The problem of output-only identification of vibrating structures with clearance nonlinearity is considered, as clearance nonlinearity exists widely in mechanical structures and the ambient excitation is usually difficult to apply or measure under operating conditions. A novel output-only time-domain nonlinear subspace identification (OOTNSI) method is proposed in this work by separately identifying the underlying linear system of nonlinear structures based on input-output data under low-level excitation, and identifying nonlinear parameters by only using output data under high-level excitation. In case the underlying linear system is known or obtained in advance, the OOTNSI method is able to operate by exclusively using the measured displacement responses of the structure, without measuring its excitation forces. The proposed method is respectively employed for the identification of three degrees-of-freedom numerical and experimental systems with clearance nonlinearity, and comparatively assessed against the existing time-domain nonlinear subspace identification (TNSI) method. The comparisons demonstrate that the proposed OOTNSI method is capable of performing output-only identification of vibrating structures with clearance nonlinearity and can achieve similar identification accuracy as the existing TNSI method operated in an input-output manner.

考虑了具有间隙非线性的振动结构的仅输出识别问题，因为间隙非线性广泛存在于机械结构中，并且在工作条件下环境激励通常难以应用或测量。本文提出了一种新的仅输出时域非线性子空间识别（OOTNSI）方法，该方法基于低电平激励下的输入输出数据分别识别非线性结构的底层线性系统，仅使用输出识别非线性参数高电平激励下的数据。如果潜在的线性系统是已知的或预先获得的，OOTNSI 方法能够通过专门使用测量的结构位移响应来运行，而无需测量其激发力。该方法分别用于具有间隙非线性的三个自由度数值和实验系统的识别，并与现有的时域非线性子空间识别（TNSI）方法进行了比较评估。比较表明，所提出的 OOTNSI 方法能够对具有间隙非线性的振动结构进行仅输出识别，并且可以获得与以输入-输出方式操作的现有 TNSI 方法相似的识别精度。