Method and device for tuning and control

A device for tuning a controller controlling a property of an industrial process having varying material flow rate, the device comprising:

• an adder for adding excitation signals to a controller output signal,
• a measurement system for measuring said property in response to said excitation signals, and
• a model based tuning unit adapted to estimate a value of at least one parameter with unknown value of a time continuous process model structure describing an effect of varying material flow rate, based on said measurements of said property and the controller output signal, the parameter being independent of the varying material flow rate, and to calculate a model that describes dynamics from controller output to controller input based on the estimated value of said parameter, to reduce a parameter update size, when an unrestricted update reaches outside an area of defined allowed parameter ranges, but making a parameter update in the same direction in a parameter space, to apply a same reduction factor to both regressors and prediction error, to be used in both parameter update and update of matrix holding information necessary in recursive estimation, thereby keeping parameter estimates within allowed ranges, and to perform model based tuning of the controller based on said model that describes the dynamics from controller output to controller input.