This paper carries out a cluster mean field analysis for spontaneous symmetry breaking in a two-lane totally asymmetric exclusion processes with an intersection. We find that the boundaries of the asymmetric phase are determined by differences of upstream segment densities and downstream segment flow rates of two lanes. The spontaneous symmetry breaking phenomenon exists when the interaction of particles is strong enough. The critical values, beyond which the phenomenon disappears, are identified through simulation and analysis, and they are in excellent agreement. The analytical results of the asymmetric phase boundaries are closer to simulation ones than those of simple mean field analysis. The analytical results of density profiles and the simulation ones are also in excellent agreement.
Hybrid excitation synchronous machines (HESMs) inherit the high-torque density of permanent magnet synchronous machines and flux regulation capability of wound rotor synchronous machines. This makes HESMs attractive candidates for vehicle traction applications. To further improve torque density, an optimised HESM with magnet shunting rotor is proposed in this study. This study presents a maximum torque control strategy with zero d-axis current. Furthermore, an optimised control strategy that utilises the coordinated operation between the field current and d-axis current is proposed. The optimised control strategy exhibits advantages of low-speed high-torque, wide constant power range, and high efficiency in flux-weakening (FW) region. A 100 kW drive system based on the optimised HESM with the proposed control strategy is developed, experimentally realised, and validated. The experimental results show that the FW range is 3.5-1, and the efficiency of the drive system is >92% in most operating region, which verify the superiority and effectiveness of the proposed HESM drive system.
This study investigates the nonsingular terminal sliding mode control (NTSMC) method for the four-degree-of-freedom (4-DOF) trajectory tracking control problem of underwater remotely operated vehicles (ROVs) in the presence of parametric uncertainties and external disturbances. Two new control algorithms have been developed for ROVs. The first one, combining a nonsingular sliding surface with a fast terminal sliding mode (FTSM) type reaching law, is nonsingular and chattering-free. The second one, introducing adaptive methodology to compensate for lumped uncertainties, is an improved version of the first algorithm and can be called adaptive NTSMC (ANTSMC). The adaptive methodology effectively reduces the chattering problem. Meanwhile, it also provides better robustness and higher tracking precision compared with the first algorithm. A corresponding stability analysis is presented using Lyapunov stability theory, and some comparative numerical simulation results are presented to show the effectiveness of the proposed approaches.
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