基于LQR控制的混合轴承动态特性分析

针对主动混合滑动轴承,给出了基于线性二次最优调节器(LQR)的控制策略,分析了轴承的动态特性。采用扰动压力法求解轴承的8个动力特性系数和灵敏系数;给出了不同权重矩阵下轴承动态特性系数的计算结果,并进行了分析讨论。结果表明,LQR控制简单易行,灵活性强,可以有效改善轴承系统的动态特性,降低交叉刚度,提高直接刚度和阻尼,从而改善系统的稳定性。     

Robust guaranteed cost control for singular Markovian jump systems with time-varying delay

This paper is concerned with the guaranteed cost control for continuous-time singular Markovian jump systems with time-varying delay. Without using the free weighting matrices method, a delay-range-dependent condition is derived in terms of strict linear matrix inequality (LMI), which guarantees that the singular system is regular, impulse free and mean-square exponentially stable with an H(∞) performance. Based on this, the existence condition of the guaranteed cost state feedback controller is proposed. A numerical example is given to illustrate the effectiveness and less conservatism of the proposed design method.     

An optimal PID controller via LQR for standard second order plus time delay systems

An improved tuning methodology of PID controller for standard second order plus time delay systems (SOPTD) is developed using the approach of Linear Quadratic Regulator (LQR) and pole placement technique to obtain the desired performance measures. The pole placement method together with LQR is ingeniously used for SOPTD systems where the time delay part is handled in the controller output equation instead of characteristic equation. The effectiveness of the proposed methodology has been demonstrated via simulation of stable open loop oscillatory, over damped, critical damped and unstable open loop systems. Results show improved closed loop time response over the existing LQR based PI/PID tuning methods with less control effort. The effect of non-dominant pole on the stability and robustness of the controller has also been discussed.     

基于T-S模型的集装箱装卸桥防摇保性能控制

基于T-S模型的保性能控制对控制带有不确定性的系统有很好的鲁棒性(如集装箱装卸桥防摇系统),将系统稳定和保性能控制转化为解一系列矩阵不等式的问题,得出最优的反馈矩阵,设计出基于T-S模型的最优保性能控制器,并将该方法进行仿真,结果表明此方法简单可行,并且具有很好的鲁棒性。     

双星编队构形保持抗干扰容错控制

为解决系统模型误差、外部干扰以及执行器故障引起的双星编队轨道控制精度低、稳定性差问题,设计一种基于观测器的抗干扰容错线性二次型调节器(LQR)控制策略.首先,根据编队双星相对运动动力学模型,设计基于双比例积分自适应律的增广观测器,同时实现对系统状态、间歇故障与快速时变故障、可建模干扰的快速精确估计,并采用H∞优化技术抑...     

Improving power system damping using a combination of optimal control theory and differential evolution algorithm

This paper presents a novel control strategy to improve the damping capability of sub-synchronous oscillations by tuning of Linear Quadratic Regulator (LQR) optimally in order to reduce the fluctuations in the power system. The proposed model includes the coordination of Power System Stabilizer (PSS) and Thyristor-Controlled Series Capacitors (TCSC) in combination with LQR controllers which is formulated as an optimal control problem. The problem is formulated as a linear regulator problem and then the Differential Evolution (DE) algorithm is utilized to optimize the proposed controlling parameters. Several cases have been studied to show the efficiency of the proposed strategy. Obtained results from a case study on a typical generator demonstrated that the proposed method has the best response and quickest function among conventional controller systems. Moreover, the coordination of the LQR with the other control systems, as an optimal linear regulator problem in order to damp system oscillations provides robust stability for optimizing system performance index. Besides, the flexibility and usability of the LQR controller guarantee the stability of the system to cope with the oscillations.     

主动悬架LQR控制加权系数多目标遗传算法优化

对多目标遗传算法NSGA-Ⅱ进行了改进,提出了基于改进NSGA-Ⅱ算法的主动悬架LQR控制加权系数设计方法。仿真结果表明,多目标遗传算法一次运行可以获得多组Pareto最优的性能指标加权系数,设计者可以根据偏好选择最终的满意解,避免了现有加权系数选择方法存在的主观性和盲目性。     

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。     

Hierarchical adaptive control of self-stabilizing electromechanical systems using artificial-immune self-tuning mechanism for state weighting-factors

Journal of Mechanical Science and Technology - This article presents a novel self-adaptive linear-quadratic-regulator (LQR) architecture to improve the robustness of self-stabilizing...     

基于可变加权矩阵的机器人雅可比矩阵规范化

末端同时具有平移和转动自由度的机器人雅可比矩阵量纲不统一,导致灵活性指标计算困难,针对此问题提出一种简洁有效的基于可变加权矩阵的雅可比矩阵规范化方法。分析现有规范化方法的原理和不足,根据机器人灵活性的本质意义,提出使对应末端两类速度的雅可比矩阵行矢量有效相对化是雅可比矩阵规范化的核心问题。从雅可比矩阵条件数的定义和各向同性位形的要求出发,给出了雅可比矩阵规范化的一般思路和方法,定义了可变加权矩阵概念。可变加权矩阵直接由雅可比矩阵自身导出,并用于雅可比矩阵规范化,避免了现有方法需要引入额外参数的缺点和不便,也证明了灵活性是机器人的固有属性,与任何额外引入的参数无关。以6R机器人为例进行的理论推导,和以平面3R机器人和Puma560机器人为例进行的数值仿真,验证了可变加权矩阵方法的有效性。     

Robust proportional-integral Kalman filter design using a convex optimization method

This paper proposes a design approach to the robust proportional-integral Kalman filter for stochastic linear systems under convex bounded parametric uncertainty, in which the filter has a proportional loop and an integral loop of the estimation error, providing a guaranteed minimum bound on the estimation error variance for all admissible uncertainties. The integral action is believed to increase steady-state estimation accuracy, improving robustness against uncertainties such as disturbances and modeling errors. In this study, the minimization problem of the upper bound of estimation error variance is converted into a convex optimization problem subject to linear matrix inequalities, and the proportional and the integral Kalman gains are optimally chosen by solving the problem. The estimation performance of the proposed filter is demonstrated through numerical examples and shows robustness against uncertainties, addressing the guaranteed performance in the mean square error sense.     

An uncertainty representation based sampling method for metamodeling in auto-motive design applications

Meta-model is frequently employed as the surrogate of high-fidelity finite element models in computer aided engineering. It helps to achieve the trade-off between computational efficiency and predictive accuracy. To improve the predictive capability of meta-models, we developed an uncertainty representation based sampling method to schedule Design of experiment (DOE) for meta-modeling. Several datasets were first generated through a modified Bootstrap method for datasets acquisition, then the influence of the input uncertainty on the output was quantified as weighting factors. The weighting factors were used to integrate the represented distributions into a single one for further sampling. Finally, the sampling results then served as the elements of the DOE matrix to construct meta-models. The proposed method was demonstrated through an analytical case and a real-world vehicle crashworthiness design problem.

     

一级倒立摆系统设计与LQR最优控制仿真

应用Lagrange力学,对一级倒立摆系统进行数学建模,得出了状态空间方程;设计了一级可控倒立摆系统,并对系统进行了性能分析;设计了直线一级倒立摆的LQR控制器,通过仿真和实验证明,LQR实时控制效果好,保证了系统具有良好的稳定性和鲁棒性。     

磁轴承飞轮控制系统设计中LQR方法的应用研究

对于具有强的陀螺效应的磁悬浮飞轮转子,将转子各自由度作为独立个体采用分散控制难以满足系统要求,而LQR方法不失为一种有效的集中控制方法。通过对LQR控制方法在飞轮转子上的仿真研究,给出了LQR方法应用于磁悬浮系统控制时,加权阵Q阵与R阵的选取原则,并对反馈阵F中各参数的物理本质进行了阐述。由仿真结果与理论推导相结合,论证了陀螺位移交叉反馈的作用,由此给出了LQR控制的一种简化实现方法。     

后装式压缩垃圾车结构有限元分析

要对后装式压缩垃圾车结构进行有限元分析,必须给出压缩垃圾对垃圾车车箱结构作用载荷的数学表达.而压缩垃圾是一种力学性质很不确定的混合物,因而其结构有限元分析具有较大难度.采用实际测试和变参数描述相结合的方法给出垃圾载荷的数学表达,利用ANSYS进行结构有限元分析调校载荷数学表达中的可变参数,保证了分析计算与实验测试结果的一致性,成功地对该结构进行了详尽的有限元分析计算,获得了该结构在各种实际工况下的应力及变形分布,为后装式压缩垃圾车的结构改进与优化设计打下了基础.     

汽包锅炉蒸汽温度的组合混合自适应预估控制器的设计

针对汽包锅炉蒸汽温度的特点，设计了一种具有预估功能的组合混合自适应控制器，它包括几个混合自适应控制器，且这几个控制器并联工作，控制信号由这几个控制器加权获得。理论分析和现场实验结果都表明此方案对解决火电厂热工过程的非线性和大时滞有显著效果，且有快速的适应性和强的鲁棒性，为自适应技术在火电厂中的进一步应用进行了尝试。     

Regulation on radial position deviation for vertical AMB systems

As a source of model uncertainty, gyroscopic effect, depending on rotor speed, is studied for the vertical active magnetic bearing (VAMB) systems which are increasingly used in various industries such as clean rooms, compressors and satellites. This research applies H^∞ controller to regulate the rotor position deviations of the VAMB systems in four degrees of freedom. The performance of H^∞ controller is examined by experimental simulations to inspect its closed-loop stiffness, rise time and capability to suppress the high frequency disturbances. Although the H^∞ is inferior to the LQR in position deviation regulation, the required control current in the electromagnetic bearings is much less than that for LQR or PID and the performance robustness is well retained. In order to ensure the stability robustness of H^∞ controller, two approaches, by Kharitonov polynomials and TITO (two inputs & two outputs) Nyquist Stability Criterion, are employed to synthesize the control feedback loop. A test rig is built to further verify the efficacy of the proposed H^∞ controller experimentally. Two Eddy-current types of gap sensors, perpendicular to each other, are included to the realistic rotor-bearing system. A four-pole magnetic bearing is used as the actuator for generation of control force. The commercial I/O module unit with A/D and D/A converters, dSPACE DS1104, is integrated to the VAMB, gap sensors, power amplifiers and signal processing circuits. The H^∞ is designed on the basis of rotor speed 10 K rpm but in fact it is significantly robust with respect to the rotor speed, varying from 6.5 to 13.5 K rpm.     

Performance improvement of PI controllers through dynamic set-point weighting

Responses of high-order systems under Ziegler-Nichols tuned PI controllers (ZNPIs) are characterized by excessive oscillation with a large overshoot. Although, a fixed set-point weighting based PI controller (FSWPI) may decrease the overshoot considerably, it fails to reduce the oscillation in the set-point response. Moreover, both FSWPI and ZNPI exhibit equally poor load regulation. Keeping in mind an overall improved performance, we propose an online dynamic set-point weighting technique for ZNPIs. The dynamic set-point weighting factor (β_d) is heuristically derived from the instantaneous process trend. Performance of the proposed dynamic set-point weighting based PI controller (DSWPI) for various second- and third-order processes including a pH process shows a significant improvement during both the set-point and load disturbance responses over other methods. Stability and robustness of the proposed DSWPI are addressed. Effectiveness of the DSWPI is demonstrated through the real-time implementation on a practical DC position control system.     

Dynamic characteristic analysis and lmi-basedh∞, controller design for a line of sight stabilization system

This paper is concerned with the design of an LMI (Linear Matrix Inequality)-basedH∞, controller for a line of sight (LOS) stabilization system and with its robustness performance. The linearization of the system is necessary to analyze various nonlinear characteristics, but the linearization entails modeling uncertainties which reduce its performance. In addition, the stability of the LOS can be adversely affected by angular velocity disturbances while the vehicle is moving. As the vehicle accelerates, all the factors that are ignored and simplified for the linearization tend to inhibit the performance of the system. The robustness in the face of these uncertainties needs to be assured. This paper employsH∞ control theory to address these problems and the LMI method to provide a suitable controller with minimal constraints for the system. Even though the system matrix does not have a full rank, the proposed method makes it possible to design aH∞ controller and to deal withR and S matrices for reducing the system order. It can be also shown that the proposed robust controller has a better disturbance attenuation and tracking performance. The LMI method is also used to enhance the applicability of the proposed reduced-orderH∞ controller for the system given. The LMI-basedH∞ controller has superior disturbance attenuation and reference input tracking performance, compared with that of the conventional controller under real disturbances.     

倒立摆控制方法的比较研究

倒立摆系统作为典型的控制对象,不仅对控制设计提出了难题,同时为很多先进控制方法的研究和应用提供了一个很好的实验平台。该文分别用PID控制法、优化控制策略的LQR及极点配置法等3种方法对单级倒立摆系统进行控制,并利用MATLAB仿真对3种控制算法的效果进行了对比,讨论了3种方法之间的优缺点。仿真实验表明:PID法与极点配置法具有较好的瞬态性,LQR法具有较好的鲁棒性。在实际应用中,可根据控制系统的具体指标要求选择适合的控制方法,具有一定的指导意义。