Controller performance assessment based on setpoint response data

A new methodology is developed to assess the performance of PI controllers from closed-loop response data for a setpoint step change. It is based on two new dimensionless performance indices, the dimensionless settling time and the dimensionless integral of the absolute value of the error. The methodology is used to quantify how far a control loop is from the best achievable performance of PI control. It also identifies poorly performing control loops, such as those that are excessively sluggish. The performance and robustness properties of the internal model control (IMC) tuning method are analyzed and are used as industrially relevant benchmarks. The proposed methodology is also applicable to PID controllers.