Mixed sensitivity H_∞ control for LTI systems with varying time delays

Designing a robust controller for a system with timevarying delays poses a major challenge. In this paper, we propose a method based on mixed sensitivity H∞ for the control of linear time invariant（LTI） systems with varying time delays. The time delay is assumed bounded and the upper bound is known. In the technique we propose, the delay affecting the plant to be controlled is treated as an unmodeled uncertainty（in form of multiplicative uncertainty）. That uncertainty is approximated and then an H∞based controller, for the plant represented by the multiplicative uncertainty and the nominal model, is calculated. The obtained H∞controller is used to control the LTI systems with varying time delays. Simulation examples are given to illustrate the effectiveness of the proposed method.

H_∞-Mixed Sensitivity Design of Roll Channel of Bank-to-Turn Autopilot for Small Diameter Bomb

According to requirements of the bank-to-turn (BTT) control for a small diameter bomb (SDB), the robust design problem for the roll autopilot was studied by H∞-mixed sensitivity control method. A roll channel dynamics model was established. Considering the couple between the yaw and roll channel as uncertain disturbance, the roll autopilot was designed using dual-loop scheme which takes a linear quadratic regulator (LQR) as inner-loop, to ensure the control effect of the certain part in model, and an H∞-mixed sensitivity control as outer-loop, to restrain coupling disturbance and strengthen the system's robust performance. The dynamic tracking performance and the robustness for the parameter disturbance of the roll controller were analyzed. The simulated results show that the roll control system functions better and robustly.

Improved Hybrid Robust Control Method for the Electromechanical Actuator in Aircrafts

In the flight process of aircrafts, their electromechanical actuators（EMA） must have the ability of enduring uncertainties caused by factors such as load disturbance, the variation of work temperature and the EMA＇s nonlinearity. At present, in order to increase the EMA＇s robustness on the uncertainties, the H, control method has been applied in aircrafts. The major problems with standard H∞ control lie in the large overshoot of step response and the high orders of the controller. For the purpose of addressing the two problems, this paper investigates several kinds of robust control strategies of the EMA. A mathematical model of the EMA is first built, and then with MATLAB software a H∞ controller and an improved hybrid robust controller composed of a reduced order H∞controller and a lead compensator are designed. In order to make a scientific comparison of the control effects of H∞ controller, hybrid controller and classic proportion-integral-differential（PID） controller, a simulation research is made in respect of the open loop frequency response and the closed loop step response of the three controllers. For comparing the robustness of the three controllers, the load torque is entered as a disturbance and the disturbance response of error and control input are thus obtained. The experiments with the three controllers are also conducted. Through giving the EMA a command and a disturbance torque successively, the transient response and disturbing process of EMA are recorded. The simulation and experiment results show that with the help of the hybrid controller, the EMA not only guarantees good dynamic characteristics, but also has strong robustness of disturbance rejection. Therefore, the excogitated H∞ hybrid control method effectively solves the problem of large overshoot in dynamic response, and moderately meets the requirement of overcoming the uncertainties in the EMA of aircrafts.

H_∞ Control of Bio-dissimilation Process of Glycerol to 1,3-Propanediol

A robust controller is designed by using the bilinear transformation and H∞ mixed sensitivity method for bio-dissimilation process of glycerol to 1,3-propanediol. Under the controller the system works near an optimal steady-state for the volumetric productivity of 1,3-propanediol attaining its maximization. The design procedure is carried out by tuning the transformation parameter and DC gain of the performance weighted function, which is an iterative and optimal search process. Simulation results are presented which show that the designed robust controller not only ensures the robust stability of the system in face of the parametric variations in the model, but also makes the system have a favourable robust tracking performance. The validity of the proposed H∞ controller has been tested.

Soft initial-rotation and H_∞ robust constant rotational speed control for rotational MEMS gyro

A novel soft initiai-rotation control system and an H∞ robust constant rotational speed controller （RCRSC） for a rotational MEMS （micro-electro-mechanical system） gyro are presented. The soft initial-rotation control system can prevent the possible tumbling down of the suspended rotor and ensure a smooth and fast initial-rotation process. After the initial-rotation process, in order to maintain the rotational speed accurately constant, the RCRSC is acquired through the mixed sensitivity design approach. Simulation results show that the actuation voltage disturbances from the internal carrier waves in the gyro is reduced by more than 15.3 dB, and the speed fluctuations due to typical external vibrations ranging from 10 Hz to 200 Hz can also be restricted to 10^-3 rad/s order.

欺骗攻击下奇异跳变系统状态感知事件触发H_(∞)-脉冲混杂反馈控制

本文研究了在欺骗攻击下奇异马尔可夫跳变系统的状态感知事件触发H_(∞)-脉冲混杂反馈控制问题。为了进一步权衡控制性能和通信效率,提出了一种可根据当前系统状态自适应地调整事件触发阈值的基于周期采样的模态相关状态感知事件触发机制。基于所提出的事件触发机制,建立了一种模态相关的脉冲混杂反馈控制器。通过构造脉冲时间相关和马尔可夫跳变模态相关的Lyapunov-Krasovskii(L-K)泛函并结合奇异值分解技术,获得了奇异马尔可夫跳变系统在欺骗攻击下的H_(∞)随机容许性准则。在线性矩阵不等式框架下实现了状态感知事件触发器和H_(∞)-脉冲混杂反馈控制器协同设计。直流电机驱动负载的仿真实例验证了本文方法的有效性。

基于H_∞鲁棒控制的挠性卫星姿态控制

针对存在未建模动态、模型参数不确定性和外力矩扰动的挠性卫星,通过选择合适的加权函数将挠性卫星姿态控制问题转化为H∞混合灵敏度问题。采用H∞优化方法设计了鲁棒控制器。最后对卫星姿态控制系统进行了仿真研究,结果表明采用鲁棒控制器的姿控系统较传统的PID控制的姿控系统具有更好的鲁棒稳定性和抗干扰性能。

热连轧卷取机踏步系统鲁棒H_∞控制研究

针对热连轧过程中的带头损失问题,开发带有位置调节和压力调节的步进式电液伺服系统,并应用一种简化的H∞控制混合灵敏度算法对系统进行闭环增益设定,其核心是确定闭环系统传递函数即T的最终希望的形状,直接设计出K,从而避免了权函数的选择。研究结果表明用此法设计的H∞控制器对于步进控制系统是有效的。

基于H_∞混合灵敏度方法的超声波电机调速控制

为提高行波型超声波电机转速跟踪的准确性和平稳性,改善因调频调速非线性带来的调速性能变化,将H∞混合灵敏度方法应用于转速控制器的设计.采用参数辨识法建立电机的频率转速模型,线性化得到电机的标称模型,将静态模型的非线性转化为标称模型的增益摄动,将动态模型的参数变化转化为标称模型的高阶未建模误差,把电机的转速模型表示为标称模型与误差模型和.根据模型误差界和调速性能指标,求取混合灵敏度加权函数,将控制器设计转化为标准的H∞优化问题,通过Matlab工具求解鲁棒控制器.仿真验证了转速闭环的稳定鲁棒性,使用数字信号处理芯片TMS320F28335在实际控制回路中实现该控制器,并测试电机调速性能.实验结果表明,鲁棒控制器应用于超声波电机调速系统可以取得良好的控制效果.

H_∞控制理论在磁悬浮轴承系统中的应用研究

讨论了鲁棒H∞控制理论灵敏度和补灵敏度加权因子的选择方法,设计了磁悬浮轴承系统的H∞控制器;研制了基于PC机的磁悬浮轴承实时数控系统,用C语言设计了H∞控制器的软件。仿真结果表明,采用H∞控制,系统具有良好的动态性能、较强的鲁棒性和抑制转子振动的能力。对一个五自由度的磁悬浮轴承系统进行试验研究,结果表明,采用H∞控制器成功实现了五自由度磁悬浮轴承系统的稳定悬浮,在最高转速30 000r/min时转子的振动峰峰值小于60μm。

柴电混合电力推进船舶负载频率H_∞鲁棒控制

[目的]风、浪及海流等多种随机不确定因素会引起船舶综合电力系统负载频率的波动。[方法]采用电池补偿柴油发电机组输出功率与船舶需求功率之间的差值,对柴油发电机组进行二次调频控制,保证船舶电网功率平衡,抑制电网频率波动。建立综合电力推进系统频率控制状态空间模型,基于H_∞混合灵敏度原理,选取合理的灵敏度与补灵敏加权函数设计鲁棒控制器,采用线性矩阵不等式(LMI)方法对设计的控制器进行求解并进行算例仿真。[结果]系统幅频特性表明,设计的鲁棒控制器具有合理性,短时冲击信号作用下的性能表现满足指标要求。与传统PI控制器的对比结果表明,设计的鲁棒控制器能显著抑制随机扰动引起的电网负载频率波动,减小柴油发电机组与电池的功率变化,电池荷电状态(SOC)变化范围明显缩小,可提高船舶电力系统鲁棒稳定性与鲁棒性能。[结论]该系统在各种工况下都能稳定运行并且使电网频率稳定,同时提高柴油发电机组燃油经济性,减小废气排放。

磁悬浮球的H_∞控制研究

设计了一种磁悬浮球实验系统,建立了磁悬浮球的控制模型。基于H∞混合灵敏度控制理论,研究了加权阵的选取规律和方法,设计了磁悬浮球的H∞鲁棒控制器。开发了功率驱动系统和光电位置检测系统,并用DSP系统实现了H∞控制算法。仿真分析和实验结果表明:该磁悬浮系统具有较高的控制精度和鲁棒性,解决了磁悬浮系统中的建模精度低,外界干扰难以避免等棘手问题。

H_∞控制器应用于船舶自动舵

应用Ｈ∞控制的Ｓ／Ｔ混合灵敏度方法于船舶自动舵设计。按机理估算模型乘性摄动上限，据此确定优化指标中的权函数Ｗ２。利用设计的控制器对闭环系统在多种环境条件下进行了仿真研究，结果是满意的。

综合飞行/推进系统H_∞控制设计

应用混合灵敏度H∞控制理论研究了综合飞行/推进系统多变量鲁棒控制器设计问题,分析并提出了合理构造和调整加权阵设计综合控制律的方法,针对混合灵敏度H∞控制设计的关键———构造加权阵问题,从加权阵的约束条件和控制系统设计的性能指标两方面入手,通过构造和调整两个加权阵频域特性,以达到对控制系统进行频域整形的目的,仿真结果证明了方法的有效性。

机翼颤振的混合灵敏度H_∞鲁棒控制器设计

主动颤振抑制技术是未来弹性飞行器设计中的一项关键技术,越来越受到广泛的关注。但传统的LQG方法鲁棒性很差,限制了其实际应用。本文采用混合灵敏度H∞控制方法,并结合回路成型技术设计了机翼颤振抑制的鲁棒控制器。此方法直接针对回路的灵敏度函数和补灵敏度函数性质,根据颤振抑制系统期望的回路频域特性要求,通过选择合适的加权函数形状获得了满意的闭环系统性能,从而实现对颤振的鲁棒抑制。其特点是能够方便直观的获得系统所期望的频域性能,并具有良好的鲁棒性和抑噪能力,非常有利于工程实用。最后利用典型的二维机翼俯仰沉浮气动弹性系统模型,分别采用混合灵敏度H∞控制器和LQG控制器对机翼颤振进行抑制。仿真结果表明,本文所设计的控制器将颤振速度提高了12.2%,能够更加有效地抑制机翼颤振。

一种改进的同伦算法与H_∞鲁棒控制器设计

提出了一种具有阶次限制的鲁棒控制器设计方法,该算法将控制系统的性能指标转化为灵敏度函数问题,并利用Nevanlinna-Pick插值算法进行求解.提出了一种改进的同伦算法,将其用于求解由灵敏度函数产生的非线性方程.基于改进同伦算法设计的鲁棒控制器不仅避免了传统H∞控制中加权函数的选择问题,而且克服了鲁棒控制器阶次较高的缺陷.最后,文章以4阶系统为例,设计了具有阶次限制的H∞鲁棒控制器,通过与传统鲁棒控制器的比较可以看出,基于本文方法设计的控制器不仅具有较低的阶次,而且其控制性能也具有明显的优越性.

一类线性切换系统H_∞状态反馈控制:LMI方法

研究一类由任意有限多个线性子系统组成的切换系统的H∞状态反馈控制问题.利用Lyapunov函数方法,给出由线性矩阵不等式(LM I)表示的控制器存在的充分条件,并设计了相应的子控制器和切换策略.最后给出一个数值仿真实例,证明了所得结论的有效性.

可控约束阻尼层结构的H_∞控制

建立了可控约束阻尼层板的一般控制微分方程。对附加可控约束阻尼层的悬臂矩形板进行了实验与理论建模 ,详细分析了模型中的不确定性 ,并进行了 H∞ 鲁棒振动控制的数值仿真与实验研究。结果表明 ,H∞ 控制能够有效抑制受控结构的模态振动 ,与位移比例反馈控制相比 ,具有更好的鲁棒稳定性。

H_∞方法在振动主动鲁棒控制中的应用

研究了振动系统频域不确定和参数不确定两种情形的Ｈ∞鲁棒控制设计问题，文中对参数不确定情形提出了结构摄动鲁棒稳定与灵敏度函数设计相结合的设计方法。对一个实例的数值仿真结果证实了所提方法的有效性，并且表明Ｈ∞方法能够较满意地处理振动控制中的不确定性，因而在振动主动鲁棒控制设计中有着较大的应用潜力。

统一潮流控制器的H_∞鲁棒控制器设计

基于H∞控制理论,运用混合灵敏度方法设计了UPFC的H∞鲁棒控制器。仿真表明:UPFC的H∞控制具有比线性最优控制更好的动态品质,并使系统具有较强的鲁棒性和稳定性。