An electro-hydraulic control system is designed and implemented for a robotic excavator known as the Lancaster University Computerised and Intelligent Excavator （LUCIE）. The excavator is being developed to autonomou...An electro-hydraulic control system is designed and implemented for a robotic excavator known as the Lancaster University Computerised and Intelligent Excavator （LUCIE）. The excavator is being developed to autonomously dig trenches without human intervention. Since the behavior of the excavator arm is dominated by the nonlinear dynamics of the hydraulic actuators and by the large and unpredictable external disturbances when digging, it is difficult to provide adequate accurate, quick and smooth movement under traditional control methodology, e.g., PI/PID, which is comparable with that of an average human operator. The data-based dynamic models are developed utilizing the simplified refined instrumental variable （SRIV） identification algorithm to precisely describe the nonlinear dynamical behaviour of the electro-hydraulic actuation system. Based on data-based model and proportional-integral-plus （PIP） methodology, which is a non-minimal state space method of control system design based on the true digital control （TDC） system design philosophy, a novel control system is introduced to drive the excavator arm accurately, quickly and smoothly along the desired path. The performance of simulation and field tests which drive the bucket along straight lines both demonstrate the feasibility and validity of the proposed control scheme.展开更多
A novel control algorithm with fixed pulse thrust, based on true proportional navigation（TPN）, is proposed for exoatmospheric intercept.According to the TPN guidance law and pulse thrust characteristics, the princip...A novel control algorithm with fixed pulse thrust, based on true proportional navigation（TPN）, is proposed for exoatmospheric intercept.According to the TPN guidance law and pulse thrust characteristics, the principle of control command is presented, the control stability and precision are analyzed.With the help of the TPN guidance law, the algorithm can automatically modulate the turn-on time and duration of the thrust, which could effectively limit the impact of measure noise of the line-of-sight（LOS） angle and rate on the interception miss-distance.At last, the number-theoretic method（NTM） is introduced to acquire the relation between control algorithm and miss-distance, even as it simulates the intercept process with initial state noise.And the reliability of the algorithm is demonstrated with the simulation result.展开更多
目的:研究观看视屏终端(Visual or Video display terminal VDT)与青少年近视的关系。方法:参加研究者来自同一中学12岁～14岁学生,设置对照组:295名非近视者,近视组:303名近视者;近视眼组用1％阿托品点眼根据调(?)麻痹后屈光的不同变...目的:研究观看视屏终端(Visual or Video display terminal VDT)与青少年近视的关系。方法:参加研究者来自同一中学12岁～14岁学生,设置对照组:295名非近视者,近视组:303名近视者;近视眼组用1％阿托品点眼根据调(?)麻痹后屈光的不同变化确定假性近视组74名,混合性近视组79名,<-6D真性近视组150名。问卷调查观看VDT情况并进行病例对照研究,用Spss+/PC软件进行分析。结果:经常观看VDT率3个近视组均比对照组要高,且差异有统计学意义(P<0.6);屏幕大小亦可能是有意义的因素(0.05<P<0.1);每日平均看电视时间(ATPD)、经常看电视年限(YOWT)二因素,其平均值近视组较对照组要大,而看电视距离(DWT)则近视组较对照组小(t检验P<0.05);本文设计VDT指数=ATPD×YOWT/DWT。在3个近视组中VDT指数与其相应相对危险度OR值之间存在剂量效应关系。结论:观看VDT与上述3种近视之间有关系。展开更多
基金supported by the Lancaster University (UK)SooChow University, China+2 种基金the UK Engineering and Physical Sciences Research CouncilUniversities’ Natural Science Research Council of Jiangsu Universities, China(Grant No. 08KJB510021)Scientific Research Foundation for the Returned Overseas Chinese Scholars, Ministry of Education of China
文摘An electro-hydraulic control system is designed and implemented for a robotic excavator known as the Lancaster University Computerised and Intelligent Excavator （LUCIE）. The excavator is being developed to autonomously dig trenches without human intervention. Since the behavior of the excavator arm is dominated by the nonlinear dynamics of the hydraulic actuators and by the large and unpredictable external disturbances when digging, it is difficult to provide adequate accurate, quick and smooth movement under traditional control methodology, e.g., PI/PID, which is comparable with that of an average human operator. The data-based dynamic models are developed utilizing the simplified refined instrumental variable （SRIV） identification algorithm to precisely describe the nonlinear dynamical behaviour of the electro-hydraulic actuation system. Based on data-based model and proportional-integral-plus （PIP） methodology, which is a non-minimal state space method of control system design based on the true digital control （TDC） system design philosophy, a novel control system is introduced to drive the excavator arm accurately, quickly and smoothly along the desired path. The performance of simulation and field tests which drive the bucket along straight lines both demonstrate the feasibility and validity of the proposed control scheme.
文摘A novel control algorithm with fixed pulse thrust, based on true proportional navigation（TPN）, is proposed for exoatmospheric intercept.According to the TPN guidance law and pulse thrust characteristics, the principle of control command is presented, the control stability and precision are analyzed.With the help of the TPN guidance law, the algorithm can automatically modulate the turn-on time and duration of the thrust, which could effectively limit the impact of measure noise of the line-of-sight（LOS） angle and rate on the interception miss-distance.At last, the number-theoretic method（NTM） is introduced to acquire the relation between control algorithm and miss-distance, even as it simulates the intercept process with initial state noise.And the reliability of the algorithm is demonstrated with the simulation result.
文摘目的:研究观看视屏终端(Visual or Video display terminal VDT)与青少年近视的关系。方法:参加研究者来自同一中学12岁～14岁学生,设置对照组:295名非近视者,近视组:303名近视者;近视眼组用1％阿托品点眼根据调(?)麻痹后屈光的不同变化确定假性近视组74名,混合性近视组79名,<-6D真性近视组150名。问卷调查观看VDT情况并进行病例对照研究,用Spss+/PC软件进行分析。结果:经常观看VDT率3个近视组均比对照组要高,且差异有统计学意义(P<0.6);屏幕大小亦可能是有意义的因素(0.05<P<0.1);每日平均看电视时间(ATPD)、经常看电视年限(YOWT)二因素,其平均值近视组较对照组要大,而看电视距离(DWT)则近视组较对照组小(t检验P<0.05);本文设计VDT指数=ATPD×YOWT/DWT。在3个近视组中VDT指数与其相应相对危险度OR值之间存在剂量效应关系。结论:观看VDT与上述3种近视之间有关系。
