The German effects studio OMStudios must really trust their custom RC Octocopter--the super high-def RED camera they're lifting costs $40,0000.

 

Via Engagdet

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Comment by Olivier ADLER on October 17, 2011 at 12:58am

 

The baro in the Wookong is the same as in MK. (MPXAZ6115A)

 

it is an analog output Baro with 0 - +5V output.

 

Obviously the precision here does certainly come mostly from the analog to digital converter precision, and carefull hardware design to avoid noise.

 

http://cache.freescale.com/files/sensors/doc/data_sheet/MPXAZ6115A....

 

For those interested in the wookong design it's here :

 

http://www.rcgroups.com/forums/showthread.php?t=1510587

 

 

Comment by Aurelio R. Ramos on October 17, 2011 at 8:41pm

It always bothered me why barometer or sonar noise has to be a problem. I would think that accel Z can be integrated twice for a short term aproximation of altitude using leaky integrators. The result can be combined with low pass filtered altitude sensor data to drive an altitude control loop. Most disturbances that upset altitude occur in the short term, when a very accurate accelerometer reading would be useful. Think of it as dead reckoning altitude control by the accelerometer, or using different sensors to satisfy different bandwidths of the desired signal. Not very critical for the bandwidths to overlap precisely as long as the total bandwidth covers the area of interest.

 

For a few months I had a local modification on ardupirates which used a similar method to implement altitude damping, so that rate of altitude change would be countered by a D term

 

leaky integral of Z + G (to eliminate the constant pull of gravity, which manifests as Z = -G when sitting level) gives short term speed, which scaled by a negative constant (experimentally tuned) to create a comfortable level of manual control of altitude by user throttle input. Integrator leak rate is also experimentally tuned.

 

For the feature to work properly I added some clamping to limit its effect on the throttle and scaled its influence down as the pitch / roll of the craft deviated from horizontal, in order to prevent the damping effect from doing anything during any maneuver other than a straight hover.

 

I was very happy with my feature, enabled me (a complete beginner) to hover at a very constant altitude just over head height) and follow the craft down a trail near my house.

 

Precise altitude hovers on AC2 require a lot of constant throttle input for me.

 

Now I am trying to teach myself better control and move beyond beginner level, but I might port the change to my local AC2 code.

Comment by Greg on October 18, 2011 at 4:17am

I think after doing everything possible to reduce the sonar and baro noise as I reported here (Sonar-nose-reduction-update) I have to agree something else is needed for better altitude control.

Comment by Nagy József on June 24, 2012 at 6:14am

My first test with scarlet-stress (gimbal and FC not fine-tuned). (stable and cold)

Technical test (payload-stress)

we next week build extended-gimbal-arm  for fitting Scarlet  COG problem. Build power connector, changing the stock pitch/roll servo, servo lipo, VTX, telemetry.... etc....etc....etc (forever? :)

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