Abstract
This semester is the WashU Robotics Club’s first year preparing for the Marine Advanced Technology Education Remotely Operated Vehicle (MATE ROV) Competition, hosted annually by the Marine Technology Society. Our capstone group designed the electronic system and control system for this submersible robot with the goal of enabling teleoperated control. The main electrical system of the robot is a custom-designed PCB, called the Power Distribution Module (PDM), to regulate power and route signals to multiple components of the vehicle. The open loop control system, called the mixer, was designed such that the driver can control the robot using an Xbox controller. The mixer is an algorithm that converts commanded forces and moments, acquired from the Xbox joysticks, into motor speeds & corresponding PWM signals sent to the motors’ electronic speed controllers. Both a 6-motor mixer and an over-actuated 8-motor mixer have been designed, where the 8-motor mixer algorithm optimizes for the lowest power motor-speed-solution. Through the design and implementation of these systems, this group, along with WashU Robotics MATE ROV team, has created a controllable remotely operated submersible vehicle. Check out the robot in Fig. 1!
Figure 1. Washu robotics mate rov
Background
The ocean plays a pivotal role in sustaining life on Earth due to the resources it can provide. As a source of food, raw materials, and a natural carbon sink, Earth’s oceans are a critical component of sustaining life. The ocean regulates the Earth’s climate and atmosphere by absorbing carbon dioxide and supporting the plankton that produce roughly half of the world’s oxygen. Our dependence upon the world’s oceans necessitates further research into how the ocean interacts with the complex ecological systems hosted by our planet.
Over the past several decades the world community has been aware that the ecological health of our oceans is on the decline [1]. There are many factors contributing to this decline, most notable of which are climate change, ocean pollution, overfishing, and habitat degradation. Though scientists can observe the impact of these issues on some oceanic ecosystems, only approximately 24.9 percent of the ocean has been explored, and a small fraction of these regions are actively monitored [2]. It is in humankinds’ best interest for the world’s oceans to regain vitality so they can turn our waste into nutrients, provide food, and support marine based economic activity [3]. Therefore, it is of paramount importance that the world works together to develop novel technologies to explore the ocean, mend damaged ecosystems, and promote the ocean’s ecological health.
In 2017 the United Nations proclaimed the years 2021-2030 the “Decade of Ocean Science for Sustainable Development” [4]. As the name suggests, the goal of this initiative is to develop scientific knowledge and promote partnerships between various stakeholders to advance ocean science and develop new technologies to support ocean health and preservation. The MATE ROV Competition helps advance the development of new ocean technologies by encouraging young scientists and engineers to design and build novel aquatic robot technologies [5]. There are four main objectives in the 2024 MATE ROV Competition, which involve relocating underwater assets, verifying the reliability of underwater communication systems, collecting data about marine environments, and using computer vision to map underwater environments [5].
Problem Statement and Justification
Given the necessity of remotely operated robots for monitoring and performing tasks in the deep ocean, our capstone group aimed to develop electrical and control systems to monitor and control the movement of a submersible robot. The technical specifications that must be met by the design are outlined in the following bullet points.
- Design, fabricate, and implement an embedded system to process sensor data, manage PWM, and communicate with Arduino MEGA and Raspberry PI.
- Design and implement a harness which connects all computers, microcontrollers, sensors, and other relevant components.
- Design and implement a Mixer algorithm, which takes forces and moments commanded by the ROV controller and outputs the optimal commanded rotor speeds to the rotors.
- Power Distribution Module Printed Circuit Board Specifications
- The PCB must safely drop power from the 48V 30A power source built by fellow members of the robotics team to 12V 20A that the motors can use and be integrated into the electrical system as a whole.
- The PCB must power an arduino uno mega, responsible for providing each motor’s electronic speed controller with a digital PWM signal.
- The PCB must follow all regulations from the rulebook. Relevant electrical regulations are detailed in section 3.3 of the rulebook. An important design consideration is that the tether must incorporate a 48 VDC power line, which must be reduced to a lower voltage while inside the vehicle. The competition rules state that teams must use standard fuses, fuse holders, and Anderson Power Connectors. Additionally, section 3.3.2 regarding independent sensors, 3.3.3 addressing Current, and 3.3.4 covering Power Connections are all relevant and may be found on pages 53-61 of the rulebook.
Conclusion
Our team successfully created an electrical system that combined topics in computer architecture, optimization methods from systems engineering, and circuit design, providing a strong foundation for future advancements in the MATE ROV competition. This project has furthermore laid out the underlying support for future development necessary for the MATE ROV competition, to which WashU Robotics plans to apply in Spring 2025. These improvements will include sensor integration, including sonar, temperature and pressure sensors, and stereo cameras, enabling enhanced data acquisition and fusion. Additionally, we aim to implement Extended Kalman Filtering for state estimation, closed-loop control for precise velocity regulation and autonomous path planning, and computer vision techniques for photogrammetry and simultaneous localization and mapping (SLAM). We also plan to add a gripper arm for object manipulation, contributing to our ROV’s versatility and functionality. Overall, these new changes are designed to improve the ROV’s performance for the upcoming competition, all of which are now possible due to the electrical system built for this capstone project.
Deliverables
The following bullet points briefly summarize what our capstone group has accomplished
- Power Distribution PCB capable of powering all of the ROVs accessories and motors.
- Mixer algorithm implemented in MATLAB to assign optimal motor speeds for minimal power draw.
- Embedded system that allows PWM signals to be controlled at high speeds, while minimizing the memory required to implement the code.
- Overall, our group was able to design the electrical and control systems of the Mate ROV!
Want more information?
The aim of this webpage is to provide a summary of the electrical engineering behind the WashU Robotics MATE ROV. If the reader is interested in further detail we invite you to read our Final Report.
References
[1] “Accelerating Loss of Ocean Species Threatens Human Well-Being.” nsf.gov. https://www.nsf.gov/news/news_summ.jsp?cntn_id=108149. (accessed Feb. 4, 2024).
[2] “How much of the ocean has been explored?” oceanexplorer.noaa.gov. https://oceanexplorer.noaa.gov/facts/explored.html#:~:text=Despite%20its%20importance%2C%20the%20majority,%2C%20geological%2C%20and%20archaeological%20aspects. (accessed Feb. 4, 2024).
[3] Byomkesh T., Nilanjana G., Richard M., Gary W., Keith W., James O. “Climate change-accelerated ocean biodiversity loss & associated planetary health impacts.” The Journal of Climate Change and Health, Volume 6, 2022, 100114, ISSN 2667-2782,https://doi.org/10.1016/j.joclim.2022.100114.https://www.sciencedirect.com/science/article/pii/S2667278222000037. (accessed Feb. 4, 2024).
[4] “United Nations Decade of Ocean Science for Sustainable Development.” unesco.org. https://www.unesco.org/en/decades/ocean-decade. (accessed Jan. 2024)
[5] 2024 Competition Manual Explorer Class. (2024). Marine Technologies Society. Accessed: January 2024. Available: https://materovcompetition.org/