We investigate under what conditions transient simulation could be used to integrate backward in time so that the initial field could be recovered from later histories. In this paper we use realistic examples and find...We investigate under what conditions transient simulation could be used to integrate backward in time so that the initial field could be recovered from later histories. In this paper we use realistic examples and find that, in long histories, traces of the initial field would be present only in the exact analytical solutions. We conclude that the recovery of initial field is possible only if the equations could be solved analytically or only short time periods are involved. In practice, it is not possible to detect those traces by measurements or observations. If numerical procedures are used, truncation and discretization errors are always present. Fine-tuning of system parameters used or transforming time into another pseudo time frame may allow numerical integration to be carried out backward in time. But numerical instability is still a problem. Large spurious increases found by numerical procedures are most likely due to numerical inaccuracy and instability.展开更多
In this paper two classes of equivalence transform methods for solving ordinary differential equations are proposed. One class of method is the equivalence integral transform method for special differential algebraic ...In this paper two classes of equivalence transform methods for solving ordinary differential equations are proposed. One class of method is the equivalence integral transform method for special differential algebraic problems. The advantage of this class of method is such that the amount of work calculating one integration with parameters becomes that of two interpolations, when the system of nonlinear equations is solved on the right hand side function. The other class of method is the equivalence substitution method for avoiding calculating derivative on the right hand side function. In order to avoid calculation derivatives, two equivalence substitution methods are proposed here. The application instances of some special effect of the equivalence substitution methods are given.展开更多
为了解决智能汽车线控制动系统结构复杂、仿真困难等问题,提出了一种新型的集成式线控制动系统(Integrated Braking Control System,IBC),基于IBC的整体结构和工作原理,建立IBC的数学模型。首先建立表贴式永磁同步电机模型,然后建立传...为了解决智能汽车线控制动系统结构复杂、仿真困难等问题,提出了一种新型的集成式线控制动系统(Integrated Braking Control System,IBC),基于IBC的整体结构和工作原理,建立IBC的数学模型。首先建立表贴式永磁同步电机模型,然后建立传动机构模型和伺服缸模型,传动机构选用行星齿轮和滚珠丝杠,其位于电机和伺服缸之间。首先通过行星齿轮进行减速增扭,再由滚珠丝杠推动伺服缸活塞运动,把制动液推动到四个轮缸以实现制动。搭建制动系统动态模型,对建立的数学模型进行验证。搭建伺服系统三闭环仿真模型,设计了位置环PID控制器、基于线性自抗扰控制(LADRC)的转速环控制器以及基于电压前馈解耦和PI反馈的电流环控制器,同时电流环控制器还结合id=0的矢量控制策略,由电流传感器采集电机的三相电流,经过Clack&Park变换将ABC三相坐标系转化为d-q两相同步旋转的平面直角坐标系,得到d、q轴实际电流。将d、q轴实际电流与期望电流的差值输入到电流环控制器得到d、q轴电压,经Park逆变换得到两相静止坐标系下的电压uα、uβ,然后经过SVPWM将uα、uβ转换为6路脉宽调制(PWM)信号,经逆变器计算出三相电流,驱动电机工作。最后对控制电机的输出进行仿真分析。研究结果表明,建立的数学模型有较高的准确性,误差控制在5%以下。基于伺服三闭环控制的电机中的位置环、转速环、电流环实际值能够很好地跟随期望值,误差低,电机响应速度快。提出的集成式线控制动系统可以提供较好的制动效果,其在能量回收、制动性能的提升和安全智能化拓展方面有着显著的提升。展开更多
A systematic approach is proposed to the theme of safety,reliability and global quality of complex networks(material and immaterial)by means of special mathematical tools that allow an adequate geometric characterizat...A systematic approach is proposed to the theme of safety,reliability and global quality of complex networks(material and immaterial)by means of special mathematical tools that allow an adequate geometric characterization and study of the operation,even in the presence of multiple obstacles along the path.To that end,applying the theory of graphs to the problem under study and using a special mathematical model based on stochastic geometry,in this article we consider some regular lattices in which it is possible to schematize the elements of the network,with the fundamental cell with six,eight or 2(n+2)obstacles,calculating the probability of Laplace.In this way it is possible to measure the“degree of impedance”exerted by the anomalies along the network by the obstacles examined.The method can be extended to other regular and/or irregular geometric figures,whose union together constitutes the examined network,allowing to optimize the functioning of the complex system considered.展开更多
通过对航空涡轴发动机数字式导叶控制系统各个环节分析计算,建立了系统的数学模型,在系统仿真分析的基础上,对PID(proportion integral derivative)控制器进行了改进设计,提出了不完全微分先行二阶PID控制方法.试验结果表明,使用不完全...通过对航空涡轴发动机数字式导叶控制系统各个环节分析计算,建立了系统的数学模型,在系统仿真分析的基础上,对PID(proportion integral derivative)控制器进行了改进设计,提出了不完全微分先行二阶PID控制方法.试验结果表明,使用不完全微分先行二阶PID控制方法,导叶控制系统性能明显改善:响应迅速,无振荡,仅有很小超调,满足了系统研制性能要求.展开更多
文摘We investigate under what conditions transient simulation could be used to integrate backward in time so that the initial field could be recovered from later histories. In this paper we use realistic examples and find that, in long histories, traces of the initial field would be present only in the exact analytical solutions. We conclude that the recovery of initial field is possible only if the equations could be solved analytically or only short time periods are involved. In practice, it is not possible to detect those traces by measurements or observations. If numerical procedures are used, truncation and discretization errors are always present. Fine-tuning of system parameters used or transforming time into another pseudo time frame may allow numerical integration to be carried out backward in time. But numerical instability is still a problem. Large spurious increases found by numerical procedures are most likely due to numerical inaccuracy and instability.
基金The project was supported by the National Natural Science Faundation of China
文摘In this paper two classes of equivalence transform methods for solving ordinary differential equations are proposed. One class of method is the equivalence integral transform method for special differential algebraic problems. The advantage of this class of method is such that the amount of work calculating one integration with parameters becomes that of two interpolations, when the system of nonlinear equations is solved on the right hand side function. The other class of method is the equivalence substitution method for avoiding calculating derivative on the right hand side function. In order to avoid calculation derivatives, two equivalence substitution methods are proposed here. The application instances of some special effect of the equivalence substitution methods are given.
文摘为了解决智能汽车线控制动系统结构复杂、仿真困难等问题,提出了一种新型的集成式线控制动系统(Integrated Braking Control System,IBC),基于IBC的整体结构和工作原理,建立IBC的数学模型。首先建立表贴式永磁同步电机模型,然后建立传动机构模型和伺服缸模型,传动机构选用行星齿轮和滚珠丝杠,其位于电机和伺服缸之间。首先通过行星齿轮进行减速增扭,再由滚珠丝杠推动伺服缸活塞运动,把制动液推动到四个轮缸以实现制动。搭建制动系统动态模型,对建立的数学模型进行验证。搭建伺服系统三闭环仿真模型,设计了位置环PID控制器、基于线性自抗扰控制(LADRC)的转速环控制器以及基于电压前馈解耦和PI反馈的电流环控制器,同时电流环控制器还结合id=0的矢量控制策略,由电流传感器采集电机的三相电流,经过Clack&Park变换将ABC三相坐标系转化为d-q两相同步旋转的平面直角坐标系,得到d、q轴实际电流。将d、q轴实际电流与期望电流的差值输入到电流环控制器得到d、q轴电压,经Park逆变换得到两相静止坐标系下的电压uα、uβ,然后经过SVPWM将uα、uβ转换为6路脉宽调制(PWM)信号,经逆变器计算出三相电流,驱动电机工作。最后对控制电机的输出进行仿真分析。研究结果表明,建立的数学模型有较高的准确性,误差控制在5%以下。基于伺服三闭环控制的电机中的位置环、转速环、电流环实际值能够很好地跟随期望值,误差低,电机响应速度快。提出的集成式线控制动系统可以提供较好的制动效果,其在能量回收、制动性能的提升和安全智能化拓展方面有着显著的提升。
文摘A systematic approach is proposed to the theme of safety,reliability and global quality of complex networks(material and immaterial)by means of special mathematical tools that allow an adequate geometric characterization and study of the operation,even in the presence of multiple obstacles along the path.To that end,applying the theory of graphs to the problem under study and using a special mathematical model based on stochastic geometry,in this article we consider some regular lattices in which it is possible to schematize the elements of the network,with the fundamental cell with six,eight or 2(n+2)obstacles,calculating the probability of Laplace.In this way it is possible to measure the“degree of impedance”exerted by the anomalies along the network by the obstacles examined.The method can be extended to other regular and/or irregular geometric figures,whose union together constitutes the examined network,allowing to optimize the functioning of the complex system considered.
文摘通过对航空涡轴发动机数字式导叶控制系统各个环节分析计算,建立了系统的数学模型,在系统仿真分析的基础上,对PID(proportion integral derivative)控制器进行了改进设计,提出了不完全微分先行二阶PID控制方法.试验结果表明,使用不完全微分先行二阶PID控制方法,导叶控制系统性能明显改善:响应迅速,无振荡,仅有很小超调,满足了系统研制性能要求.
