实现自适应有源噪声控制算法时,次级通路辨识是其关键环节.由于环境干扰等因素的存在,实际的次级通路特性不是恒定的,而是在一定范围内随机变化.次级通路传递函数建模结果与实际通路之间会存在随机偏移误差,将影响自适应有源控制算法的收敛性能,严重的可能导致系统不稳定,因此研究此种情况下的系统收敛性能十分必要.以单频噪声为例,通过建立滤波-x最小均方算法(Fx LMS)的等效传递函数,用线性时不变(LTI)系统的稳定性判据求解算法稳定条件,求得次级通路误差存在时收敛系数的取值范围,然后通过系统极点来分析此时算法收敛特性,并研究收敛系数取值对次级通路误差的承受能力.最后,通过实验证明了分析的有效性.%Implementation of adaptive active noise control requires an estimate model of the secondary path. In practice, the characteristics of physical secondary path are not constant but vary randomly within a specific range because of the environmental disturbance. Thus, random shifting errors, which can lead to low convergence performance or instability, will exist between the modeling results and the physical path. In this paper, the equivalent transfer function of filtered-x LMS (FxLMS) algorithm was applied to calculate the stable conditions of the algorithm according to the stability criterion of linear time invariant (LTI) system. Convergence performance of the algorithm was studied by analyzing the root locus of the equivalent transfer function. Then the effect of adaptive step on the secondary path estimation error tolerance was studied. Finally, an experiment was done to validate the analysis.
展开▼
