Source-linked AI summary
An Autonomous, 3D Printed, Waterjet-Powered, Open-Source Robotic Trimaran for Environmental Inspection and Monitoring
Reuben O'Brien, Martin Lambrechtse-Reid, Minas Liarokapis
TL;DR
Manned research vessels are resource-intensive and cannot access many freshwater monitoring sites. This paper presents a low-cost, 3D-printed waterjet trimaran as an alternative. The authors report successful bathymetry and water-quality testing at speeds of 2 m/s.
Problem
Manned research vessels are resource-intensive and cannot access numerous freshwater rivers, streams, and wetlands where monitoring is needed.
Source: §I · p. 1Method
The paper presents an autonomous robotic trimaran built with off-the-shelf components and 3D printing, using a housed waterjet impeller for propulsion.
Source: §I · p. 2, 3) Propulsion · p. 4Results
Successful bathymetry and water-quality testing at speeds of 2 m/s demonstrate the platform’s practical utility.
Source: §IV · p. 7Takeaways & Limitations
The authors present the lightweight, low-cost, open-source trimaran as an alternative to resource-intensive research vessels for aquatic inspection and monitoring.
Source: §IV · p. 7Branches and algae can catch on the hull and jet housing, potentially reducing efficiency over extended run time.
Source: B. Platform Testing · p. 7
Abstract
from arXiv · showhide
Versatile, autonomous robotic boats can offer excellent environmental inspection and monitoring solutions for remote, dangerous, hard to reach, or access protected water bodies. This paper introduces such a platform in the form of an autonomous, cost-effective, waterjet-powered robotic trimaran. Motivated by the need for an efficient aquatic monitoring, particularly in Aotearoa - New Zealand's diverse environments, the trimaran provides an efficient, low-cost, and easy to replicate alternative to resource-intensive research vessels. The proposed platform, costs $600-1,500 USD to develop (depending on the sensing system configuration), weighs under 5 kg, and excels in bathymetry and water quality testing. The trimaran can reach speeds of up to 2 m/s offering obstacle avoidance of natural features, such as rocks. Utilizing off-the-shelf components and 3D printing technology, the proposed platform offers excellent reproducibility and robustness while operating in shallow waters with its jet propulsion system. The paper presents in detail the design characteristics, the sensing system employed, testing results focusing on bathymetry, and highlights the ability of vessel and the potential for future research and data collection.
I. INTRODUCTION
Aotearoa–New Zealand’s aquatic environments require monitoring, but manned research vessels are resource-intensive and cannot access many freshwater sites. The paper proposes an affordable, reproducible waterjet-powered USV using off-the-shelf components and 3D printing.
I. INTRODUCTION
- USVs have diverse aquatic applications, including scientific exploration, environmental monitoring, and resource management.Their flexibility and adaptability support tasks from data collection to environmental surveillance.Source: §I · p. 1
- Manned research vessels are resource-intensive and cannot access numerous freshwater rivers, streams, and wetlands needed for ecosystem monitoring.The cited strategy calls for seafloor and freshwater photogrammetry to support habitat mapping, characterization, and study of aquatic species distributions.Source: §I · p. 1
- Research USVs commonly use fiberglass or molded-plastic catamaran hulls, support waypoint tracking, and start at $3,000 USD, while a commercial alternative exceeds $4,200 USD.The lowest-cost cited design uses an off-the-shelf plastic container hull and costs $1,557.Source: §I · p. 1
- USV work addresses trajectory mapping and collision prevention, with approaches including LiDAR and camera sensing, YOLO, and coordinated swarms.The cited literature also explores probabilistic mission-capability assessment and avoidance maneuvers for ships or objects.Source: §I · pp. 1–2
- The proposed waterjet-powered USV costs $600–1,500 USD to develop and uses off-the-shelf components and 3D printing.The platform is presented as an affordable, easy-to-replicate, and robust response to the monitoring need.Source: §I · p. 2
II. DESIGN
The design targets a small, light freshwater vessel with consumer-grade affordability and speeds around 1.5–2 m/s. Its righting-lever assessment reports a peak at 38.2° and vanishing stability at 120° under the specified 5 kg condition.
II. DESIGN
- The design targets freshwater operation, a budget capped at $1,500 USD, dimensions no greater than 1 m by 0.5 m, weight no more than 5 kg, and average speed of 1.5–2 m/s.The requirements prioritize single-person handling and allow faster operation when needed.Source: §II · p. 2
- The maximum development cost is $1,533.68 USD, while removing non-crucial sensors lowers the minimum viable cost to $592.62 USD.The listed removable components are the Raspberry Pi, camera, LiDAR, and sonar; the reduced configuration relies on GPS and IMU positioning.Source: §II · p. 2
- The platform views show the hull’s inverted bow, tapered stern, and jet inlet.The side and bottom views are identified in the figure caption.Source: Figure 3 · p. 3
- Across deck inclination (roll) angles, the trimaran hull’s righting lever peaks at 38.2°, while the point of negative lever, indicating unrecoverable roll, occurs at 120°.Source: Figure 4 · p. 3
A. Trimaran Design
The trimaran configuration balances roll stability with a single propulsion system and is sized for a 5 kg vessel reaching 2 m/s. Detachable side hulls make the platform easier to transport.
A. Trimaran Design
- The trimaran was chosen to provide catamaran-like roll stability while requiring only one propulsion system.The passage contrasts this with monohull roll instability and catamaran dual propulsion, which adds weight and power consumption.Source: A. Trimaran Design · p. 3
- The platform is optimized to 850 mm long and 500 mm wide for a 5 kg weight and speeds of 2 m/s.Source: A. Trimaran Design · p. 3
- Bolted, detachable side hulls reduce the transport package to 850 mm × 250 mm × 200 mm.Source: A. Trimaran Design · p. 3
1) Trimaran Form:
The hull form combines a tapered stern and inverted bow with a flat bottom around the jet inlet. Its wake simulation is idealized and depicts interactions among the three hulls.
1) Trimaran Form:
- The tapered stern is intended to smooth water flow and reduce vortices, while the inverted bow is intended to reduce wake and prevent pitching by piercing waves.The passage says an axe bow was not selected because anticipated propulsion-induced pitch could increase water riding up the sides.Source: 1) Trimaran Form · p. 3
- At 2 m/s, an idealized trimaran free-surface simulation, ignoring viscosity and wave breaking, shows waves from each hull interacting to produce a 50 mm peak and 40 mm trough from the waterline.Source: Figure 5 · p. 3
- A flat bottom tapering from the jet inlet minimizes submerged hull height, increases shallow-water buoyancy, and avoids snag-prone keel or sharp-V surfaces.Source: 1) Trimaran Form · p. 3
- The electronics diagram groups components into power, control, actuation, and sensing categories, with the flight controller as the core control component.The caption distinguishes these groups by red, blue, yellow, and green, respectively.Source: Figure 6 · p. 4
2) Simulation:
The simulation evaluates trimaran stability and wake behavior at the 5 kg design weight. It places electronics to align the center of gravity with the buoyancy centers and reports stability and wake characteristics.
2) Simulation:
- The hull’s waterline is 46 mm at 5 kg, and electronics are positioned along its base to keep the center of mass below the center of buoyancy.The longitudinal center of buoyancy is 310 mm from the stern; the text says aligning the center of gravity with the buoyancy center in both directions is crucial for stability.Source: 2) Simulation · p. 4
- At 5 kg with batteries 30 mm above the base, the peak righting lever is 38.2° and the point of vanishing stability is 120°.The text cites a guideline requiring a righting lever above 30° but no less than 25°.Source: 2) Simulation · p. 4
- More than a meter behind the stern, the wake disperses from the center and leaves the water relatively undisturbed.The wake’s waves build into peaks and troughs toward the edges as the disturbance moves aft.Source: 2) Simulation · p. 4
3) Propulsion:
The trimaran uses a housed, vectoring waterjet for shallow-water operation and maneuverability, with trade-offs in turning without thrust and reversing. Its multi-part hull is designed for consumer-grade 3D printing, while fiberglass alternatives were excluded because they require specialized resources.
3) Propulsion:
- The jet drive can operate from 60 mm depth without additional clearance beneath the submerged hull, and its housed impeller addresses safety concerns for an unmanned vessel.The housing permits stronger impeller materials such as stainless steel, which the text says improve durability and efficiency compared with plastic alternatives.Source: 3) Propulsion · p. 4
- The 1.5 m turn radius improves on cited similar-sized systems at 2.5 m [14] and 5 m [12], while single-nozzle thrust provides steering without dual propulsion motors.The jet cannot turn without thrust; reversing requires an actuated bucket, which permits speeds up to 0.5 m/s but is inefficient and unstable.Source: 3) Propulsion · p. 4
- The route-traverse figure shows sonar depths of 0.3–0.7 m, a 4° steady pitch at 2 m/s, and hull roll from −6° to 6° during 90° turns.The route comprised nine 15–20 m straights joined by nine 2 m sections.Source: Figure 7 · p. 5
4) Fabrication:
- The hull parts are sized for consumer printers with a minimum 250 mm × 210 mm × 210 mm bed, and PETG is preferred over PLA and ABS for outdoor printing.A multi-part design accommodates the required payload despite the printer-bed constraint; TPU is used for the deformable nose, and epoxy and M3 bolts secure parts and components.Source: 4) Fabrication · p. 5
- Fiberglass bodies could be more robust and lighter, but specialized skills, materials, and equipment led the authors to exclude that manufacturing route.Vacuum forming a submerged hull as a single piece would require access to a vacuum former larger than 1 m².Source: 4) Fabrication · p. 6
B. Control and Sensing Hardware
The control and sensing hardware combines redundant power, autonomous navigation, and onboard data logging. The flight controller processes LiDAR for obstacle avoidance, while a Raspberry Pi supports logging and more complex control.
B. Control and Sensing Hardware
- Separate auxiliary and propulsion batteries provide redundancy: if the auxiliary battery fails, the vessel can return by GPS or manual control, and if propulsion power runs out, it can still locate itself and send commands to the remote laptop.The two power sources are shown as separate supplies for flight control/GPS and propulsion.Source: B. Control and Sensing Hardware · p. 6
- Ardupilot serves as the central flight controller, with GPS and its built-in IMU locating and orienting the vessel within 2 m outdoors while LiDAR is filtered into four sectors spanning 180° for obstacle avoidance.A wireless controller can switch between auto and manual modes for recovery if autonomous control fails.Source: B. Control and Sensing Hardware · p. 6
- A PI controller controls steering rate and thrust against desired location and speed, while the Raspberry Pi logs camera and other onboard sensor data and is needed for more complex controllers such as MPC.The route-traverse figure includes sonar depth, pitch, and roll measurements; the hull wake is described as closely resembling the simulated estimate.Source: B. Control and Sensing Hardware · p. 6, Figure 9 · p. 6
A. Power and Speed
The power model is representative within 20% for future speeds and scaled designs, though its error varies across tests and speed. Platform trials also report operation amid bio-fouling, with debris and spray identifying practical constraints.
A. Power and Speed
- At 2 m/s, Test 1 differed from predicted power by 17%, while Test 2’s prediction was 8% below measured power; the model is representative within 20% for future speeds and scaled designs.The MAXSURF prediction used the Van Oortmerssen model and assumed 40% overall propulsion efficiency.Source: A. Power and Speed · p. 6
- With the current 6S 5000 mAh battery, estimated continuous run time is 1 hour at 1 m/s, 38 minutes at 1.5 m/s, and 27 minutes at 2 m/s.The tested trimaran weighed 3.8 kg against a 5 kg design weight; a 10,000 mAh battery would add 0.7 kg and double run time at each speed.Source: A. Power and Speed · p. 6
B. Platform Testing
- The rock-obstacle experiment used the ‘bendy-ruler’ algorithm with 2D LiDAR data.The figure locates the test at Western Springs lake in Auckland, New Zealand.Source: Figure 10 · p. 7
- The jet continued running despite vegetation wrapping around its input shaft, but branches and algae snagged on the hull fronts and jet housing and could reduce efficiency over extended operation.Above 2 m/s, water rode over the side hulls and caused spray at the mounting tubes; the bow remained submerged as intended.Source: B. Platform Testing · p. 7
C. Autonomous Testing
Autonomous testing showed the trimaran could navigate around pond rocks and track planned paths, while its hull motion supported 2D LiDAR use in calm water. The paper also points readers to experimental video, CAD files, and code for replication and further development.
C. Autonomous Testing
- The trimaran completed a path despite vegetation overgrowth missing from the satellite image, with a largest recorded tracking error of 1.6 m.The authors identify local obstacle avoidance alongside global path planning as valuable in this setting.Source: C. Autonomous Testing · p. 7
- Hull roll ranged over 12 degrees, was asymmetric during turns, and was zero during constant yaw; the authors suggest weight distribution or nozzle trim may explain the asymmetry.The hull tracked 2 m/s on straights, with speed fluctuating between 1 and 2.5 m/s around corners and pitch peaking at 9 degrees.Source: C. Autonomous Testing · p. 7
- The trimaran dynamically avoided pond rocks using 2D LiDAR and a bendy-ruler algorithm, with a 5 m look-ahead and 2 m avoidance distance.Outdoor LiDAR detection was reliable to 5 m; the tested 16 m-range alternative performed worse, including failure to detect black surfaces at 5 m.Source: C. Autonomous Testing · p. 7
D. Video, CAD Files, Code
- Experimental validation video, CAD files, and code are available to support replication and further development.The authors describe open-source dissemination as intended to allow others to replicate and develop the results.Source: D. Video, CAD Files, Code · p. 7
IV. CONCLUSIONS
The authors conclude that the lightweight, low-cost, open-source waterjet trimaran is a practical platform for aquatic inspection and monitoring. They identify LiDAR-camera fusion and a dynamic boat model as future directions.
IV. CONCLUSIONS
- Successful bathymetry and water-quality testing at 2 m/s supports the trimaran’s practical utility for aquatic monitoring.The paper presents the platform as a promising alternative to resource-intensive research vessels.Source: §IV · p. 7
- The research contributes a lightweight, low-cost, open-source, waterjet-powered trimaran that is designed to be easy to replicate.The authors frame it as particularly relevant to Aotearoa–New Zealand’s diverse water bodies.Source: §IV · p. 7
- Future work includes integrating LiDAR and camera data and deriving a dynamic model for more complex scenarios and sophisticated planning and avoidance algorithms.Source: §IV · p. 8