However, these methods in [15; 16; 17; 18; 19] only take into account of some air-ground platform characteristics, such as nonlinearity and strong coupling, but the possible time-varying delay of the system and actuator time-varying failure are not considered, and so it will be unable to do anything to stop the sudden failure situation of the system from being in danger. In reality, many systems have time-varying delays, and so research about them is particularly important [20; 21]. In [22; 23], the stability of time-varying delay systems is studied, and the relevant stability criteria are given. Reference [24] studies the stability of stochastic nonlinear time-delay systems with external disturbances. However, reference [22; 23; 24] do not focus on specific control objects, but only provide macroscopical research ideas to solve such kind of problems. In addition, there are few studies on fault-tolerant control for time-varying delay systems [25]. Taking the four rotor UAV as the control object, the fault-tolerant control scheme proposed in [26] takes into account the factors such as model uncertainty and external interference, but does not consider the influence of system time-varying delay. In [27; 28], a fault-tolerant compensation controller by auxiliary variable method is constructed, but only analyzes the influence of time-varying fault. References [29; 30] take the spacecraft attitude as the control object and in the case of actuator failure, it is designed and proved that the attitude reaches the sliding surface in a limited time, but other situations are less considered. Considering the above information, the author proposes the active fault-tolerant control method to be applied to air-ground platform. Under the conditions of knowing the time-varying delay term and the upper bound of external interference and meeting with the assumption constraints, a robust fault observer is designed to reduce the occurrence of false alarm. Meantime, the adaptive fault estimation method [25] is used to estimate the overall fault condition, and appropriate fault-tolerant control rate is designed to realize attitude stability control. Finally, the Lyapunov method is used to analyze the closed-loop stability and verified by simulation. The main contributions of this paper are as follows:  
* Considering the time-varying fault of actuator, system parameter uncertainty and system state delay, the attitude stability control problem of air-ground platform in complex environment is effectively solved;
* The integral sliding control method is used to effectively reduce the chattering problem in the fault-tolerant control of the air-ground platform actuator;
* Selecting the appropriate nonlinear function as the ideal control input to optimize the transient performance of the system shows that the overshoot is not very large and the convergence speed is accelerated. The rest of the paper is arranged as follows. Section 2 introduces the air-ground platform model, fault model, and related hypothesis; Section 3 introduces the fault detection method and adaptive fault estimation method; in Section 4, an active fault-tolerantcontroller is designed; the effectiveness of the method is proved by simulation experiments in Section 5; and, finally, conclusions are given in Section 6.