基于Cole-Cole模型的水下主动电场定位系统有限元模拟

Finite-element simulation study of an underwater active electrolocation system based on Cole-Cole model

水下主动电场定位方法是一种模拟弱电鱼水下主动电场定位器官的新型水下终端导航定位方法.水下主动电场定位系统的幅值频率特性(amplitude information-frequency characteristics)存在探索死区(DFDZ)和转折频率点(FIP)现象,基于传统理想电磁场理论的水下主动电场定位系统模型无法模拟出上述现象.为从理论上解释和模拟出主动电场定位系统的DFDZ和FIP现象,受勘探地球物理的启发,猜想该现象与被测物体和周围溶液之间的界面上产生激发极化效应相关;为验证猜想的正确性,采用最为广泛使用的激发极化效应模型——Cole-Cole模型来模拟激发极化效应,并在此基础上建立了基于Cole-Cole模型与理想电场模型耦合的有限元模型对主动电场定位系统的幅值频率特性进行模拟计算.计算结果表明:(1)该模型能够有效模拟出水下主动电场定位系统转折频率现象并与实验结果相吻合;(2)证实了采用激发极化效应来解释水下主动电场定位过程中存在的频率转折现象的合理性.该模型的建立有助于深入理解主动电场定位物理机制,并对主动电场定位系统的工程设计具有指导作用.

The underwater active electrolocation method is a promising technology, which can be used to locating and navigation. This method is invented by simulating a kind of weakly electric fish detect target. This kind of fish can generate a low frequency electric field by its electric organ discharges（EOD）, and can sense the electric field change in surrounding area by its electroreceptors. This function of weakly electric fish is called active electrolocation system. The weakly electric fish can detect the target in complete darkness by their active electrolocation system. In order to understand the active electrolocation system, it has been researched by biologists for almost 60 years. At recently two decades, the underwater active electrolocation system has been investigated by many engineers. All of these scientists focused on setting up the active electrolocation test platform by experiment or building the active electrolocation system model by theoretical analysis or the finite element emulation method. But the physical mechanism of the active electrolocation system of weakly electric fish still is a contentious issue. In previous experiments, the amplitude information-frequency characteristics（AIFC） for active electrolocation system has been studied, and the detect frequency dead zone（DFDZ） and frequency inflection point（FIP） phenomena of AIFC for active electrolocation system has been found. In this paper, to understand this special phenomenon, a finite element model based on the ideal electromagnetic theory was built to simulate the active electrolocation system. But the DFDZ and FIP phenomena of AIFC for active electolocation system cannot be really simulated by this model. Then, we assumed that DFDZ and FIP phenomena are induced by phenomenon（IP） effect at the boundary between the target and water in the process of detecting target. In order to validate this assumption, the Cole-Cole model was used to fits the IP effect, and a finite element model of coupling the Cole-Cole model and ideal electromagnetic theory was created. Large numbers of simulation calculations based on this new finite element model were carried out. The simulation calculations results of the new finite element model were found to be in line with the experimental results. The simulation calculations calculation results of the new model indicate that：（1） the underwater active electrolocation system can be simulated by the new finite element model of coupling the Cole-Cole model and ideal electromagnetic theory;（2） it is a reasonable fact that the DFDZ and FIP phenomena of AIFC for underwater active electrolocation system can be explained by the IP effect;（3） the frequency inflection point（FIP） is varies with the parameters of the Cole-Cole model, and it is also can be speculated that the parameters of the Cole-Cole model reflect the changing of the DFDZ and FIP phenomenon of AFIC for electrolocation system. In this paper, the IP effect is introduced to the model of underwater active eletrolocation system for the first time. It will be of great benefit to us to understand the physical mechanism for active electrolocation system of weakly electric fish and provided an active electrolocation system finite element model for simulation. And it may be helpful for designing the equipment of active electrolocation system.