NAVIONICS TEAM
Coined by a past electrical lead, “navionics” is a merging of “electronics” and “naval” not unlike how avionics refers to aircraft instruments. Navionics members focus on the designing, building, and testing of the electrical system of our robots. Members are accepted regardless of experience with circuits or electronics and are aided with lessons and one-on-one pairing. The team’s goal is to ensure that all members have the opportunity for hands-on experiences and learning that is often lacking in the traditional classroom.
About the Subteam
The Navionics Subteam designs, builds, and tests all of the custom electronics in our Autonomous Underwater Vehicle (AUV). Due to the tight space constraints, we custom build the majority of our electronics to ensure they best fit the needs of the vehicle in the smallest possible size. We design our own custom Printed Circuit Boards (PCBs) in Altium Designer, an industry standard PCB design tool. The Navionics team is additionally responsible for assembling and testing our circuit boards, giving members skills in advanced SMD soldering and design validation. We strive to ensure that each member gets the opportunity to take on a project that they find the most interesting, and get real world engineering experience.
This year Navionics has taken on three large projects- The Mark 2 Electronics, Firmware, and Smart Battery Housings – all working to make Talos, our new robot, more stable and easier to work with. Read more about these projects below and see examples of what our Subteam works on.
The Mark 2 Electronics
Our first, and largest project this year, was the Mark 2 electronics. We fully redesigned our electronics this year for our new vehicle, Talos. We took the lessons learned from our previous Mark 1 electronics used in our previous vehicle Tempest, to make a more stable and reliable electronics system. Mark 2 marked a lot of firsts for the Navionics team, including switching to a distributed architecture, improving our fault resiliency and improving robustness of the communications on the vehicle. If you want to learn about how to design resilient systems, and be able to see your electronics designs running in our vehicle, join our Navionics Subteam. Members get firsthand experience creating and validating advanced designs to best handle the challenging task of running AUVs.
All of our board design files are available on our GitHub, along with the exported PDF Schematics.
Mark 2 System Architecture
The Mark 2 Architecture consists of 6 custom designed boards, all handling a separate responsibility of the vehicle. The port side of the vehicle contains the four primary circuit boards, known as the Board Stack (see the picture above). The starboard side of the vehicle contains the computational and sensor elements of the vehicle, with the NVIDIA Jetson Orin at the heart. Additionally we use a StereoLabs Zed 2i for 3D vision, and a VectorNav VN-100 IMU for sensing orientation and acceleration. We use CAN Bus as the primary communication link between the main computer and the rest of the electronics system. This is the only data protocol traveling between systems in the vehicle, improving the ease and reliability of communication between systems.
Mark 2 Power Board
The Mark 2 Power Board is responsible for deriving the various power rails required by the AUV. It has two TDK-Lambda Voltage Regulators, capable of providing up to 250W of power. It additionally contains the Kill Switch circuitry to cut off power to the thrusters, ensuring the AUV is in a safe state when the kill switch is removed. It also contains several sensors to provide telemetry on the current state of the electronics system, such as reading the voltage of the various voltage rails as well as board stack temperature.
View Schematic
Mark 2 ESC Board
The Mark 2 Electronics contains 2 ESC boards, each containing 4 Electronic Speed Controllers (ESCs) which are required to control the vehicle’s thrusters. We use 8 APD 80F3 speed controllers on our vehicle, using the DShot digital protocol to send commands. Switching to DShot not only increases resilience to noise, but also provides telemetry back from each of the ESCs to ensure that each thruster is operating as expected.
View Schematic
Mark 2 Actuator Board
The RoboSub competition has several tasks that our vehicle must be able to perform, such as picking up objects with a claw, dropping markers, or firing torpedoes through a target. These competition task mechanisms require additional control and circuitry that is not part of other systems on the vehicle. The Actuator Board contains all of the necessary components to drive these task mechanisms to allow the robot to perform the required tasks for competition. This board was designed with flexibility to support three generations of task mechanisms to ensure that we are able to support whatever the vehicle requires.
One of the most challenging designs on the Mark 2 electronics was the Torpedo Driver system. The previous year’s torpedo system was driven by several large coils which accelerate a metal rod through a tube, to fire the object. To run this electrically, a large capacitor bank needs to be charged, and then rapidly discharge during the firing sequence while simultaneously clamping the large spikes of negative voltage due to inductive effects. This was challenging to design, with several iterations over the previous generations of electronics, but with Mark 2 we now have a reliable circuit to drive these torpedoes.
View Schematic
Mark 2 Camera Cage Breakout Board
The Camera Cage contains several off the shelf components, each with their own power and communication requirements. To simplify the wiring in this side of the vehicle, the Camera Cage Breakout Board takes in a single harness from the Electronics Stack and breaks out connectors for each of the components on the starboard side of the vehicle. It additionally has a microcontroller to poll the Blue Robotics Depth Sensor and provide control to power cycle the computer, manage the cooling, and provide temperature information for the computer cage.
View Schematic
Firmware Development
As part of the Distributed Architecture in the Mark 2 Electronics, each circuit board now has its own dedicated microcontroller to handle interfacing that board’s electronics to the rest of the vehicle. Each of these microcontrollers needs code written for it, referred to as Firmware. These are low cost computational devices optimized for interfacing to electronics. As such they have fewer resources and require special attention to ensure that the resources are being efficiently used. This code is the responsibility of the Navionics Subteam, rather than the Software Subteam, due to the tight constraints that microcontrollers face, with constant collaboration required between the board designers and firmware developers to ensure that the microcontrollers are effectively utilized. If you find that you enjoy working on both Electronics and Software and writing efficient, simple code, you might find that Firmware is the right place for you on the Underwater Robotics Team.
Our team primarily uses the RP2040 microcontroller, due to its low cost, availability during the chip shortage, and support for Micro-ROS. Lost cost was an important requirement as each Mark 2 board requires its own individual microcontroller. Micro-ROS is also an important requirement, as it enables interfacing with ROS (Robot Operating System), the set of libraries the Software team uses for managing and operating the vehicle. This reduces the time spent working on designing an effective interface between software and electrical systems, and instead allows us to quickly create new interfaces to share data between the two systems. This year as part of this firmware project, we pushed to not only write firmware for the new devices, but also improve the insight we have into the electronics system, with the goal of never needing to open the vehicle to debug an issue.
All of our firmware is open source on our GitHub. Feel free to explore if you are interested!
Smart Battery Housings
This year Navionics worked on creating a Smart Battery system which adds a Battery Management IC to each battery for the vehicle. This provides additional telemetry and protection for our vehicle’s MaxAmps 5S 8000 mAh LiPo Batteries. The smart battery housings use the Texas Instruments BQ40Z80 Lithium-Ion battery pack manager IC, which provides charge balancing, state of charge estimation, and battery protection features. We additionally created a display board which allows a magnet to be brought towards the battery to read the current charge level for the pack. The microcontroller connects to the rest of the vehicle with a CAN bus link, allowing for the remaining charge estimation to be viewed by the vehicle operator.
The smart battery housings was one of our most ambitious projects to date, pushing our design, assembly, and testing capabilities further than we have gone before. If you want to be a part of this and make the next big project, reach out to us and join Navionics!
View the schematics for the Battery Management Board and the LCD Board
