Who needs QP for linear MPC anyway?

Conventional MPC uses quadratic programming (QP) to minimise, on-line, a cost over n linearly constrained control moves. However, stability constraints often require the use of large n thereby increasing the on-line computation, rendering the approach impracticable in the case of fast sampling. Here, we explore an alternative that requires a fraction of the computational cost (which increases only linearly with n), and propose an extension which, in all but a small class of models, matches to within a fraction of a percent point the performance of the optimal solution obtained through QP. The provocative title of the paper is intended to point out that the proposed approach offers a very attractive alternative to QP-based MPC.     

带控制量约束的数控铣削过程广义预测控制

首先综合考虑伺服系统动特性加工过程中刀具变形等因素,将数控铣削过程简化为二阶模型。其次构造数控铣削过程广义预测控制律,并依据实际需要提出控制量约束条件和具体算法,计算机仿真结果表明,与无约束算法相比,闭环系统的性能可能得到显著改善,最后提出基于快速信号处理板的硬件及接口方案,并通过试验验证算法的正确性和有效性,结果表明,合理选择控制前景,输出前景和权因子,可避免因切深或切宽突变而引起的控制输入过大     

Constraint-based deductive model checking

We show that constraint logic programming (CLP) can serve as a conceptual basis and as a practical implementation platform for the model checking of infinite-state systems. CLP programs are logical formulas (built up from constraints) that have both a logical interpretation and an operational semantics. Our contributions are: (1) a translation of concurrent systems (imperative programs) into CLP programs with the same operational semantics; and (2) a deductive method for verifying safety and liveness properties of the systems which is based on the logical interpretation of the CLP programs produced by the translation. We have implemented the method in a CLP system and verified well-known examples of infinite-state programs over integers, using linear constraints here as opposed to Presburger arithmetic as in previous solutions. Published online: 18 July 2001     

多级安全数据库设计中的约束处理

安全约束为多级安全数据库系统提供了一种有效的分类策略，可用来为基于时间、语境和内容的数据分派安全等级．本文讨论了数据库设计过程中的安全约束处理技术，并提出了处理基于关联的约束、简单约束和逻辑约束的算法．     

基于成对约束的交叉熵半监督聚类算法*

极大熵聚类(MEC)目标函数中缺乏成对约束的有效信息表达,在拥有少量成对约束的情况下,可能导致有效监督信息的浪费.在MEC的基础上,文中提出基于成对约束的交叉熵半监督聚类算法.利用样本交叉熵表达成对约束信息,并作为惩罚项引入至MEC的目标函数中,通过拉格朗日最优化处理目标函数,得出聚类中心与隶属度的迭代公式.实验表明,文中算法能有效利用少量的成对约束监督信息提高聚类性能,在实际数据应用中性能较好     

Bi-level multi-objective mathematical model for job-shop scheduling: the application of Theory of Constraints

This study highlights a different systematic approach to the application of Theory of Constraints (TOC). The work describes the decisions involved in the implementation of TOC in a job-shop environment as a bi-level multi-objective mathematical model. On the first level, the decision is made by minimising idle time on the bottleneck to generate the initial schedule. The second level decision is to improve additional performance measurements by applying the multi-objective technique, while maintaining the bottleneck sequence obtained from the first level decision. Moreover, the concept of transfer lot is also adopted in this model to reduce the waiting time on each machine by allowing overlapped operations. The concept of transfer lot is applied as the constraint on earliest starting time for each job on each machine in the proposed mathematical model. Additionally, the machine set up time and product demands are also adopted to make the model practical to use in the real situation. The numerical examples for both single and multiple bottleneck cases are given to demonstrate how this approach works. The commercially available optimiser, the LINGO 10 software package, is used to solve the examples and the result shows how this approach works in practice.     

船用管件弯曲成型的有限元建模与实验验证

基于弯曲成型理论并结合船用管件弯曲成型的实际工况,采用ABAQUS/CAE模块建立了20钢管件的数控弯曲成型有限元模型,对建模过程中的力学模型、几何模型、单元定义、网格划分及其敏感性分析和约束接触设置等步骤进行了详细的说明。通过提取弯曲段横截面的最小壁厚值,与变形前的截面壁厚相比,定义了弯管外侧壁厚的减薄率。同时,通过提取畸变后的管件截面的椭圆长短轴,推导出了截面畸变程度质量指标的计算方法。与实验结果比较,有限元模型的计算结果与实验测量数据之间的相对误差较小,从而验证了有限元模型计算的精确度和可靠性,为管件的弯曲成型加工提供了理论依据,可应用于加工后管件质量的评价。     

基于开放式约束配置平台的车削参数优化研究

在分析传统的基于遗传算法的切削参数优化方法的基础上,开发了一个基于遗传算法开放式的约束配置平台。这个约束配置平台在遗传算法中利用不可行度选择操作处理约束条件和选用约束主导原理指导进化过程选择操作,这样不但考虑到了不可行解在搜索中的作用,使得GA群体搜索的特点得到了很好的利用;而且可以根据具体加工环境和加工工艺情况进行开放式的增减约束,使得本模型具有很好的通用性和鲁棒性。最后通过算例验证了约束配置平台的优越性。     

3D geometric constraint solving using the method of kinematic analysis

In this paper, an approach based on kinematic method for solving 3D geometric assembly constraints is presented. The relative generalized coordinates and generalized recursive formulations used in kinematic analysis are utilized to reduce the size of constraint equations. Based on the cut-constraint method, this approach can be used to solve all kinds of configurations. In the case of an open-loop constraint system, the geometric constraints can be satisfied by sequentially determining the values of relative generalized coordinates. With respect to a closed-loop constraint system, the proposed approach converts it to a spanning tree structure by cutting constraints and introducing cut-constraint equations. Furthermore, a topological analysis method is also developed to obtain the spanning tree with the minimal number of cut-constraint equations, and the analytical Jacobian matrix of cut-constraint equations is derived to enhance computational efficiency. In the end, the proposed approach is demonstrated and validated using two examples of closed-loop geometric constraint system.     

基于多约束的机器人关节空间轨迹规划

当机器人进行快速运动且运动时间确定时,由于受到驱动机构性能等因素的制约,机器人进行运动轨迹规划时需要考虑角加速度约束、角速度约束和角度约束等多个约束条件。通过对运动约束进行分析,提出基于梯形速度曲线的多约束条件下机器人关节空间轨迹规划方法。根据无约束条件下规划出的最小加速度运动轨迹,在角加速度满足约束的情况下对其进行优化,获得满足角速度约束和角度约束的最小角加速度运动轨迹。对加速度达到最大时的轨迹也无法满足约束条件的情况进行讨论。该轨迹规划方法兼顾机器人的运动平稳性与约束要求,并且能够充分发挥机器人关节的驱动性能。仿真结果表明了该方法的可行性。