Re: [Flightgear-devel] Digitrak and three axis gyro
On Wed, 2005-09-14 at 20:35 -0400, Steve Knoblock wrote: The Digitrak is described as employing gyroscopic rate sensors are installed so as to sense motion about each of the major axes (roll, yaw and pitch). I assume they mean there is a spinning gryo around which three sensors are arranged, to sense motion in each axis, pitch, roll and yaw. The sensors report how much the aircraft has moved around the gyro for each axis. Gyroscopic rate sensors measure rotation rate around a single axis with respect to whatever they're mounted on. To measure 3 axis motion requires a minimum of 3 sensors. There are no gimbals or spinning objects (vibrating parts yes). Tracking orientation with them requires integrating the signals in a rotating reference frame. You also need an absolute reference because the integrated signals will drift. Here's something google turned up: http://www.smalltimes.com/document_display.cfm?section_id=76document_id=7451 From what I can see of the various default instruments in FlightGear, the only source of roll angle from an instrument is the attitude indicator or indirectly, the turn coordinator, which the Digitrak does not use. I conclude that to model the Digitrak fully, I would need to create C code to represent this three axis gyro using the gyro.*** code that the attitude indicator depends on. I have a little experience with C, but not much. I nearly understand how the attitude indicator works with the gyro model, but I still have to many questions to comprehend all it is doing. I also assume that using /orientation/roll-angle is the best substitute currently available. I would appreciate any help with this and please correct me if I am wrong in any of this. The only way to really know what the Digitrak is doing is to know what it's really doing ;-) I think the Digitrak would make an interesting contribution to FlightGear. It would, but you may be limited to just a visual representation and some other autopilot code. It would be really hard to know exactly what their software is doing without access to source code. -Paul ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Digitrak and three axis gyro
I don't know how detailed you want to get with the digitrak modeling, but as a first pass, you could just assume that what ever the digitrak is doing, it's keeping a pretty good estimate of reality. If you make that assumption, then you could just use the raw pitch, roll, yaw values from FG and move on to the higher level modeling. As Paul suggests, if you want to really model all the internal sensors, you really have to know exactly what they are, how they are calibrated to some absolute reference, what math is going on behind the scenes, etc. etc. Curt. Paul Kahler wrote: On Wed, 2005-09-14 at 20:35 -0400, Steve Knoblock wrote: The Digitrak is described as employing gyroscopic rate sensors are installed so as to sense motion about each of the major axes (roll, yaw and pitch). I assume they mean there is a spinning gryo around which three sensors are arranged, to sense motion in each axis, pitch, roll and yaw. The sensors report how much the aircraft has moved around the gyro for each axis. Gyroscopic rate sensors measure rotation rate around a single axis with respect to whatever they're mounted on. To measure 3 axis motion requires a minimum of 3 sensors. There are no gimbals or spinning objects (vibrating parts yes). Tracking orientation with them requires integrating the signals in a rotating reference frame. You also need an absolute reference because the integrated signals will drift. Here's something google turned up: http://www.smalltimes.com/document_display.cfm?section_id=76document_id=7451 From what I can see of the various default instruments in FlightGear, the only source of roll angle from an instrument is the attitude indicator or indirectly, the turn coordinator, which the Digitrak does not use. I conclude that to model the Digitrak fully, I would need to create C code to represent this three axis gyro using the gyro.*** code that the attitude indicator depends on. I have a little experience with C, but not much. I nearly understand how the attitude indicator works with the gyro model, but I still have to many questions to comprehend all it is doing. I also assume that using /orientation/roll-angle is the best substitute currently available. I would appreciate any help with this and please correct me if I am wrong in any of this. The only way to really know what the Digitrak is doing is to know what it's really doing ;-) I think the Digitrak would make an interesting contribution to FlightGear. It would, but you may be limited to just a visual representation and some other autopilot code. It would be really hard to know exactly what their software is doing without access to source code. -- Curtis Olsonhttp://www.flightgear.org/~curt HumanFIRST Program http://www.humanfirst.umn.edu/ FlightGear Project http://www.flightgear.org Unique text:2f585eeea02e2c79d7b1d8c4963bae2d ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
[Flightgear-devel] Digitrak and three axis gyro
The Digitrak is described as employing gyroscopic rate sensors are installed so as to sense motion about each of the major axes (roll, yaw and pitch). I assume they mean there is a spinning gryo around which three sensors are arranged, to sense motion in each axis, pitch, roll and yaw. The sensors report how much the aircraft has moved around the gyro for each axis. From what I can see of the various default instruments in FlightGear, the only source of roll angle from an instrument is the attitude indicator or indirectly, the turn coordinator, which the Digitrak does not use. I conclude that to model the Digitrak fully, I would need to create C code to represent this three axis gyro using the gyro.*** code that the attitude indicator depends on. I have a little experience with C, but not much. I nearly understand how the attitude indicator works with the gyro model, but I still have to many questions to comprehend all it is doing. I also assume that using /orientation/roll-angle is the best substitute currently available. I would appreciate any help with this and please correct me if I am wrong in any of this. I think the Digitrak would make an interesting contribution to FlightGear. Thanks, Steve ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
