How do you perform systematic control loop performance assessment?

Comprehensive loop assessment methodology: data collection (time series of PV, SP, OP, status flags), statistical analysis (mean, variance, standard deviation), oscillation detection (autocorrelation, spectral analysis), valve performance (backlash, stiction from MV-OP analysis), controller utilization (time in auto, saturation frequency), economic impact analysis (variability cost, constraint violations). Key metrics: IAE (Integral Absolute Error), Harris index (actual vs minimum variance), valve travel, oscillation period and decay ratio. Use automated tools for plant-wide assessment, prioritize loops by economic impact, and track improvements through KPIs.