Actuator Fault-Tolerant Control for Mechatronic Systems and Output Regulation with Unknown Reference Signals

Today, mechatronic systems are required to operate reliably and safely. However, actuators can fail, causing the system to malfunction or, in the worst case, resulting in an accident. A clear example of this is the motors of unmanned aerial vehicles. If any of them fail, the vehicle loses control, resulting in a catastrophe and potentially leading to the partial or total loss of the system. Therefore, there is a need to design robust control strategies that allow the system to continue operating even with the loss of one of its actuators. Based on the above, this work presents a controller capable of performing output regulation while tolerating actuator faults in actuated robotic platforms. In contrast to traditional output regulation theory, where a known exosystem provides the reference signal, the proposed approach employs a High-Gain Observer (HGO) to estimate and generate the reference signal from an unknown exosystem. Additionally, an Unknown Input (UI) observer is used to estimate actuator faults, enabling the computation of a fault-tolerant control. The methodology is tested in simulation and real-time experiments on the well-known Furuta pendulum system to illustrate the effectiveness of the proposed approach.