摘要
研究了多输入时滞反馈控制作用下斜拉梁主共振问题.采用多尺度法,推导了位移时滞和速度时滞反馈控制作用下斜拉梁非线性主共振的解析解,分析了主共振响应随参数变化的规律,控制参数时滞和控制增益对系统非线性主共振响应的影响.结果表明:合理地调整时滞值、控制增益可以提高振动控制的效率,拓宽减振频率范围,且在参数的调节中时滞较控制增益对减振更为有效.
斜拉梁作为一种重要结构形式,在工程结构中广泛存在,如斜拉桥、大型场馆等.随着跨度增大,结构体系的刚度有所下降,在外部荷载的作用下拉索、主梁易产生大幅振动,其非线性动力学及振动控制问题引起了众多学者的关
Nakamura
与此同时,Olgac
本文将采用多输入时滞反馈控制对斜拉梁非线性动力响应开展研究.采用多尺度法求解其非线性方程,通过幅频响应曲线反映其控制效果,分析不同参数条件下受控系统非线性主共振响应.
本文所研究斜拉梁模型如
(1) |

图1斜拉梁振动控制模型图
Fig.1 Diagram of vibration control model of cable-stayed beam
无量纲参数和变量如下
(2) |
其中,分别为索(梁)单位长度质量; 分别为索(梁)的长度;分别为索(梁)的弹性模量;分别为索(梁)的横截面面积;为拉索初始张力的轴向分量;为梁的轴向力;为拉索倾角;和为梁横截面的惯性矩;;为单位长度方向上的粘性阻尼系数.和是索和梁的近似动态应变,表达式如下
(3) |
为了方便书写,将
(4) |
几何条件和力学条件为
(5) |
其中,,.定义位移向量,运用Galerkin方法,令
(6) |
其中,是广义坐标,是模态函
(7) |
其中外部激励,在本文中主要讨论多输入时滞反馈控制,采用位移和速度时滞反馈策略进行振动控制,则控制力为
(8) |
其中,和分别为位移和速度反馈控制器的控制增益,和分别为位移和速度反馈的时滞.将
(9) |
采用多尺度
(10) |
其中,调整系数,令
(11) |
其中,为激励频率,为小参数,为调谐参数.将
(12) |
(13) |
(14) |
(15) |
其中,,代表前面各项的共轭复数.将
(16) |
将
(17) |
令,其中和是的实函数,代入
(18) |
(19) |
其中,令,将
(20) |
其中
(21) |
同时,由方程(20)可得主共振响应幅值的峰值为
(22) |
相应的临界激励幅值为
(23) |
当时,
本节主要对斜拉梁第一阶模态的主共振响应进行数值分析,讨论时滞和控制增益与主共振响应的关系.其中梁及索的几何尺寸和材料特性参数如

图2 斜拉梁主共振响应峰值和临界激励幅值曲线
Fig.2 Peak resonance amplitude and critical excitation amplitude curve of cable-stayed beam
如

图3 时滞值和控制增益对幅频曲线的影响
Fig.3 The influence of time-delay value and control gain with the amplitude-frequency curve
减振率可见

图4 不同增益下斜拉梁结构的主共振响应幅频曲线(改变)
Fig.4 The amplitude-frequency curves of main resonance response of cable-stayed beams with different gain (Change the )

图5 不同增益下斜拉梁结构的主共振响应幅频曲线(改变)
Fig.5 The amplitude-frequency curves of main resonance response of cable-stayed beams with different gain (Change the )
可以得出,在多输入时滞反馈控制下,对减振效果的影响,时滞值变化较大于控制增益变化的影响,而且在只改变控制增益的情形下,减振效果主要受到位移时滞反馈控制的影响,速度时滞反馈控制的介入更多地影响了时滞反馈控制控制域的带宽.
本文主要研究了采用多输入时滞反馈控制斜拉梁的主共振问题.利用时间多尺度法研究了主共振响应,得到结论如下:斜拉梁非线性动力系统采用多输入时滞反馈控制进行振动控制效果明显,在参数的调节中时滞对减振效果的影响大于控制增益的影响.当只改变控制增益值时,振动控制效果取决于位移时滞反馈控制的参数,速度时滞反馈控制增益则有效增大其振动控制域的带宽.
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