However, due to the inherentnonlinearity, complexity and uncertainty of the accurate system, it is usually difficult to obtain an accurate mathematic model.
由于实际系统固有的非线性、复杂性及不确定性，建立系统的模型通常是困难的。
2
BP network with the strong nonlinearity mapping ability can summarize the rule from acquired data to obtain the inherent laws of these data automatically.
BP网络具有很强的非线性映射能力，能从已有数据中自动地归纳规则，获得这些数据的内在规律。
3
Due to the inherent hysteretic nonlinearity, the giant magnetostrictive actuator (GMA) can cause position error in the open-loop systems, and cause instability in the closed-loop systems.