How will the helicopter behave when the GPS signal is lost

[Peta (Petr Mamula)]

Hi,

How will the helicopter behave if it loses the GPS signal, or loses the GPS signal and the compass?
If heli only loses GPS, will be able to fly for some time with degraded position accuracy?

If I connected an optical IMU with mechanical gyroscopes, would I be able to fly without GPS? I ask because I got a mechanical IMU (only gyro and acc, i need to use internal sensor fusion (kalman)).

It is big and heavy, but they could also be very accurate. I saw that Ardupilot can connect an external accelerometer and gyroscope. How is it possible to program my own device?

My mechanical IMU communicates via RS232, the protocol is simple. I read information from it through a USB->RS232 converter. I think it could also work with ardupilot.

Thank you for help.

[LupusTheCanine]

You would have to write a driver for it then tune EKF.
See

External IMU configuration

Hello, If you want to add a new external IMU, it is possible. You need to add a new backend in AP_inertialsensor and modify your hal to use it, and adapt the EKF gain for it… Quite a big work But unless you are paying a quite expensive IMU (>1000$) you won’t have much improvement… Default imu on pixhawk serie are quite good. At 1000$ it would be better to replace the whole controller … Could you details what you mean by very big error ? I fear that you are thinking that the imu is faulty whe…

For a very brief overview of the task.

PS I would start by writing a simple program to connect the unit to the PC and measure it’s accuracy and consistency to compare it’s performance to IMUs mounted on quality FC.

[Ferrosan (Ferruccio Vicari)]

@Peta

How will the helicopter behave if it loses the GPS signal,

I normally set to switch to Alt-Hold flight mode. I wouldn’t rely too much on dead-reckoning, to be safe always consider you have to fly home manually.
So plan to install fpv camera and good long range stuff on your aircraft.

[Peta (Petr Mamula)]

We are talking about IFOS-500, IFOS-500 | FOS

I would like to use internal EKF.

[Peta (Petr Mamula)]

I am afraid, this is not possible. The helicopter has a range of around 300km. Right now our datalink range is around 50km. I am currently doing a feasibility study. My idea is based on the fact that airliners can fly according to the inertial unit.

[LupusTheCanine]

SpecSheet is good enough to check if the IMU is worth it. Writing a simple driver would have made it easier to write the Ardupilot driver later.

Nowadays nobody in the civilian world uses purely Inertial navigation and even before GPS it was Doppler-Inertial systems or celestial navigation that was used for crossing the oceans not to mention a few ground based radio navigation systems.

As recent incidents over Africa have shown modern civilian airliners doesn’t handle GPS jamming well, they are clearly reliant on GNSS for navigation.

In an piloted aircraft drifting 50 or even 100nm North or South of the target while crossing the Atlantic wasn’t that big of a deal because you would intercept radio navigation aid that would direct you to the correct place anyways. UAS need sub 10m positioning to be autonomous, preferably sub 1m and they typically don’t use other navigation sources than gps-inertial navigation.

IMHO typical iMU used in quality AP compatible flight controllers are good enough for GPS inertial navigation and emergency short term (less than 1-2 min dead reckoning more if you have velocity source like Doppler radar or optical flow with rangefinder).