Necessary and Sufficient Conditions for Difference Flatness
Bernd Kolar, Johannes Diwold, Markus Schöberl · IEEE Transactions on Automatic Control · 2022
In this article, we show that the flatness of a nonlinear discrete-time system can be checked by computing a unique sequence of involutive distributions. The well-known test for static feedback linearizability is included as a special case. Since the computation of the sequence of distributions requires only the solution of algebraic equations, it allows an efficient implementation in a computer algebra program. In case of a positive result, a flat output can be obtained by straightening out the involutive distributions with the Frobenius theorem.