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Aiming at the accurate speed tracking control of electric vehicles (EV) driven by permanent magnet synchronous motors (PMSM) under external load torque disturbances, this paper proposes an approach for prescribed performance back-stepping control based on a disturbance observer. Firstly, a controller was designed using the back-stepping technique, and a second-order sliding mode differentiator was introduced to approximate the derivative of the virtual control law, which can solve the "differential explosion" problem in traditional back-stepping control techniques. Secondly, in order to reduce the influence of motor load disturbances in the driving process of EV, a novel disturbance observer was proposed, bolstering the anti-interference capability of system. In addition, to achieve the preset high transient and steady-state speed tracking performance, a prescribed performance control strategy was incorporated to guarantee tracking errors within predefined boundaries. Finally, the Lyapunov function was utilized to verify the system stability. The simulation results showed that, compared with traditional PI control, the designed controller significantly increased motor speed tracking precision by more than 5 times, demonstrating a superior speed tracking performance and enhanced anti-interference capability.

This paper explores a reinsurance and asset liability management problem in a factor model with dependent risks, considering economic factors as non-Markovian processes impacting the appreciation rate, volatility, and value of liabilities. It encompasses various stochastic volatility (SV) models like Hull-White, Heston, 3/2, and 4/2 models as special cases. The model addresses dependent risks through a common shock in claim number processes. The insurer's aim is to minimize variance in terminal net wealth while achieving a certain expected terminal net wealth, balancing reinsurance, new business, and asset allocation. The paper employs linear-quadratic (LQ) control and backward stochastic differential equation (BSDE) theory to derive both the efficient strategy and the efficient frontier. To illustrate our results, numerical examples are provided in two special cases, the 3/2 and 4/2 SV models. [ABSTRACT FROM AUTHOR]

This study sought to ascertain the existence of convergence in environmental taxation among EU countries. By employing the sequential panel selection method and the panel KSS unit root test, it is demonstrated that the environmental taxation sequences in Luxembourg, Germany, Spain, France, and Cyprus diverge, while those of the remaining 22 countries converge. Similarly, the energy tax sequences of Croatia, Spain, Germany, and France are unstable, indicating divergence, while the remaining 23 countries exhibit significant convergence. Finally, transport taxes show a convergent trend across all EU countries. The convergence of environmental taxation can be explained by the catch-up and spatial spillover effects, and the non-convergence of a few EU countries is attributed to their minimal implementation of environmental goals. This study provides recommendations for improving environmental policies. [ABSTRACT FROM AUTHOR]