As a key factor in model-based control technique

model fidelity has significant influence on control performance.Model-plant mismatch(MPM)is an important step in the procedure of control performance monitoring and system maintenance.A subspace-based MPM approach for control systems was proposed.First

the residual was constructed through subspace transformation.Then the residual was analyzed by using statistical local approach

from which an indicator could be constructed to detect the mismatch.Using orthogonal subspace

it was not needed to estimate system states and residual could be obtained only by using input and output data.Furthermore

based on the state space model

the proposed approach was suitable for MIMO process.The effectiveness of the proposed approach was illustrated by both simulation and industrial applications.