Active steering wheel shimmy control for electric vehicle by sampled-data output feedback

In this paper, a new two Degree of Freedom (DOF) shimmy dynamic model of an Electric Vehicle (EV) with independent suspension subject to uncertain disturbances is built via Lagrange’s theorem firstly. Secondly, Based on the built model, an active control method is proposed to solve the shimmy problem of the steering system via a sampled-data output feedback controller. The output feedback domination approach is also used to dominate uncertain disturbances by using a scaling gain. With the help of these tools, the sampling period and scaling gain are calculated to guarantee global stability and disturbance attenuation for the closed-loop control system. Finally, simulations and tests are conducted to verify the effectiveness of the sampled-data output feedback controller for the EV’s shimmy problem under different conditions.     

Function projective synchronization between integer-order and stochastic fractional-order nonlinear systems

In this paper, the function projective synchronization between integer-order and stochastic fractional-order nonlinear systems is investigated. Firstly, according to the stability theory of fractional-order systems and tracking control, a controller is designed. At the same time, based on the orthogonal polynomial approximation, the method of transforming stochastic error system into an equivalent deterministic system is given. Thus, the stability of the stochastic error system can be analyzed through its equivalent deterministic one. Finally, to demonstrate the effectiveness of the proposed scheme, the function projective synchronization between integer-order Lorenz system and stochastic fractional-order Chen system is studied.     

On the stability of rods laying on a nonlinearly elastic bed under stochastic parametric excitation

The problem of simulating undisturbed behavior of a nonlinear system subjected to the action of deterministic and stochastic parametrical load is examined and the stability of undisturbed motion of the system is analyzed. It has been revealed that the trajectory motion of points changes greatly, if we take into account one or several components in deflection expansion while examining the deterministic and stochastic parametrical problem. In this case it is possible to stabilize the unstable undisturbed motion of the rod by superimposing the stochastic component in the form of a stationary Gaussian process with hidden periodicity to the deterministic load. By stability we mean the almost certain stability and average stability and mean square stability (stability with respect to the first- and second-order statistic moments).     

基于幂函数型双稳随机共振的故障信号检测方法

在实际的故障诊断中,有用信号经常淹没在噪声中,特征信息提取非常困难。为了提取强噪声背景中的微弱信号,将幂函数型单势阱模型与Gaussian Potential模型相结合提出一种新型的双稳随机共振系统,称为幂函数型双稳随机共振系统。首先,以平均信噪比增益为衡量指标,提出一种寻找最优系统参数组合的算法,使微弱信号、噪声及系统产生最佳的共振效果;然后,基于幂函数型双稳随机共振系统对Levy噪声背景下的仿真信号进行检测;最后提出一种基于小波变换和幂函数型双稳随机共振的微弱信号检测方法并应用于轴承故障信号检测中。仿真实验表明,幂函数型双稳随机共振模型在故障信号检测中是有效和可靠的。     

基于XPE的变尺度级联随机共振系统研究

随机共振作为一种新颖的信号处理手段在各个领域得到了广泛应用,在随机共振的基础上讨论了级联随机共振的构成方式,采用模拟电路的形式对其进行实现,并基于该电路构成嵌入式变尺度级联随机共振系统.此系统硬件采用ETX技术,可以对CPU主板功能进行全新整合,软件上通过定制XPE操作和采用EWF技术,加强了系统的稳定性,同时变尺度算法和最佳级联随机共振判断程序在系统中的移植可以使之在较高频率的场合准确应用.最后给出了应用实例,验证了该系统对信号提取的准确性.     

Identification of feasible scaled teleoperation region based on scaling factors and sampling rates

The recent spread of scaled telemanipulation into microsurgery and the nano-world increasingly requires the identification of the possible operation region as a main system specification. A teleoperation system is a complex cascaded system since the human operator, master, slave, and communication are involved bilaterally. Hence, a small time delay inside a master and slave system can be critical to the overall system stability even without communication time delay. In this paper we derive an upper bound of the scaling product of position and force by using Llewellyn’s unconditional stability. This bound can be used for checking the validity of the designed bilateral controller. Time delay from the sample and hold of computer control and its effects on stability of scaled teleoperation are modeled and simulated based on the transfer function of the teleoperation system. The feasible operation region in terms of position and force scaling decreases sharply as the sampling rate decreases and time delays inside the master and slave increase.     

时间序列模型中的随机共振现象

在滑动自回归(auto regressive and moving average,简称ARMA)时间序列模型的基础上,利用模态稳定性图来确定系统真实模态,描述了在求解过程中产生的随机共振现象。借助悬臂梁的有限元模型,利用精细时程积分方法计算得到了其加速度脉冲响应函数,建立了用于振动模态识别的ARMA模型。在利用模态稳定性图来确定系统真实模态的过程中发现,加入合适的噪声信号可以有效地改善识别结果,剔除虚假模态,即产生了随机共振现象。对悬臂梁进行时变化处理后,随机共振现象较之前不变系统更加显著,对最终识别结果产生了明显的优化作用。     

Stability of a flat arch subjected to deterministic and stochastic loads taking into account nonlocal damping

In the example of a flat arch, a problem of vibrational stability of systems subjected to deterministic and stochastic loads is considered taking into account the geometric nonlinearity and nonlocal damping of a material, which is characteristic of certain types of composites and nanomaterials. To study the stability of arch motion within the deterministic statement of the problem (stability in the sense of Lyapunov) and the stability in the almost certain stochastic statement, a method is used which is based on the calculation of the maximal Lyapunov’s exponent. The influence of damping and loading parameters on the degree of system stability is analyzed.     

汽车半主动悬架随机振动稳定性与可靠性分析

考虑路面随机因素的影响,首先建立二自由度汽车半主动悬架的随机非线性动力学模型,运用随机平均法,将Hamilton函数表示为一维扩散过程,并运用奇异边界理论分析系统的全局随机稳定性,建立可靠性函数所满足的Backward Kolmogorov(BK)方程,结合初始条件和边界条件得出数值结果.数值结果表明,系统状态在接近安全域边界时变化很快,而初始状态远离安全域边界时,则可将对应的失稳时刻推后.     

FUZZY GLOBAL SLIDING MODE CONTROL BASED ON GENETIC ALGORITHM AND ITS APPLICATION FOR FLIGHT SIMULATOR SERVO SYSTEM

To alleviate the chattering problem, a new type of fuzzy global sliding mode controller (FGSMC) is presented. In this controller, the switching gain is estimated by fuzzy logic system based on the reachable conditions of sliding mode controller(SMC), and genetic algorithm (GA) is used to optimize scaling factor of the switching gain, thus the switch chattering of SMC can be alleviated. Moreover, global sliding mode is realized by designing an exponential dynamic sliding surface. Simulation and real-time application for flight simulator servo system with Lugre friction are given to indicate that the proposed controller can guarantee high robust performance all the time and can alleviate chattering phenomenon effectively.     

Proportional damping approximation using the energy gain and simultaneous perturbation stochastic approximation

The design of vector second-order linear systems for accurate proportional damping approximation is addressed. For this purpose an error system is defined using the difference between the generalized coordinates of the non-proportionally damped system and its proportionally damped approximation in modal space. The accuracy of the approximation is characterized using the energy gain of the error system and the design problem is formulated as selecting parameters of the non-proportionally damped system to ensure that this gain is sufficiently small. An efficient algorithm that combines linear matrix inequalities and simultaneous perturbation stochastic approximation is developed to solve the problem and examples of its application to tensegrity structures design are presented.     

Model tracking dual stochastic controller design under irregular internal noises

Although many methods about the control of irregular external noise have been introduced and implemented, it is still necessary to design a controller that will be more effective and efficient methods to exclude for various noises. Accumulation of errors due to model tracking, internal noises (thermal noise, shot noise and 1/f noise) that come from elements such as resistor, diode and transistor etc. in the circuit system and numerical errors due to digital process often destabilize the system and reduce the system performance. New stochastic controller is adopted to remove those noises using conventional controller simultaneously. Design method of a model tracking dual controller is proposed to improve the stability of system while removing external and internal noises. In the study, design process of the model tracking dual stochastic controller is introduced that improves system performance and guarantees robustness under irregular internal noises which can be created internally. The model tracking dual stochastic controller utilizing F-P-K stochastic control technique developed earlier is implemented to reveal its performance via simulation.     

集成电路芯片管脚尺寸自动检测系统的状态分析

机器视觉自动检测系统的稳定性将直接影响产品检测的质量。本文根据随机过程的理论,利 用SAS软件对研究开发的集成用路芯片管脚尺寸检测系统的工作状态进行了分析测试。测试 结果表明,整个系统的测量结果是一个具有各态历经性的平稳随机过程,因此,我们利用一段 样本值就能估计整个过程的均值和标准差,从而获得整个过程的性质。     

Finite-time stabilization for a class of stochastic nonlinear systems via output feedback

This paper investigates the problem of global finite-time stabilization in probability for a class of stochastic nonlinear systems. The drift and diffusion terms satisfy lower-triangular or upper-triangular homogeneous growth conditions. By adding one power integrator technique, an output feedback controller is first designed for the nominal system without perturbing nonlinearities. Based on homogeneous domination approach and stochastic finite-time stability theorem, it is proved that the solution of the closed-loop system will converge to the origin in finite time and stay at the origin thereafter with probability one. Two simulation examples are presented to illustrate the effectiveness of the proposed design procedure.     

A receptance based formulation for modal scaling using mass perturbations

Normalization of modes obtained from operational modal analysis has received significant attention since the seminal paper on the use of mass perturbations by Parloo et al., in 2002. The contribution in this paper is a formulation where the square of the scaling constants are computed from an over-determined linear system of equations, obtained by evaluating the pole residue form of the receptance at the eigenvalues of the perturbed system. The formulation is exact when there is no truncation and, independently of truncation, for all conditions where existing solutions are exact. Given that identification results are stochastic, the normalization constants are random variables and the paper examines performance in terms of the bias and the standard deviation of the error distribution. The advantage of the receptance approach over other existing techniques is illustrated.     

Predictive cloud control for multiagent systems with stochastic event-triggered schedule

This paper addresses a predictive cloud control problem for a linear multiagent system with random network delays and noises. To reduce communication cost, a stochastic event-triggered schedule is introduced to decide whether current measurements need to be transmitted. An optimal state estimation algorithm is designed to compensate random network delays in the feedback channel. Subsequently, a predictive cloud control scheme is proposed for the multiagent system to achieve both stability and consensus. Simultaneously, random network delays in the forward channel is compensated actively. Sufficient and necessary conditions of stability and consensus for the closed-loop multiagent system are derived. Finally, a numerical example is provided to verify correctness and effectiveness of the proposed methods.     

A Lagrangian stochastic model for turbulent dispersion

A Lagrangian stochastic model is adopted for the calculations of turbulent dispersion in turbulent channel flows. Dispersion of a fluid particle and relative dispersion between two particles released at the same location are investigated and compared with the classical scaling relations for homogeneous turbulence. The viscous effect is realized by adding a Browinian random walk to the calculation of the position of a particle. The near-wall accumulation of particles is examined.     

Delay-dependent anti-windup synthesis for stability of constrained state delay systems using pole-constraints

This paper proposes the design of anti-windup compensator gain for stability of actuator input constrained state delay systems using constrained pole-position of the closed-loop. Based on Delay-Dependent Lyapunov-Krasovskii functionals and local sector conditions, a new LMI characterization is derived that ensures closed-loop asymptotic stability of constrained state delay systems while accounting upper bound fixed state delay and largest lower bound of the system’s pole-position in the formulation of anti-windup gain. Besides, at saturation, the method significantly nullifies the inherent slow dynamics present in the system. It is shown in the comparative numerical examples that the LMI formulation draws stability with improved time-domain performance.     

A scaling method for combustion stability rating of coaxial gas-liquid injectors in a subscale chamber

A scaling method to examine combustion-stability characteristics of a coaxial injector is devised based on the acoustics and combustion dynamics in a chamber. The method is required for a subscale test of stability rating with a model chamber, which is cost-effective compared with an actual full-scale test. First, scaling and similarity rules are considered for stability rating and thereby, three conditions of acoustic, hydrodynamic, and flame-condition similarities are proposed. That is, for acoustic similarity, the natural or resonant frequencies in the actual chamber should be maintained in the model chamber. And, two parameters of density ratio and velocity ratio are derived for the requirement of hydrodynamic and flame-condition similarities between the actual and the model conditions. Next, one example of an actual combustion chamber with high performance is selected and the proposed scaling method is applied to the chamber for understanding of the method. The design operating condition for a model test is presented by mass flow rates of propellants. Stability boundaries can be identified on the coordinate plane of chamber pressure and mixture ratio of fuel and oxidizer by applying the scaling method.     

一种参数不确定系统的鲁棒二次保稳定设计方法

研究了不确定线性系统的鲁棒二次保稳定设计问题。在建立的鲁棒回差方程的基础上,给出了闭环系统鲁棒二次保稳定的一个充分条件,以及增益和相位裕度描述形式。进一步还给出了相应的鲁棒二次保稳定控制系统设计方法