The water medium hydraulic retarder is the latest type of auxiliary braking device and has the characteristics of high power density,large braking torque,and compact structure.During traveling,this device can convert ...The water medium hydraulic retarder is the latest type of auxiliary braking device and has the characteristics of high power density,large braking torque,and compact structure.During traveling,this device can convert the kinetic energy of a vehicle to the heat energy of the cooling liquid and replace the service brake under non-emergency braking conditions.With regard to the constant-speed function of the water medium hydraulic retarder,this study designs a controller based on the neural network proportional-integral-derivative(PID)algorithm to achieve the steady traveling of the vehicle at constant velocity during a downhill course by controlling the filling ratio of the water medium hydraulic retarder.To validate the algorithm’s effectiveness,the dynamic model of the heavy-duty vehicle in the downhill process and the physical model of the water medium hydraulic retarder are developed.Three operating conditions,including a fixed slope,step-changing slope,and continuous changing slope,are set,and a simulation test is carried out in the MATLAB/Simulink environment.The neural network PID algorithm has better adaptability in controlling than the traditional PID algorithm.Thus,it controls the water medium hydraulic retarder such that the braking requirements of heavy-duty vehicles under a changing slope working condi-tion are satisfied,and it performs constant-speed control when the vehicle travels downhill.Therefore,the proposed control method can significantly improve the safety of road traffic.展开更多
对AHRI Standard 210/240-2017标准中关于HSPF的计算方法进行分析,并对一台额定制热量为17kW的北美定速房间空调器进行试验研究,分析室内风量、室外风量、制冷剂充注量以及制热衰减系数CD对制热季节能效HSPF的影响。结果表明:合理的室...对AHRI Standard 210/240-2017标准中关于HSPF的计算方法进行分析,并对一台额定制热量为17kW的北美定速房间空调器进行试验研究,分析室内风量、室外风量、制冷剂充注量以及制热衰减系数CD对制热季节能效HSPF的影响。结果表明:合理的室内机风量(额定风量100%)有助于提升系统的HSPF;过高的室外风量(超过额定风量100%)对系统的制热能力提升影响并不大,风机功率的增加反而导致HSPF明显下降;存在最佳充注量使HSPF最大,充注量偏大时,在除霜工况下,蒸发器结霜换热恶化,功耗增大,能效降低,且压缩机有湿压缩风险;HSPF随制热衰减系数CD值增大呈下降的趋势,因此,优化设计热泵系统的同时,降低CD值是一种提高HSPF比较直接、经济的途径。展开更多
现有全脉冲结构波形与处理方法,如相位编码波形匹配处理存在多普勒容忍度差的固有缺陷,线性调频(linear frequency modulation,LFM)波形加窗处理降低了距离分辨率和信噪比(signal-to-noise ratio,SNR)增益,难以适应高速多目标探测的任...现有全脉冲结构波形与处理方法,如相位编码波形匹配处理存在多普勒容忍度差的固有缺陷,线性调频(linear frequency modulation,LFM)波形加窗处理降低了距离分辨率和信噪比(signal-to-noise ratio,SNR)增益,难以适应高速多目标探测的任务需求。为此,本文提出了一种面向高速目标探测的多子脉冲结构波形设计与处理方法。首先,构建具有多子脉冲结构波形的回波模型,利用分段子脉冲压缩处理和子脉冲间相参处理方法,导出多子脉冲结构波形的距离-多普勒响应函数;然后,根据感兴趣的目标距离速度区间,建立恒模约束下以最小化加权积分距离-多普勒旁瓣电平为目标函数的多子脉冲结构波形优化设计问题;最后,引入坐标下降(coordinate descent,CD)优化框架,将高维非凸约束优化问题的求解转变为多个一维优化问题的迭代求解,且推导出这些低维问题的闭式解。仿真表明,所设计的多子脉冲结构波形具有较好的多普勒容忍度和较低的局部距离-多普勒旁瓣电平,且在高速多目标认知探测场景下,相比于LFM波形、模糊函数优化波形和LFM-noise波形具有更好的高速目标探测能力。展开更多
基金funded by The National Key R&D Program of China(2016YFB0101402).
文摘The water medium hydraulic retarder is the latest type of auxiliary braking device and has the characteristics of high power density,large braking torque,and compact structure.During traveling,this device can convert the kinetic energy of a vehicle to the heat energy of the cooling liquid and replace the service brake under non-emergency braking conditions.With regard to the constant-speed function of the water medium hydraulic retarder,this study designs a controller based on the neural network proportional-integral-derivative(PID)algorithm to achieve the steady traveling of the vehicle at constant velocity during a downhill course by controlling the filling ratio of the water medium hydraulic retarder.To validate the algorithm’s effectiveness,the dynamic model of the heavy-duty vehicle in the downhill process and the physical model of the water medium hydraulic retarder are developed.Three operating conditions,including a fixed slope,step-changing slope,and continuous changing slope,are set,and a simulation test is carried out in the MATLAB/Simulink environment.The neural network PID algorithm has better adaptability in controlling than the traditional PID algorithm.Thus,it controls the water medium hydraulic retarder such that the braking requirements of heavy-duty vehicles under a changing slope working condi-tion are satisfied,and it performs constant-speed control when the vehicle travels downhill.Therefore,the proposed control method can significantly improve the safety of road traffic.
文摘对AHRI Standard 210/240-2017标准中关于HSPF的计算方法进行分析,并对一台额定制热量为17kW的北美定速房间空调器进行试验研究,分析室内风量、室外风量、制冷剂充注量以及制热衰减系数CD对制热季节能效HSPF的影响。结果表明:合理的室内机风量(额定风量100%)有助于提升系统的HSPF;过高的室外风量(超过额定风量100%)对系统的制热能力提升影响并不大,风机功率的增加反而导致HSPF明显下降;存在最佳充注量使HSPF最大,充注量偏大时,在除霜工况下,蒸发器结霜换热恶化,功耗增大,能效降低,且压缩机有湿压缩风险;HSPF随制热衰减系数CD值增大呈下降的趋势,因此,优化设计热泵系统的同时,降低CD值是一种提高HSPF比较直接、经济的途径。
文摘现有全脉冲结构波形与处理方法,如相位编码波形匹配处理存在多普勒容忍度差的固有缺陷,线性调频(linear frequency modulation,LFM)波形加窗处理降低了距离分辨率和信噪比(signal-to-noise ratio,SNR)增益,难以适应高速多目标探测的任务需求。为此,本文提出了一种面向高速目标探测的多子脉冲结构波形设计与处理方法。首先,构建具有多子脉冲结构波形的回波模型,利用分段子脉冲压缩处理和子脉冲间相参处理方法,导出多子脉冲结构波形的距离-多普勒响应函数;然后,根据感兴趣的目标距离速度区间,建立恒模约束下以最小化加权积分距离-多普勒旁瓣电平为目标函数的多子脉冲结构波形优化设计问题;最后,引入坐标下降(coordinate descent,CD)优化框架,将高维非凸约束优化问题的求解转变为多个一维优化问题的迭代求解,且推导出这些低维问题的闭式解。仿真表明,所设计的多子脉冲结构波形具有较好的多普勒容忍度和较低的局部距离-多普勒旁瓣电平,且在高速多目标认知探测场景下,相比于LFM波形、模糊函数优化波形和LFM-noise波形具有更好的高速目标探测能力。
