FrankenDrone USV - The DIY Unmanned Surface Vehicle
FrankenDrone USV - The DIY Unmanned Surface Vehicle
FrankenDrone USV is a modular and affordable approach to building flexible unmanned surface vehicles for work or play.
FrankenDrone USV is a modular and affordable approach to building flexible unmanned surface vehicles for work or play. Read more
About this project
What can you do with a FrankenDrone USV?
The FrankenDrone Unmanned Surface Vehicle (USV) is designed to explore and play in, around and under the water. About half of us live less than 100km from some coastline, so there is ample opportunity to get your marine explorer on or just ferry beer out to your buddies on a boat.
Though intended primarily for hobbyists, we anticipate a number of potential applications for this vehicle because of its utilitarian design. Among these are
- Camera/sensor platform for marine/littoral research
- Commercial photography
- Pond maintenance services
- Underwater inspection of boats, docks, bridges, etc.
- Hydrographic sonar surveys.
So, get a FrankenDrone USV and the world is your oyster. Well, maybe not, but they sure are fun!
What have we done so far?
Check out the FrankenDrone channel on YouTube.
We have learned a lot, made some design changes and are now ready to move onto the production model of the FrankenDrone USV.
FrankenDrone USV Design Features
The key idea behind FrankenDrone is to leave the overall design up to the user as much as possible. As a result, we refer to the design in a component (or building block) way. The assembly of a FrankenDrone USV similar to the one depicted here would require
- (1) 6-Body
- (1) 6-Body End Cap
- (1) 6-Body Propulsion Section
- (2) 3-Body
- (4) 3-Body End Caps of various types
- (4) Struts.
The 6-Body is a 152mm (6in) inner diameter tube, 500mm (19.7in) in length. It has six longerons running the length of the body, which not only strengthen it, but also serve as attachment points for struts, pontoons, payloads and accessories. The longerons have a hole pattern for 8-32 fasteners. The interior can be accessed by removing the nose or tail sections as well as through an access panel amidships and a pair of ports. Batteries, switches and other frequently serviced items can be placed in proximity of this access panel. The body can be functionally divided into three sections. The forward section consists of payloads, the center section of power and the aft section of controls. Currently, however, the interior layout is left up to the user to finish, but we plan to offer a slide in equipment tray in the near future.
6-Body End Cap
The 6-Body End Cap serves as the primary internal payload station and is usually placed at the front of the body. They employ a seal and tight fit for water proofing and attach via four fasteners. The end caps will be interchangeable depending on the application. We will initially offer the following core types
- Optical dome
- Blank cylinder.
As need develops, we will produce a wider variety of shapes as well as customized versions of these shapes. For example, the wedge shape will eventually evolve into a gimbaled payload mount as well as a winch mount for lowering cameras into the water. In true DIY fashion, the blank cylinder can be cut (with a hot wire knife) into any shape the user wants.
6-Body Propulsion Section
The FrankenDrone USV is unique in that it employs a thrust vectoring electric motor and propeller for propulsion and steering in an airboat fashion. We went with this approach to keep propellers out of the water. It allows the vehicle to go into very shallow water as well as through surface muck. Also, if you are filming underwater, it will not stir up sediment.
While additional testing is needed, the current motor installed on the prototype (Axi 28XX with 30 amp speed controller (ESC) and three blade propeller) appears to be more than adequate. As the motor and its controller are a considerable portion of the vehicle cost, however, an important part of our testing will be to determine a range of acceptable motor/ESC combinations. The user, as always can choose any propulsion source they want, but we do plan to offer a few motor/ESC options to circumvent any issues with mounting and protection of the motor from the marine environment.
Unlike the prototype, the TVC servo is embedded within the propulsion section to protect it from the marine environment. This servo must be programmable and digital due to the range of motion required for steering. The current range used in the prototype has resulted in some pretty amazing steering capabilities and we believe there may be some room for improvement for certain configurations.
The 3-Body is 76mm (3in) inner diameter tube, 500mm (19.7in) in length. It has a single longeron like that of the 6-Body. Unlike the 6-Body, this body does not currently have built in provisions for internal placement of equipment or power sources. This may change for at least the power situation in the near future so as to alleviate the difficulties of implementing underwater lights.
3-Body End Caps
The 3-Body End Caps are similar in shape and function to that of the 6-Body. We will initially offer the following shapes
- Tangent ogive
- Truncated cone
- Blank cylinder
- Optical dome.
Future caps may include
- Blank rectangle
- Lateral thrusters
- Traditional marine propellers.
In a traditional pontoon role, the 3-Body should be equipped with a hemispherical or tangent ogive nose cap and tangent ogive or truncated cone tail cap to reduce hydrodynamic drag.
- Connect the bodies to each other
- Serve as routing pathways for tubing and wiring
- Serve as mounting locations for payloads and accessories
- Serve as launch lug mounting points.
They are not necessarily required, but they are the only means by which to significantly control the height of the primary hull above the water.
Due to its innovative propulsion design, the FrankenDrone USV only needs two R/C channels for control. One is used for TVC while the other is the traditional throttle control. We believe the minimum R/C radio should be a six-channel system which allows for the spare channels to be used for payloads such as a pan/tilt gimbal. We have yet to settle on an official radio system though we tend to favor Hitec and Spektrum due to their telemetry capabilities. All servos will employ metal gears for durability.
Our future plans in this area are big considering our backgrounds in unmanned aircraft controls. We definitely see a GPS-based autopilot with long range data link as well as a first person viewing (FPV) option. In fact, for many applications, we see at least FPV being a requirement due to the range available to even R/C radios.Power
One of the most attractive FrankenDrone USV capabilities will be the ability to use sealed lead acid batteries instead of the usual lithium polymer (LiPo) and/or nickel metal hydride (NiMH). While weight can still be an issue in some configurations, establishing a standard 12V system built around a single battery to power everything onboard will be quite welcomed by hobbyists and a requirement for commercial applications.
As with other aspects of this design, users are free to power their vehicles as they wish. Our prototype currently uses a LiPo/NiMH combination for control and propulsion as well as separate battery powered cameras and lights. Though a logistical challenge and a bit of a pain when launching and recovering the vehicle, the approach works. It is also cost effective for hobbyists that may already have R/C power systems lying around the shop.
We plan to offer a 12V unified power system centered on a 12V lead acid battery or 11.1V LiPo battery. The design will feature master and function switches, a fuse panel and a distribution panel.Payloads & Accessories
The sky is the limit on the types of payloads and accessories the user can add to the FrankenDrone USV. We believe you will run out of money before you run out of payload capacity on this vehicle. A short list of potential payloads and accessories might be
- HD, thermal, low-light, underwater video cameras
- Still cameras
- Wireless video link
- WiFi access point
- High gain microphones
- Running lights
- Laser designator
- Pan/tilt gimbal
- Above and below the waterline lights
- Infrared illuminators
- Bait bags
- External cargo pouches (i.e. for carrying an adult beverage to thristy mariners)
- Solar panels
- Magnetic payload rails
- The list goes on...
Body tubes are an off-the-shelf core product cut to length. The longerons are machined wood. All parts are sealed with a 2-part, marine grade epoxy. Bodies will be available for sell at this point for those users who wish to apply a composite skin or perform their own paint jobs. We will also offer the bodies with a marine grade primer coat. Future plans also include offering painted components in a variety of colors using marine grade paint.
The core end caps will be molded EPS foam. They will be initially offered as unfinished (i.e. straight from the vendor) as well as sealed with a 2-part, marine grade epoxy. In this case, however, the epoxy layer is not considered durable enough for most applications. Therefore, until these parts are offered with a composite skin, it is recommended that they be covered by the user or checked frequently for dings and dents. Our testing with the FrankenDrone USV prototype has shown that most bumps and minor collisions only result in dents in the foam understructure. We have yet to see a perforation of the epoxy skin. Also, as with the bodies, we plan to offer parts with a primer coat and eventually painted in a variety of colors.
Struts & Mounts
Struts, various types of mounting brackets and other metal parts on the FrankenDrone USV will be fabricated from 5086 or 6061 aluminum in a machine shop. All parts will be initially supplied with a corrosion resistant primer and eventually marine grade paint.
Larger sub-assemblies will be initially provided as a kit for the user to assemble. Plans call for us to provided assembled sections as well as completely assembled vehicles in the near future as an option.
Kickstarter Funding Use
The primary use of our surplus Kickstarter funds will be to design and fabricate tooling and pay for initial production runs which will ultimately lower the unit cost of body and foam parts. Remaining funds will be applied towards additional testing to address risks and determine vehicle performance.
Risks and challenges
1. Marine environment effects.
Our single biggest concern is protecting the motor from this environment, particularly salt water. Since we are adapting a component that was not originally designed for this purpose, we will focus a great deal of effort on encapsulating the motor (while allowing proper cooling) and developing operating and maintenance procedures to minimize the effects.
2. Watertight bodies.
Our experience with the prototype and a remotely operated vehicle proves that keeping water out can be difficult at times. We are confident in the current design, but we want to conduct a great deal of testing as well as developing some back up designs and redundant design features.
Overloading and poor balance are bad for stability. With our prototype and early production vehicles, we will find the stability limits and determine how to mitigate the effects.
4. Open Water Performance.
We do not know how well the vehicle will perform in higher seas. The prototype's interaction with boat wakes and small waves thus far has been encouraging, but we need to test in some larger waves. This additional testing will help us determine 1) the conditions in which we can operate with low risk of vehicle loss and 2) at what point do conditions make the use of this vehicle for a given application not worth the effort and cost.
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