System identification of time-delay with single fractional pole heating process considering rate limit effect

The heat transfer dynamic is extremely common in industry process. The time-delay with single fractional pole (TDSFP) model gives higher accuracy than first-order plus time-delay (FOPTD) model for the ideal heat transfer process. Actuator rate limit is a common and important phenomenon in heating process control and is becoming a stumbling block in precision process control. The actuator will get saturated for a certain duration when the identification test signal is a step function. The time duration when actuator rate is saturated can be misidentified as the delay of the process model, which misleads the controller design and generates unsatisfactory performance. This paper proposes a new model structure in identifying a TDSFP process under the step test signal and this model structure considers actuator rate limit. Parameters sensitivity is analyzed to access the effect of identification accuracy resulting from parameters estimation mismatch. An illustrative example is given to show the effectiveness of the proposed identification method and the sensitivity of system parameters.