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971.
This paper investigates the problem of H∞ observer-based event-triggered sliding mode control (SMC) for a class of uncertain discrete-time Lipschitz nonlinear networked systems with quantizations occurring in both input and output channels. The event-triggered strategy is used to save the limited network bandwidth. Then, based on the zero-order-hold (ZOH) measurement, a state observer is designed to reconstruct the system state, which facilitates the design of the discrete-time sliding surface. Considering the effects of quantizations, networked-induced constraints and event-triggered scheme, the nonlinear state error dynamics and sliding mode dynamics are converted into a unified linear parameter varying (LPV) time-delay system with the aid of a reformulated Lipschitz property. By using the Lyapunov-Krasovskii functional and free weighting matrix, a new sufficient condition is derived to guarantee the robust asymptotic stability of the resulting closed-loop system with prescribed H∞ performance. And then the observer gain, event-triggering parameter and sliding mode parameter are co-designed. Furthermore, a novel SMC law is synthesized to force the trajectories of the observer system onto a pre-specified sliding mode region in a finite time. Finally, a single-link flexible joint robot example is utilized to demonstrate the effectiveness of the proposed method. 相似文献
972.
In this paper, an active fuzzy fault tolerant tracking control (AFFTTC) scheme is developed for a class of multi-input multi-output (MIMO) unknown nonlinear systems in the presence of unknown actuator faults, sensor failures and external disturbance. The developed control scheme deals with four kinds of faults for both sensors and actuators. The bias, drift, and loss of accuracy additive faults are considered along with the loss of effectiveness multiplicative fault. A fuzzy adaptive controller based on back-stepping design is developed to deal with actuator failures and unknown system dynamics. However, an additional robust control term is added to deal with sensor faults, approximation errors, and external disturbances. Lyapunov theory is used to prove the stability of the closed loop system. Numerical simulations on a quadrotor are presented to show the effectiveness of the proposed approach. 相似文献
973.
针对谐波有功损耗测量问题,文中改进了Emanuel功率理论中非线性负载等效模型,并结合基于Emanuel功率理论的IEEE 1459标准中视在功率分解公式,推导了基于改进的非线性负载等效模型的谐波有功损耗测量表达式;利用Matlab仿真分析非线性负载有功损耗的3种测量方式;通过比较得出所提测量方法能更准确方便地测量非线性负载有功损耗。最后,利用电能质量测量仪器,实测某电网10 kV负载谐波含量,结合所提方法计算负载有功损耗,验证了该方法的有效性及其带来的经济效益。 相似文献
974.
975.
S. L. WEISSMAN 《International journal for numerical methods in engineering》1996,39(14):2337-2361
This paper presents a family of low-order high-accuracy three-dimensional brick elements. The elements are formulated via a three-field variational principle. The assumed (independent) strain field is constructed from two disjointed distributions. The first contains the lower-order distribution and its dimension is the minimum required to satisfy stability requirements. An energy constraint, which is enforced weakly at the element level, is used to relate the second distribution to the first. The stress field is chosen to a priori satisfy a similar energy constraint. As a result, internal constraints (e.g. incompressibility) are automatically satisfied by these fields, and locking behaviour is avoided. A J2-plasticity model illustrates the proposed elements' performance in nonlinear solids. The excellent performance of the proposed elements is demonstrated with numerous challenging examples, including many that are usually modelled by shell elements. 相似文献
976.
We consider the problem of stabilizing a discrete-time nonlinear system using a feedback which is not necessarily smooth. A sufficient condition for global dynamical stabilizability of single-input triangular systems is given. We obtain conditions expressed in terms of distributions for the nonsmooth feedback triangularization and linearization of discrete-time systems. Relations between stabilization and linearization of discrete-time systems are given. 相似文献
977.
This paper is concerned with the computer-based sliding mode control of flexible rotor—magnetic bearing systems (FR-MBS). The plant dynamics consisting of actuator dynamics and flexible rotor dynamics are described. The reduced-order model for controller design is given by eliminating higher-order modes of the mechanical and electrical magnetic interaction system. A discrete-time sliding mode controller with a new robust reduced-order variable structure system (VSS) observer is proposed and its robust performance is evaluated with several simulations based on a calculation model. This digital controller is implemented to replace a linear analogue PID compensator. Levitation tests using the proposed digital controller are performed and compared with those of the PID compensator. The unstable modes can be easily controlled with the good stability and the spillover phenomena due to ignored higher-order modes are not generated. It is indicated that the discrete-time sliding mode control has robustness to the model parameter variations and external disturbances. Using the discrete time sliding mode controller with the reduced-order VSS observer, the test rig of the magnetic bearing system can be successfully rotated in a speed range of 0–35 000 rpm, which includes the first critical shaft frequency of the flexible rotor. 相似文献
978.
基于神经网络非线性模型的开关磁阻电机调速系统动态仿真 总被引:2,自引:0,他引:2
实现开关磁阻电机调速系统(SRD)的准确动态仿真是进行系统参数优化、控制策略研究的重要依据.本文在以实测开关磁阻电机(SRM)准确特性曲线为样本数据,并基于BP神经网络建立SRM非线性模型的基础上,构建了Matlab环境下SRD系统的整体动态仿真模型.通过仿真揭示了SRD系统的稳态、动态运行特性,实现了系统性能的准确分析,为设计SRD系统高性能控制提供了理论依据.经与实测电流、转速波形对比,验证了本文提出的SRD动态仿真方法的有效性. 相似文献
979.
将混合遗传算法应用于飞行器气动参数辨识。该方法结合了遗传算法的全局寻优能力和极大似然法的局部寻优能力,使得混合遗传算法不受极大似然法初值选取的影响,同时也解决了遗传算法收敛速度慢和收敛精度较低的问题。在混合遗传算法寻优过程中,仅对最优个体和变异后的个体执行局部寻优操作,从而使得混合遗传算法的计算量维持在一个适当的水平。最后,一个飞行器纵向模型气动参数的辨识仿真表明:混合遗传算法的收敛性和精度都远高于没有采用局部寻优策略的遗传算法。 相似文献
980.