William Premerlani's Comments

Comment Wall (80 comments)

At 1:11am on November 11, 2011, Li, Liang said…

and what is the 214format and 115format?

At 1:12am on November 11, 2011, Li, Liang said…

about the code, is there some more detailed document about these problem can share with me? thanks for your time

At 5:00pm on November 16, 2011, Jan Vervoorst said…


in the Arducopter implementation of DCM (file AP_DCM.cpp), a boolean variable called "_centripetal" is used to check whether to remove centrifugal acceleration by calling "accel_adjust()" or not. Line 131 of the code

1. when would it ever be advantageous NOT to cancel centrifugal acceleration?
2. where is this flag "_centripetal" defined, I was unable to trace where this flag is initialized or whether its value is ever changed.

Thanks for the help, Jan

At 8:18pm on February 15, 2012, Randy Cutshaw said…

Hello Bill,

At the end of your 5/17/2009 paper on DCM, you commented that you were planning to write a separate paper on how to implement the DCM algorithm in C code.  Is that paper available today?

Regards, Randy

At 10:49am on February 29, 2012, Pubo said…

Hello William, I am still very new to this so forgive me if my questions seem ood.  I'm designing a UAV for my senior project and I just wanted to clearification on something. For my design i am actually using a bluetooth module (bluesmif gold) as opposed to a radio receiver and transmitter due to a limited budget. My first question is that in the Wapoints.h file do I have to set "No_Radio" as 1 since im not going to be using the input receiver channels but rather using the bluetooth module like a RS232 connection setup.


I also plan on using Happy Kilmore's Ground Control Station, I don't know if you are familiar with this software package but it seems pretty descent and easy to use. I intend on using this software and a Xbox 360 controller for manual control let me know what you think.


thank you!!!

At 5:18am on March 26, 2012, Don Kim said…

Hi William Premerlani,

Sorry for replying late. I was away for a week, and really thank you very much for your time and tips. I would implement this design in Matlab. I have sent a message to Paul Bizard but he might be busy to reply my questions. I will try to contact him again. Finally REALLY I am appreciated for your concern. I hope to finish my design.

Best wishes,


At 2:51pm on April 16, 2012,
Adam Rivera


Regarding your question about auto PID tuning, I am doing some relevant work, but taking a slightly different approach. The idea is to determine the dynamic model of the aircraft (LaPlace transform) from flight data. Once you know the dynamic model, you can synthesize the ideal controller (its not a PID), and select optimal values of the gains. The method should work for both fixed wing and rotor craft.

Sounds way above my head! :-) I will wait to read about your findings.

By the way, Adam, a few years ago I did some consulting work for Johnson Controls. I stayed at the Phister Hotel. One summer, during ItaliaFest, I almost wound up in jail in Milwaukee. Would you care to hear the story?

Hah! I know several people at Johnson Controls, my wedding reception was at the Pfister, and I first met my wife when I was 11 years old at Italian Fest! I have never been in Milwaukee's jail, thankfully, but I would love to hear how you almost ended up there.


At 9:24am on April 18, 2012,
Adam Rivera


Did you write an application to do the modeling of the dragonflyer? Is your method published anywhere I could peek at it?


At 12:54pm on April 18, 2012,
Adam Rivera


Thank you very much for the links. I am excited to check this out!


At 2:44pm on May 1, 2012,
Adam Rivera


Have you given any thought to applying your offset learning algorithms to the accelerometers?


At 3:58pm on October 5, 2012, Gavin said…

hi bill ,

Before I make the drone and learn form DIY,and now i do by myself to desgin the new drone.so i want to learn from you.

At 6:31pm on October 15, 2012, vvirball said…


Thank you for a quick and detailed response. I am not intending on writing my own firmware for this part of the problem. And I have read, but not yet totally undertsood, all of your discussions about DCM. I had not even considered that the paparazzi page might be referring to the mounting orientation. I thought that the comment was referring to the viability of DCM in certain situations.... I am aware of gimbal lock and didn't think that that was a DCM problem.

At the top level I am trying to decide between the ardu system and the paparazzi system. And I was concerned, that if the paparazzi comment about DCM for an AHRS was valid, that ardu as an option was being ruled out.

I really appreciate your response, and your obvious love for the topic and your willingness to share all of your expertise.

Thank you.

At 5:07pm on December 5, 2012, Fabien Bruning said…

Thanks for the wind estimation info, now I'll go and see what I can get working myself. Good to hear it has since been thoroughly tested!

At 11:00pm on January 22, 2013,
James Goppert

Hey Bill. I really appreciate you taking the time to look at the EKF stuff! If we get into a heated debate about a bunch of math I think that is a good thing and I don't take it personally. That is what engineers are supposed to do. :-). I think I have a lot to learn from all of you experience with the DCM algorithm and really value your input.

At 5:21pm on January 28, 2013, Dan Wilson said…

Hi Bill,

I too have enjoyed the dialog as it's always interesting/beneficial to hear other peoples approaches to an interesting problem. It's good to hear that we share much common ground so I look forward to more discussion in the future! 

As for the magnetometer topic, I think I now understand your approach and thank you for your patience!

Best regards,


At 5:32am on February 5, 2013, Marek Mamczur said…

Hi Bill,

Thanks for your reply.

Our hardware is based on a mixture of the UDB3 and the UDB4. I've attached a note describing the technical history of the design.

The zip file contains the C30 source. We are using MPLAB IDE v8.85.

If you would like a board to play with, please let me know and I'll pop one in the post (even if it's just as a present for helping us!).AWS.zipAWS%20C%20-%20Schematic.pdfAWS%20summary.pdf



At 6:38am on May 26, 2014, xuzeyang said…


im a freshman to uav.

i read you paper named Roll-Pitch Gyro Drift Compensation.im being closely understanding....but i cant get the idea that the cross product of two vectors is the error

Regards ,knight

At 11:47pm on May 31, 2015, Guy-François MESNIL said…

Hello Bill, I have posted a request on gentlenav discussion forum about the indices of the R matrix on last 22nd of may. Could you please have a look. Many thanks of all your works given to the community. GF Mesnil

At 7:30pm on September 23, 2015, Bharat said…


I'm trying to figure out the working of the speed scaler function in the attitude code and would really appreciate if you could explain to me how the synthetic airspeed is calculated and how the scaling speed for an aircraft can be determined.


At 6:02pm on February 23, 2016, Phillip Schmidt said…
Thank for taking the effort to upload the magnetometer document. Was thinking of trying to adapt your alignment method to my IMU.
Regards, Phillip

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