The disturbance decoupling problem for nonlinear control systems

Necessary and sufficient conditions are derived for the solution of the disturbance decoupling problem for general nonlinear control systems. Some conceptual algorithms needed are discussed.     

Doubled power density from salinity gradients at reduced intermembrane distance

The mixing of sea and river water can be used as a renewable energy source. The Gibbs free energy that is released when salt and fresh water mix can be captured in a process called reverse electrodialysis (RED). This research investigates the effect of the intermembrane distance and the feedwater flow rate in RED as a route to double the power density output. Intermembrane distances of 60, 100, 200, and 485 μm were experimentally investigated, using spacers to impose the intermembrane distance. The generated (gross) power densities (i.e., generated power per membrane area) are larger for smaller intermembrane distances. A maximum value of 2.2 W/m(2) is achieved, which is almost double the maximum power density reported in previous work. In addition, the energy efficiency is significantly higher for smaller intermembrane distances. New improvements need to focus on reducing the pressure drop required to pump the feedwater through the RED-device using a spacerless design. In that case power outputs of more than 4 W per m(2) of membrane area at small intermembrane distances are envisaged.     

Invertibility of affine nonlinear control systems: a geometric approach

The paper deals with the invertibility of multivariable non-linear control systems. By using the recently developed theory on controlled invariant and controllability distributions necessary and sufficient conditions for invertibility are derived.     

Robust control of an electromagnetic active suspension system: Simulations and measurements

This paper considers the control of a novel high bandwidth electromagnetic active suspension system for a quarter car model in both simulations and experiments. The nature of the control problem with multiple objectives that have to be optimized as well as the uncertain parameters of the plant call for an H_∞-controller. By changing weighting filters different controllers can be designed, emphasizing either comfort or handling. Using the high bandwidth of the actuator comfort can be improved by 40% over the passive BMW whilst keeping suspension travel within the same limits. Using a different controller, handling can be improved up to 30%, limited by RMS actuator force.     

Self-tuning of a switching controller for scanning motion systems

For a class of switching motion control systems, in particular scanning stage systems, a self-tuning method is proposed to find the optimal switching control parameters. In this method, a combined model/data-based approach is used to derive the gradients with respect to these parameters. The gradients are used in an update scheme which subsequently renders an updated set of parameters. Each set is applied to the machine while operating under closed-loop conditions. By repeating the process, the switching control parameters show convergence to an optimized set of values that induce servo performance inaccessible to linear control. This is because high-gain feedback is incidentally switched on to suppress large amplitude oscillations and is otherwise switched off to avoid amplification of small amplitude noises. In time-domain this gives improved low-frequency disturbance rejection properties with minimal deterioration of the sensitivity to high-frequency noises. Stability and convergence of the switching control system and optimization scheme in the face of perturbations is proved using Lyapunov analysis. Servo performance is demonstrated on a commercial and nano-positioning scanning motion system.     

小型滚动轮胎摩擦特性和刚度特性的试验与数值研究

当今轮胎行业在设计新轮胎时普遍采用虚拟试验,因其能在节省大量开发时间的同时降低成本。虚拟试验除了模拟轮胎静态响应,还可以同时研究轮胎在道路上行驶的动态状况。这项工作可以进行不同条件下的轮胎试验,获取模型参数所需要的摩擦特征。其缺点就是无法控制的环境条件和轮胎结构会影响到试验结果。因此,在更多可控制条件下进行的小型试验更具有优势。胶料摩擦性能的试验特征因综合测量系统的必然性而有局限性。LATl00型实验室磨耗和滑动性能试验机（如图1所示,下称试验机）是针对轮胎行业的胶料测试而设计开发的,其利用特制摩擦盘模拟路况,测量直径为80mm小型滚动轮胎的湿滑、牵引力和磨耗,从而将结构复杂的轮胎简化为由一种胶料制造的实心轮胎,以研究滚动轮胎与道路之间的相互作用。     

Development and Evaluation of a High-Volume Aerosol-into-Liquid Collector for Fine and Ultrafine Particulate Matter

This study presents a novel high-volume aerosol-into-liquid collector, developed to provide concentrated slurries of fine and/or ultrafine particulate matter (PM) to be used for unattended, in situ measurements of PM chemistry and toxicity. This system operates at 200 liters per minute (L/min) flow and utilizes the saturation–condensation, particle-to-droplet growth component of the versatile aerosol concentration enrichment system (VACES), growing fine or ultrafine PM to 3–4-μm droplets, in conjunction with a newly designed impactor, in which grown particles are collected gradually forming highly concentrated slurries. Laboratory evaluation results indicated an excellent overall system collection efficiency (over 90%) for both monodisperse and polydisperse particles in the range of 0.01 to 2 μm. Field evaluations illustrated that overall a very good agreement was obtained for most PM_2.5 species between the new aerosol collection system and the VACES/BioSampler tandem as well as filter samplers operating in parallel. Very good agreement between the new system and the VACES/BioSampler was also observed for reactive oxygen species (ROS) in ambient PM_2.5 samples, whereas lower ROS values were obtained from the water extracts of the filter, likely due to incomplete extraction of water insoluble redox active species collected on the filter substrate. Moreover, the field tests indicated that the new aerosol collection system could achieve continuous and unattended collection of concentrated suspensions for at least 2 to 3 days without any obvious shortcomings in its operation. Both laboratory and field evaluations of the high-volume aerosol-into-liquid collector suggest that this system is an effective technology for collection and characterization of ambient aerosols.

Copyright 2013 American Association for Aerosol Research