Design of a data-driven two-degree-of-freedom control system considering robustness

Virtual reference feedback tuning (VRFT) and fictitious reference iterative tuning (FRIT) are well-known as the data-driven tuning schemes for directly designing feedback controllers. These schemes have been already extended to two-degree-of-freedom (2DOF) control systems in recent years. The conventional design schemes of 2DOF controllers need a complicated two-stage tuning process. This paper describes a one-stage tuning scheme for the 2DOF control system using a fictitious exogenous signal based on a data-driven method. In the proposed scheme, 2DOF controllers are designed with one criterion, and the least squares method is applied to find the optimal set of 2DOF controller parameters. According to the proposed scheme, the reference models are determined based on the stability margin that is quantified by the sensitivity function. It is also possible to design a control system taking robustness into account. Finally, the effectiveness of the proposed scheme is numerically verified by using a simulation example. © 2019 The Institute of Electrical Engineers of Japan.