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关键词： pneumatic systems   nonlinear model-predictive control   hysteresis   nonlinear systems   observers  

摘要： This contribution presents two real-time capable nonlinear model-predictive control (NMPC) approaches for an electro-pneumatic clutch for heavy trucks: a centralized control approach and a cascaded one. A clutch is necessary at start-up or during gear shifts to connect or disconnect the combustion engine and the gear box. This automated actuator disburdens the driver and provides the necessary actuation force according to the large torque typically transmitted through the drive train. The force characteristic of the clutch, however, is subject to hysteresis, which is described by a generalized Bouc-Wen model and used for a feedforward hysteresis compensation in the control algorithm. The proposed NMPC-algorithm involves (i) a minimization of the difference between the desired and predicted state vector at the end of the prediction horizon and (ii) flatness-based techniques to compute desired trajectories for the complete state vector as well as the control input. The optimal control is given by an additional, minimum-norm control input that minimizes the difference between the predicted state vector and the desired one at the end of the prediction horizon. Thereby, the computation effort of the NMPC approaches can be kept relatively small, and a real-time evaluation becomes possible. A reduced-order observer estimates an effective pressure in the clutch that also accounts for an uncertain disturbance force. Thereby, a disturbance compensation and a high tracking accuracy is achievable for the piston position as controlled variable. The efficiency of the two proposed control structures is emphasized by experimental results from a dedicated test rig.

关键词： nest predation   developmental strategy   parental care   reproductive effort   fledgling mortality   age-specific mortality   LIFE-HISTORY EVOLUTION   POSTFLEDGING PARENTAL CARE   AGE-SPECIFIC MORTALITY   NEST PREDATION   ENERGY-EXPENDITURE   BROOD DIVISION   DEVELOPMENTAL RATES   FLEDGLING OVENBIRDS   JUVENILE SURVIVAL   WILSONIA-CITRINA  

摘要： Causes of evolved differences in clutch size among songbird species remain debated. I propose a new conceptual framework that integrates aspects of traditional life-history theory while including novel elements to explain evolution of clutch size among songbirds. I review evidence that selection by nest predation on length of time that offspring develop in the nest creates a gradient in offspring characteristics at nest leaving (fledging), including flight mobility, spatial dispersion, and self-feeding rate. I postulate that this gradient has consequences for offspring mortality rates and parental energy expenditure per offspring. These consequences then determine how reproductive effort is partitioned among offspring, while reproductive effort evolves from age-specific mortality effects. Using data from a long-term site in Arizona, as well as from the literature, I provide support for hypothesized relationships. Nestling development period consistently explains fledgling mortality, energy expenditure per offspring, and clutch size while accounting for reproductive effort (i.e., total energy expenditure) to thereby support the framework. Tests in this article are not definitive, but they document previously unrecognized relationships and address diverse traits (developmental strategies, parental care strategies, energy requirements per offspring, evolution of reproductive effort, clutch size) that justify further investigations of hypotheses proposed here.

关键词： 机械式自动变速器   离合器   载荷特性   电控气动   积分滑模控制   位置伺服控制  

摘要： 为了实现电气离合器执行系统的位置伺服控制，构建了离合器气动执行系统。通过运用引入死区的滑模控制算法于系统，采用不基于模型的控制实现离合器气动执行系统对参考运动轨迹的跟踪，利用轨迹跟踪过程中气缸的气压驱动力间接估计离合器的载荷特性。理论上采用此方法间接估计到的值误差小，更加贴近离合器在此种轨迹运动下实际的载荷特性。试验表明引入估计得到的离合器载荷特性模型于基于模型的积分滑模控制器可以很大程度提高离合器气动执行系统轨迹跟踪精度。

关键词： 铰链四杆机构   类型判别   教学实践  

摘要： "铰链四杆机构的类型判别"是职业技工学校《机构与零件》中的重要内容。本文对该部分内容进行了教学设计与反思,深刻践行了"理论与实践相结合"的原理,运用多媒体技术对专业课教学中"实践"的运用进行了探索。

关键词： 离合器   常见问题   排除方法  

摘要： 汽车传动系统部件中的一个重要的组成部分就是离合器,它是连接到发动机上,主要的功能是让司机对它的驱动从动部分进行操作,从而使汽车能够平稳地启动。若离合器打滑,会让它处于一种没有完全结合的状态,不能可靠地传递扭矩,该车就会出现动力不足的情况,如果不及时地分析和处理,离合器等部件就会受到影响,有的都能被损坏,所以,从实际问题出发对离合器的故障进行研究,并确定排除的方法,让离合器的可靠性和正确使用性得到保证。

关键词： 离合器   从动片磨损   报警装置  

摘要： 通常,驾驶员根据离合器踏板自由行程的高低来判断离合器从动片的磨损程度。但是,如果驾驶员经验不足,易造成离合器从动片磨损严重而导致摩擦片上的铆钉裸漏,造成飞轮和压盘工作面不可修复的损伤,出现飞轮和压盘同时报废的情况。为避免此类情况的发生,制作离合器从动片磨损报警装置。此装置具有结构简单、成本低、实用性强的特点,具有很好的推广价值。

关键词： 吊篮式移栽机   槽轮机构   ADAMS   试验  

摘要： 吊篮式移栽机具有成穴和移栽一次完成的特点,但是在使用时喂苗人员劳动强度较大,且易出现漏苗现象。针对这一问题,设计了一套旋转杯式喂苗机构,该机构利用外销多槽轮机构带动苗杯进行间歇式转动,可以给工作人员充足的时间进行投苗,减轻工作人员劳动强度的同时提高了移栽效率;利用ADAMS平台,对槽轮机构进行动力学仿真,得到了槽轮机构角速度曲线和角加速度曲线;通过移栽单体试验,得出合适的移栽频率为58-66株/（min·行）。

关键词： 变速器   干式双离合器   膜片弹簧   自调节原理  

摘要： 基于某干式双离合器,采用激光点云扫描技术扫描其膜片弹簧表面,并结合CATIA软件生成膜片弹簧实体模型。用ANSYS/Workbench软件分别对实体模型进行有限元分析,得到自由状态膜片弹簧小端载荷位移曲线,并通过台架试验证明了曲线趋势的合理性。在此基础上,对干式双离合器的自调节原理进行了详细分析。

关键词： J37-315双点闭式压力机   床身瓦座   离合器   制动器   润滑方式  

摘要： 经过对设备床身四个瓦座修复、离合器卸荷套结构改造、制动器修复、离合器修复、润滑部分改造等工作,使设备的结构更加合理,恢复了设备精度和正常工作。

关键词： 无碳小车   结构设计   变心齿轮   轨迹   重力  

摘要： 针对全国大学生工程训练综合能力竞赛命题"无碳小车"的要求,进行了创新结构设计,改变了一般齿轮定心啮合为变心啮合,导致后轮形成速度差使车体走似简谐波,从而达到转向要求。运用matlab进行了运动轨迹的模拟分析,结合工程实践,并设计制造出实物。实践表明,运行轨迹符合大赛要求,小车运行平稳,行程远,避障多。