In all control loops, the location where the disturbance enter and where the manipulated variables are measured is not the same. Therefore the process dead time makes it difficult to maintain the controlled variable at the desired point. This is particularly true when the magnitude of disturbance change is large, or the load variable changes so frequently in relation to the process dead time. In this case, feedforward control strategy is very useful.
The determination of the feedforward controller is divided into two problems. One is the design of controller structure and the other is the search of the optimal controller parameters after selecting the controller structure. In the first problem, there was an effort to design the controller structure by using the pole-zero concellation of the entering disturbance. In the second problem, there was an effort to include the dynamic compensation in the the determination of the feedforward controller gain, and to find the optimal parameters by introducing the measure of controller performance after selecting the controller structure.
In this study, the feedforward controller structure is determined as delayed lead-lag controller and then the controller performanc index is modified to find better controller parameters. The problem of finding the controller parameters is divided into three different cases and the performance of each parameter is compared. Simulation results show that the case of introducing the line integral term to consider all combination of disturbances is the best, and giving the weighting to controller performance index is helpful.