A new trajectory tracking control scheme is proposed for mobile robots based on the fuzzy control and extended state observer in this paper. The fuzzy logic control adjusts the three parameters of the speed controller online, so as to achieve better control effect. The extended state observer is designed to estimate the unknown disturbance information of the system and compensate it. The trajectory tracking controller can track the reference trajectory expeditiously and accurately. And the position errors of the mobile robot eventually converges to zero. The simulation results show that the control scheme is effective and reliable.

Cascading failure should be modeled before accident in order to preventing large scale blackout. Based on the probability analysis model of fault chain of security science, the prediction index of middle segments of fault chain based on flow of network is presented to establish the fault chains, in which the cascading failure probability is quantified. The method is simple to compute and is ended by the system collapse. The results can be used not only for on-line analysis of cascading failure, but also for risk assessment and preventive control. The simulation on IEEE 39 buses system testifies the validation of the proposed method.