学设计过程中,引导学生以问题驱动的形式思考和分析问题,融入思政元素,将知识点与辩证思想联系起来,践行“三全育人”理念,提高学生分析问题和解决问题的能力,逐步培养学生理论联系实际的能力。

轧机浇铸液位自动控制系统研究应用

采用高温铝液专用激光液位计配合步进电机与杠杆机构实现液位的自动控制。由于铝液存储槽的下流口孔口较大,通过锥形塞控制其开度的难度较大,锥形塞的向上或向下的微小变化,会导致流量变化很大,常规PID算法无法实现有效控制。根据步进电机的特性采用变参数增量PI控制算法,通过增量控制算法来控制步进电机正转(或反转),增量控制算法的优劣直接影响着浇铸铝液契口的铝液位控制效果。

威布尔极值分布及其参数估计方法在储罐底板RBI计算中的应用

在常压储罐底板定量风险评估(RBI)过程中,底板腐蚀速率的选取会影响储罐整体风险等级的确定。基于威布尔极值分布理论,针对储罐边缘板,采用最佳线性无偏估计(BLUE)的方法计算了威布尔分布参数;针对储罐中幅板,采用简单线性无偏估计(GLUE)的方法计算了威布尔分布参数,随后通过线性回归理论分别计算了边缘板和中幅板的腐蚀速率,并将其赋予为腐蚀速率专家值对储罐底板进行了RBI计算。结果表明,威布尔极值分布理论计算可以科学合理地预估储罐底板腐蚀速率,边缘板的腐蚀速率为0.133 mm/a,中幅板的腐蚀速率为0.095 mm/a,与理论算法腐蚀速率的误差为3.6%,储罐底板风险等级为中高风险,在一定程度上解决了储罐RBI计算过程中腐蚀速率选取的难题,可为今后检验检测机构RBI的评估工作提供一定的技术支撑。

基于正交试验法的爆破参数优化

为了降低矿石的大块率和贫化率,通过正交试验,利用极差分析方式,研究孔深、边孔角、扇形孔排面倾角三个水平因素对矿石的大块率和贫化率试验指标的影响。经实践证明利用正交试验对爆破参数进行优化,有效改善了地下爆破效果,提高了生产效率,对于大块率和贫化率指标,扇形孔排面倾角是影响最显著的因素。以某金属矿为例,通过优化最终得到最优爆破参数为孔深16m,边孔角55°,扇形孔排面倾角90°,对地下矿山进一步控制大块率和贫化率具有一定的参考意义。

遵义红花椒油树脂提取工艺及其风味产品的制备

为探究遵义红花椒油树脂的最佳提取工艺,提高遵义红花椒风味产品的制备效率。以遵义红花椒的实生苗、嫁接苗及九叶青花椒的椒皮为试验材料,通过设计三因素三水平正交试验,采用超临界CO_(2)萃取技术、高效液相色谱技术研究不同种源花椒、不同萃取压强及不同萃取温度对遵义红花椒油树脂提取工艺的影响,通过感官分析对遵义红花椒油树脂风味产品进行评价。结果表明,遵义红花椒油树脂的最佳提取工艺以实生苗在温度55℃,压力25 MPa下萃取2 h效果最佳,其花椒油树脂得率最高达10.79%。对提取后3种花椒油树脂中的酰胺物质、挥发油物质及脂肪进行检测发现,遵义红花椒实生苗油树脂中的酰胺物质含量和挥发油含量均为最高(160.43 mg/g和58.33%),明显大于遵义红花椒嫁接苗与九叶青花椒中的酰胺物质含量(126.80 mg/g和130.10 mg/g)和挥发油含量(41.80%和50.44%)。感官评价结果表明,遵义红花椒油树脂风味产品花椒风味酱的综合口感得分随着花椒油树脂含量的增加,呈先增加再降低的趋势,当花椒油树脂的添加量为4 mL时,花椒风味酱的综合口感得分达到最高。

齿轮钢中非金属夹杂物检测方法对比及其对疲劳性能的影响

为了更全面和准确地确定齿轮钢中非金属夹杂物的含量,对现行的两种钢中非金属夹杂物含量的测定方法(传统的标准评级图显微检验法和极值分析法),进行对比检测分析,结果表明,极值分析法评价出的钢中非金属夹杂物的含量较为精准。同时,通过旋转弯曲疲劳试验测定齿轮钢锻坯的疲劳性能,得到与用极值分析法评价的齿轮锻坯中非金属夹杂物的最大预测尺寸L max所对应的齿轮钢的疲劳极限,当非金属夹杂物的最大预测尺寸L_(max)=67.47μm时,钢的疲劳极限为701 MPa;L_(max)=48.90μm时,钢的疲劳极限为1011 MPa;L_(max)=35.88μm时,钢的疲劳极限为1070 MPa,得出通过极值分析法测定的钢中非金属夹杂物的最大预测尺寸L_(max)越小,所对应的钢的疲劳极限值越高。当受疲劳试验时间和试验条件等因素限制而无法进行钢材的疲劳试验时,可通过极值分析法评价钢材中非金属夹杂物的最大预测尺寸L max的值来初步判断所选用钢材的疲劳强度是否能达到要求。

Welding Deviation Detection Algorithm Based on Extremum of Molten Pool Image Contour

The welding deviation detection is the basis of robotic tracking welding, but the on-line real-time measurement of welding deviation is still not well solved by the existing methods. There is plenty of information in the gas metal arc welding（GMAW） molten pool images that is very important for the control of welding seam tracking. The physical meaning for the curvature extremum of molten pool contour is revealed by researching the molten pool images, that is, the deviation information points of welding wire center and the molten tip center are the maxima and the local maxima of the contour curvature, and the horizontal welding deviation is the position difference of these two extremum points. A new method of weld deviation detection is presented, including the process of preprocessing molten pool images, extracting and segmenting the contours, obtaining the contour extremum points, and calculating the welding deviation, etc. Extracting the contours is the premise, segmenting the contour lines is the foundation, and obtaining the contour extremum points is the key. The contour images can be extracted with the method of discrete dyadic wavelet transform, which is divided into two sub contours including welding wire and molten tip separately. The curvature value of each point of the two sub contour lines is calculated based on the approximate curvature formula of multi-points for plane curve, and the two points of the curvature extremum are the characteristics needed for the welding deviation calculation. The results of the tests and analyses show that the maximum error of the obtained on-line welding deviation is 2 pixels（0.16 ram）, and the algorithm is stable enough to meet the requirements of the pipeline in real-time control at a speed of less than 500 mm/min. The method can be applied to the on-line automatic welding deviation detection.

Extremum response surface method of reliability analysis on two-link flexible robot manipulator

In order to present a new method for analyzing the reliability of a two-link flexible robot manipulator,Lagrange dynamics differential equations of the two-link flexible robot manipulator were established by using the integrated modal method and the multi-body system dynamics method.By using the Monte Carlo method,the random sample values of the dynamic parameters were obtained and Lagrange dynamics differential equations were solved for each random sample value which revealed their displacement,speed and acceleration.On this basis,dynamic stresses and deformations were obtained.By taking the maximum values of the stresses and the deformations as output responses and the random sample values of dynamic parameters as input quantities,extremum response surface functions were established.A number of random samples were then obtained by using the Monte Carlo method and then the reliability was analyzed by using the extremum response surface method.The results show that the extremum response surface method is an efficient and fast reliability analysis method with high-accuracy for the two-link flexible robot manipulator.

Analysis on membrane wrinkling using stress extremum method

A stress extremum method is developed based on Von Karman equations for analysis of membrane wrinkles in this paper. A mechanical model is also established for analyzing shear membrane wrinkles. Expressions of wrinkling wavelength,amplitude and angle are obtained in terms of the stress extremum method. A numerical analysis approach-directly disturbing method is proposed to analyze the configuration parameters of shear membrane wrinkles by introducing out-of-plane disturbing forces to trigger wrinkle formation,while it timely removes the applied forces in order to eliminate the effect of disturbing forces on analytical results. The simulation results agree well with analytical results,which demonstrate that the proposed approach is capable for analyzing the membrane wrinkles with good accuracy.

Distributed collaborative extremum response surface method for mechanical dynamic assembly reliability analysis

To make the dynamic assembly reliability analysis more effective for complex machinery of multi-object multi-discipline(MOMD),distributed collaborative extremum response surface method(DCERSM)was proposed based on extremum response surface method(ERSM).Firstly,the basic theories of the ERSM and DCERSM were investigated,and the strengths of DCERSM were proved theoretically.Secondly,the mathematical model of the DCERSM was established based upon extremum response surface function(ERSF).Finally,this model was applied to the reliability analysis of blade-tip radial running clearance(BTRRC)of an aeroengine high pressure turbine(HPT)to verify its advantages.The results show that the DCERSM can not only reshape the possibility of the reliability analysis for the complex turbo machinery,but also greatly improve the computational speed,save the computational time and improve the computational efficiency while keeping the accuracy.Thus,the DCERSM is verified to be feasible and effective in the dynamic assembly reliability(DAR)analysis of complex machinery.Moreover,this method offers an useful insight for designing and optimizing the dynamic reliability of complex machinery.

Reliability-based design optimization for flexible mechanism with particle swarm optimization and advanced extremum response surface method

To improve the computational efficiency of the reliability-based design optimization(RBDO) of flexible mechanism, particle swarm optimization-advanced extremum response surface method(PSO-AERSM) was proposed by integrating particle swarm optimization(PSO) algorithm and advanced extremum response surface method(AERSM). Firstly, the AERSM was developed and its mathematical model was established based on artificial neural network, and the PSO algorithm was investigated. And then the RBDO model of flexible mechanism was presented based on AERSM and PSO. Finally, regarding cross-sectional area as design variable, the reliability optimization of flexible mechanism was implemented subject to reliability degree and uncertainties based on the proposed approach. The optimization results show that the cross-section sizes obviously reduce by 22.96 mm^2 while keeping reliability degree. Through the comparison of methods, it is demonstrated that the AERSM holds high computational efficiency while keeping computational precision for the RBDO of flexible mechanism, and PSO algorithm minimizes the response of the objective function. The efforts of this work provide a useful sight for the reliability optimization of flexible mechanism, and enrich and develop the reliability theory as well.

DYNAMIC HUNTING EXTREMUM CONTROL METHOD BASED ON MEASURE AND ESTIMATION

Objective To propose a dynamic hunting extremum control method based on comparison of the estimated value and measured value. Methods The output linear group of the system is approximately expressed as an nth order system with large time constant or with time delay. Moreover, the relation between input drive reversal of the logic circuit and dynamic output of the system is analyzed in detail. The calculating formulae for the drive reversal are given for different extremum control systems. Based on principles above, a controller using a micrprocessor and a testing laboratory plant were designed and implemented. Results With this new method, the controller achieves fast optimum point hunting process, good performance in extremum control systems for high order processes, and robust result under sudden change or drift of the extremum characteristics. Conclusion The new control owns the merits of rapid optimizing dynamics, robusticity, and wide applicability.