Many identification strategies for closed loop system structure assume that an open loop system is closed by a feedback mechanism, which contains a known and linear controller. This assumption means these identification strategies are feasible under some prior knowledge of feedback controller. To relax this assumption for some complex systems with unknown controller or nonlinear controller, a new stealth identification strategy is proposed to tackle the identification problem for closed loop system with unknown controller or nonlinear controller. Stealth identification modifies closed loop system, so that the new prediction error and inverse covariance matrix are all independent of the unknown controller or nonlinear controller. This independence simplifies the problem of estimating parameter vector and designing optimal input. The Robbins-Monro algorithm is applied to identify the unknown parameter vector in closed loop system with unknown controller, and the nonlinear controller is replaced by its equivalent linear time invariant controller. Some consideration about the linear approximation to nonlinear system are studied, and two linear approximation forms are constructed to approximate the nonlinear system. The effectiveness of our proposed stealth identification strategy is demonstrated through simulation example.

中文翻译：

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闭环系统结构的隐身识别策略

许多闭环系统结构的识别策略都假设开环系统是由反馈机制闭合的，反馈机制包含一个已知的线性控制器。这个假设意味着这些识别策略在反馈控制器的一些先验知识下是可行的。针对一些未知控制器或非线性控制器的复杂系统放宽这一假设，提出了一种新的隐身识别策略来解决具有未知控制器或非线性控制器的闭环系统的识别问题。隐身识别修改了闭环系统，使得新的预测误差和逆协方差矩阵都与未知控制器或非线性控制器无关。这种独立性简化了估计参数向量和设计最优输入的问题。应用Robbins-Monro算法识别控制器未知的闭环系统中的未知参数向量，将非线性控制器替换为其等效线性时不变控制器。研究了非线性系统线性逼近的一些考虑，构造了两种线性逼近形式来逼近非线性系统。通过仿真实例证明了我们提出的隐身识别策略的有效性。并构造了两个线性逼近形式来逼近非线性系统。通过仿真实例证明了我们提出的隐身识别策略的有效性。并构造了两个线性逼近形式来逼近非线性系统。通过仿真实例证明了我们提出的隐身识别策略的有效性。