Adaptive fault-tolerant control based on boundary estimation for space robot under joint actuator faults and uncertain parameters

Fault estimation and fault tolerance control for spacecraft formation systems with actuator fault and saturation

“…Remark In this study, a decentralized fault estimation strategy is developed, namely, an augmented unknown input observer is designed to estimate both angular velocity and unknown actuator fault, while control theory is used to ensure the asymptotically stability of the derived observer error system. Different from the adaptive or sliding mode fault estimation observer designed in References 12,13, 17,21 and 22, the adaptive fault update algorithm is not used in this article, therefore the pressure of closed loop online calculation is reduced. Moreover, the decentralized observer design approach could reduce the difficulty of observation and is easy to implement in actual aerospace engineering.…”

“…For example, a nonlinear observer is designed in Reference 12 for a class of satellite formation flying systems with model uncertainty, input and environmental disturbances to achieve fault detection, isolation and estimation. In Reference 13, an adaptive fault tolerant control algorithm is designed for space robot in the case of actuator partial loss of control effectiveness, such that the dynamic performance of the faulty system is maintained. A fault estimation scheme base on adaptive technique for a nonlinear system is proposed in Reference 14, it could detect and separate fault categories.…”

“…The main contributions of this article are given as follows. Compared with the traditional adaptive observer designed in References 12,13 and 17, the decentralized unknown input observer is designed in this study to estimate unknown actuator fault occurred in each follower spacecraft. It does not require the adaptive fault estimation algorithm and could reduce the pressure of online calculation.…”

Analysis of exit probability for a trajectory tracking robot in case of a rare event

“…In ref. [16], an adaptive fault-tolerant control algorithm is designed for a space robot system with uncertain parameters. Using the Euler-Lagrange system, the authors first set up the basic second-order differential equation by taking model uncertainties into account as an additional disturbance effect on the dynamics.…”

Disturbance observer-based robust fixed-time integrated trajectory tracking control for space manipulator

“…The initial conditions of the fixed-time disturbance observer are set as ve = v e (0) and δ = [0, 0, 0] T . Moreover, the control parameters of the compared nominal fixed-time PD-like controller(17) are selected as k 1 = 0.4, k 2 = 0.8, h 1 = 0.1, h 2 = 0.2, α 1 = 1/3, α 2 = 1/2, β 1 = 5/3, and β 2 = 5/4.The control parameters of the compared conventional sliding mode controller(39) are selected as μ = 2, k = 1, η = 0.1, and ε = 0.01.The simulation results for performance comparisons are presented in Figs.4-7. Figures4 and 5show the time histories of the position and velocity tracking, respectively.…”