基于混沌最优控制的二级倒立摆的实验研究

为解决LQ控制多变量系统时,权矩阵参数难以确定的问题,在引入一种与系统动态性能密切相关的性能指标基础上,提出混沌全局粗搜索和局部细搜索相结合优化LQ控制二级倒立摆.该方法既是线性二次型泛函意义下的最优,又能解决具有快速、强非线性、绝对不稳定系统的控制问题.二级倒立摆实验结果证实了该方法的有效性.     

四旋翼飞行仿真器的多变量控制器设计与研究

针对目前工程领域中的多输入、多输出(MIMO)系统,以四旋翼飞行仿真器为研究平台,设计了两套控制器,分别采用线性二次型(LQ-Linear Quadratic)最优控制方法和一种类似于规则分解的多变量模糊控制法。在Matlab/Simulink中建立其控制模型,并利用实时工具箱(Real-Time-Workshop)实现实时控制。实际控制结果表明,线性二次型最优控制器在合理选择加权矩阵Q、R基础上,所设计的控制器对于系统从初始状态至零位的阶跃响应和给定输入的轨迹跟踪有良好的控制性能。采用多组二维模糊控制器,通过分析被控对象机理特性,对输出进行整合多变量模糊控制器,其控制性能与线性二次型控制器相近,两者对于线性、定常、具有强耦合的多变量控制系统都具有良好的控制效果。     

环形倒立摆系统改进遗传算法的LQR控制研究

在一级环形倒立摆系统中,针对线性二次型控制器(LQR)加权矩阵Q和R选择策略的不足,提出一种通过改进遗传算法优化LQR加权矩阵Q和R的方法。该方法选取二次型性能指标J作为个体适应值,在传统遗传算法的基础上通过对交叉率和变异率按S曲线和高斯分布曲线自适应调整等策略来提高遗传算法的全局搜索能力和收敛速度,实现对Q和R矩阵的优化。仿真结果表明:用改进遗传算法优化后的一级环形倒立摆系统LQR控制具有更好的自适应性,系统连杆和摆杆的调节时间分别减少了2 s和1.5 s,有效地提高了系统的稳定性。     

基于LQ最优控制的PWM整流器参数整定

针对传统PID调节器参数整定方法的不足,基于线性二次型最优控制理论,由跟踪问题得出状态反馈增益阵与PID调节器参数之间的关系,并将此结论应用于PWM整流器电压外环调节器的参数整定中。对加权矩阵Q和正常数R进行适当的选取,实现了PWM整流器的参数最优化。使用MATLAB/Simulink进行了仿真分析,验证了参数优化的可行性,并通过dSPACE实时系统对控制策略进行了实验验证,实验结果验证了该方法的有效性。     

桥式吊车系统基于遗传算法的LQR控制

针对欠驱动系统--桥式吊车系统提出了基于遗传算法的LQR控制方法.首先,通过牛顿力学建立数学模型,再通过遗传算法选取的Q和R矩阵,结合线性二次型最优控制方法实现吊车系统的最优控制.仿真试验的结果表明了该方法是有效的.     

桥式吊车系统基于遗传算法的LQR控制

针对欠驱动系统——桥式吊车系统提出了基于遗传算法的LQR控制方法。首先，通过牛顿力学建立数学模型，再通过遗传算法选取的Q和R矩阵，结合线性二次型最优控制方法实现吊车系统的最优控制。仿真试验的结果表明了该方法是有效的。     

基于LQR理论的电磁轴承控制系统鲁棒稳定性分析

线性最优控制理论中采用的数学模型与实际物理模型总存在一定的差异，据此设计的控制参数不一定能满足实际系统稳定性的需要。针对这一问题，提出了一种分析线性最优控制系统鲁棒稳定界限的方法，并将其应用在基于LQR理论的电磁轴承控制系统的鲁棒稳定性分析中。结果表明：电磁轴承控制系统对模型矩阵摄动的鲁棒性在参数α确定时仅与加权矩阵Q、R的相对大小有关；选择较小的参数α和相对于加权矩阵R较大的Q阵、传感器采取外侧安装方式有利于提高电磁轴承控制系统对模型矩阵摄动的鲁棒性。此结论为主动电磁轴承控制器的设计和结构的设计提供了一定的理论依据。     

轮式移动机器人轨迹跟踪的最优控制

深入分析了轮式移动机器人的运动状态,建立了WMR路径偏差系统的非线性数学模型。应用小偏差线性化理论,将该多输入多输出非线性系统简化成一个单输入单输出线性系统。然后基于线性二次型调节器理论进行了系统最优控制器的设计,并针对该理论中加权矩阵Q与R难以确定的问题,从控制效果出发,采用自适应遗传算法对其进行了优化。实现了移动机器人对预定轨迹的满意鲁棒跟踪,同时满足了实时性要求。实验结果证明了该方法的正确性与实用性。     

一类工程LQ问题最优控制的综合方法

给出一类具有实际工程意义的LQ问题最优控制的综合方法。其最优控制律的计算只是简单的矩阵运算,且计算公式为封闭形式。同时,通过对该类系统及二次性能指标的合理变换,避免直接选择加权阵。一个工业应用实例的设计描述了该方法的综合步骤。     

电液控制系统基于LQR的最优控制研究

电液控制系统作为一种精密、有效的控制方式,广泛应用于现代工业中.现代电液控制技术的发展与控制策略的最新发展密切相关,由于电液控制系统往往是复杂的非线性系统,为了获得高精度、高响应,高可靠性以及好的鲁棒性,必须有与之相适应的控制策略.该文将现代控制理论中的线性二次型最优控制理论应用于电液控制系统,并基于液压挖掘机工作手臂的动臂电液控制系统建立数学模型,利用MATLAB控制系统工具箱,设计了LQR最优控制器,基于仿真研究,探讨LQR最优控制器中的加权矩阵Q、R的选取以及其变化对系统动态特性的影响.     

一种多周期随机需求生产/库存模型

为使存贮、生产和缺货等费用的总和最小，建立了一种多周期随机需求生产／库存模型，该模型采用（S，Q）策略对生产和库存进行控制，即当成品库存降至8时准备生产，生产量为Q。通过对该模型费用函数特性的分析，设计了一种迭代学习算法，根据该算法可以得出系统的最优生产准备点及最优生产量。将所提出的迭代学习算法与遗传算法进行了比较，结果显示，两者所得到的控制量是吻合的，且迭代学习算法的求解速度更快，从而证实所建立的模型和提出的迭代学习算法是正确有效的。     

改进粒子群算法在LQR半主动悬架的应用

针对车辆半主动悬架LQR控制中Q矩阵和R矩阵往往由经验取值的问题,提出一种基于改进粒子群算法的LQR控制方法。该算法采用随机惯性权重代替了传统粒子群算法的固定惯性权重,提高了求解精度和效率,得到了更加具有适应性的LQR控制矩阵系数。为验证此方法的有效性,基于天棚阻尼模型建立1/4车被动悬架模型和半主动悬架模型,利用线性二次最优控制建立LQR控制器,并利用优化算法得到新的控制矩阵。通过仿真对比被动悬架、LQR控制的LQR半主动悬架、改进粒子群算法优化后的优化LQR悬架的各项性能参数,发现优化LQR悬架在悬架动挠度没有受到影响的前提下,使车辆的垂向加速度和轮胎动载荷得到有效降低,提高了车辆的行驶平顺性和操纵安全性。     

Finite-time state-dependent Riccati equation for time-varying nonaffine systems: Rigid and flexible joint manipulator control

This article investigates finite-time optimal and suboptimal controls for time-varying systems with state and control nonlinearities. The state-dependent Riccati equation (SDRE) controller was the main framework. A finite-time constraint imposed on the equation changes it to a differential equation, known as the state-dependent differential Riccati equation (SDDRE) and this equation was applied to the problem reported in this study that provides general formulation and stability analysis. The following four solution methods were developed for solving the SDDRE; backward integration, state transition matrix (STM) and the Lyapunov based method. In the Lyapunov approach, both positive and negative definite solutions to related SDRE were used to provide suboptimal gain for the SDDRE. Finite-time suboptimal control is applied for robotic manipulator, as finite-time constraint strongly decreases state error and operation time. General state-dependent coefficient (SDC) parameterizations for rigid and flexible joint arms (prismatic or revolute joints) are introduced. By including nonlinear control inputs in the formulation, the actuator׳s limits can be inserted directly to the state-space equation of a manipulator. A finite-time SDRE was implemented on a 6R manipulator both in theory and experimentally. And a reduced 3R arm was modeled and tested as a flexible joint robot (FJR). Evaluations of load carrying capacity and operation time were investigated to assess the capability of this approach, both of which showed significant improvement.     

基于牛顿迭代法的S形加减速时间算法研究

S形加减速控制涉及求解多元高次方程或者不等式,且要求求解出来的最终解是非负数,为此根据时间最优原则和速度、加速度的限制条件,把S形加减速控制中所涉及的五元非线性方程组分解为2个二元非线性方程组和1个一元线性方程。采用牛顿迭代法和迭代修正的方式逐步求解出符合要求的加减速时间,进而求出速度曲线,进行插补运算。仿真与实验结果证明,该算法简明高效、运行稳定,能够满足高速高精数控要求。     

Polyolefin and poly(alkyl methacrylate) mixed additives as mineral lubricating oil rheology modifiers

Some rheological properties of mineral lubricating oils containing polyolefin (OCP) (ethylene/propylene copolymer) and poly(alkyl methacrylate) (PAMA) mixed additives over a wide composition range have been examined. Increasing the OCP content significantly increases the viscosity and shear stability of solutions, whereas the viscosity index is directly proportional to the PAMA content. The pour point values of the additive solutions investigated are lower than −30°C even for the smallest concentration of PAMA in the polymer mixture of 15 wt.% (at a total polymer mixture concentration in oil of 2 wt.%). The viscosities of dilute mixed additive solutions obey the typical Krigbaum‐Wall equation and, due to the negative viscometric interaction parameter values (Δb₁₂ < 0), the OCP/PAMA mixture is found to be immiscible. The immiscibility becomes more pronounced on increasing the overall polymer concentrations. The viscosities of concentrated mixed additive solutions decrease significantly with an increase of OCP content, showing a minimum of half the initial value at a polymer ratio of about 50/50. On decreasing the polymer concentration to practical levels as well as increasing the temperature, the viscosity values approach the ideal additivity law. Based on the ratio of specific viscosities at 40 and 100°C (Q), the OCP additive solution shows a better thickening effect at lower temperatures (Q < 1). On the other hand, the PAMA additive solution shows a better effect at higher temperatures (Q > 1) with more coherent thickening with temperature change. The mixed polymer additive, containing ∼10 wt.% OCP and ∼90 wt.% PAMA, is a nearly optimal viscosity‐index improver showing the same thickening effect at different temperatures. The results obtained are promising as regards the design of lubricant formulations with mixed polymeric additives.     

Estimation of Optimum Genetic Control Parameters for Job Shop Scheduling

Genetic algorithms (GA) have demonstrated considerable success in providing good solutions to many non-polynomial hard optimization problems. GAs are applied for identifying efficient solutions for a set of numerical optimization problems. Job shop scheduling (JSS) has earned a reputation for being difficult to solve. Many workers have used various values of genetic parameters. This paper attempts to tune the control parameters for efficiency, that are used to acceleate the genetic algorithm (applied to JSS) to converge on an optimal solution. The genetic parameters, namely, number of generations, probability of crossover, probability of mutation, are optimized relating to the size of problems. The results are validated in job shop scheduling problems. The results indicate that by using an appropriate range of parameters, the genetic algorithm is able to find an optimal solution faster. RID=" ID=" <E5>Correspondence and offprint requests to</E5>: Dr S. G. Ponnambalam, Department of Production Engineering, Regional Engineering College, Tiruchirapalli, 620 015, India. E-mail: pons&commat;rect.ernet.in     

State-dependent differential Riccati equation to track control of time-varying systems with state and control nonlinearities

This work studies an optimal control problem using the state-dependent Riccati equation (SDRE) in differential form to track for time-varying systems with state and control nonlinearities. The trajectory tracking structure provides two nonlinear differential equations: the state-dependent differential Riccati equation (SDDRE) and the feed-forward differential equation. The independence of the governing equations and stability of the controller are proven along the trajectory using the Lyapunov approach. Backward integration (BI) is capable of solving the equations as a numerical solution; however, the forward solution methods require the closed-form solution to fulfill the task. A closed-form solution is introduced for SDDRE, but the feed-forward differential equation has not yet been obtained. Different ways of solving the problem are expressed and analyzed. These include BI, closed-form solution with corrective assumption, approximate solution, and forward integration. Application of the tracking problem is investigated to control robotic manipulators possessing rigid or flexible joints. The intention is to release a general program for automatic implementation of an SDDRE controller for any manipulator that obeys the Denavit–Hartenberg (D–H) principle when only D–H parameters are received as input data.     

一种非朗伯表面SFS的快速粘性解算法

针对传统的非朗伯表面明暗恢复形状(SFS)算法存在运行时间长、精度不高的问题,提出了一种粘性意义下的明暗恢复形状快速算法。首先,非朗伯物体表面采用Oren-Nayar模型描述其表面反射属性,摄像机镜头使用适合于实际成像过程的透视投影模式,同时假设光源置于镜头像方主点附近,建立了上述情况下的图像辐照度方程,此方程蕴含着非朗伯表面的高度信息。其次,将辐照度方程转化为Hamilton-Jacobi(H-J)类偏微分方程,运用Legendre变换和最优控制理论得到H-J方程对应的Hamilton函数的控制形式。接着,建立了Hamilton函数的逼近算法,使用非线性规划原理构建Hamilton函数最优问题的等价约束问题,利用得到的最优控制并通过Newton法最终得到了H-J方程的粘性解,该粘性解即是非朗伯物体表面的高度。实验结果表明,提出的算法与典型的基于Lax-Friedrichs方法的算法相比,所需要的运行时间大幅度减少,重构的物体表面的高度平均误差与均方根误差也有较大幅度降低。     

Fuel optimal control of parallel hybrid electric vehicles

A mathematical model for fuel optimal control and its corresponding dynamic programming (DP) recursive equation were established for an existing parallel hybrid electric vehicle (HEV). Two augmented cost functions for gear shifting and engine stop-starting were designed to limit their frequency. To overcome the problem of numerical DP dimensionality, an algorithm to restrict the exploring region was proposed. The algorithm significantly reduced the computational complexity. The system model was converted into real-time simulation code by using MATLAB/RTW to improve computation efficiency. Comparison between the results of a chassis dynamometer test, simulation, and DP proves that the proposed method can compute the performance limitation of the HEV within an acceptable time period and can be used to evaluate and optimize the control strategy. __________ Translated from Journal of Shanghai Jiaotong University, 2006, 40(6): 947–951, 957 [译自: 上海交通大学学报]