Hot answers tagged

22

You may want to consider a Magnetically Coupled Drive. Use a standard motor with a magnetic coupling to transmit the torque to your prop. This would allow your motor to be completely sealed inside your vehicle: From Eric Stackpole's article mentioned above. Image used without permission, but with attribution. This solution may or may not be suitable ...


22

I'm not sure if an 'aquabot' is a fully submersible vehicle, or a surface one. If it's a surface vehicle, then you just need to look at RC boats. They've got this solved pretty well. The seal that prevents water entering the boat is called a stuffing box (4 on the diagram). It's simply a tube stuffed with grease. The grease prevents any water leaking into ...


14

The best commonly available battery technology when it comes to power density versus weight, and at reasonable cost, is LiPo. I would prbably recommend LiFePO4 batteries. LiFePO4 are somewhat more expensive than LiPo for the same watt-hours, and weigh somewhat more, but they hold the charge better, they age much better, and they can be re-charged five to ...


12

If you're looking for a very cheap way to do it (as in, educational budget cheap), check out the Sea Perch ROV build manual. Full disclosure, I used to work at the MIT lab that heads up this educational program. On page 9 of that PDF it starts talking about how to waterproof a hobby motor with a film canister and toilet bowl wax. The entire housing ...


8

There is no right answer. However, I think I can clarify what you've read so far. You need a buoyancy engine to supply the thrust, wings to direct that thrust, and some ability to change your pitch angle when you change the buoyancy. So, you'll need to balance the strength of your engine with the drag created by your wings. At the same time, your wings ...


6

When taking into account size / weight / Ah, fuel cells and micro power turbines have an energy per kilogram and (with liquid fuels) an energy per liter that is an order of magnitude better than any battery. In particular, I keep hearing that liquid methanol fuel cells are "relatively practical". a b c d e. And I've heard that Hyuk Kim and Seungdoo Park ...


5

Lithium Ion Polymer batteries are probably your best bet. They will present the least amount of magnetic interference (followed by Alkaline... NiCD interferes the most). Unlike the regular lithium ion cells (which are usually round), these ones will stack nicely. I hope you'll check the manual before trying this -- many of them are pressure tolerant. ...


4

Mags are used in almost all UAVs. It will be useful and it will be a unique source of information. Adding a some shielding between the mag and your computers and power lines will greatly reduced the noise. Noise can be further reduced by twisting all of the wires that carry significant current (wires to motors and ESCs). Be aware that the measurement will ...


2

You don't gave all information that are needed for such calculations. However, the technical details of the Thrusters give a peak consumption of 350 Watts each. So you have 6 of them, makes overall 2.1kW/h. Lets assume your Batteries have the following details: 6S 22.2V 3300mAh. Therefore the amount of energy the Batterie stores is: 22.2V*3.3Ah = 73.26W/h. ...


2

I have come across all the suggestions in the other posts. I don't understand why people are suggesting complex and expensive solutions which are also not feasible. A mechanical seal is the simplest answer for sealing the motor or making it of IP 68. We can use this motor to a depth of 20 m in sea water. The construction is like a WET pit. Such types of ...


2

I think you need to step back a bit and think beyond the math. An (E)KF is used to estimate the true value of a signal in the presence of noise; it's only because of this noise that we even need the algorithm. When you set R to zero you are saying "I have a perfect measurement". In this case there is no need for an estimate. In practice, I think you have ...


1

As mentioned in the previous answer, many small, low-cost underwater (and aerial) vehicles use a magnetic compass. You need a good procedure for both hard-iron and soft-iron calibration of your magnetometer. Constantly having to calibrate them sucks, but they're way less expensive than a FOG. With good calibration, you should be able to achieve adequate ...


1

On one of my remotely controlled boats, I used this design... The blue discs are flywheels. They are attached to the green rods which are hooked to both sides of a flexible, waterproof membrane. The membrane is fixed to both sides of the casing so it will transmit the motion, but it will not let water through.


1

We are using for the AUV-Avalon a simulation called Mars http://rock-robotics.org/master/documentation/simulation/index.html Unfortunately there is no ROS integration, but a Rock integration. Rock supports HIL in general. For AUVs there are multiple integrations available which are collected in the mars-core package https://github.com/rock-simulation/...


1

We are using the P900 multibeam sonar. So far our interface hasn't any problem. But we requested a new version of the library from teledyne which works now in our case. sonar = new BVTSDK::Sonar(); head = new BVTSDK::Head(); int ret = sonar->Open("NET", hostAddress); //error handling ret = sonar->GetHead(1, head); //again error handling I will ask ...


1

I understand exactly what you are talking about. I am developing my own ROV that will have a track system and crawl on the sea floor. If I may suggest placing your motor in a high point in your ROV with the gear drive close to the bottom, you can install a pressurized air system that will allow air into the chamber as the ROV goes deeper. Think of it like a ...


1

Take it for what it's worth, I was next to the OpenROV booth at Maker Faire and their answer was 'let it leak and dry it off later'. They said they were surprised that water getting into the motor didn't cause issues for them. 'course I haven't tried this myself and I may have misheard them -- or perhaps nothing had failed for them yet :-) It may be ...


1

All seals leak. If you are able to enclose the motor so that the shaft is the only exit point, fill the motor with a low viscosity non conductive oil such as mineral oil. This greatly reduces the pressure difference across the seal.


Only top voted, non community-wiki answers of a minimum length are eligible