William Premerlani's Blog (34)

Helical turn controls

First of all, thanks to Peter Hollands, who produced the above picture of a helical flight trajectory from one of his HILSIM test flights of the latest version of fixed wing flight controls for the open source MatrixPilot project, also known as the UAVDevBoard. For the last year or so, Peter has been helping me…


Added by William Premerlani on June 18, 2015 at 5:00pm — 4 Comments

MatrixPilot precision navigation algorithms

The above flight track highlights the performance of the latest version of the navigation algorithms in MatrixPilot. Flight tracks are from a flight that Peter Hollands conducted. (Thank you, Peter.) The red and the green tracks represent flight segments in opposite directions between the same pair of waypoints. The tracks are nearly perfect straight lines 243 meters long, with…


Added by William Premerlani on June 20, 2013 at 1:49pm — 17 Comments

global waypoint range for MatrixPilot

UAVDevBoard users:


MatrixPilot trunk, r1817 now has global waypoint range, provided that:

1. You use absolute waypoints. Specify longitude, latitude, and altitude for each waypoint.
2. Each pair of points in the sequence,…

Added by William Premerlani on November 23, 2012 at 7:37pm — 1 Comment

Acceleration compensation: flight testing


I have recently performed flight tests on a major change in the way acceleration is accounted for in performing roll-pitch drift compensation from accelerometer measurements. The theory behind the idea was recently published in a…


Added by William Premerlani on May 1, 2012 at 9:30am — 22 Comments

Measuring Tilt Dynamics of Multicopters


Presently I am doing work on multicopter modeling and control. One topic of interest to me is how can the tilt dynamic model of a multicopter be accurately determined from flight data, without disabling the controls or injecting any sort of intrusive signals. It turns out it can be done from normal flight data using a few basic concepts from signal…


Added by William Premerlani on March 4, 2012 at 6:00pm — 29 Comments

Magnetometer alignment


The above picture shows an interesting side effect of magnetometer misalignment: complete reversal of the measured horizontal component of the earth's magnetic field.

The effect was discovered by Peter Hollands during his analysis of the data from one of Ric Kuebler's flights. Ric was using the…


Added by William Premerlani on October 16, 2011 at 2:56pm — 31 Comments

Magnetometer offsets revisted

The above is a plot of the 3 components of estimated magnetometer offsets computed during spin tests at 78 RPM of an improved method for estimating and removing magnetometer offsets. There is a report available with theory and implementation. The method will work equally…


Added by William Premerlani on October 14, 2011 at 4:30pm — 20 Comments

sustained rotations : pushing the envelope

This is an update of a previous post, with a link to a report that I promised that I would write. The above plot shows the results of the automatic calibration of the Z axis gyro during tests of methods to improve the performance of attitude estimation during sustained, high rate rotations. In… Continue

Added by William Premerlani on June 19, 2011 at 3:50am — 21 Comments

A simple dead-reckoning algorithm


After experimenting with several dead-reckoning algorithms over the past 2 years, I finally have a simple algorithm that I like. The above pictures show a comparisons of a GPS reported trajectory (without compensation for GPS latency),…


Added by William Premerlani on April 16, 2011 at 7:00am — 34 Comments

landing altitude control

There is a simple control technique to get good altitude control during autonomous landings. Turn off the throttle and follow a glide path defined by 2 waypoints. The first point is the approach point, and should be about 10 meters above the beginning of the runway. The second point defines the glide path, and should have a negative height, and be unreachable.

Whenever the plane is above…


Added by William Premerlani on September 20, 2010 at 5:34pm — 20 Comments

rudder-roll stabilization

If you are flying a UAV DevBoard in a plane without ailerons, you should be interested in a recent revision to MatrixPilot that will tighten the turns in waypoint mode, without overshoot. The above picture is the track of a portion of a test flight in an EasyStar. The control mode was switched from stabilized mode to waypoint mode with…

Added by William Premerlani on August 31, 2010 at 11:19am — 7 Comments

Invensense gyros in the UAV DevBoard

UAV Devboard users,

The UAV Devboard, version 3, is now available from SparkFun. It is the same as version 2,…

Added by William Premerlani on August 19, 2010 at 1:30pm — 41 Comments

Three more autonomous flights with MatrixPilot

Hi guys,

Today MatrixPilot controlled three more autonomous flights. All three flights were executed with the transmitter turned off. The picture above is the track of the first landing. It was aiming for the midpoint between the two fields, along a line that connects the centers of those two circles.

Recently I posted three flights of my GentleLady flying…


Added by William Premerlani on June 25, 2010 at 11:00am — 28 Comments

Triple autonomous flights with MatrixPilot

Yesterday, my GentleLady sailplane, under the guidance of MatrixPilot running on a UAV Devboard with an EM406 GPS and Jordi's magnetometer, achieved 3 consecutive autonomous flights, with the transmitter off most of the time. The above picture shows the tracks of the three landings. Waypoints 18 and 19 were arranged so that the plane was supposed to land halfway between them. The…


Added by William Premerlani on June 19, 2010 at 3:11pm — 20 Comments

Programmers for the UAV DevBoard

UAV DevBoard pilots:

SparkFun is out of stock for both their Olimex ICD2s, which is what I've been recommending to program the UAV DevBoard, as well as their Olimex PICPOCKET, which I do not have enough information right now to provide any recommendations one way or another. SparkFun is discontinuing the ICD2, it is their intent to sell the PICPOCKET instead. Those are out of stock right now.…


Added by William Premerlani on February 17, 2010 at 6:30pm — 26 Comments

Waypoint firmware for the UAV DevBoard is revised

Sigh....I am going to give Peter Hollands an award for finding the "juiciest bug" in the released waypoint firmware for the UAV DevBoard. The bug has been fixed, and the firmware has been re-released as version 1.8b.

The bug was in the yaw drift gyro compensation calculation. It would only show up for waypoint legs with a heading between 327 degrees and 360 degrees. The result was that the actual heading would slowly vary between…

Added by William Premerlani on October 29, 2009 at 2:48pm — 39 Comments

AileronAssist versions 1.7 and 1.8 released

UAV DevBoard pilots:

This is an update of a previous post.

I deleted version 1.6 of AileronAssist firmware and released version 1.7.

The reason is that I noticed that the firmware fail safe does not work in version 1.6. Although the commanded return to launch will work just fine in version 1.6, loss of signal return to launch does not. If you turn off your transmitter, and if your radio does not have a fail safe, its not… Continue

Added by William Premerlani on September 17, 2009 at 3:30pm — 15 Comments

Altitude hold for UAV DevBoard

UAV DevBoard pilots,

I am putting the most recent releases of MatrixNav and AileronAssist back on line. I briefly reverted to the previous releases while I investigated a system issue that I just ran into.

I just bought an EasyStar, ready to fly, with radio, servos, ESC, and radio already installed. I did some flying with MatrixNav. Most of the time it worked fine, but once in a while there were problems that popped up at…

Added by William Premerlani on September 2, 2009 at 2:26pm — 10 Comments

ICD2 for programming the UAV DevBoard is back in stock

If you have a UAV DevBoard, but you are waiting to purchase an ICD2 PIC programmer from SparkFun in order to program it, please be aware that they are now back in stock.

Best regards,

Bill… Continue

Added by William Premerlani on August 17, 2009 at 3:02pm — 7 Comments

UAV DevBoard firmware progress report

UAV DevBoard pilots,

This is an update on a few UAV DevBoard related activities.

There is a new release (1.6) of MatrixNav, that now includes rudder-elevator mixing, and yaw stabilization in both stabilized and and RTL mode. It is available under the UAV DevBoard tab.

Ben Levitt just created a couple of groups in the DevBoard code repository. The groups… Continue

Added by William Premerlani on August 13, 2009 at 4:51pm — 4 Comments

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