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

Abstract

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.