In this paper, an iterative learning control algorithm is proposed for discrete linear time-varying systems to track iterationvarying desired trajectories. A high-order internal model(HOIM) is utilized to describe the...In this paper, an iterative learning control algorithm is proposed for discrete linear time-varying systems to track iterationvarying desired trajectories. A high-order internal model(HOIM) is utilized to describe the variation of desired trajectories in the iteration domain. In the sequel, the HOIM is incorporated into the design of learning gains. The learning convergence in the iteration axis can be guaranteed with rigorous proof. The simulation results with permanent magnet linear motors(PMLM) demonstrate that the proposed HOIM based approach yields good performance and achieves perfect tracking.展开更多
Many high schools in the northeastern United States have suffered from declining enrollment due to a declining population of school-age children in the region.Administrators,counselors and teachers perceive many impac...Many high schools in the northeastern United States have suffered from declining enrollment due to a declining population of school-age children in the region.Administrators,counselors and teachers perceive many impacts of the implementation of an international student program at a rural high school.This qualitative case study reveals that the rural high school’s unique nature impacts international student programs,international students influence both school culture and programming,and international students suffer from isolation.School leaders would benefit from considerations in the form of professional development both prior to implementation of an international student program and ongoing throughout its duration.It is important for schools to find ways to respectfully honor student cultures and optimize learning experiences.School leaders would be wise to determine desired size of international student programs and make efforts accordingly to achieve that size for optimal effectiveness for the benefit of both host and international students.Implications and recommendations for future research include further exploration of the perceived experiences of European and Chinese international students,understanding the unique nature of rural high schools and international student experiences,and examination of school practices.展开更多
针对高速电主轴动态模型中耦合电压的非线性变化对主轴动态性能所产生的影响,通过对比前馈控制和内模控制(Internal model control,IMC)的电压解耦机理,指出IMC能够避免前馈控制时电压解耦效果依赖主轴模型参数与实际参数相匹配的不足,...针对高速电主轴动态模型中耦合电压的非线性变化对主轴动态性能所产生的影响,通过对比前馈控制和内模控制(Internal model control,IMC)的电压解耦机理,指出IMC能够避免前馈控制时电压解耦效果依赖主轴模型参数与实际参数相匹配的不足,并利用170MD15Y20油雾润滑型电主轴和Matlab/Simulink软件分别对两种控制方法进行试验和仿真分析。结果表明,主轴的耦合电压主要受频率和转矩电流变化的影响,改变磁链子系统和转矩子系统的给定电压、以及耦合回路中无功功率在输入功率中的比例,不仅可以对主轴的功率因素、输出转矩、抗扰动能力和动态速度跟随精度等特性参数产生影响,而且使主轴的转矩脉动程度、带负载能力和转差率等随耦合电压的大小成反比例变化。因此可以根据包含上述特征信息的机械特性曲线、功率因素曲线和恒转矩曲线的变化趋势,准确判断高速电主轴的解耦效果,并预测主轴在该控制方式下的动态性能。展开更多
基金supported by National Basic Research Program of China(973 Program)(No.2012CB316400)National Natural Science Foundation of China(Nos.61171034 and 61273134)
文摘In this paper, an iterative learning control algorithm is proposed for discrete linear time-varying systems to track iterationvarying desired trajectories. A high-order internal model(HOIM) is utilized to describe the variation of desired trajectories in the iteration domain. In the sequel, the HOIM is incorporated into the design of learning gains. The learning convergence in the iteration axis can be guaranteed with rigorous proof. The simulation results with permanent magnet linear motors(PMLM) demonstrate that the proposed HOIM based approach yields good performance and achieves perfect tracking.
文摘Many high schools in the northeastern United States have suffered from declining enrollment due to a declining population of school-age children in the region.Administrators,counselors and teachers perceive many impacts of the implementation of an international student program at a rural high school.This qualitative case study reveals that the rural high school’s unique nature impacts international student programs,international students influence both school culture and programming,and international students suffer from isolation.School leaders would benefit from considerations in the form of professional development both prior to implementation of an international student program and ongoing throughout its duration.It is important for schools to find ways to respectfully honor student cultures and optimize learning experiences.School leaders would be wise to determine desired size of international student programs and make efforts accordingly to achieve that size for optimal effectiveness for the benefit of both host and international students.Implications and recommendations for future research include further exploration of the perceived experiences of European and Chinese international students,understanding the unique nature of rural high schools and international student experiences,and examination of school practices.
文摘针对高速电主轴动态模型中耦合电压的非线性变化对主轴动态性能所产生的影响,通过对比前馈控制和内模控制(Internal model control,IMC)的电压解耦机理,指出IMC能够避免前馈控制时电压解耦效果依赖主轴模型参数与实际参数相匹配的不足,并利用170MD15Y20油雾润滑型电主轴和Matlab/Simulink软件分别对两种控制方法进行试验和仿真分析。结果表明,主轴的耦合电压主要受频率和转矩电流变化的影响,改变磁链子系统和转矩子系统的给定电压、以及耦合回路中无功功率在输入功率中的比例,不仅可以对主轴的功率因素、输出转矩、抗扰动能力和动态速度跟随精度等特性参数产生影响,而且使主轴的转矩脉动程度、带负载能力和转差率等随耦合电压的大小成反比例变化。因此可以根据包含上述特征信息的机械特性曲线、功率因素曲线和恒转矩曲线的变化趋势,准确判断高速电主轴的解耦效果,并预测主轴在该控制方式下的动态性能。
