中立型时滞反馈扭转控制系统的稳定性分析

研究了中立型时滞动力吸振器抑制扭转系统的振动问题.针对一类强迫扭转振动系统,采用动力系统的稳定性理论分析了动力吸振器与扭转振动系统的稳定性问题,以时滞为参数,分别得到了动力吸振器与扭转振动系统的稳定区域,并研究时滞变化时动力吸振器对于主振动系统振动的吸收效果,通过与时滞动力吸振器对比,得到了更大的吸振器和减振系统时滞稳定工作区域,通过数值模拟验证了结论的正确性.     

LQR控制和时滞反馈控制在汽车整车减振中的应用

本文建立了具有动力吸振器的汽车整车模型,分别研究了LQR控制和时滞反馈控制在降低汽车整车垂向振动方面的应用。对于LQR控制,选取了包含车身位移、速度和控制力在内的性能指标,借助matlab求解得到反馈增益矩阵;对于时滞反馈控制,首先采用特征值法分析了系统的稳定性,其次从理论上研究了时滞和反馈增益系数对吸振器减振效果的影响,并进行了数值验证。结果表明,与被动式吸振器相比,在LQR控制下吸振器使车身加速度幅值降低了51.38%,在时滞反馈控制下,当g=0.25 kg,τ=0.006 s时吸振器使车身加速度幅值降低了65.13%。     

动力吸振器对转子系统气流激振稳定性影响分析

针对气流激振引起离心压缩机转子振动失稳的问题,提出了采用动力吸振方法提高转子系统的稳定性.首先建立流体激励作用下转子 吸振系统动力学模型;其次采用Lyapunov理论研究附加吸振器后流体激励作用下转子系统的稳定性;分析了吸振器参数变化对转子系统稳定性的影响;最后采用数值方法进行验证.结果表明,动力吸振方法能够有效地提高转子系统失稳转速,吸振器固有频率和阻尼比对转子稳定性有较大的影响.     

橡胶动力吸振器在艉轴上的应用

针对艉轴的振动噪声控制要求,利用动力吸振技术降低设备系统在特定频率处的振动,降低设备振动向壳体的传递,减小水下辐射噪声。采用理论设计、仿真分析与测试相结合的方法,对所设计的圆盘式橡胶动力吸振器进行仿真分析,获取动力吸振器的设计参数及预期吸振效果。通过分析动力吸振器的基本性能,并结合实际应用,进行动力吸振器的吸振效果测试。结果表明：设计的橡胶动力吸振器具有较好的吸振效果。     

铰支柔性梁主参数共振的时滞反馈控制

研究了时滞反馈控制作用下铰支柔性梁主参数共振问题.采用多尺度法,从理论上推导了时滞位移反馈控制作用下铰支柔性梁非线性主参数共振,分析了时滞、反馈控制增益,非线性系数等系统参数对系统非线性主参数振动的影响,分析了主参数动力响应随参数变化的规律.结果表明:随着反馈增益的增大,系统响应幅值得到明显抑制,合理地控制系统参数选取可提高振动控制的效率.     

含时滞轨道吸振器的建筑结构的动力学分析

本文研究了具有时滞轨道非线性吸振器的建筑结构的动力响应及其控制效果.采用谐波平衡法和弧长延拓法给出了简谐激励作用下主结构的幅频响应曲线,并与龙格库塔法的结果进行了对比.考察了不同参数情况下幅频曲线的变化情况,揭示了系统的复杂运动现象.结果表明,轨道非线性会导致幅频曲线向左偏转.时滞反馈控制能够降低主结构的位移幅值,并可抑制混沌响应.     

高速列车转向架的主动稳定性研究

提出了基于构架横向振动的高速列车稳定性主动控制方法,讨论了采用惯性作动器控制构架横向振动,以及对动力转向架驱动系统采用主动弹性悬挂这两种实施方式.以车辆蛇行稳定性指标和控制力作为两个目标函数,利用遗传算法(NSGA-II)来优化控制参数和驱动系统悬挂参数.研究表明构架横向振动控制可以有效地提高转向架蛇行稳定性.同时发现当直接反馈构架状态实现构架振动控制时,控制系统时滞易导致系统失稳,因此提出一种通过反馈附加振子状态的方法来减小时滞的影响,合理的附加振子悬挂参数有利于提高车辆系统稳定性.较硬的附加振子可提高转向架控制系统的蛇行临界速度裕度,但会导致控制系统在一定的时滞内出现不稳定的现象.因此,在优化附加振子悬挂参数时,必须同时兼顾转向架蛇行稳定性和控制系统稳定性.本文对于涉及的350 km/h高速列车转向架,得出了附加振子的最佳固有频率和阻尼比.     

转子-电磁轴承非线性系统时滞减振研究

电磁轴承具有与转子无接触、可施加主动控制等特性,越来越多地被应用于高速旋转机械的支撑与减振.为了研究转子-电磁轴承系统中时滞的减振作用,在主共振情况下推导了八极电磁轴承支撑的转子非线性振动方程.应用多尺度法获得了振动方程的近似解,并利用Lyapunov方法对解的稳定性进行判定.结果表明,时滞的某些取值会使转子在x和y方向上的振幅相对于无时滞时减小,称之为时滞的“减振区域”,并且x和y方向上“减振区域”不同;通过计算不同比例系数与微分系数下的时滞-振幅曲线,发现比例系数对“减振区域”的范围影响更大;同一时滞量参数不能保证所有转速下均减振,当时滞量选取不合适时,会造成系统失稳;通过计算偏心率-振幅曲线,发现时滞控制能有效降低由于转子不平衡所产生的振幅,并且消除了非线性现象如多值、突跳等,系统稳定性增加.数值模拟验证了解析结果的正确性.     

奇异时滞系统对时滞参数的自适应控制

针对一类状态时滞奇异系统,研究状态反馈控制器的设计问题。基于Lyapunov稳定性理论和线性矩阵不等式（LMI）工具,当时滞常数精确已知时,设计带有记忆的状态反馈控制器,使得相应的闭环系统渐近稳定;当时滞常数不能精确已知时,通过求解相应的线性矩阵不等式,得到满足设计要求的对时滞参数的自适应控制器,使得时滞系统镇定。最后,仿真实例表明此方法的有效性。     

动力吸振式升沉补偿系统控制性能仿真研究

针对6 000 m中国大洋多金属结核采矿系统,提出了一种动力吸振器与蓄能器复合作用的升沉补偿系统.分析说明了系统的组成及工作原理,建立了系统的数学模型;应用Matlab编程计算得到了动力吸振系统中吸振器的质量、弹簧刚度和阻尼系数;对系统进行了控制效果仿真研究.研究结果表明,在整个四级海况下,动力吸振器与蓄能器复合作用的...     

Tuned vibration absorber for suppression of hand-arm vibration in electric grass trimmer

Prolonged use of electric grass trimmer exposes the user to the risk of hand-arm vibration syndrome. A simple approach for the suppression of hand-arm vibration in electric grass trimmer is presented. The proposed system is a tuned vibration absorber (TVA). Modal analysis and operating deflection shape analysis of the electric grass trimmer were carried out and a TVA was designed and fabricated for testing. The results indicated that minimum vibration level was related to the position of the TVA on the shaft of electric grass trimmer. The TVA was found to have best performance with 95% reduction on the acceleration level at position 0.025L. The results from modal analysis and operating deflection shape revealed that the presence of TVA has successfully reduced the large deformations of the handle where the node was shifted nearer to the handle location. The effect of TVA was also evaluated during field test involving grass trimming operation and subjective rating. The results indicated that average reduction of frequency-weighted rms acceleration in the Z_h- axis was 84% and 72% in X_h- axis for the cutting operation. For the no cutting operation, the reduction is 82% in Z_h- axis and 67% in X_h- axis. The presence of TVA in the electric grass trimmer has amplified the vibration level in Y_h- axis by 19% (no cutting) and 21% (cutting). From the field test, subjective rating of vibration perception consistently rate better for controlled electric grass trimmer.

Relevance to industry

The tuned vibration absorber when installed to the electric grass trimmer attenuated the vibration total value by 67%. This significantly reduces the risk of hand-arm vibration syndrome.     

Performance‐based near‐optimal vibration control for nonlinear offshore platforms with delayed input

This paper investigates the vibration control problem for offshore platform, where the nonlinear characteristics, delayed input and external wave force are considered in time domain. By introducing a delay‐free reconstructional vector and applying the maximum principle, the original vibration problem for offshore platform is formulated as a nonlinear two‐point‐boundary‐value (TPBV) problem with delayed items. The major contribution of this paper is that a performance‐based near‐optimal vibration control strategy is proposed by solving this nonlinear TPBV problem, which includes a feedback item with offshore platform system state, a feedforward item with wave force state, and a compensator for nonlinear and delayed items with infinite supersensitive component. In particular, the designed compensator is calculated from two group series of linear differential equations by introducing a parameter for expending the Maclaurin series of nonlinear and delay items. Meanwhile, an iterative algorithm is designed to make the proposed vibration control scheme computable based on the control performance in each iterative procedure. Finally, experimental results show that the displacement, velocity and performance index of an employed offshore platform achieved small values under the proposed control strategy and designed algorithm.     

无杆气缸驱动的柔性机械臂振动控制

提出了一种无杆气缸驱动的柔性机械臂定位和振动抑制系统,采用脉冲码调制(pulse code modulation,PCM)方法实现.首先,推导了气动驱动柔性臂的系统模型,对采用的复合定位和振动抑制控制算法进行理论分析.其次,气缸行程长、气体具有压缩性以及气动驱动存在非线性和阀门开关有时延等因素会引起控制作用的滞后问题,容易激发高阶模态的极限环振荡,导致观测和控制溢出,这将影响控制系统的稳定性.为了克服上述问题,在控制算法中引入时延补偿、低通滤波法.最后,进行气动驱动柔性臂同时定位和振动抑制的试验研究.试验结果表明,采用的气动驱动控制方法可以有效地抑制柔性臂的低频模态振动,并同时实现定位.     

Postural stability after whole-body vibration exposure

Fall injuries to operators of heavy mobile equipment are more frequent during egress rather than while climbing onto the equipment. One possible contributing factor is a loss of postural stability during egress. Because many of these operators are exposed to prolonged periods of whole-body vibration (WBV) while controlling the equipment, a study was conducted to determine if postural stability is impaired by WBV exposure. Subjects were tested for a difference in standing postural sway before and after seated WBV exposure. The WBV consisted of 40 minutes of vertical vibration generated by a motion platform, which emulated actual vibration levels of an operating under-ground shuttle car. Two independent variables, each at two levels, consisted of vibration and vision. The measured dependent variables were postural sway amplitude and velocity of sway. No significant difference between the vibration and no vibration conditions were found. Based on the results of this study, it cannot be concluded that WBV at the exposed frequencies influences postural stability. The results suggest that other factors may be the primary contributors to fall injuries while exiting the vehicle, such as problems with foot placement accuracy or egress system design.     

Efficient predictive vibration control of a building‐like structure

This paper presents the design of a model predictive controller (MPC) based on Laguerre functions for vibration control. The controller is tested in a building‐like structure consisting on a three‐story building with a passive vibration absorber. The structure is connected to an electromagnetic shaker, which excites the support of the superstructure, providing forces with a wide range of excitation frequencies, including some resonance frequencies of the structure. The overall controller is a hybrid vibration absorber conformed of (i) an active absorber, that is a predictive vibration control scheme, synthesised to actively attenuate the vibratory system response via (ii) a passive absorber, known as a tuned mass damper (TMD), located over the third story building to reduce the vibrations caused by harmonic forces acting on the base of the structure. The proposed predictive control strategy proves to be effective and efficient, improving system's performance with guaranteed stability and feasibility. Experimental and numerical results are included to illustrate the overall system performance.