Narrowing Trees for Syntactically Deterministic Conditional Term Rewriting Systems

A narrowing tree for a constructor term rewriting system and a pair of terms is a finite representation for the space of all possible innermost-narrowing derivations that start with the pair and end with non-narrowable terms. Narrowing trees have grammar representations that can be considered regular tree grammars. Innermost narrowing is a counterpart of constructor-based rewriting, and thus, narrowing trees can be used in analyzing constructor-based rewriting to normal forms. In this paper, using grammar representations, we extend narrowing trees to syntactically deterministic conditional term rewriting systems that are constructor systems. We show that narrowing trees are useful to prove two properties of a normal conditional term rewriting system: one is infeasibility of conditional critical pairs and the other is quasi-reducibility

Towards building of an underwater robot monitoring fish appetite for feeding management: Development of sensors for measuring fish-generated underwater currents as indicator for feeding behavior

Predicting fish feeding behavior is crucial in improving marine aquaculture production. We are addressing this problem using a novel approach – measuring underwater currents generated by fish, especially at feeding times. In this paper, we present our development of a suite of sensors that will collect these measurements, as we investigate their relationship with fish behavior during feeding. We added we have further developed our sensor suite by adding another current sensor for calibrating the previously developed propeller sensors and tested them along a narrow river to examine the relationship of their measurements. While a strong linear relationship was observed between the measurements, it is difficult for the propeller sensors to measure currents accurately at slower currents. Experiment at the fish farm is still needed to determine if this constraint is acceptable in our application.ロボティクス・メカトロニクス講演会2021 (ROBOMECH2021), 2021年6月6日～8日, 大阪 (オンライン開催

Reflection Coefficient Estimation through the Modelling of Ultrasonic Transmission

In food industry, shortage of workers is one of a serious problem. Automation of food handling is a critical isSsue nowadays. To alleviate the damage caused by food picking operation by robotic hand, we propose non-contact acoustic impedance estimation with ultrasonic wave, which should be preceded before the picking for optimization of grasp stiffness. We have the assumption of the correlation between hardness and acoustic impedance. The impedance is calculated by the product of sonic velocity and density of a medium. From the point of view, the harder the medium is, the larger the impedance should be. We built up ultrasonic transmission model considering attenuation by ultrasonic reflection and absorption, then, made an experiment to estimate internal reflection of samples with two overwrapped media of different acoustic impedance.The 2022 International Conference on Artificial Life and Robotics (ICAROB 2022), January 20-23, 2022, on line, Oita, Japa

Acoustic Impedance Measurement through the Modelling of Ultrasonic Wave Transmission

In food industry, shortage of workers is a serious problem. Automation of food handling is a critical nowadays. To alleviate the damage during food picking by robotic hand, we propose non-contact acoustic impedance estimation with ultrasonic wave. We have the assumption of the correlation between hardness and acoustic impedance, and, built up ultrasonic transmission model considering attenuation by reflection and absorption, then, made an experiment to estimate the impedance. As the result, we succeeded in detecting acoustic impedance without contact.The 2021 International Conference on Artificial Life and Robotics (ICAROB 2021), January 21-24, 2021, Higashi-Hiroshima (オンライン開催に変更

Motion control considering the effects of cable deflection caused by gravity and fluid resistance for Cable-restricted Underwater Vehicle

For efficiently observing the marine resources, we developed an observation device with low operational risk and a wide observable area. The observation device consists of a seafloor station and an underwater vehicle tethered by a cable. As experimental validation result, we found that the vehicle tethered by a cable was able to navigate with an error of less than 0. 071m compared with the planned trajectory. The vehicle is controlled using the cable restraint condition and the forces exerted by the thrusters while considering the effect of the cable slack, without the need of any feedback signal.OCEANS 2021, San Diego – Porto, September 20-23, 2021 (In-Person & Virtual

Ultrasonic Cleaner using Two Transducers for Ship Hull Cleaning Robot

Fuel consumption of the ship gets worse by barnacles and stains put on its bottom, so that the ship hull should be cleaned regularly. Usual methods such as cleaning by special divers and cleaning after pulling up to the dock are not used frequently due to those high cost and the heavy burden on cleaners. We proposed a cleaning method using underwater vehicle with brushes, however there is a possibility to remove paints on the hull. To improve cleaning performance of the underwater vehicle, the ultrasonic cleaner is developed by using cavitation occurred by sound waves of the acoustic transduces. The cleaner generates sound waves with sound pressure of 0.2MPa or more required to occur cavitation at the point where sound waves from two transducers overlap. In experimental results, the cleaner occurred cavitation enough to make two holes in the aluminum foil located 50mm away from transducers.The 2022 International Conference on Artificial Life and Robotics (ICAROB 2022), January 20-23, 2022, on line, Oita, Japa

Development of current sensors for digitizing expert knowledge in fish feeding towards sustainable aquaculture

Improving the efficiency of fish feeding contributes to achieving sustainable expansion of the aquaculture industry. However, expert knowledge on feeding remains reliant on experience. This paper presents a new approach of digitizing such knowledge by measuring underwater currents induced by fishes as indicator of their behavior and appetite. A prototype current sensor suite was constructed to measure the current around the fish cage, especially during feeding.The 2021 International Conference on Artificial Life and Robotics (ICAROB 2021), January 21-24, 2021, Higashi-Hiroshima (オンライン開催に変更

Underwater Current Measurements for Fish Feeding Control in Marine Aquaculture

One of the key issues in improving marine aquaculture is achieving efficient control of feeding, which accounts for large percentages of the production costs in aquaculture operations. To quantify the feeding behavior in seas where the environment conditions are variable, we propose to measure underwater currents generated by fish movement in a feeding activity. We developed a sensor suite consisting of custom-made current sensors and underwater cameras. We deployed this prototype in two sea fish cages and measured the changes of currents during a feeding activity. Results suggest that changes in current may be related to the feeding behavior of the fishes, but more data needs to be collected and analyzed to understand this relationship. To improve on the experiences from the initial experiment, we designed a modular sensor system that will measure currents at more than one side of the fish cage during a feeding activity.OCEANS 2021, San Diego – Porto, September 20-23, 2021 (In-Person & Virtual

Motion Control of a Ship Hull Cleaning Robot

As the fuel cost will rise continuously, the reduction of fuel consumption and CO2 emissions are required more severely in the transportation industry. To achieve more efficient ship transportation, the prevention of marine biofouling is inevitable. Anti-fouling paint is effective to prevent biofouling to the ship hulls like barnacles, however, even the painted hull acquires slime-like biofouling caused by marine alga on its surface easily. In general, the cleaning of the ship hull is carried out during inspection in dockyard once a year or by divers, which are high costs and high risk task. Frequent cleaning during the ship berthing is desirable to keep good fuel efficiency, and if possible, ships can keep good fuel efficiency that contributes the reduction of costs and CO2 production. As a solution for this issue, we have been introducing underwater robots for ship hull cleaning. In this paper, the motion control system of the robot is described.The 2022 International Conference on Artificial Life and Robotics (ICAROB 2022), January 20-23, 2022, on line, Oita, Japa