1. A nonlinear controller for a closed-loop system, having PID parameter values as inputs (variable values K.sub.I, K.sub.C, K.sub.D) and a process response related and setpoint related signal value as input, wherein said nonlinear controller contains a processor mechanism for generating an output signal value u for controlling said closed-loop system from said inputs and wherein said processor mechanism is a neutral network trained on inputs e, K.sub.I, K.sub.D, K.sub.C, which are generated by a model of the system to be controlled.