This paper presents an adaptive control scheme via combining with an unknown system dynamics estimator (USDE) for attitude control of quadrotors subject to both parametric uncertainties and external disturbances. The presented controller is designed by effectively merging an adaptive control with an USDE via backstepping, where the extraneous uncertainties are addressed by USDE, and the adaptive law driven by tracking errors accounts for identifying unknown inertial moment constants. The unique characteristic is that a reinforced attitude controlling can be realized benefiting from the separate handling of parametric uncertainties and disturbances via an adaptive updating and a concise disturbance observation, significantly releasing the learning load of USDE and a high gain can be avoided in feedback loops. Meanwhile, Lyapunov analysis demonstrates that all error variables are uniformly ultimately bounded in the closed-loop system. Eventually, simulations substantiate the utility of suggested control strategy.
Increasing number of network applications require authentication of the user's identity which is the first step to ensure security. This paper analyzes the security performance of one proposed remote two-factor user authentication scheme and discusses the attacks it suffers. Then we propose an improved scheme based on the RSA cryptography and one-way secure hash function to avoid the attacks it suffers. After that we prove the proposed scheme is autonomous and effective for both sides in the authentication process.
In this paper, an actor critic neural network-based adaptive control scheme for micro-electro-mechanical system (MEMS) gyroscopes suffering from multiresource disturbances is proposed. Faced with multiresource interferences consisting of parametric uncertainties, strong couplings between axes, Coriolis forces, and variable external disturbances, an actor critic neural network is introduced, where the actor neural network is employed to estimate the packaged disturbances and the critic neural network is utilized to supervise the system performance. Hence, strong robustness against uncertainties and better tracking properties can be derived for MEMS gyroscopes. Aiming at handling the nonlinearities inherent in gyroscopes without analytically differentiating the virtual control signals, dynamic surface control (DSC) rather than backstepping control method is employed to divide the 2nd order system into two 1st order systems and design the actual control policy. Moreover, theoretical analyses along with simulation experiments are conducted with a view to validate the effectiveness of the proposed control approach.
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