Fixed-Time Sensor Fault Detection Observer With Actuator Fault Decoupling for Attack-Free Consensus Systems

This paper studies a fixed-time attack-free actuator fault decoupling observer (FTAF-AFDO) for sensor fault detection in multi-agent systems employing the attack-free consensus protocol, where only the local information of the monitored agent and the relative output information between agents measured by its internal sensors are available. The main difficulty is that the sensor faults studied here directly affect the control signal rather than the agent's local output, causing traditional observers based on control inputs and outputs to fail in detecting such sensor faults. In addition, sensor faults and actuator faults are coupled, as the relative output information measured by sensors is directly involved in the design of attack-free consensus protocol. To tackle these difficulties, we developed the FTAF-AFDO, inspired by unknown input observer and Luenberger observer. This observer generates a sensor fault indicator signal that fully decouples from estimation errors and actuator faults within a fixed time, without needing any prior knowledge of the actuator faults. Additionally, leveraging the proposed FTAF-AFDO, a distributed attack-free consensus protocol is developed, capable of completely isolating the impact of actuator faults. The effectiveness of the proposed method is validated through simulations of a formation-flying transport aircraft system.