This paper describes a wheeled underwater robot developed for locating chemical sources autonomously under stagnant flow conditions. In still water, the released chemical stays in the immediate vicinity of the source location. The search for chemical sources under such conditions is extremely laborious since the presence of a chemical source cannot be detected from a distant place. The chemical sensors on the robot show no response unless a chemical substance released from the source arrives at the sensors. Crayfish in search of food are known to actively generate water currents by waving their small appendages with a fan-like shape. It is considered that the generated water currents help their olfactory search. The smell of food is carried to their olfactory organs from the surroundings by the generated flow, and then is perceived. The robot presented in this paper employs arms mimicking the maxillipeds of a crayfish to generate water currents and to draw chemicals to its sensors. By waving the arms vertically, a three-dimensional flow field is generated and water samples are drawn from a wide angular range. The direction of a chemical source can be determined by comparing the responses of four laterally aligned electrochemical sensors. Experimental results show that the flow field generated by the maxilliped arms is more effective in collecting chemical samples onto the sensors than that generated by a pump. The robot equipped with the maxilliped arms can detect the presence of a chemical source even if the source is placed off the trajectory of the robot.

An underwater robotic system with a chemical sensing capability is proposed. Crayfish that prefer stagnant flow conditions are known to generate water currents by beating exopodites of maxillipeds to enhance the chemical perception. The developed robotic system consists of an array of electrochemical sensors and a pair of fanning devices mimicking the maxillipeds. The fanning devices beaten vertically enable the robot to draw water samples from a wide horizontal angular range and to detect the chemicals in the surroundings. Successful demonstrations are presented to show the robot's ability to search for a chemical source in a stagnant water pool.I.

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This paper describes an underwater wheeled robot designed to search for a chemical source under stagnant flow conditions. In the absence of the flow, the released chemical stays in the immediate vicinity of the source. Therefore, no chemical is detected even if the robot is only a few centimeters away from the source. Crayfish in search for food are known to actively generate water currents using their maxillipeds, i.e., the fanning appendages. The generated flow field draws odor samples from distant places to the chemoreceptors. The proposed robot generates water currents by waving small arms that mimic the crayfish maxillipeds. Electrochemical sensors with four carbon working electrodes detect the collected chemical substance. Depending on the direction of the chemical source, the patch of a chemical substance was drawn to a different sensor. Experimental results are presented to show that the flow field generated by waving maxilliped-like arms is more effective in enhancing chemical reception than that generated by a pump. The proposed crayfish robot can localize a chemical source with high success rate if the source is placed within the range in which the generated water currents can draw chemical substance to the sensors.