An Inner-Outer Loop Approach to Identify and Control Unstable Plants Implementation on a Multi-Rotor

Identification of unstable systems always has been a challenging issue in the field of controller design. The purpose of this study is to provide a new way to identify and design the control of unstable systems in the loop. For this purpose, after stabilizing the system with a simple controller (Inner Controller), the Inner Loop is identified and then an accurate controller (Outer Controller) will be designed for this loop. For validation, this method is simulated on an inverted pendulum and also implemented on a laboratory system. Because the multi-rotor is unstable, the Inner controller is designed and simulated on a low-precision model. After implementing the Inner controller on the real system and data gathering, the dynamic model of the Inner Loop is identified and finally, with the exact model of the inner loop, the design of the Outer controller is done to Improve stability and performance. The simulation and test results show the interesting and very good performance of this method.