Direct Online Rainflow-counting and Indirect Fatigue Penalization Methods for Model Predictive Control

The standard material fatigue estimation process is implemented in an Economic Nonlinear Model Predictive Controller. The process comprises cycle identification, mean-stress effect, Wöhler curves and Linear Damage Accumulation. For cycle identification, this novel implementation uses a standard Rainflow-algorithm which is substituted periodically by linear functions based on its output. The implementation is compared to two straightforward methods for fatigue penalization using a wind turbine model and exhibits higher profit over the entire range of tested reference wind velocities.