The thesis examination of the doctoral student (Akram Hashim Hameed), majoring in Control Engineering, was conducted at the Control and Systems Engineering Department, the University of Technology. The thesis is entitled: (Advanced Barrier Function Sliding Mode Control and Observer Techniques for Electromechanical Systems with Unmatched Perturbations) The examination was accomplished in Hall no. 9 at 9:00 A.M on Monday 16-9-2024. Then, the student was awarded the Ph.D. degree in Control Engineering. The discussion committee consisted of the following members: 1- Prof. Dr. Safana Mudher Raafat / Chairman 2- Prof. Dr. Imad Qasim Hussein / Member 3- Prof. Dr. Abbas Hussein Issa / Member 4- Asst. Prof. Dr. Ayman Daoud Salman / Member 5- Asst. Prof. Dr. Wissam Esmat Abdel Latif / Member 6- Prof. Dr. Shibli Ahmed Hamid / Member and Supervisor 7- Prof. Dr. Amjad Jalil Hamidi / Member and Supervisor Practically, the Electro-Mechanical systems are dealt with as perturbed systems, either by considering the parametric uncertainty or exerted disturbances. The case of such a perturbed system is the non-vanishing unmatched perturbation. In this thesis, a novel one-instant flux observer that can provide an accurate flux estimation with minimizable ultimate bound estimation error is proposed, mathematically proved, and simulated. The proposed barrier function integral sliding mode (BFISM) observer is tested alongside the relevant observers on the rotor flux observation for the three-phase induction motor. The proposed observer has been compared with the open-loop observer, the nonlinear observer, and the conventional Wallcot-Zak sliding mode (SM) observer. Moreover, backstepping based on a barrier function integral sliding mode controller (BS-BFISMC) has been designed and tested on three electromechanical systems named the IM speed control, DC motor-driven EV speed control, and throttle angle position control of ETV. The proposed controller is compared to relevant controllers where the performance indices of the comparison are the percentage ratio of the RMSE of the tracking error, the perturbation estimation error, and the root mean square input (RMSI) of the control effort.