Underwater Active Electrolocation Research Articles

Long-range and high-precision localization method for underwater bionic positioning system based on joint active–passive electrolocation

Active electrolocation organ of weakly electric fish act as a proximity detection system with high accuracy in recognizing object parameters such as size and shape. In contrast, some fish with passive electrolocation organ are able to detect objects at a greater range. This paper proposes a joint active–passive electrolocation algorithm for long-range and high-precision underwater localization, inspired by the active and passive electroreceptive organs of fish. The study begins by designing a large experimental platform for the underwater localization system to investigate the response of underwater objects to active and passive electric fields. Based on the response, the paper proposes separate underwater active and passive electrolocation algorithms, which are then combined to form a joint algorithm. Experimental results demonstrate that the proposed algorithm achieves high localization accuracy and long detection distance. The joint active–passive electrolocation algorithm has potential applications in submarine resource exploration, underwater robotics, and maritime military projects, while also providing new ideas for future research on long-range underwater object detection and identification based on electrolocation.

The Effect of Object Geometric Features on Frequency Inflection Point of Underwater Active Electrolocation System

Biologists have discovered a kind of weakly electric fish that identifies its prey by using active electrolocation in virtual darkness. In this study, we built an underwater active electrolocation system platform designed to investigate the biological mechanism allowing these fish to distinguish objects and determine how the amplitude information-frequency characteristic (AIFC) response are affected by the geometric characteristics of target objects in the active electrolocation system. We used a single-frequency sinusoidal signal to scan metal objects in different orientations and observed the amplitude information response variation of the disturbed detection signal. The detection frequency dead zone (DFDZ) and the frequency inflection point (FIP) were used to characterize the variation. In addition, we repeated the experiments after replacing the metal objects with objects of different materials and geometric characteristics to summarize the general laws. Our results showed that the FIP value of the detection signal was lowest when the object was detected in the orientation of its corner and highest when the object was detected in the orientation of its surface. The geometrical characteristics of metal objects in different orientations have a certain influence on the amplitude of the detection signal. Article Highlights: (1) The general law between the shape of metal probed objects, and electric field detection signal was found and summarized. (2) We used a single-frequency sinusoidal signal to scan regular metal probed objects, and it was found that the frequency inflection point (FIP) of the metal probed objects edge was the highest, whereas that of the corner was the lowest. (3) The shape of a metal object can be recognized by scanning regular metal objects with an electric field signal.

Amplitude information-frequency characteristics for multi-frequency excitation of underwater active electrolocation systems

Underwater active electrolocation technology is a new kind of technology for underwater detection and environmental perception, whose discovery was inspired by the active electrolocation systems of weakly electric fish. The amplitude information-frequency characteristics (AIFC) obtained by an underwater active electrolocation system (UAES) can effectively assess information about probed objects, such as their material composition, shape, and conductivity. Traditionally, single-frequency excitation has been employed in a UAES, which can make object detection inefficient and time-consuming. We employed multi-frequency signals for excitation in a UAES, to improve the efficiency of detection. We used three kinds of multi-frequency excitation signals—square wave, single pulse, and biphasic pulse, to detect objects under water. To improve the accuracy of measurements, we developed an AIFC recognition algorithm. The experimental results showed that the multi-frequency excitation detection method is effective and feasible. We demonstrated that the electrodes are strongly coupled to the UAES and can result in non-negligible errors that have often been previously ignored. In addition, graphite electrodes performed much better than titanium electrodes for multi-frequency signal detection, and bio-inspired multi-frequency pulse excitation signals gave more accurate results than the square-wave signal.

The influence of the edge characteristics of detected objects on underwater active electrolocation system

The influence of the edge characteristics of detected objects on underwater active electrolocation system

Research on Location Characteristics and Algorithms based on Frequency Domain for a 2D Underwater Active Electrolocation Positioning System

AbstractWeakly electric fish has an ability to generate a low-frequency electric field actively to locate the surrounding object in complete darkness by sensing the change of the electric field. This ability is called active electrolocation. In this paper, we designed a two-dimensional (2D) experimental platform of underwater active electrolocation system by simulating weakly electric fish. On the platform, location characteristics based on frequency domain were investigated. Results indicated that surface shape of 3D location characteristic curves for the 2D underwater active electrolocation positioning system was convex upwards or concave down which was influenced by the material of probed objects and the frequency of the electric field excitation signal. Experiments also confirmed that the amplitude of the electric field excitation signal and the size of the probed object will only influence the amplitude corresponding to 3D location characteristic curves. Based on above location characteristics, we present three location algorithms including Cross Location Algorithm (CLA), Stochastic Location Algorithm (SLA) and Particle Swarm Optimization (PSO) location algorithm in frequency domain and achieved the task of the underwater positioning system. Our work may have reference value for underwater detection study.

A Numerical Simulation Model of the Induce Polarization: Ideal Electric Field Coupling System for Underwater Active Electrolocation Method

Active electrolocation is a promising method for underwater terminal navigation. In our previous work, the amplitude information-frequency characteristic (AIFC) of an underwater active electrolocation system has been investigated, and the detect frequency dead zone (DFDZ) and the frequency inflection point (FIP) of AIFC has been found. In this paper, to explain these phenomena, a finite-element model (FEM) of underwater active electrolocation system based on Maxwell theory has been built. In addition, the steel cylinder was selected as the object in the FEM simulation. However, neither DFDZ nor FIP appeared in the simulation results. Inspired by exploration geophysics, we speculated that these phenomena might be caused by the induce polarization (IP) effect. Then, another FEM, which is based on the coupling Cole–Cole model and Maxwell theory, of the underwater active electrolocation system has been built as well. In the simulation based on this model, the steel cylinder and copper cylinder were selected as the object. According to the simulation results, it could be concluded that: 1) the IP effect is a reasonable mathematical explanation for the DFDZ and FIP phenomenon of AIFC; 2) the DFDZ and FIP of AIFC can be simulated by the Cole–Cole model; and 3) the turning frequency of object is related to parameters of the Cole–Cole model.

A Research on Effect of Probed Object Shape on Frequency Inflection Point (FIP) of Underwater Active Electrolocation System

Weakly electric fish can orient and navigate in dark environment by their active electrolocation system. Bio-inspired active electrolocation sensor has been investigated. In previous work, amplitude information-frequency characteristics (AIFC) of the active electrolocation system have been investigated. Detect frequency dead zone and frequency inflection point (FIP) of AIFC for the electrolocation system were found. And FIP have relevance to the material properties and geometric features of the probed object and the conductivity of surrounding water. But how to the shape of the probed object influence on FIP has not been deeply researched. In order to deeply study on how to the probed object shape influence on FIP of the active electrolocation system, three different materials probed object with two different shapes with similar geometric features of the probed object were selected for the active electrolocation system experiment. The following conclusions were obtained: for the similar size and the same material of the probed object, the shape of the probed object has significant effect on FIP of AIFC for the electrolocation system. So the shape of the probed object may affect the electric image. It may have a reference value for active electrolocation system designing.

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

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.

A study of amplitude information-frequency characteristics for underwater active electrolocation system

Weakly electric fish sense their surroundings in complete darkness by their active electrolocation system. For biologists, the active electrolocation system has been investigated for near 60 years. And for engineers, bio-inspired active electrolocation sensor has been investigated for about 20 years. But how the amplitude information response will be affected by frequencies of detecting electric fields in the active electrolocation system was rarely investigated. In this paper, an electrolocation experiment system has been built. The amplitude information-frequency characteristics (AIFC) of the electrolocation system for sinusoidal electric fields of varying frequencies have been investigated. We find that AIFC of the electrolocation system have relevance to the material properties and geometric features of the probed object and conductivity of surrounding water. Detect frequency dead zone (DFDZ) and frequency inflection point (FIP) of AIFC for the electrolocation system were found. The analysis model of the electrolocation system has been investigated for many years, but DFDZ and FIP of AIFC can be difficult to explain by those models. In order to explain those AIFC phenomena for the electrolocation system, a simple relaxation model based on Cole–Cole model which is not only a mathematical explanation but it is a physical one for the electrolocation system was advanced. We also advance a hypothesis for physical mechanism of weakly electrical fish electrolocation system. It may have reference value for physical mechanism of weakly electrical fish active electrolocation system.