基于NURBS曲线轨迹规划与速度规划的研究

提出了一种基于非均匀有理B样条曲线(NURBS)的运动轨迹规划插补算法,与传统插补方法相比,该插补器能够保持高速度和高精度加工性能,而且能够抑制在插补过程当中产生的轮廓误差和速度波动.在插补过程中由于限制轮廓误差的需要而产生了一些速度尖点,在这些尖点处的加速度和加加速度往往都非常大,这些对机床的伺服马达产生很大的冲击力,提出的插补算法能够根据允许的最大轮廓误差、最大加速度、最大加加速度来对插补速度进行自适应调整,使其满足插补要求.通过一个NURBS曲线插补的MATLAB仿真的例子,说明了该曲线插补算法能够满足高速、高精度加工的要求.     

Variable feedrate interpolation of NURBS Toolpath with geometric and kinematical constraints for five-axis CNC machining

Variable feedrate interpolation algorithms for five-axis parametric toolpath are very promis- ing but still rather limited currently. In this paper, an off-line feedrate scheduling method of dual NURBS curve is presented with geometric and kinematical constraints. For a given dual parametric curve, the feedrates of sampling points are first scheduled sequent with confined feedrate of cutter tip and machine pivot, chord error, normal acceleration and angular feedrate. Then, the feedrate profiles of angular feed acceleration sensitive regions of the path are adjusted using a bi-directional scanning algorithm. After that, a linear programming method is used to adjust the feedrate profiles of linear feed acceleration sensitive regions and control the linear feed acceleration of both cutter tip and machine pivot within preset values. Further, a NURBS curve is used to fit the feedrates of sampling points. Finally, illustrative examples are carried out to validate the feasibility of the proposed feedrate schedul- ing method. The results show that the proposed method has the ability of effectively controlling the angular feed characters of cutter axis as well as the chord error and linear feed characters of cutter tip and machine pivot, and it has potential to be used in high accuracy and high quality five-axis machining.     

基于速度障碍法的多UAV可飞行航迹优化生成

研究无人飞行器(unmanned aerial vehicle, UAV)在线可飞行航迹的自主规划对UAV适应非结构化环境、提高机动作战能力具有重要的现实意义。提出了一种基于Pythagorean-Hodograph (PH)曲线的UAV在线航迹生成算法,可以根据UAV当前的飞行状态、目标点信息及传感器探测信息实时规划出曲率连续的可避碰飞行航迹。考虑系统动态性能约束,采用分布估计算法对航迹参数进行优化选取,提出基于区间选优的全局精英个体概率选择机制,提高了航迹生成的速度及精度。根据速度障碍法原理,结合PH曲线的特点,给出了高动态环境下多UAV的实时动态避碰规划算法,该算法能使轨迹快速趋近于目标。对一组UAV的航迹规划在不同环境下进行了仿真实验,仿真结果证明了算法的有效性和实用性。     

反向间隙误差对螺旋转子精铣精度的影响及其仿真

为实现大模数少齿数螺旋转子的高效精加工,研究了数控机床旋转轴反向间隙积累误差对转子精加工法向齿厚的影响。首先建立螺旋面的方程并计算其法向矢量,求得球头铣刀精加工刀位数据;然后推导反向间隙积累误差的估算公式,分别采用空间环形走刀和空间平行走刀对转子加工过程进行仿真,得到走刀循环次数与反向间隙积累误差值之间的关系曲线。仿真结果和数控机床试切结果表明,当转子法向齿厚尺寸较小时,采用空间环形走刀方式效率较高且能保证精度;当法向齿厚处于临界值时,可以采用空间环形走刀,但需对端面型线作出一定角度的旋转以抵消误差积累;当法向齿厚较大时,应该采用空间平行走刀方式规划刀具路径。     

Time-optimal interpolation for CNC machining along curved tool pathes with confined chord error

In this paper, two new interpolation algorithms lot CNC machining along curve~l tom pathes are proposed： a time-optimal interpolation algorithm under chord error, feedrate, and tangential acceleration bounds, and a greedy interpolation algorithm under the chord error and tangential jerk bounds. The key idea is to reduce the chord error bound to a centripetal acceleration bound which leads to a velocity limit curve, called the chord error velocity limit curve. Then, the velocity planning is to find the proper velocity curve governed by the acceleration or jerk bounds ＇~under＂ the chord error velocity limit curve. For two types of simple tool pathes, explicit formulas for the velocity curve are given and the methods are implemented in commercial CNC controllers.     

Tool orientation planning for five-axis CNC machining of open free-form surfaces

For the geometry characteristics of open free-form surfaces, it is hard to consider global interference during the planning of feasible domains. Therefore, the optimal kinematic orientation of tool axis will no longer be confined to the boundary of feasible domains. In this paper, according to the principle demanding that the tool should be fitted to a surface as close as possible and relevant processing parameters, a feasible domain of tool orientation for each cutter contact is planned in the local feed coordinates system. Then, these feasible domains of the tool orientation are transformed into the same coordinates system of the machine tool by the inverse kinematics transformation. The linear equations based feasible domain method and Rosen gradient projection algorithm are used to improve the optimization process in precision and efficiency of the algorithm. It constructs the variation of tool orientation optimization model and ensures the smoothness of tool orientation globally. Simulation and analysis of examples show that the proposed method has good kinematics performance and greatly improves the efficiency.     

一种基于导频的OFDM系统信道估计方法

提出一种使用矩形导频图案的OFDM信道估计方法。接收端首先在频率方向估计信道,然后在时间方向插值。该方法仅需累加和少量乘法运算就能估计出信道冲激响应,复杂度低,实时性高。在未编码16QAM-OFDM系统中,通过仿真将提出的方法与线性、cubic和MMSE插值法进行均方误差和误比特率的比较。结果表明该方法性能优于前两者,接近后者。     

A control algorithm for rapid movements near the radius compensation singularity in five-axis end milling

When the five-axis CNC system executes the 3D cutter radius compensation function, the angle between two adjacent radius compensation vectors might become very large and the linear axes would move too fast if the tool orientation vector is close to the surface normal. The reason that results in this phenomenon is analyzed based on building the transmission relationship between the cutter contact point and the cutter location point. By taking the square-end tool as an example, an optimization algorithm to control the undesired movements is advanced. For the singular area where sudden change exists, the number of interpolation cycles is determined by the cutter feedrate, the limit speeds of machine axes and the maximum allowable angle between radius compensation vectors of adjacent NC blocks. The radius compensation vector of each interpolation cycle is obtained by a kind of vector rotation method. By maintaining the perpendicularity between the radius compensationvector and the tool orientation vector, the rapid movements of the linear axes are eliminated. A trial-cut experiment is performed to verify the correctness and the effectiveness of the proposed algorithm.     

基于粒子群优化算法的USV集群协同避碰方法

针对无人水面艇(unmanned surface vessel, USV)集群在路径规划中的协同避碰问题,提出了基于滚动优化策略结合粒子群优化算法的USV集群协同避碰方法。首先,通过已有雷达、光电等传感器参数指标建立综合视域模型;其次,采取基于正切函数的惯性权重调整结合线性调整学习因子的方法来提高粒子群优化算法的全局搜索能力,同时,在适应度函数中加入转艏角控制来提高路径的平滑性;最后,利用改进后的粒子群优化算法规划出每个综合视域内的路径。仿真实验结果表明,该优化算法能实现USV集群的实时避碰,并快速为USV集群规划出平滑、安全的全局最优无避碰路径。     

空基双探测端分布式定位系统的航迹控制

针对空中运动目标参数的实时解算和定位精度问题,基于运动多站无源定位技术,设计了空基分布式定位系统,利用测向交叉定位原理建立了双机协同被动定位模型。模型中完成信息保障任务战斗机的存在使得目标定位误差迅速最小化。通过动态规划法进行双机航迹控制算法设计。使用带有线性策略的共轭梯度法解算信息保障机的最优航迹。仿真表明,该控制算法可以得到信息保障机的最优航迹,双探测端分布式定位系统通过航迹优化,实现了对目标的快速高精度定位。     

电厂湿法烟气脱硫过程优化控制研究

深入研究了具有混杂系统特性的电厂湿法烟气脱硫(WFGD)过程的优化与控制问题;运用混合逻辑动态的建模方法(Mixed Logical Dynamic)建立了WFGD过程的MLD模型,基于MLD模型的预测控制方法把WFGD过程优化问题转化为实时求解混合整数规划(MIQP)问题,实时给出了WFGD过程优化运行的连续决策变量(吸收塔浆液的PH值设定)和离散决策变量(循环浆液泵开启台数)的最优解;用同样方法实现WFGD过程基础回路级中具有非线性动态的PH对象的控制;仿真表明基于MLD模型预测控制方法很好地解决了WFGD过程的优化与控制问题。     

Tool Orientation Optimization and Path Planning for 5-Axis Machining

Tool path generation is a fundamental problem in 5-axis CNC machining, which consists of tool orientation planning and cutter-contact(CC) point planning. The planning strategy highly depends on the type of tool cutters. For ball-end cutters, the tool orientation and CC point location can be planned separately;while for flat end cutters, the two are highly dependent on each other. This paper generates a smooth tool path of workpiece surfaces for flat end mills from two stages: Computing smooth tool orientations on the surface without gouging and collisions and then designing the CC point path. By solving the tool posture optimization problem the authors achieve both the path smoothness and the machining efficiency. Experimental results are provided to show the effectiveness of the method.     

7-DOF核工业机器人的轨迹规划与仿真

为实现7-DOF核工业机器人在空间相贯焊缝探查作业过程中平稳、连续及控制的实时性，提出采用五次多项式函数进行轨迹插补，避免通过求解Jacobian逆矩阵实现从欧氏空间到关节空间轨迹规划结果的转换而涉及矩阵求逆等繁杂运算。该方法具有结构简单，运算量小，能够实时计算机器人运动的位移、速度与加速度，并生成运动轨迹。结合实际探查的空间相贯曲线，对各关节的运动轨迹进行了计算仿真，结果表明：该方法能够保证关节角度、角速度及角加速度的连续性，保证了机器人工作的平稳性，能够满足工作要求。     

基于ACO算法和Bezier曲线优化的巡航导弹航路规划

在巡航导弹低空突防前提下,针对蚁群算法规划的导弹航路存在转向点个数较多和转向角度较大的问题,提出一种基于蚁群算法和Bezier曲线优化的三维航路规划方法。将蚁群算法生成的路径节点作为生成Bezier曲线航路的控制点,将曲线航路分段形成折线化航路。采用广度优先搜索算法对航路生成中出现的不可航行路段进行微调处理,得到可行的规划航路。仿真结果表明：生成的航路兼顾了随机搜索全局优化的同时,避免了大角度转向,缩减了飞行航程和转向点个数,保证了巡航导弹飞行过程中的连续稳定。     

平面二自由度冗余驱动并联机构的最优运动控制及其仿真

以平面二自由度冗余驱动并联机构为研究平台，对机构的高速高精度的最优运动控制进行了研究。首先建立了并联机构的动力学模型，然后以包含有误差和控制量的二次正定函数的性能指标进行最优控制器设计。对单纯点到点控制方式下的最优参数设计问题进行了设计与分析。为了解决点到点运动控制时运动速度较低的问题，采用了插补策略。通过计算机仿真，研究了利用插补点数目进行高速和高精度的轨迹跟踪控制的设计问题，并对比分析了各参数对提高精度和快速响应的影响及其关系。     

Approximation methods of mixed l_1/H_2 optimization problems for MIMO discrete-time systems

The mixed l1/H2 optimization problem for MIMO (multiple input-multiple output) discrete-time systems is considered. This problem is formulated as minimizing the l1-norm of a closed-loop transfer matrix while maintaining the H2-norm of another closed-loop transfer matrix at prescribed level. The continuity property of the optimal value in respect to changes in the H2-norm constraint is studied. The existence of the optimal solutions of mixed l1/H2 problem is proved. Because the solution of the mixed l1/H2 problem is based on the scaled-Q method, it avoids the zero interpolation difficulties. The convergent upper and lower bounds can be obtained by solving a sequence of finite dimensional nonlinear programming for which many efficient numerical optimization algorithms exist.     

切向加速度与弦误差约束的CNC系统时间最优轨迹规划

针对计算机数控(CNC)系统给定参数化路径, 给出了一种求解时间最优轨迹规划问题的凸优化方法. 轨迹规划问题考虑切向加速度约束与弦误差约束. 通过建立两种约束下的状态容许空间, 分析约束对时间最优轨迹的影响. 通过非线性变量代换, 时间最优轨迹规划问题被表述为一个与时间无关的凸最优控制问题. 基于控制向量参数化(CVP)方法, 问题被进一步转化为易于求解的凸优化问题. 以路径参数对时间的二阶导数(参数加速度)为优化变量, 序列二次规划(SQP)方法获得问题数值解. 文末通过求解两个测试路径的时间最优轨迹规划问题, 验证方法的有效性.     

New approach to training support vector machine

1.INTRODUCTIONThe support vector machine(SVM)[1]has been suc-cessful as a high-performance classifier in several do-mains including pattern recognition,data mining,and bioinformatics.It has strong theoretical founda-tions and good generalization capability.Ali mitationof the SVMdesign algorithm,particularly for largedata sets,is the need to solve a quadratic program-ming(QP)probleminvolving a densen×nmatrix,wherenis the number of points in the data set.Since QProutines have highcompl…     

非线性约束最短路问题的启发式算法

多约束QoS路由优化是当前网络研究中的一个重要课题,而受限最短路问题(RSP)是QoS路由的一个基本问题。它是NP-完全的,并有许多具有多项式时间和伪多项式时间的启发式求解算法。然而这些方法只能求解一些带有线性约束的RSP。对一些非线性的约束(比如丢失率约束)大都用数学方法转化成线性约束来求解,这增加了问题的复杂性。本文提出了一种新的具有伪多项式时间的启发式算法来求解这类带非线性约束的RSP。主要思想是将非线性约束作为检验条件来使用。当每得到一个解时,检查解是否满足非线性约束。如满足,则得到最终解;否则在原问题中添加一个线性约束。该新约束将去除已经找到的解,从而使原问题的解空间进一步缩小,直到得到最终解。仿真算例说明了算法的有效性。     

Predictive Control with Velocity Observer for Cushion Robot Based on PSO for Path Planning

This paper proposes a novel model predictive control method with velocity estimation simultaneously constraining trajectory and velocity tracking errors for a cushion robot. The authors investigated a path planning method using improved particle swarm optimization(PSO) combined with Dijkstra's algorithm and obtained a real-time desired optimal motion path for obstacle avoidance.The authors designed a velocity observer to estimate the unmeasurable speed, while the asymptotic stability of the observer error system was established. A predictive controller with error-constrained performance was derived by solving a quadratic programming problem with incremental control. Simulation and experimental results confirm the effectiveness of the proposed method and verify that the error constraints adopted in the cushion robot provide safe motion while avoiding obstacles.