基于遗传算法非线性PID的柴油机共轨压力控制

高压共轨柴油机共轨压力随不同工况的调节能力及其压力的稳定性,从根本上影响着柴油机系统的燃油经济性与排放性能;针对共轨压力的控制,给出了在起动、过渡、正常、停机以及故障等工况下的轨压控制策略,设计了带预控制的积分分离非线性PID控制器,采用遗传算法对PID参数进行了在线自适应整定,实现了在不同柴油机工况下对不同轨压变化的优化控制;台架实验结果表明,在不同工况下采取的控制策略是适用的,采用的积分分离技术能减少控制超调,预控制技术能缩短轨压稳定时间并减少轨压波动,遗传算法对非线性PID控制器参数的在线优化,平均可在柴油机起动后6.7 s内完成,所设计的非线性PID控制器可把轨压控制偏差稳定在1.4%以下。     

Progress in bulk MgCu2-type rare-earth iron magnetostrictive compounds

Studies of bulk MgCu2-type rare-earth iron compounds with Laves phase are reviewed. The relationship between magnetostriction and structural distortion and the consequent crystallographic method for measuring magnetostriction are introduced at first. Then we review recent progress in understanding bulk magnetostrictive Laves phase materials, especially the magnetostriction and the minimization of the anisotropy of the light rare-earth Pr- and Sm-based compounds. Finally, a summary and outlook for this kind of compounds are presented.     

Large elastocaloric effect in Ti–Ni shape memory alloy below austenite finish temperature

Solid refrigeration technology based on the elastocaloric effect has a great potential alternative to the conventional vapor compression cooling. Here we report the large elastocaloric effect in Ti–Ni(50 at%) shape memory alloy below its austenite finish temperature A_f under different strain. Both Maxwell's and Clausius–Clapeyron equations are used to estimate the entropy change. The strain-induced entropy change increases with raising the strain and gets a maximum value at a few kelvins below A_f. The maximum entropy changes ?S_(max) are-20.44 and-53.70 J/kg·K, respectively for 1% and2% strain changes. Large entropy change may be obtained down to 20 K below A_f. The temperature of the maximum entropy change remains unchanged before the plastic deformation appears but moves towards low temperature when the plastic deformation happens.