The goal of the thesis is to contribute to the investigations and developments required to enable EMA operation in primary flight control systems in a hybrid actuator configuration with EHSA. The focus in this thesis lies on the parallel operation and the synchronized closed-loop control of parallel electro-mechanical and electrohydraulic actuators. The position synchronization and load control task in this case is more difficult compared to the conventional system with redundant EHSA, because the different physical actuation principles lead to inherently different characteristic dynamics. Based on the investigations of these actuator differences and their implications on the parallel operation in the conventional operating modes active/passive and active/active, a new operating mode is proposed, denoted as active/no-load mode, in which the EMA follows the motion of the surface, driving its own inertia without carrying external loads, while the surface position is controlled by the EHSA.
For each of the three operating modes, the new active/no-load, the active/active, and the active/passive mode, two different control approaches are investigated. The first control approach is based on the conventional decentralized single-loop concept described above with the same focus on simplicity in controller structure to ease certification and implementation effort. In the second approach EMA, EHSA, and the control surface are considered as a single plant with several inputs and outputs. For this multi-input-multi-output (MIMO) system a robust multivariable controller is designed to explore the possible gain in performance with more advanced control methods. The developed controllers are analyzed and compared both in simulations and in verification experiments on a test rig.