Home        Store        Learn        Blog

Failsafe-Return to Home via GPS it is possible?

Hello! I looked through the program interface QgroundControl, studied the user manual, but I understand that the return home (RTH) was specially removed from the program interface, including when the signal is lost (failsafe)? I will explain the problem - the students and I are designing an underwater vehicle ROV, it will have positive buoyancy, and it is important for us that if, for example, a fiber-optic cable breaks (or if the ROV gets tangled at the bottom among the branches, it could cut the cable itself), it can float up on its own (positive buoyancy) and after a few seconds the return home via GPS should turn on - after all, it will be above the water and will be able to receive satellites. Thus, the ROV will be able to return to the starting point itself. But I understand that today it is not implemented in software, while everything is available in hardware for this.

Please tell me how you can implement this? So far, I came up with the idea of ​​putting a separate engine-thruster with a rudder as a normal boat and putting a separate autopilot with its own GPS. After surfacing, the device will be able to return home on this autopilot like an ordinary boat. But it is expensive, cumbersome and unreliable - you need to install a servo motor for the steering wheel. Yes, it’s silly to do all this, since ARdusub already has everything for this.

Help solve this problem! Thank you very much and greetings from cold Siberia!

1 Like

How far away from your “home” position are you expecting to operate the ROV?

1 Like

This is a good question, I am planning to use thin optical fiber (2-3mm dia.) up to 1-1.5 kilometers long for communication. Of course, it all depends on the battery and the current ROV, but I plan to use a homemade 18650 battery with a capacity of about 50-60 Amp.h. The typical cruising range I think will be about 500 meters.

Therefore, this is a very important question for me - automatic return to home after automatic ascent. Of course, I have provided a radio modem 433MHz with an antenna, even if the connection is broken, I can control ROV through the radio modem, but I would like to have an automatic return home as a means of rescue, especially since everything is in hardware for this in Ardusub. But I’m not a programmer, so it’s hard for me to figure out how to rewrite the program code to add a “return home” option to a failsafe.

1 Like

As far as I understand, the GPS system is not supported at all in Ardusub. It was also impossible to return home after the ascent of the ROV. It was a great surprise for me, since I have been making fly drones for 10 years and started with Multiwii and in the simplest system with GPS there is already a return home. I was sure that this is also in Ardusub, since everything is there in hardware - autopilot, compass, external GPS. As I understand it, the problem is only in the software solution, although it is strange that the Ardu system (for cars, helicopters, drones and ordinary boats) has a return home and holding a position. - apparently these functions were removed from Ardusub.

This means I will have to install a separate autopilot with firmware for a regular boat and install a separate engine with a rudder. This makes the implementation much more difficult, but there seems to be no other choice.

I have a question - in the current configuration Ardusub, will a normal 433 MHz radio modem work together with a wire connection - optics or LAN? In the event of a fiber break, I planned to use manual control via a radio modem, because it has a range of 1-3 kilometers above the water.

Hi.

A serial GPS will work fine, but RTL is not implemented.

A secondary telemetry link will work fine. But I would try to get the antenna as high above the water as possible.

1 Like

Hi Willian. Thanks! I understand that the serial GPS will be able to give its coordinates to a map with a ground station- QGroundControl, at the moment when the ROV surfaced, or floats on the surface. In any case, this is very useful for various things - for example, I will find something interesting at the bottom and I will need to know the coordinates of this place - I will be able to surface and see the coordinates - it is clear that this will not be particularly accurate and depends on the depth of the ascent - most likely there will be some sideways drift. But the error should not be especially large for a depth of 30-60 meters.

The fact that the second telemetry link will work very well too - it can be used as a backup control channel in case of a break in the communication wire. Moreover, the device itself will surface and the serial GPS will transmit its current location and in theory it should not be difficult to return it, even without a video link - just look at the map of the ground station and the distance.

Tell me, is the possibility of introducing the RTL function being considered in the future? (Of course, when the ROV is on the surface and behaves like an ordinary boat). I am not a programmer and I do not know the full complexity of the task - I thought that maybe pieces of program code from Arduboat will help here … In any case, thanks for your participation!