Most of the existing PID parameters tuning methods are only effective with pre-known accurate system models, which often require some strict identification experiments and thus infeasible for many complicated systems....Most of the existing PID parameters tuning methods are only effective with pre-known accurate system models, which often require some strict identification experiments and thus infeasible for many complicated systems. Actually, in most practical engineering applications, it is desirable for the PID tuning scheme to be directly based on the input-output response of the closed-loop system. Thus, a new parameter tuning scheme for PID controllers without explicit mathematical model is developed in this paper. The paper begins with a new frequency domain properties analysis of the PID controller. After that, the definition of characteristic frequency for the PID controller is given in order to study the mathematical relationship between the PID parameters and the open-loop frequency properties of the controlled system. Then, the concepts of M-field and θ-field are introduced, which are then used to explain how the PID control parameters influence the closed-loop frequency-magnitude property and its time responses. Subsequently, the new PID parameter tuning scheme, i.e., a group of tuning rules, is proposed based on the preceding analysis. Finally, both simulations and experiments are conducted, and the results verify the feasibility and validity of the proposed methods. This research proposes a PID parameter tuning method based on outputs of the closed loop system.展开更多
针对传统的RSSI (received signal strength indication)定位方法会受到室内无线信道传播特性影响的问题,首先在密闭走廊、开放走廊和实验室三种不同场景下,对无线信号强度进行测试并统计其概率分布,构建室内无线信道传播特性模型。然后...针对传统的RSSI (received signal strength indication)定位方法会受到室内无线信道传播特性影响的问题,首先在密闭走廊、开放走廊和实验室三种不同场景下,对无线信号强度进行测试并统计其概率分布,构建室内无线信道传播特性模型。然后,锚节点定期测量移动节点信标信号的RSSI,中心节点利用最大似然法和信道传播特性模型来估算其坐标位置、移动速度和行进方向。实验结果证明,该方案可以实现不同室内环境下移动节点的跟踪定位,并满足精度要求。展开更多
目的研究刷牙次数对中国成人肥胖和慢性病的影响。方法通过2013年和2018年两次国家卫生服务调查(National Health Service Survey,NHSS),两次横断面调查均采用多阶段分层整群随机抽样以获得全国代表性样本。采用多元Logistic回归分析刷...目的研究刷牙次数对中国成人肥胖和慢性病的影响。方法通过2013年和2018年两次国家卫生服务调查(National Health Service Survey,NHSS),两次横断面调查均采用多阶段分层整群随机抽样以获得全国代表性样本。采用多元Logistic回归分析刷牙次数对超重肥胖和慢性病的影响。结果2013年及2018年调查中,分别有219609人,205777人纳入研究对象。在2013年,不刷牙的人数占总调查人数的3.64%,而在2018年,不刷牙的人数增长到4.67%(P<0.001)。与每天刷牙不到2次的人群相比,每天规律刷牙2次或2次以上的人超重肥胖的风险降低12%(OR=0.88,95%CI0.87~0.90),患慢病的风险降低10%(OR=0.90,95%CI0.89~0.92)。结论刷牙次数与中国人群超重肥胖及慢病风险密切相关,对我国口腔卫生健康教育的开展与慢病的防治有重要指导意义。展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.61473282,61203340,61305120)
文摘Most of the existing PID parameters tuning methods are only effective with pre-known accurate system models, which often require some strict identification experiments and thus infeasible for many complicated systems. Actually, in most practical engineering applications, it is desirable for the PID tuning scheme to be directly based on the input-output response of the closed-loop system. Thus, a new parameter tuning scheme for PID controllers without explicit mathematical model is developed in this paper. The paper begins with a new frequency domain properties analysis of the PID controller. After that, the definition of characteristic frequency for the PID controller is given in order to study the mathematical relationship between the PID parameters and the open-loop frequency properties of the controlled system. Then, the concepts of M-field and θ-field are introduced, which are then used to explain how the PID control parameters influence the closed-loop frequency-magnitude property and its time responses. Subsequently, the new PID parameter tuning scheme, i.e., a group of tuning rules, is proposed based on the preceding analysis. Finally, both simulations and experiments are conducted, and the results verify the feasibility and validity of the proposed methods. This research proposes a PID parameter tuning method based on outputs of the closed loop system.
文摘针对传统的RSSI (received signal strength indication)定位方法会受到室内无线信道传播特性影响的问题,首先在密闭走廊、开放走廊和实验室三种不同场景下,对无线信号强度进行测试并统计其概率分布,构建室内无线信道传播特性模型。然后,锚节点定期测量移动节点信标信号的RSSI,中心节点利用最大似然法和信道传播特性模型来估算其坐标位置、移动速度和行进方向。实验结果证明,该方案可以实现不同室内环境下移动节点的跟踪定位,并满足精度要求。
文摘目的研究刷牙次数对中国成人肥胖和慢性病的影响。方法通过2013年和2018年两次国家卫生服务调查(National Health Service Survey,NHSS),两次横断面调查均采用多阶段分层整群随机抽样以获得全国代表性样本。采用多元Logistic回归分析刷牙次数对超重肥胖和慢性病的影响。结果2013年及2018年调查中,分别有219609人,205777人纳入研究对象。在2013年,不刷牙的人数占总调查人数的3.64%,而在2018年,不刷牙的人数增长到4.67%(P<0.001)。与每天刷牙不到2次的人群相比,每天规律刷牙2次或2次以上的人超重肥胖的风险降低12%(OR=0.88,95%CI0.87~0.90),患慢病的风险降低10%(OR=0.90,95%CI0.89~0.92)。结论刷牙次数与中国人群超重肥胖及慢病风险密切相关,对我国口腔卫生健康教育的开展与慢病的防治有重要指导意义。
