MECHANICAL TEAM
Mechanical members focus on designing, building, and testing the main hull, chassis, and external systems needed to run our robots. The vast majority of design work the team does is in SolidWorks and members utilize various machine shops on campus to realize projects. New members are accepted regardless of experience or academic year 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 majority of our design work is done in SolidWorks, the same CAD software that is taught in ME courses. In addition to design, we also use SolidWorks to run stress/strain and other simulations of our designs. We apply the fundamental principles of Mechanical & Aerospace Engineering, Materials Science, and ergonomic design to create the systems our robots need to run.
Members machine much of the parts needed for our designs. Whether drilling and tapping holes into a small plastic part or shaping a block of aluminum, members can get experience on the Bridgeport, lathe, CNC, waterjet and more! Additionally we often modify/create systems by hand, as seen in a picture at the bottom of the page, wrapping the coils for our Gauss-Gun Torpedo Launcher.
Everyone is welcome, regardless of skill level. Being part of the mechanical team will give you real design, manufacturing, and system analysis experience. Whether you are interested in design, mechanics, failure analysis, or robotics – you’ll find a fit with UWRT.
Talos
The largest project for the Mechanical Team this year was developing the new vehicle, Talos. The four main projects on Talos included the chassis redesign, new smart batteries, improving the task mechanisms, and creating electronics cages for the Mark 2 Electronics. Using Tempest’s hull as the base, these projects all contributed to forming this year’s new vehicle, Talos.
These issues helped shape the requirements for Talos. A list of criteria was used in a decision matrix to down-select different concepts to find the best to pursue. During the design process, there were several design reviews to ensure the new vehicle would meet the needs of the team and to gain feedback on the design. The new chassis was designed for manufacturing, allowing it to be fabricated easily.
The new structure resulted in several benefits. Talos improved the rigidity while removing 2.7 kilograms of weight by swapping the material to 6061 aluminum and selecting tall cross sections to increase the area moment of inertia. The structure is arranged in triangular shapes interconnected with steel tensioning cables, and all assemblies underwent FEA simulations to verify the structural integrity. Notably, the modular task mechanism mounting system was integrated into the structural beam below the hull. This location ensures the thruster wash does not interfere with the task mechanisms. With the new chassis, the width of the vehicle was reduced by 54.7%, enabling it to easily pass through a doorway.
Maneuverability also benefited from the new chassis. Drag from the thruster cables was reduced by shortening the cable path and by fabricating a new lid for the cables to come out more streamlined to the vehicle. Next, improvements to the center of mass and buoyancy locations made more orientations possible. Adjustability in the center of mass location was allowed by shifting the batteries forwards and backwards on indexing rails. This new mounting system allows the batteries to be positioned repeatably and they snap in with compliant clips allowing for fast, toolless swapping. Buoyancy foam is located in between the hull and on the bottom beam to adjust the displaced volume of the vehicle.
Check out the assembly instructions!
The team’s previous battery housings have been implemented on UWRT’s AUVs since 2017. Due to the age of the old housings, mechanical failures occurred at the sealing surface due to worn out gaskets, inconsistent sealing due to installation error, and poorly secured pressure relief valves. The team saw the need to replace these housings as an opportunity to improve upon the entire system.
Mechanically, each of the smart battery housings were CNC milled from aluminum blocks with iso-griding placed on each lid to reduce the total assembly weight, including electronics, by 0.68 kilograms. The lid is secured to a sealing face with an o-ring, generating a more reliable seal. This allowed the housing to only be opened for maintenance which reduces the possibility of the seal falling from installation error. Each battery housing features a window to view a visual display, allowing an operator to obtain information about the battery state. Battery hulls are fitted with a pressure relief value for safety and with two SubConns for power and telemetry.
The new layout of the Mark 2 electronics required a complete redesign for the electronics housing. The original goal for designing Tempest’s housing was to reduce the number of steps it takes to access the electronics. That vision was not fully realized through Tempest. The old electronics housings were secured on the rails through dovetail slots. This allowed for consistent alignment front to hull but not starboard to port.
In the electronics cage redesign, a snap fit piece printed of TPU was designed to both provide tactile feedback as well as consistent positioning. This design process for the new camera and board cages was considerably more collaborative with software and navionics, respectively. Navionics was able to send CAD files for each board. This allowed for better designing around connectors and other features.
The cages additionally added support for new features of Mark 2, such as improved cooling for the electronics as well as LED status strips to display vehicle state.
Safety Stack
A large portion of setup time for pool tests was spent on assembling the robot network. The original setup required three individual components (router, switch, and wifi gateway) to be unpacked and connected. This time to set up as well as debugging errors that occurred from wrong connections cost precious time during the pool test.
The safety stack was developed out of a DeWalt box, with a custom designed interior frame to hold the necessary electronics together. These hold the network switch, router, and a Raspberry Pi with a touchscreen to connect the stack to the internet. A second Raspberry Pi was added to connect to a handheld kill switch and stack light. This Raspberry Pi connected into the vehicle network to allow for the vehicle to be remotely killed from the side of the pool. Additionally, the stack light showed the current vehicle’s kill and movement status to the swimmers and other observers.
The safety stack simplifies pool side setup, only requiring power and the vehicle tether to be plugged in. The software team’s laptops can then connect either over wireless or the Ethernet ports on the top of the stack to manage the vehicle. This has been a staple at all previous pool tests, simplifying the packing and setup, and will be an important tool to bring to RoboSub.
