Hi. I was wondering something about gyroscopes used in RC helicopters or planes. Are the gyro readings being integrated? Because I can't think of how a rate gyro could be used to keep a helicopter in the right direction unless the reading was being integrated. But I also get the impression that something simpler is being used and the gyro readings are not being integrated, but something else is happening.

 

I've also been wondering about that issue. I assume you are talking abou tthe yaw gyro. The rc gyros output a servo compatible PWM signal which I presume is fed back into a coupling servo but I believe that this is modified by the control coming from the "pilot". I think that the really sophisticated system use integration but the simple ones rely on hand trimming. I believe drift is an issue as the system can't be 100% accurate. I recall seeing some where that you should recalibrate before each flight.

Sparkfun has IMUs with both gyros and accelerometers. I assume that the gyro is used to determine the angular rate and the accelerometer is to determine the axis and angle so no integration is needed.

 

Yes, it modifies the servo signal coming from the pilot's radio. But what I am wondering is whether or not the electronics are integrating the gyro's rate output in order to compensate or if it is just using the angular velocity data directly (in which case I do not udnerstand how it would work).

It just seems that if the drify is high the plane might eventually be flying upside down (ie. for the roll gyro).

 

I haven't seen any sites that talk about roll (or pitch) gyros. Mostly chopper stuff which uses it for yaw. I doubt there is integration going.

I assume that using an accelerometer in conjunction with gyros renders the issue moot. I'm not sure this stuff is accurate enough for autopilot/autonomous flight, though.

 

So you're saying it's more like the chopper doesn't correct it's own position all the time, but rather only corrects for drift while the pilot has the control stick off center?

There are some autpilots I am looking at right nowfor the club and they use Analog Devices gyros and accelerometers. I'm just wondering how they deal with the drift. They do say it's not accurate enough to dead-reckon though.

 

I realized I was missing some pieces of the puzzle and did some looking. there appear to be 2 types of heli yaw gyros - standard (for lack of a better term) and heading hold ones introduced about 6 years ago. The standard ones need trimming to compensate for drift, even in mid flight. The HH ones integrate and require no trimming. Futaba makes a number HH gyros.

so the answer is some do. some don't....