A characteristic modeling method of error-free compression for nonlinear systems

The existence of error when compressing nonlinear functions into the coefficients of the characteristic model is known to be a key issue in existing characteristic modeling approaches, which is solved in this work by an error-free compression method. We first define a key concept of relevant states with corresponding compressing methods into their coefficients, where the coefficients are continuous and bounded and the compression is error-free. Then, we give the conditions for decoupling characteristic modeling for MIMO systems, and sequentially, we establish characteristic models for nonlinear systems with minimum phase and relative order two as well as the flexible spacecrafts, realizing the equivalence in the characteristic model theory. Finally, we explicitly explain the reasons for normalization in the characteristic model theory.