In this paper, a novel fuzzy adaptive nonlinear fault tolerant control design scheme is proposed for attitude dynamics of quadrotor UAV subjected to four sensor faults (bias, drift, loss of accuracy, loss of effectiveness). The sensor faults in Euler angle loop are transformed equivalently into a mismatched uncertainty vector, and other unknown items involving faults, uncertain parameters and external disturbances in angular velocity loop are lumped into an unknown nonlinear function vector.Fuzzy logic systems with adaptive parameters are used to approximate the mismatched uncertainty and lumped nonlinear function vectors. Dynamic surface control is applied to design the fault tolerant controller, and sliding mode control is introduced to improve the control accuracy. All signals of the closed-loop control system are proved to be semi-global uniformly ultimately bounded. Simulations demonstrate the effectiveness of the proposed approach for sensor faults. KEYWORDS dynamic surface control, fault tolerant control, fuzzy logic system, Quadrotor unmanned aerial vehicle, sensor fault, sliding mode control
Viscoelastic oscillator (VEO) is the basic model extracted from viscoelastic damping structures. To precisely understand the dynamic behavior of VEO, generalized modeling of fractional viscoelastic oscillator (FVEO) is proposed and its frequency response is deduced. For demonstrating
purpose, frequency response of three FVEOs is studied. As an engineering application case, the viscoelastic suspension mounted in a heavy crawler-type vehicle is considered and its vibration model is built by FVEO, whose time-domain solution is numerically derived by matrix differential theory.
The results indicate that FVEO is a valid approach to evaluate the dynamic response of viscoelastic damping structures.
The fractional model considering geometric factor of viscoelastic damping systems is proposed by adopting fractional viscoelastic oscillator. To obtain dynamic responses of the fractional model, a numerical method is derived based on matrix function theory and Grumwald-Letnikov discrete form of fractional derivative. As a special engineering application example, the vibration response of the viscoelastic suspension installed in heavy crawler-type vehicles is studied through the proposed model. Furthermore, the parameter influence on the vibration control capability of the viscoelastic suspension is researched. The results indicate that the fractional viscoelastic oscillator is a favorable choice to characterize the dynamic behavior of viscoelastic damping structures. Additionally, the parameters in fractional viscoelastic oscillator namely geometric factor and fractional order exert considerable impact on the dynamic response of viscoelastic damping structures.
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