UAV Build Log

Norridgewock aerial survey

2010-11-18T16:20:00.000-08:00

Tucker and I completed an aerial survey of a mitigated wetland area in Norridgewock, ME this past summer. We used the 2 pound WASP UAV to fly over the survey area while capturing images from around 500 feet above ground level. Here are a few stand alone images we captured. We will be uploading the entire photo mosaic shortly which we hope can be used as a base map for future biological research missions.

Wasp UAV Testing

2010-06-26T07:45:00.000-07:00

Here's a video from Wasp UAV testing. Now that the control surfaces (elevons) are trimmed we will start integrating the autopilot. Stay tuned for updates.

"Wasp" Airframe

2010-06-23T11:03:00.000-07:00

Over the past few days Dan and I built our new UAV airframe dubbed the "Wasp." We chose the EPP foam Zagi XS flying wing as our new platform because it's designed for beginner pilots and has a small wingspan (48''). We hope this combination will enable beginner pilots to operate the UAV more easily - with less damaging crashes and more successful flights.

First we began by gluing both wings together with 3M-77 Spray adhesive. This adhesive is both lighter and stronger than the hot glue we used on airframes in the past.

Next we inserted strengthening spars in both sides of the wing and fuselage. These spars make the flying wing more rigid and resistant to bend during high G forces. We placed ten pound weights on each side to ensure it held its aerodynamic shape through the drying process.

After spraying down the foam with adhesive, we applied the thin colored packing tape. The contrast between the black and yellow should help with visual orientation when the plane is in the air. We then installed the provided plastic fuselage covers.

We attached the two elevons (control surfaces) using PVC tape hinges. The servos for these hinges are imbedded in the wing.

Wasp UAV: Stats and packing list

Wing span: 48''
Wing area: 2.8 sq ft
Wing Loading: 8.75 oz sq ft
Servos: HS-81 Hitec
Motor: Grayson Hobby Micro Jet V3 Brushless Outrunner
Battery: 1000 mah Zippy Lithium Polymer
Speed Controller: 20 amp Super Tigre Brushless ESC
Parachute: Red Arrow Hobbies 30'' diameter
Autopilot: Attopilot V 1.9
Receiver (Rx): Spektrum AR500

Transceiver (Tx): Spektrum Dx7

Camera: FUJIFILM - FinePix 10.0-Megapixel Digital Camera

Wasp UAV: Component weights

Plane: 16.05 oz

Camera: 4.5 oz

Autopilot and sensors: 3.8 oz

1000 mah lithium battery: 3.17 oz

Parachute: 1.2 oz

Total: 28.72 oz

We will be testing the new airframe and once we're operational we'll be flying several missions for Colby professors involved in research around the Belgrade Lakes Watershed. Biology professor Cathy Bevier, who has generously funded this latest airframe build, has asked us to create a high resolution map of a mitigated wetland area in Norridgewock where she is conducting research. We're also working with Professor Jim Fleming, the project's conceptual advisor and honorary flight crew member, to provide images of other areas pertinent to the Belgrade Lakes project.

Crash Test with Fail-Safe

2010-05-13T09:35:00.000-07:00

Yesterday we tested the fail-safe parachute a few times and it worked well - reducing the planes crash velocity significantly. This was our first crash (out of many over the past 8 months) which left the ready to fly after wards. Video below.

Fail-safe parachute test

2010-05-09T13:57:00.000-07:00

Today Tucker and I tested our 30'' nylon fail-safe parachute on the Manta airframe at Colby. The idea here is that we can remotely release the parachute while the plane is crashing. Once released the parachute will slow down the plane and we'll be able to land it safely. Here's a video of an initial test.

Downsizing plane

2010-05-04T15:49:00.000-07:00

Over the past two months Foster and I have crashed our new flying wing airframe twice. Although the plane is made out of foam it still carries weight in the 5 amp battery and Pentax Optio camera on board. Unfortunately in our last crash our camera and battery catapulted forward towards the autopilot circuit board in the front of the plane and damaged some of the electrical components. Over the summer, in order to mitigate damage during crashes, Foster, Tucker, and I will downsize the weight of the plane by using a smaller flying wing and a battery with 1/5 of the amperage. These changes will downsize the plane weight to under 2 pounds. If we do crash again the decrease in weight should seriously mitigate any potential damage to on-board components.

In addition we will integrate a fail safe parachute into the plane which can be deployed during a crash. The 30 inch nylon parachute should decrease the plane's crash speed significantly. Here's a video which uses a similar parachute system.

Airframe success at Popham Beach

2010-03-17T16:46:00.000-07:00

Last Friday Foster and I hiked the 80 miles down to Popham beach from home base in Waterville to capture aerial photos. We hoped to document the changes in flow of the tidal Morse inlet which has been drastically eroding the beaches protective sand dunes. We programmed the autopilot to fly above the tidal inlet while taking a vertical picture every few seconds. The plane flew just around 2 kilometers in automated flight mode at an average speed of 68 km/h. The two minute flight felt an order of magnitude longer as we passed over control to the autopilot and anxiously awaited the planes safe return. The plane flew great and we got some interesting data. With our new 5 amp battery our plane will be able to complete hour long mapping missions covering at least 30 times the area of this photo mission.

Here's a low quality version of the 33 image Popham mapping compilation. We will georeference this compilation on the digital globe using ArcGIS software and compare to older aerial and satellite photos.

Here's a zoomed in snapshot of the facility in the east end of the parking lot from our high quality version. This is an example of the image quality we can feasibly capture during mapping missions.

To many Popham Beach enthusiast's delight the tidal inlet over the past week and a half dramatically switched it's course to a more direct route to sea. For the long term this means that the beach will be much larger and erosion will not threaten the dunes by the parking lot. We captured data before and after the channel shift and will be analyzing the associated sedimentological changes. The new tidal channel can be seen in the southwestern portion of our map.

Manta EPP Build

2010-03-14T18:00:00.000-07:00

After weeks of waiting around for parts all of the parts of our new UAV airframe came and we started building.

Here is an outline of the materials we used,

EPP Manta Flying Wing from Rob @ flyingwings.co.uk

1100 KV Burshless motor from Grayson Hobby

APC 9x6 pusher prop

Packing and covering tape from flyingwings.co.uk

two HS81 servos

Following the build directions sent to us by Rob and Gary Mortimer, the build took 6 hours max. During the build we documented the process.

Cutting the hole for the HS81 servo with a pocket knife in the wing.

After installing the servo, we sank the control line into the foam so that it wouldn't effect the covering of the plane.

The tremendous amount of space in the Manta makes it easy and stress free to pack all of the batteries, camera and Attopilot sensors and wires into the fuselage.

Our RX-7 Radio for scale.

Now that the servos and motor are installed its time to cover the wing.

A closer look...

After spraying the bottom of wing with 3mm spray on adhesive, we covered the leading and trailing edges with packing tape. In addition we covered spots that we thought would have contact in landing, like the bottom of the fuselage.

Next we covered the fuselage with covering tape. Despite flying a British/South African design and built aircraft, we went with a USA theme covering job.

The covering tape is much lighter than the packing tap and provides structural support and protection of the EPP foam.

A closer look...

To keep weight down, we minimized overlap and only put down one layer.

The finished, patriotic product.

The directions were vary easy and the build went off with out a hitch. Stay tuned for attopilot install pictures.

Old Glory Flight Test

2010-03-10T14:23:00.000-08:00

Today Foster and I finished building our EPP flying wing and went out for a test flight on Runnals Hill. After a few failed launches we trimmed the control surfaces to provide more initial lift. With the adjustments we we're able to fly for about half an hour. The platform is amazingly quiet and super resistant to crashes.

Here's some videos of the flight. We'll be posting build photos soon.

Near loss of UAV Leads to New Airframe

2010-02-28T18:15:00.000-08:00

Two weeks ago we launched our UAV on a routine flight over the Colby campus in light winds. After hand launching the Easystar based UAV form the Lacrosse field, I flew the plane up to about 200 feet AGL (above ground level) and switched over to autonomous mode. The plane started gaining altitude in a circle pattern to the mission perimeters of 400 feet AGL. As the UAV gained altitude, the wind picked up and pulled the plane towards I95. At first we thought that this was merely the UAV following its flight path, but as the it flew farther and father away we realized that something was surely wrong and I retook manual control. By this time the plane was merely a speck on the horizon and I had no idea of the planes orientation because of the planes circling patterns. Operating on false instinct I picked a direction and leveled the plane out. Unfortunately, i guess wrong and steered the further away from us. Flustered, I attemped to gain altitude and turn the plane around, but by this time it was to late and the plane dropped bellow the horizon about a mile from the original launch.

Fearing the worst, Dan and I raced to the car and headed in the direction of the crash. Using a tree as a point of reference we drove up a drive way and to our surprise found the Easystar UAV laying a field of snow unharmed by its emotional run from home. Seriously shaken by the near death of our UAV, Dan enlisted the help of the godfather of our UAV's AttoPilot, the much revered Dean Goude. After looking at the metadata from our flight, Dean sent us this email,

"Daniel,

I plotted stabilization data from the 6 flights contained in your LOG file, and compared changes in behavior with tuning progression. I didn't realize (maybe forgot) you are flying a super dynamically stable airframe. This explains the inability to tune pitch stabilization, at least with the recommended forward C.G. for this airfame type. Too low pitch P gain (in SET line $5) then pitch won't hold to target (pitch tends to stay level no matter what) and higher P gain (you went from 10 --> 25 between flight #2 and #3) causes gross oscillation. If pitch is positive there's natural presure pushing nose back down, but with symmetrical gains. On the other hand, Atto simply considers pitch error symmetrically wether or not actual pitch is above or below target. In other words, magnitude of elevator deflection depends simply on pitch error and direction of control surface depends on sign of the error.

AttoPilot's 50Hz attitude control isn't required for such stable planes, and in fact the inherent stability of airframe is a strong detriment to good tuning and flights. Atto is wanting (and more than able) to stabilize squirrely planes but an overly stable model (anything with "Easy" in the name probably) is just fighting Atto from doing its job.

Chris McNair and I talked about this at length on the phone today. As you might know Chris has a Masters in aerodynamics... and his insights here were really key to us figuring out how to help you. Our recommendations to progress on tuning:

1) Move the C.G. rearward, and do so enough so that the airframe is noticably less stable in pitch. Another option is to switch airframes to something with much less dynamic stability... planes with little or no dihedral and with wing NOT much above centerline of airframe. Think of planes like E-Flite Funtana (zero wing dihedral, wing vertical placement positiondown low and on the centerline of thrust)

2) Re-start the tuning process, but with certain values "seeded" as follows:

a) Turn down Alt_D from 10 to 5

b) Steer D to 0 or 2 at most, depending on the amount of dihedral. Polyhedral wings (rudder planes like Miss2) require 0 on Steer_D, but since you have some aileron wing version, and I assume it has only di-hedral (not poly) then maybe 2 on Steer_D. Dynamically stable in roll means Steer_D is not needed very much

c) turn all servo D gains to zero.

I have been able to tune airframes such as yours (Miss2 Old Timer type), but my most honest opinion is these airframes are for simple beginner RC pilots to learn flight. They make great FPV platforms in RC mode, or with simple autopilots like Picopilot (which in fact is tailored for motor gliders, and only similar planes), BUT they are not good airframes for 50Hz attitude control.

Don't get me wrong, I am not saying Atto can't control such planes, but not with nose-heavy CG. De-stabilizing the pitch will allow Atto to control pitch much better. I am working with some customers that use powered parachutes, and they absolutel must control altitude via throtte. Once I get this behavior option coded in and available via SET file, it will control the "Easy" style plane altitude much more directly even with typical nose-forward C.G.

Try the suggestions above, and I do think we can make it work for now. When I say move CG more aft I mean by a healthy amount; perhaps (probably) just outside the recommended rear limit by manufacturer.

Dean
--
AttoPilot LLC
Dean Goedde, Manager"

In layman's terms this means that our Easystar was too inherently stable, sending the Attopilot on a form of infinite loop, and that the Attopilot effectively spent all of its time fixing a problem it couldn't fix. Effectively our highly capable autopilot is designed to fly planes that are harder to fly than our Easystar and doesn't handle inherently stable airframes. This failure to stabilize combined with the high winds caused our near catastrophic crash.

So Dan and I went back to the drawing board. We needed an airframe that was inexpensive, crash resilient, had a large payload, less stable than the Easystar and could handle the variable weather of central Maine. After many hours of research, Dan and I settled upon an EPP Manta flying wing. Flying wings were originally developed during the WWII as long range bombers due to their high efficiency and ability to cary a lot of weight. Here is a video of the EPP Manta in action.

Manta EPP from Gary Mortimer on Vimeo.

Ours should be here on Monday and we will start building and testing immediately.

I-95 Winter fly over

2010-02-25T09:06:00.000-08:00

A few weeks ago Foster and I did a UAV mission over I-95. We configured out autopilot to capture a vertical image every 5 seconds. Post-flight we stitched together 9 images from the flight using PTGUI software. Click on the image below and you'll be brought to our Picasa page where you can download the photo. Zoom in and you'll be able to see some roadside details.

Placing our pictures on the globe

2010-01-31T15:25:00.000-08:00

Over Jan Plan I worked with Manny Gimond in Colby's Geographic Information System (GIS) lab. Manny taught me how to georeference our aerial photos using ArcGIS software. We use the software to ultimately assign a latitude/longitude coordinate to each pixel within our aerial photo. Once georeferenced our imagery can then be used by popular GIS software like Google Earth.

The tie lines here show points where pixels in our aerial image match points found in an already georeferenced aerial map. ArcGIS software uses the tie lines we demarcate to georeference our image.

Here's a screenshot of ArcGIS showing our georeferenced aerial photo of Colby's new football field. Soon we'll be able to use our UAV's on board GPS unit to record the place (lat/long coordinates) at which each of our images are taken. In the future this GPS meta-data will help us automate the georeferencing process.

Popham Beach

2010-01-30T10:51:00.000-08:00

Over the last two weekends I've been venturing to Popham Beach in Phippsburg, Maine for a geology project. I'm investigating the dune erosion caused by the encroaching Morse River. The Morse River is eating up the sand barrier which houses the foundation for a new bath house constructed in the last few years. I hope to document the erosion with aerial photos captured from our UAV over the spring semester. In doing so we may be be able to evaluate erosion, deposition, and sediment flow rates of Morse River.

A video I captured flying our small V-tail hornet remote control over Morse River. There was no autopilot on board so the flight's a bit shaky...weak stomached beware!

Picnic benches down at the margin of erosion.

The new bath house complex standing ominously in the distance.

View of the Morse River with Tucker for scale.

A video Foster took of the Morse river. This is active Geology!

Waypoint Flight over Colby

2010-01-14T16:08:00.000-08:00

Today Foster and I along with a few guests flew a 6 way point path over Colby. We used Google Earth to plan our flight and upload 3 dimensional way points to our autopilot. Our planned path is delineated below in white. Our actual path is shown in pink. We took off at the turf field, flew over Johnson Pond, around Miller Library, and over the football field. Next step is getting our camera to fire images at distance intervals while in flight.

Analytics from Friday's flight

2010-01-11T17:03:00.000-08:00

Our autopilot records flight data 5 times per second while in the air. Manny Gimond, the GIS instructor at Colby, helped us manipulate that data in Excel and graph some of our flight metrics vs. time. The graphs depict a time series of autonomous mode sandwiched by two manual modes. During manual modes the plane is either taking off or landing and we are in control through a radio. During autonomous mode the autopilot is in control and attempting to achieve mission targets.

Mission targets:
Flight path - holding circle (picture in our last blog post)
Altitude - 208 meters above sea level
Speed - 45 km/h

Autopilot Adjustments

2010-01-09T12:56:00.000-08:00

In order to adjust the way our autopilot controls autonomous flight we tinkered with parameters defined in it SET file. The SET file defines particulars about an aircraft which assists the autopilot in flight. Our goal was to control the planes altitude control more effectively. With help from the attopilot's creator, Dean, and other's at support forums, we decided to change the pitch and roll gains. Higher gains equate to higher physical responses to changes in pitch and roll. We need higher pitch gains in particular because our plane has a large glider like wingspan. After a few flights with different pitch gain adjustments we we're able to control altitude much better in our holding circle. Here's our flight path from google earth. The plane held altitude at around 130 meters above ground.

Google Earth Flight Log

2010-01-06T13:57:00.000-08:00

Attopilot records over 70 flight data parameters at 5hz into its "black box" aka log file. Using ground control software we can upload the log file into google earth to visualize the flight track. Here's a 3D screen shot of the flight path in google earth. The white path indicates remote control mode while the red indicates autonomous mode. You can see on the flight path where we retook radio control at the crest of the flight pattern.

First UAV launch

2010-01-05T16:38:00.000-08:00

Today Foster and I launched our UAV for the first time out of the Colby lacrosse turf field. We set the plane to fly a circular holding pattern around the field to see how the autopilot controlled the planes stability, altitude, and velocity. We launched the plane in remote controlled mode and switched into autonomous flight mode soon after. The plane flew very stably with a consistent airspeed but continually gained altitude beyond the limit we set in the autopilot. We believe this has something to do with the elevator control surface servo which we'll test out again this week. Here's some videos of our first autonomous flight.

Autopilot Ground Test

2009-12-14T13:08:00.000-08:00

Today we tested the thermopile sensors of our autopilot. They stabilize the plane in yaw, pitch, and roll by analyzing infrared heat discrepancies between the sky and land. The videos below show our test.

Over January we will mount our digital camera beneath the Big Easy's wing and start making maps of Colby's Campus.

Autopilot installation

2009-12-13T18:06:00.000-08:00

Over the past few days we have been configuring and installing the brains of our UAV, a.k.a our autopilot. We decided to use an "off the shelf" autopilot called Attopilot V 1.8 which navigates by using a GPS sensor and pre-loaded 3 dimensional waypoints (longitude, latitude, and altitude). The Attopilot manipulates 4 control surfaces (rudder, elevator, ailerons, and throttle) to both stabilize and control the plane along its set course.

This is the cluster of wires coming out of the Attopilot. These wires connect to the remote control radio receiver (Rx), control surfaces, and sensors.

Thermopiles
The XYZ thermopiles detect long wave infared light anywhere from 5.5 to 15 microns in length and log this data at 5 hz (5 times per second). The thermopiles are used to detect a heat gradient between the land and sky in order to stabilize the aircraft in yaw, pitch, and roll.

Picture of the XY thermopile.

Pitot Tube
The pitot tube determines the plane's relative airspeed by calculating the pressure differential between an externally and internally mounted tube. As the plane's speed changes the pressure from the external pitot tube should change while the internally placed tube's pressure should remain constant.

1/8'' diameter brass pitot tube. Tucker used a mini pipe cutter to trim the length of the Pitot tube.

Power Sensor
The power sensor falls in line between the electronic speed controller (ESC) and the Lithium Polymer batter (Lipo). The sensor measures and records the voltage and amount of miliamp hours consumed by the Lipo. The milliamp hours can then be divided by kilometers traveled to create a "mileage" of sorts in order to assess flight efficiency.

Global Positioning System (GPS)
The GPS use a number of satellites to triangulate the planes position.

GPS is the square sensor mounted on the nose of the fuselage.

Easy Star fuselage modified with Easy Glider wing. In our final setup we will attach our Pentax camera beneath the wing.

Attopilot Case Design/Build

2009-12-13T13:15:00.001-08:00

Given the high cost and delicacy of the Attopilot, we designed a case to protect the device from impact in the event of a crash. We wanted to strike a balance between accessibility and protection. This meant being able to remove the Attopilot from the case with ease while also ensuring a tight and secure fit.

We started with some basic pencil and paper sketches before moving on to a 3D Google Sketchup model and then the real deal. We made a box out of plexiglass (cut by an exacto knife and fixed with super glue) and hot glued packing foam to the walls. For vertical stability we glued some EPP foam to the underside of the top of the case. We also built a removable door with holes for the two 1/4 inch silicon pressure sensor tubes. It is secured in place with an elastic band for easy access.

Sketchup model of the case without the foam or the removable door (download the file here)

Notice the opening in the top to run the wires out of the case

Pano image stitch

2009-12-07T08:05:00.000-08:00

I used a free trial version of Pano stitching software to stitch together two of our aerial images from last friday. The software detects visual similarities between pictures and overlaps them based on those control points it creates. Here the software used the white soccer field lines to mash the two pictures together.

For our map making we will be using photo stitching software called Pic't Earth. Pic't Earth will use the GPS meta data associated with each of our images to stitch them together and georeference them on a digital map.

Google Earth Vs. Colby: I-95

2009-12-06T15:55:00.000-08:00

Here's a comparison of the image we captured roughly 250 feet above I-95 to the same stretch of highway in Google earth. Our picture below has no post-processing digital zoom. We used our Pentax Optio A40 12 megapixel camera fixed below the wing of our EPP Hornet to grab the shot. This image represents the photo quality which we'll use to construct aerial maps.

The Inevitable: Plane Crashes

2009-12-06T15:50:00.000-08:00

The question is not if you will crash an RC plane but when. Over the last two months, we have spent hours climbing in trees, running anxiously through fields, and climbing over hills to find our crashed planes. All of our planes have crashed at least once and many have been retired to garbage cans and recycling bins throughout the Maine area. Anticipating these imminent crashes, we opted to go with foam airframes from early on. Not only are foam airframes very resilient but they are very easy to fix. Quick fixes maximize the amount of time we can keep are planes in the air and greatly decreases the amount of time it takes to learn how to fly.

Here is a brief tutorial we made that shows how to fix EPP with a glue gun. We were flying again 60 seconds after the end of the video.

A crash on the Maine Coast near Fort Williams in Cape Elizabeth.

First images with our Pentax Optio A40

2009-12-06T09:45:00.000-08:00

Last Friday Foster and I went out to the Colby soccer field with our Pentax Optio A40 12 megapixel camera to test our remote image firing system. We attached an Infared Prism trigger to our camera and Rx reciever on board of our EPP v-tail hornet. Flipping a switch on our remote control radio triggers the Prism to send a infared signal to the Pentax camera to capture a digital image.

Foster and I testing the Prism trigger with the camera mounted under the wing of the hornet.

From Build Log

We sent up the plane and took some pictures of the soccer field and I-95. The high winds (20 mph) made it difficult to stabilize the plane for clear pictures, we did manage to get a few good ones though. In the upcoming weeks when we install our autopilot sensor suite onto the plane it should make for much more stable flights (i.e more consistently sharp pictures). The autopilot uses infared thermopile sensors which detect the heat gradient between the sky and land. The autopilot software uses this gradient to stabilize itself in yaw, pitch, and roll attitude directions.

Here's some of the sharp pictures we captured.

From Build Log

Here's some of the blurry images. We think this was caused by a sudden change in yaw, pitch, or roll of the plane's attitude mid photo capture.

From Build Log

Flight Tests on December 2

2009-12-02T21:21:00.001-08:00

Today, Dan tucker and I were at the field testing airframes. We tested the standard Easy Star with an extended rudder with both 2 cell and 3 cell batteries, the Easy Star with a modified Easy Glider wing with the 2 cell and 3 cell, and our new V-Trainer with both the 2 cell and 3 cell batteries.

Discussion of a 3 cell lipo.

The EPP V-Trainer. We are thinking of using this for mapping in places without fields to land such as beaches and mountains.

Our Easy Star UAv airframe.

A look from above over Frat Row and Miller with an Easy Star with a 3 cell lipo.

Blackberry Video

2009-11-30T07:44:00.000-08:00

Foster and I wanted a cheap way to grab some First Person View (FPV) footage to show to our professors, friends, and family as a proof of our concept. We decided to cut a hole in our Easy Star air plane fuselage to mount my Blackberry Curve. Mounted in our airframe my Blacberry could capture low quality video. I bought a 2 Gigabyte SD card from Rite Aid for $19.99 to increase video storage space and the phone was ready to film. Although the video quality is rather poor we think the smartphone serves as a cool platform to broadcast FPV in real time through its data channel. The mobile app Ustream could help us and others broadcast live video streams to the internet. Now I just have to convince my friend to mount his iphone 3GS onboard and we'll get some better quality!

This flight below was filmed with the Blackberry. We were flying RC but will be integrating attopilot into our easy star as soon as it arrives.

UPDATE: The new Motorola Droid phone has the capability of broadcasting 720 X 480 video live through Qik. See an example video here.