Research About Observer Based Active Fault Tolerant Control For Quad-rotor Helicopters

With the improvement of helicopter’s performance, the flight quality, security and faulttolerability are more and more emphasized. As an important part of the quad-rotor helicopter, theflight control system plays a key role in maintaining the flight performance and security. However,due to strong turbulence, birds and other unpredictable and uncontrollable external factors, thehelicopter’s flight qualities and security may be seriously affected and even degraded. Therefore, thestudy of fault-tolerance problem for helicopter control system is typical required and has theimportant value. Fault tolerant control not only maintains the flight performance in the fault-free case,but aims at continuing the flight task in the presence of faults by adjusting the controllers with certainrequirements of stability and maneuverability. In this paper, several active fault tolerant controlmethods, based on H-infinity robust control theories and linear matrix inequalities (LMI) toolbox, aredesigned for the quad-rotor helicopter.First, an introduction of research methods and development status of active fault tolerant controltechnology is presented. Then, based on the quad-rotor flight dynamics characteristics, an actuatorfault model is established.Secondly, based on the established fault model, a multiple observers based fault diagnosismethod that combines the Luenberger fault detection observer and fault estimation observer isproposed. This converts the case that fault distribution matrix is not full column rank into the normalcase, and make the fault estimation algorithm solvable by using LMIs toolbox.Then, according to the fault detection and fault estimation results, a feedback fault tolerantcontroller is designed. This maintains the flight control performance in in the presence of the faultoccurring in the single channel. In this paper, both the state feedback controller and the outputfeedback one are designed, and the feedback gains are obtained by using LMI toolbox. Thecomparison between the two methods is also made. A more practical controller is further providedaccording to the simulation results.Finally, the proposed active fault tolerant control methods are applied to the Quanser3-DOFHover semi-physical system. It shows from the experimental results that the theoretical algorithmscan effectively compensate for the faults’ effect and stabilize the system.