## 2 Materials and Methods
### Underwater ROVs  
The underwater ROV developed in this research serves as a system component specifically designed for the integration of various remote control and mobile communication technologies. This self-developed underwater vehicle system incorporates multiple water quality sensors and underwater camera equipment, enabling the precise measurement of environmental parameters such as water temperature, pH level, dissolved oxygen concentration, and other key indicators. Additionally, it provides real-time underwater image transmission capabilities. The hardware architecture features a waterproof housing design that protects internal electronic components from water pressure and corrosion. The main structure is constructed using PVC pipes and adapter fittings, effectively balancing lightweight design with structural strength. The waterproof performance was verified through vacuum testing. The propulsion system incorporates RM-168 brushless motor thrusters paired with 20 A electronic speed controllers (ESCs) with a maximum operating current of approximately 5 A. This system is configured with both horizontal and vertical forward and reverse motors, ensuring full three-dimensional spatial mobility. Figure 6 shows the prototype of the self-developed underwater ROV with its complete hardware configuration. Figure 6: Prototype of the self-developed underwater ROV. The system employs a modular design that facilitates the rapid replacement or expansion of sensing modules based on monitoring requirements, thereby enhancing environmental adaptability. The precise weight distribution design enables the vehicle to achieve stable underwater hovering, effectively reducing energy consumption and improving control flexibility. The processing and computing architecture utilizes a Raspberry Pi 3 B+ (Raspberry Pi Foundation, Cambridge, UK) as the central computing unit, in conjunction with an STM32F103C8T6 (STMicroelectronics, Geneva, Switzerland) to create a dual-processor collaborative framework. The STM32F103C8T6 is dedicated to motor control and the collection of raw sensor data, while the Raspberry Pi manages high-level computing and network communication tasks, including image processing, data acquisition, and remote transmission. This dual-controller design significantly enhances multitasking capabilities, ensuring that the underwater ROV can efficiently execute multiple remote control commands and maintain stable bidirectional data transmission through the mobile communication module. The power management system of the underwater ROV utilizes a dual-battery configuration to optimize operational efficiency and ensure system reliability. Comprehensive power consumption testing was conducted to evaluate the system's endurance performance under various operational conditions. The control system employs a 3.7 V/10 Ah (10,000 mAh) lithium battery to power the Raspberry Pi 3 B+ and its associated processing components. Power consumption measurements indicate that the Raspberry Pi maintains an average consumption of 5.1 W during normal operation, providing approximately 7.25 h of continuous operation. This configuration ensures sufficient operational duration for extended monitoring missions while maintaining stable communication and data processing capabilities. The propulsion system is powered by a separate 14.8 V/10.5 Ah (10,500 mAh) battery pack designed to meet the high-current demands of the four-thruster motor configuration. Detailed current consumption testing was performed across different operational modes, with results presented in Table 2.  
The test results revealed significant variations in power consumption based on operational conditions. Maximum current consumption occurred during high-intensity maneuvers in water, with individual motors drawing up to 21.5 A, which limited the operational duration to approximately 0.13 h under peak load conditions.