Van Anh Pham

Bioinspired robotic fish have garnered significant interest in recent decades due to their agile maneuverability and diverse marine applications. However, accurate modeling and physical prototyping of flexible fan-shaped membranous pectoral fins remain challenging. This paper presents the mathematical framework, modular design, and fabrication of an underwater robotic fish propelled by a pair of single-degree-of-freedom (DOF) membranous fins. To capture the complex fluid-structure interactions, the Morison force model is applied to establish a dynamic formulation that couples the fin motion, the robot body, and the surrounding fluid. A crank-rocker mechanism is proposed to drive the fin rays, generating fan-shaped membrane undulations for backward fluid propulsion while allowing straightforward phase shift adjustments. Experimental results demonstrate that the fabricated prototype achieves a peak forward swimming speed of approximately 0.59 body lengths per second (BL/s) and a turning radius of 0.14–0.53 BL. Furthermore, the modular architecture accommodates a water-quality monitoring payload, thereby demonstrating its capability for in situ measurement of total dissolved solids (TDS) and turbidity. This work provides a validated computational and experimental framework for advanced control and environmental monitoring in aquatic applications.

Light-emitting diodes (LEDs) play a crucial role in various practical applications. This paper presents a simple and cost-effective approach for detecting faults in LED boards with a large number. The types of faults detected include open circuits and short circuits. The proposed solution is based on a voltage threshold and a statistical algorithm to filter out noise. The paper first outlines the design concept, followed by the development and fabrication of a fault classification module. Subsequently, a control center is established to collect signals from all fault classification modules connected to LED boards in pairs. The received signals are processed and stored on a memory card. Finally, the resulting data can be accessed either from the memory card or directly via an external computer through a USB port. The experimental results demonstrate that the proposed design and fabricated device can accurately detect and classify faults on the tested boards. The data obtained can be used for statistical analysis and root cause investigation to enhance product quality.

In considering the problem of saving spaces during the transportation of items from one station to another, for example, in warehouses, factories, hospitals, etc., an automatic transportation system (ATS) that could take advantage of the above ceiling spaces for the transportation of products is considered. Such a system guarantees that the activities occurring in the floor area will be maintained as usual. To achieve this requirement, the ceiling spaces of a building are used to construct an automatic multi-station multi-container (MSMC) transportation system. This system can transport items from one place to another in the whole system. This system is designed to utilize the spaces above the ceiling, and it has the advantage of saving floor space for transportation operations. This will increase the operational capability of the industries and also improve the productivity of the industry in which this system is implemented. The entire transportation system includes (1) the essential conveying system (which is a functional conveyor module with a specified number of containers); (2) the control block that can monitor and operate the system; and (3) the sensor block for detecting and identifying the containers. The content of this article focuses on the introduction of the mechanical system (1); the control system (2); and the operating principle of the whole system (3).

SUMMARY: Biological fish can create high forward swimming speed due to change of thrust/drag area of pectoral fins between power stroke and recovery stroke in rowing mode. In this paper, we proposed a novel type of folding pectoral fins for the fish robot, which provides a simple approach in generating effective thrust only through one degree of freedom of fin actuator. Its structure consists of two elemental fin panels for each pectoral fin that connects to a hinge base through the flexible joints. The Morison force model is adopted to discover the relationship of the dynamic interaction between fin panels and surrounding fluid. An experimental platform for the robot motion using the pectoral fin with different flexible joints was built to validate the proposed design. The results express that the performance of swimming velocity and turning radius of the robot are enhanced effectively. The forward swimming velocity can reach 0.231 m/s (0.58 BL/s) at the frequency near 0.75 Hz. By comparison, we found an accord between the proposed dynamic model and the experimental behavior of the robot. The attained results can be used to design controllers and optimize performances of the robot propelled by the folding pectoral fins.

Flexible fins own outstanding advantages in robotic fish locomotion, especially in high propulsive efficiency. This paper proposes a mechanism for changing the moving direction of fish robots in two-dimensional planes using flexible pectoral fins. Firstly, a mathematical model of the fish robot equipped with non-uniform flexible pectoral fins is introduced. In this model, the influences of fluid inertia, and drag of the surrounding fluid exerting on the fin surface is considered as the Morison force. Based on the energetic method, the Assume Mode Method (AMM) and Rayleigh-Ritz method, the solution for the body motion and deformation of the points on the flexible fins is derived. Secondly, the mechanism for steering the direction of robot swimming motion is proposed. Due to the complex influence of lift forces which are generated by pectoral fins on the robot orientation, a fuzzy logic controller is designed to stabilize the angle trajectory of the fish robot. Finally, the numerical simulations, the movement performances, and the control effectiveness are illustrated.

Pectoral fin types of biological fish have an enormous diversity, and they play an essential role in locomotion of fish. The adaptation to shapes and movement mechanism of pectoral fin types helps swimming motion of the main body effectively, that results in the high flexibility and maneuverability of locomotion. This paper proposes a hydrodynamic model of a type of flexible pectoral fin (FPF), which can be used to increase the robotic fish motion efficient and reduce the consumed energy. The pectoral fin has the symmetrical shape and varying thickness along the symmetrical axis. Based on the Lagrange energetic method, Assumed Mode Method (AMM), and Rayleigh-Ritz method, the mathematical model of deformation and estimated thrust of the pectoral fin is described explicitly. The effect of inertia and damping factors are modeled by the Morison force. The numerical simulations and some initial experiments are demonstrated to verify the agreement of theoretical and empirical model. The proposed model is expected to support in issues of modeling whole of robotic fish and control design effectively.