Gerris USV - hydrodrone from scratch!

Today, "In the Workshop" is about a slightly larger project - that is, about an unmanned vessel used, for example, for bathymetric measurements. You can read about our first catamaran, adapted to the radio-controlled version, in the 6th issue of "Young Technician" for 2015. This time, the MODELmaniak team (a group of experienced modellers affiliated with the Kopernik Model Workshops Group in Wrocław) faced the friendly challenge of designing from scratch a floating measurement platform even better adapted to gravel conditions. quarry, expandable to a stand-alone version, giving the operator more breathing room.

Started with customization...

We first encountered this problem when we were asked a few years ago about the possibility of introducing actuators and adaptation to radio control trailed bathymetric (i.e. a measuring platform used to measure the depth of bodies of water).

1. The first version of the measurement platform, only adapted to the RC version

2. The drives of the first hydrodrone were slightly modified aquarium inverters - and they worked quite well, although they definitely did not have “construction resistance”.

The simulation task was to design and manufacture actuators for prefabricated PE stretch-blow molded floats (RSBM – similar to PET bottles). After analyzing the operating conditions and available options, we chose a rather unusual solution - and, without interfering with the hulls below the waterline, we installed aquarium circulator-inverters as drives with the added ability to rotate 360 ​​° and lift (for example, when an obstacle hits or during transportation) ) . This solution, additionally supported by a separate control and power supply system, allowed control and return to the operator even in the event of failure of one of the sections (right or left). The solutions were so successful that the catamaran is still in operation.

3. When preparing our own project, we analyzed in detail (often personally!) Many similar solutions - in this illustration, German ...

4.…here is an American (and a few dozen more). We rejected single hulls as less versatile, and drives protruding below the bottom as potentially problematic in operation and transportation.

However, the sensitivity of the disks to water pollution turned out to be a disadvantage. Although you can quickly remove the sand from the rotor after an emergency swim to shore, you need to be careful with this aspect when launching and swimming close to the bottom. Because it does, however, include the expansion of measurement capabilities, and it has also expanded over this time. scope of hydrodrone (on the rivers) our friend showed interest in a new development version of the platform specially designed for this purpose. We took on this challenge - in accordance with the didactic profile of our studios and at the same time giving the opportunity to test the developed solutions in practice!

5. Quick-folding modular cases were very inspiring with their versatility and ease of transportation 3 (photo: manufacturer's materials)

Gerris USV - technical data:

• Length/width/height 1200/1000/320 mm

• Construction: epoxy glass composite, aluminum connecting frame.

• Displacement: 30 kg, including carrying capacity: not less than 15 kg

• Drive: 4 BLDC motors (water-cooled)

• Supply voltage: 9,0 V… 12,6 V

• Speed: working: 1 m/s; maximum: 2 m/s

• Operating time on a single charge: up to 8 hours (with two batteries of 70 Ah)

• Project website: https://www.facebook.com/GerrisUSV/

The exercises continued - that is, assumptions for a new project

The guiding principles we set for ourselves when developing our own version were as follows:

• two-hull (as in the first version, guaranteeing the greatest stability necessary to obtain accurate measurements with an echo sounder);
• redundant drive, power and control systems;
• displacement, allowing the installation of on-board equipment weighing min. 15 kg;
• easy disassembly for transportation and additional vehicles;
• dimensions that allow transportation in an ordinary passenger car, even when assembled;
• protected from damage and contamination, duplicated drives in the bypass of the body;
• universality of the platform (the ability to use it in other applications);
• the ability to upgrade to a standalone version.

6. The original version of our project involved modular division into sections built using different technologies, which, however, could be assembled as easily as popular blocks and receive various uses: from radio-controlled rescue models, through USV platforms, to electric pedal boats

Design vs technology i.e. learning from mistakes (or up to three times more than art)

At first there were, of course, studies - a lot of time was spent searching the Internet for similar designs, solutions and technologies. They inspired us so much hydrodronium various applications, as well as modular kayaks and small passenger boats for self-assembly. Among the first we found confirmation of the value of the double-hull layout of the unit (but in almost all of them the propellers were located under the seabed - most of them were designed to work in cleaner waters). Modular solutions industrial kayaks prompted us to consider splitting the model hull (and workshop work) into smaller pieces. Thus, the first version of the project was created.

7. Thanks to the Jakobsche editor, the subsequent 3D design options were quickly created - necessary for implementation in filament printing technology (the first two and last two segments of the body are the result of the printing space limitations of the printers owned).

Initially, we adopted mixed technology. In the first prototype, the bow and stern sections had to be made of the strongest material we could find (acrylonitrile-styrene-acrylate - ASA for short).

8. With the expected accuracy and repeatability of module connections, the middle parts (half a meter long, eventually also one meter) required appropriate equipment.

9. Our top plastics technologist made a series of test modules before the first extreme ASA element was printed.

Ultimately, after proof of concept, in order to realize subsequent cases more quickly, we also considered using impressions as hooves to create molds for lamination. The middle modules (50 or 100 cm long) had to be glued together from plastic plates - for which our real pilot and specialist in plastics technology - Krzysztof Schmit (known to readers of "At the Workshop", including as a co-author (MT 10 / 2007) or radio-controlled machine-amphibian-hammer (MT 7/2008).

10. The printing of the end modules was taking a dangerously long time, so we started to create positive body templates - here in the classic, rebated version.

11. Plywood sheathing will require some puttying and final painting - but, as it turned out, this was a good protection in case of a possible failure of the navigational brigade ...

3D design of the new model for print, edited by Bartłomiej Jakobsche (a series of his articles on 9D electronic projects can be found in the issues of "Młodego Technika" dated 2018/2–2020/XNUMX). Soon we started printing the first elements of the fuselage - but then the first steps began ... Accurately accurate printing took ambiguously longer than we expected, and there were costly defects resulting from the use of much stronger than usual material ...

12. …who made a similar hoof out of XPS foam body and CNC technology.

13. The foam core also had to be cleaned.

With the acceptance date approaching alarmingly fast, we decided to move away from modular design and 3D printing for hard and better known laminate technology - and we started working in two teams in parallel on different types of positive patterns (hooves) corps: traditional (construction and plywood) and foam (using a large CNC router). In this race, the "team of new technologies" led by Rafal Kowalczyk (by the way, a multimedia player in national and world competitions for radio-controlled model constructors - including the co-author of the described "On the Workshop" 6/2018) gained an advantage.

14. ... be suitable for making a negative matrix ...

15. …where the first glass epoxy float prints were soon made. One gel coat was used, which is clearly visible on the water (since we had already abandoned the modules, there was no reason to interfere with the work with two-color decorations).

Therefore, the further work of the workshop followed Rafal's third design path: starting from the creation of positive forms, then negative ones - through the imprints of epoxy-glass cases - to ready-made IVDS platforms (): first, a fully equipped prototype, and then subsequent, even more advanced copies of the first series. Here, the shape and details of the hull were adapted to this technology - soon the third version of the project received a unique name from its leader.

16. The assumption of this educational project was the use of publicly available, modeling equipment - but this does not mean that we immediately had an idea for each element - on the contrary, today it is difficult to count how many configurations were tried - and the design improvement did not end there.

17. This is the smallest of the batteries used - they allow the platform to run for four hours under workload. There is also an option to double the capacity - fortunately, service hatches and greater buoyancy allow a lot.

Gerris USV is a lively, working kid (and with his mind!)

Garris this is the Latin generic name for horses - probably well-known insects, probably rushing through the water on widely spaced limbs.

Target Hydrodrone Hulls Manufactured from multi-layer glass epoxy laminate – strong enough for the harsh, sandy/gravel conditions of the intended job. They were connected by a quickly dismantled aluminum frame with sliding (to facilitate draft setting) beams for mounting measuring instruments (echo sounder, GPS, on-board computer, etc.). Additional conveniences in transportation and use are covered in outlines of cases. discs (two per float). Dual motors also mean smaller propellers and more reliability, while at the same time being able to use even more simulation than industrial motors.

18. A look at the salon with motors and an electrical box. The visible silicone tube is part of the water cooling system.

19. For the first water trials, we weighted the hulls to make the catamaran behave adequately for the conditions of the intended work - but we already knew that the platform could handle it!

In subsequent versions, we tested various propulsion systems, gradually increasing their efficiency and power - therefore, subsequent versions of the platform (unlike the first catamaran of many years ago) with a safe margin of speed also cope with the flow of every Polish river.

20. Basic set - with one (not yet connected here) sonar. The two user-ordered mounting beams also allow the measurement devices to be duplicated and thus increase the reliability of the measurements themselves.

21. The working environment is usually gravel with very turbid water.

Since the unit is designed to operate from 4 to 8 hours continuously, with a capacity of 34,8 Ah (or 70 Ah in the next version) - one in each of the cases. With such a long running time, it is obvious that three-phase motors and their controllers need to be cooled. This is done using a typical modeling water circuit taken from behind the propellers (an additional water pump turned out to be unnecessary). Another protection against possible failure caused by the temperature inside the floats is the telemetric reading of the parameters on the operator's control panel (i.e. a transmitter typical of modern simulations). On a regular basis, in particular, engine speeds, their temperature, temperature of regulators, voltage of supply batteries, etc. are diagnosed.

22. This is not the place for sleek cropped models!

23. The next step in the development of this project was the addition of Autonomous Control Systems. After tracing a reservoir (on a Google map or manually - according to the flow around the contour unit of the measured reservoir), the computer recalculates the route according to the estimated parameters and after turning on the autopilot with one switch, the operator can comfortably sit down to observe the operation of the device with a soft drink in his hand ...

The main task of the entire complex is to measure and save in a separate geodetic program the results of water depth measurements, which are used later to determine the interpolated total reservoir capacity (and thus, for example, to check the amount of selected gravel since the last measurement). These measurements can be made either by manual control of the boat (identical to a conventional remote controlled floating model) or by fully automatic operation of a switch. Then the current sonar readings in terms of depth and speed of movement, the status of the mission or the location of the object (from an extremely accurate RTK GPS receiver, positioned with an accuracy of 5 mm) are transmitted to the operator on an ongoing basis by the dispatcher and the control application (it can also set the parameters of the planned mission) .

Practice versions of the exam and development

described hydrodrone It has successfully passed a number of tests in various, typically working conditions, and has been serving the end user for more than a year, painstakingly "plowing" new reservoirs.

The success of the prototype and the accumulated experience led to the birth of new, even more advanced units of this unit. The versatility of the platform allows it to be used not only in geodetic applications, but also, for example, in student projects and many other tasks.

I believe that thanks to successful decisions and the diligence and talent of the project manager, there will soon be gerris boats, after being converted into a commercial project, they will compete with American solutions offered in Poland, which are many times more expensive in terms of purchase and maintenance.

If you are interested in details not covered here and the latest information on the development of this interesting structure, please visit the project website: GerrisUSV on Facebook or traditionally: MODElmaniak.PL.

I encourage all readers to bring their talents together to create innovative and rewarding projects together—regardless of the (familiar!) “Nothing pays here.” Self-confidence, optimism and good cooperation to all of us!