基于耗散性理论的汽车底盘集成非线性鲁棒约束优化控制

针对汽车主动前轮转向子系统和直接横摆力矩控制子系统集成控制问题,基于耗散性理论设计了一种非线性鲁棒控制器。将未建模动态、模型参数和反馈信号测量误差作为系统的加性不确定性和乘性不确定性,建立包含车身侧向和横摆运动自由度的汽车底盘集成控制模型;基于耗散性理论设计汽车底盘集成非线性L2增益控制律来抑制系统的加性不确定性对系统性能的影响,并采用投影修正法设计自适应律来实时估计和补偿系统的乘性不确定性;采用逐步二次规划法来实现汽车底盘集成非线性L2增益控制律输出的校正横摆力矩约束优化分配。最后,结合车辆动力学仿真软件对所提出的汽车底盘集成非线性鲁棒控制器的可行性和有效性进行了验证。

Chaos Control and Modified Projective Synchronization of Chaotic Dissipative Gyroscope Systems

This paper proposes the chaos control and the modified projective synchronization methods for chaotic dissipative gyroscope systems. Because of the nonlinear terms of the gyroscope system, the system exhibits chaotic motions. Occasionally, the extreme sensitivity to initial states in a system operating in chaotic mode can be very destructive to the system because of unpredictable behavior. In order to improve the performance of a dynamic system or avoid the chaotic phenomena, it is necessary to control a chaotic system with a periodic motion beneficial for working with a particular condition. As chaotic signals are usually broadband and noise like, synchronized chaotic systems can be used as cipher generators for secure communication. This paper presents chaos synchronization of two identical chaotic motions of symmetric gyroscopes. Using the variable structure control technique, control laws are established which guarantees the chaos control and the modified projective synchronization. By Lyapunov stability theory, control lows are proposed to ensure the stability of the controlled and synchronized system. Numerical simulations are presented to verify the proposed control and the synchronization approach. This paper demonstrates that synchronization and anti-synchronization can coexist in dissipative gyroscope systems via variable structure control.

Entransy analyses of the thermodynamic cycle in a turbojet engine

The analysis and the design of turbojet engines are of great importance to the improvement of the system performance.Many researchers focus on these topics,and many important and interesting results have been obtained.In this paper,the thermodynamic cycle in a turbojet engine is analyzed with the entransy theory and the T-Q diagram.The ideal thermodynamic cycle in which there is no inner irreversibility is analyzed,as well as the influences from some inner irreversible factors,such as the heat transfer process,the change of the component of the working fluid and the viscosity of the working fluid.For the discussed cases,it is shown that larger entransy loss rate always results in larger output power,while smaller entropy generation rate does not always.The corresponding T-Q diagrams are also presented,with which the change tendencies of the entransy loss rate and the output power can be shown very intuitively.It is shown that the entransy theory is applicable for analyzing the inner irreversible thermodynamic cycles discussed in this paper.Compared with the concept of entropy generation,the concept of entransy loss and the corresponding T-Q diagram are more suitable for describing the change of the output power of the analyzed turbojet engine no matter if the inner irreversible factors are considered.

Thermal performance analysis of non-uniform height rectangular fin based on constructal theory and entransy theory

A model of non-uniform height rectangular fin, in which the variation of base's thickness and width are taken into account, is established in this paper. The dimensionless maximum thermal resistance(DMTR) and the dimensionless equivalent thermal resistance(DETR) defined based on the entransy dissipation rate(EDR) are taken as performance evaluation indexes. According to constructal theory, the variations of the two indexes with the geometric parameters of the fin are analyzed by using a finite-volume computational fluid dynamics code, the effects of the fin-material fraction on the two indexes are analyzed. It is found that the two indexes decrease monotonically as the ratio between the front height and the back height of the fin increases subjected to the non-uniform height rectangular fin. When the model is reduced to the uniform height fin, the two indexes increase first and then decrease with increase in the ratio between the height of the fin and the fin space. The fin-material fraction has no effect on the change rule of the two indexes with the ratio between the height of the fin and the fin space. The sensitivity of the DETR to the geometric parameters of the fin is higher than that of the DMTR to the geometric parameters. The results obtained herein can provide some theoretical support for the thermal design of rectangular fins.