System identification method based on subspace band constraint

The invention discloses a system identification method based on subspace band constraint. The method comprises the steps that input and output dynamic data of a system are collected and preprocessed; based on the preprocessed input and output dynamic data, a black box state space model containing the input and output dynamic data is identified through a subspace system identification method, a state space matrix is obtained, and the state space matrix comprises a state matrix, an input matrix and an output matrix; constructing constraints about the state space matrix through priori knowledge; keeping a state matrix and an input matrix in the state space matrix unchanged, and calculating to obtain an output matrix meeting the constraint, or keeping the state matrix and the output matrix unchanged, and calculating to obtain an input matrix meeting the constraint; calculating a step response model of the system based on the state space matrix satisfying the constraint; and fitting the step response model into a