Composite Observer-Based Adaptive Dynamic Surface Control for Fractional-Order Nonlinear Systems with Input Saturation

This article proposes an adaptive neural output feedback control scheme in combination with state and disturbance observers for uncertain fractional-order nonlinear systems containing unknown external disturbance, input saturation and immeasurable state. The radial basis function neural network (RBFNN) approximation is used to estimate unknown nonlinear function, and a state observer as well as a fractional-order disturbance observer is developed simultaneously by using the approximation output of the RBFNN to estimate immeasurable states and unknown compounded disturbances, respectively. Then, a fractional-order auxiliary system is constructed to compensate the effects caused by the saturated input. In addition, by introducing a dynamic surface control strategy, the tedious analytic computation of time derivatives of virtual control laws in the conventional backstepping method is avoided. The proposed method guarantees that the boundness of all signals in the closed loop system and the tracking errors converge to a small neighbourhood around the origin. Finally, two examples are provided to verify the effectiveness of the proposed control method.

Finite-time fuzzy dynamic surface control for permanent magnet synchronous motor stochastic systems with input constraint and load disturbance

In this paper, a finite-time adaptive fuzzy dynamic surface control (DSC) method is proposed for the position tracking control of permanent magnet synchronous motors (PMSMs) stochastic nonlinear system with input constraint and load disturbance. First, the stochastic disturbance of PMSMs is considered in operation, and the fuzzy control method is applied to cope with the stochastic nonlinear function in the motor model. Second, the DSC technique is applied to avoid the “explosion of complexity” in the backstepping design. Moreover, the finite-time control is applied to the stochastic nonlinear system of PMSMs to improve the convergence speed of the system, tracking accuracy, and anti-interference ability. Conclusive, simulation results are given to verify the method that can achieve fast tracking of the desired signal.

Precise surface control of cathode materials for stable lithium-ion batteries

Precise surface control of cathode materials for stable Li-ion batteries: materials design, kinetics control and stabilization mechanism.

Improvement of monodispersity and shape symmetry of silica shell for PbS quantum dots by introducing surface silanization and adjusting reverse micelle size

Increasing the thickness of the quantum dot silica coating layer reduces monodispersity and shape symmetry. This paper reports three effective ways to solve this problem and achieve a large silica-coated QDs, i.e., proper silanization on the QD surface, control of reverse micelle size by adjusting the amount of QD solvent, and two-step formation of silica shell. Proper substitution of ligands on the QD surface in the early stages of silica shell formation was important for uniform coating reaction. An amount of toluene as QD solvent determined the size of reverse micelles during the silica shell formation. There was an optimum combination of inverse micelle size and silica shell size to obtain silica-coated QDs with good monodispersity and high shape symmetry. We succeeded in growing the thick silica shell with expanding reverse micelle size by additionally supplying toluene with the raw material using the optimum silica-coated QDs as growth nucleus