We show that every forward-flat nonlinear discrete-time system with two inputs can be transformed into a structurally flat normal form by state- and input transformations. This normal form has a triangular structure and allows to read off the flat output, as well as a systematic construction of the parameterisation of all system variables by the flat output and its forward-shifts. For flat continuous-time systems, no comparable normal form exists.

中文翻译：

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两输入正展非线性离散时间系统的范式

我们表明，每个具有两个输入的前向扁平非线性离散时间系统都可以通过状态和输入变换转换为结构上平坦的法线形式。该标准形式具有三角形结构，并允许读取平面输出，以及通过平面输出及其前移对所有系统变量的参数化进行系统化构造。对于平坦的连续时间系统，不存在可比较的标准形式。