【作者】 李嘉全；

【导师】 王永；

【作者基本信息】 中国科学技术大学 ， 控制科学与工程， 2008， 博士

【摘要】 潜艇的声隐身能力是关系其生命力和战斗力的重要因素之一,因此降低潜艇的振动噪声水平是一件非常重要的工作。浮筏是目前广泛应用于各国潜艇的一种减振降噪设备,它能显著地降低艇内设备的高频段振动向艇体的传递,但在低频段的减振效果却不甚理想。本文以提高浮筏的低频减振能力为目标,开展浮筏系统的振动主动控制研究。研究主要包括以下几个方面的内容:带有主动吸振器的浮筏系统的建模,主动吸振器安装位置的优化配置,单频简谐振动的自适应前馈控制,考虑作动器饱和约束的自适应前馈控制,以及在模拟浮筏系统上的振动主动控制实验研究。浮筏是一种结构复杂的组合式系统,在理论分析中通常需要对它的结构进行一些简化。本文首先将浮筏的中间筏架用一个规则形状的薄板近似;然后再将浮筏系统分解成若干个子系统,如板式筏架子系统、弹性基础子系统等,运用四端参数网络建立了它们的动力学传递方程,传递特性由导纳矩阵描述;接着,将动力吸振器和主动吸振器的分析统一于一个框架内,获得了与吸振器耦合的板式筏架子系统的动力学传递特性;最后,根据各子系统在各界面上的作用力和速度的相互关系,通过子系统结构导纳综合方法获得了整个板式浮筏系统的动力学传递方程,并在此基础上获得了系统的力传递函数模型。由于浮筏的主体结构是由弹性体组成的,因此在对它进行振动主动控制之前,必须研究作动器的优化配置问题。本文着重研究了作动器安装位置的优化配置,提出了两种配置准则:基于状态反馈的闭环优化配置准则和基于分段加权面积性能指标的优化配置准则。其中,前者适用于结构振动主动控制的作动器配置,而后者适用于宽频振动主动控制的作动器配置。最后,分别运用提出的优化准则,确定了主动吸振器在板式浮筏系统上的最佳安装位置在简谐振动的自适应前馈控制中,准确、稳定的参考信号是控制成功的关键,但在工程应用中却很难直接获得。为此,本文提出了一种基于自适应带通滤波器的信号频率估计方法,并在此基础上人工生成参考信号。该方法通过自适应调整滤波器参数,使滤波器的通带频率与待估计信号频率相同,此时带通滤波器输出的平方最大。由于带通滤波器的带宽可以设置的很窄,这样通带频率以外的信号进入滤波器后都将大幅衰减,从而提高了待估计信号的信噪比,保证了本文提出的信号频率估计方法具有较好的抗噪声能力。本文采用基于滤波x-最小均方(Least Mean Square;LMS)算法的自适应前馈控制实现对单频简谐信号激励的浮筏系统的振动主动控制。从系统特性对滤波x-LMS算法性能的影响出发,得出了增加系统控制通道的等效阻尼能够显著提高滤波x-LMS算法性能的结论。提出了两种增加控制通道等效阻尼的方法:闭环子系统阻尼补偿和自适应前馈等效阻尼补偿。在此基础上,分别推导出了相应的改进滤波x-LMS算法,并通过仿真实验验证了改进算法的有效性。本文在考虑作动器饱和约束对采用自适应前馈控制律的振动主动控制效果影响的基础上,提出了一种理想抗饱和策略:在控制器自适应更新过程中,一旦输出控制量幅值达到饱和约束值时,控制器就停止(或基本停止)更新。给出了该策略的两种截然不同的LMS算法实现:基于控制量连续约束的抗饱和LMS算法和预测变步长抗饱和LMS算法。理论分析和仿真实验结果都表明,基于两种抗饱和LMS算法的前馈控制器都严格地满足控制量饱和约束条件,同时也最大程度地降低了误差信号。最后将两种算法推广到滤波x-LMS算法情形,得到了相应的抗饱和滤波x-LMS算法。建立了一套具有4个主动吸振器的模拟浮筏振动主动控制物理实验系统,并采用基于分段加权面积性能指标的作动器优化配置准则确定了主动吸振器的最佳安装位置。采用实验建模的方式,离线辨识出了系统16个控制通道在10～30Hz频段内各实验频率点处的有限脉冲响应序列模型。进行了单频简谐信号激振条件下的模拟浮筏振动主动控制实验。其中,控制律采用本文提出的基于预测变步长抗饱和滤波x-LMS算法的多变量自适应前馈控制律,人工生成参考信号,信号频率通过本文提出的自适应带通滤波器估计方法获得。实验结果表明,本文研究的振动主动控制方法可以显著地提高模拟浮筏物理实验系统在实验频段内的减振能力。更多还原

【Abstract】 Acoustic hiding ability is a key factor related with submarines’ vitality and fighting strength,hence it is important to decrease their vibrations and noises. Floating raft is currently widely equipped in lots of nation’s navy for vibration and noise attenuation in submarine.The high-frequency band vibration produced by equipments mounted on the raft can be reduced a lot by it,while low-frequency band vibration can’t be depressed much.Research in this paper is focused on improving floating raft’s ability in decreasing low-frequency band vibration via active vibration control.It includes following contents:modeling of floating raft with active absorbers,optimization of mounting positions of active absorbers,adaptive feed-forward control on mono-frequency vibration,adaptive feed-forward control with actuator saturation,and experiment study on active vibration control of simulative floating raft system.In order to have theoretical analysis on floating raft system,it often needs to do some simplification on its structures.In this paper,the raft is approximated by a thin plate with regular shape at first.Then the floating raft system is divided into several subsystems,such as plate raft,elastic foundation,etc,which are respectively modeled by four-parameter net method.After that,dynamic absorber and active absorber are put into a uniform frame to obtain the model of plate raft subsystem coupling with them.At last,according to the force and velocity relationship among each subsystem’s interfaces,the entire plate floating raft system is modeled by subsystem structural admittance synthesis method.As the main structure of floating raft system is elastic,it is inevitably to study the optimization of actuators’ mounting positions before designing control law.In this paper,two new criterions are proposed for it.They are close-loop allocation criterion based on states feedback and allocation criterion on the basis of piecewise weighing area performance index.The former one is appropriate for actuators’ allocation in structure active vibration control,and the latter is applicable for allocation in wind-band vibration control.Finally,the best mounting positions of absorbers on floating raft are determined by using the criterion above.Accurate and steady reference signal is a key point that decides control’s success in adaptive feed-forward control on simple harmonic vibration.A new frequency estimation method,which is based on an adaptive band-pass filter,is proposed.The estimated frequency is then used to generate reference signal.The band-pass frequency of filter is equal to that of estimated signal when filter’s parameter is tuned to right value,and square of filter’s output reaches its maximum.Because the band-pass can be set very narrow,signals except one with the band-pass frequency are attenuated much when pass the filter.Therefore,the proposed frequency estimation method is an anti-noise method.In this paper,the active vibration control on floating raft system is achieved by adaptive feed-forward control law with the core of Filtered x-Least Mean Square (LMS)algorithm.Influence imposed by system characteristics on Filtered x-LMS algorithm performance is studied,and a fact is realized that the performance of algorithm can be improved by increasing control path’s damping ratio.Two realizations are given:damping compensation by forming close-loop subsystem and adaptive feed-forward damping compensation.Corresponding improved Filter x-LMS algorithms are derived,and the effectiveness and effect of them are confirmed by simulations.Active vibration control performs worse if the actuator saturation happens.An ideal anti-saturation strategy for adaptive feed-forward control is proposed in this paper.Its main idea is that the controller will stop updating when its output reaches the maximum amplitude allowed.Two different realizations in the form of LMS algorithm are put forward,which are anti-saturation LMS algorithm via continuous constraints on control quantity and predictive variable step anti-saturation LMS algorithm.Both the theoretical analysis and simulation results show their strict obedience to the saturation constraints along with the desirable control performance. In the end,algorithms mentioned above are widened to anti-saturation Filter x-LMS algorithms,which can be directly used in active vibration control.At the End of this paper,the experiment study on active vibration control of floating raft system is executed.A simulative floating raft system with 4 active absorbers is established firstly.Then,the optimal mounting positions of 4 active absorbers are determined by utilizing the wide-band criterion based on piecewise weighing area performance index.Finite Impulse Response(FIR)models of 16 control paths of system in 10～30Hz are identified offline by LMS algorithm.The experiment of active vibration control on simulative floating raft system is then carried out.In the experiment,the floating raft is excited by mono-frequency simple harmonic signal,and is controlled by multiple variables adaptive feed-forward control law based upon predictive variable step anti-saturation Filtered x-LMS algorithm.The reference signal is man-made,of which the frequency is estimated by adaptive band-pass filter.Experiments results demonstrate that the damping ability of simulative floating raft system in experimental frequency band is significantly improved by active vibration control methods proposed in this paper.更多还原