The MakerBot is finally here! After waiting around for 2 months (8-weeks), it suddenly showed up one afternoon in May. Yes, I know, here it is July and I am finally posting about it. I just haven’t had the time to finally put everything up. I have had too much fun printing things!
The story of how it came to be was simple. I remember being at a Home Brew Robotics club meeting about two months ago, and having a conversation something to the effect of …..”If you wait another month to order it, that will be yet another month you will kick yourself that you didn’t order it” ….I ordered it the next day! Eight, nail biting weeks later, it showed up!
Yay, I am printing things in 3D!
It was very easy to to set up, and make some few initial prints with it, however, it was difficult to get the print quality to be good and consistent without modifying it. MODIFY YOU SAY?? YES! Time to hack it and I only had it a week!
The first big problem was, that printed parts would not stick to the build platform, and tear itself up early in a print, or that corners of the part being printed would peel up, and you would end up with a warped item. Much discussion online pointed to the problem that the building envelope was not fully enclosed, so any breeze in the room could cause strange cooling effects on the plastic being printed, and allow it to let go of the build platform.
Modification #1 – Enclose the build area with a hood, and covers out of Laser Cut Acrylic
I downloaded this design from ThingVerse and modified it to suit my needs:
Modification #2 – Level the Build Platform
I found this little mount for a dial indicator on ThingVerse, printed it out, and in no time I was able to level my build platform completely using a dial indicator I already owned.
Next thing I know, I have beautiful prints coming out of the machine!
Robo-Magellan Robot Project – “Odyssey”
After many months of effort, here is Odyssey, our SRS/Servo Robo-Magellan contest entry. What is Robo-Magellan you ask? It is a contest devised by the Seattle Robotics Society, inspired by the problems to be solved for the DARPA Grand Challenge. It is an outdoor, autonomous, robotic navigation contest. A Robo-Magellan robot must be able to autonomously drive around a 500ft. square area of the Seattle Center, avoiding trees, rocks, park benches, garbage cans, light posts, railings, sculptures, and many other obstacles, and find orange road cones placed at specific waypoints. The GPS coordinates of the cones are given out 30 minutes in advance of the contest, and the robot that navigates autonomously from the start to the finish cone in the shortest amount of time, wins the contest. The only remote control that is allowed is for a safety shut-off switch should the robot run into trouble. Each robot gets three tries to navigate to the final cone. The best time of three is used for their final score.
Our robot is a monster. The contest rules state that the robot cannot weigh more than 50 pounds, Odyssey weighs in at 48 pounds even. Bob and I have worked hard and long on this robot, and inside, it contains a culmination of all our electronics efforts to-date. Of course, this robot would never have come together, if it weren’t for our sponsor, NPC Robotics (plug-plug). They provided the excellent motors, and a motor controller that can easily move this beast over almost any terrain with ease, without any shortage of power or torque.
Bob shot the initial snapshot above during the final assembly phase of the robot. Notice once again, Bob’s excellent CAD design, and how close the final product closely resembles the drawing. I think the only major changes that were made was the tail-wheel assembly, and the location of the GPS dome. Since weight was such an issue, Bob literally weighed every nut and bolt on the robot, and had the CAD program calculate the final weight, so we knew if we built the design, we would be under the 50 pound weight limit.
Here is a laundry list of technologies we have on-board:
Almost every single board in our BotStack robot bus, main, sensor, CPU, navigation, camera, radio, and motor control.
Environmental Grade Sonar Array
GPS System with WAAS correction
6-degree of freedom inertial guidance system (The grey box on top of the robot)
2-axis Magneto-Inductive Compass
20fps Camera & Computer Vision System
R/C Receiver for Remote Safety Fail-Safe.
12v Permanent Magnet Motors with optical-encoder feedback for closed loop control and odometery.
100amp Motor Controller
Here is another photo of it from the front, and the inside:
Navigating the Robo-Magellan course could be accomplished in a number of different ways. We chose to use GPS, combined with a 2-axis compass, and a home-brew inertial navigation system. We chose a WAAS enabled, OEM model of GPS unit made by Garmin. The GPS-18 LVC. Since it is an OEM unit it needs a mechanism for reading and storing waypoints, off of the robot. We built this nifty handheld unit to walk the course and store the waypoints, and then download them from the handheld device into the Robot just before the competition.
Here is our home-made inertial navigation unit. It has three ceramic gyro’s, and two accelerometers to yield 6-degrees of freedom of inertial measurement. The compass board mounts just below the gyro board, with the same footprint, and all of this is housed in the square box on the top of the robot. All of these measurement instruments, combined with the GPS should give us fairly accurate position and heading computations as the robot moves through the course, with or without a consistent GPS signal.
Finding the Cone:
Tracking a red or orange target and driving a robot to it is a problem we had already solved before on two other robots. The tabletop challenge robot finds a red box on a table and pushes it into a shoebox, and the balancing robot tracks someone wearing red and follows them around. Operating outdoors is the only additional challenge. The lighting conditions can vary dramatically. ere is the view through the lens of the camera looking at the cone outside.
|Direct Sunlight wo/Filter||Direct Sunlight w/Filter|
|Shadow wo/Filter||Shadow w/Filter|
I spent a considerable amount of time looking at the cone under various scenarios, such as the robot being in the bright sun, with the cone in the shadows, or visa-versa. Notice that the cone becomes quite washed out in direct sunlight, and the reflection makes it almost look white. The addition of a neutral density filter seems to cut back on this problem, but creates additional issues when the cone is in shadow. It has a tendency to make the cone blend in with the background, and not stand out when in shadowed conditions. Currently we are using a CMUcam-2 as our vision system, however, we are currently working on our own FPGA based camera system in order to do assist with multi-target tracking, and high-speed vision processing of the terrain the robot is traveling over and around.
The Robo-Magellan Contest 2004:
The contest was tremendously fun! I think out of the 12 robots who entered, 10 of them showed up for the contest. The course was much more difficult than I anticipated. In hindsight I should have shot more photos of the course, and where some of the cones were located. It was tricky to say the least. The starting point was on a small asphalt path back in a grove of trees, right up next to a building. Most of the contestants GPS did not work properly in that location, so it made for an interesting start. I don’t think any of the contestants emerged from the wooded area on their first try. They all ran into rocks, or trees or got stuck along the way somehow. Each time had a bit of time between each trial, so I think most of them did some minor tweaking to get out of the woods by their 2nd try.
As you can see from the photos, it was fun for the spectators too. It was like watching a golf tournament. The robot would move along its course on the way to the cones, and this big crowd, of what seemed like over a 100 people would follow along to see how the robot would fare. Usually there was a big cheer or gasp from the crowd every time one of the robots cleared a difficult obstacle, or happened to run into an obstacle or get stuck. It was really exciting to watch.
Dave Hylands shot lots of video, and some excellent still photos of some of the competitors. He needed a website to host all this great stuff, so I volunteered. Here are all of Dave’s photos and videos from Robothon 2004.
There was lots of stress, and last minute preparation to get our entry going, but it finally all came together. Here are some photos and video clips of Odyssey during it’s second and third try to reach the final cone. The photo above is the 2nd try, and the photo to the left is the 3rd try. We ran into a rock about 20 feet from the starting line on our first try. Once again, although you see Bob holding a remote control unit in his hand, it is only used as a safety shutoff. This robot is totally autonomous.
It was a difficult contest. For the first year the contest was held, I thought it was excellently orchestrated, and I was impressed with how many robots showed up at the starting line on Saturday morning. Out of all the robots, and all their three runs, nobody touched a cone. It was that difficult. Since nobody reached the final destination, the judges made a subjective decision on who the winners were. How did we do in the contest? We placed 2nd. Here we are with the robots, and the awards at the Robothon. Flexo, the latest incantation of the balancing robot with the camera on top, took the “Best Engineered Robot” award in the open category for the show.
RoboMagellan at the SF RoboGames 2005:
Although we had several months to make improvements after Seattle, of course we waited until the last minute to really get cranking on the lessons learned from Seattle. Here is Odyssey making his third and final run during the RoboGames.
Here is how our runs went:
On our first run, we had major software problems, and ended up not able to make the first important turn in the course, thus sending us off down into some trees that were the wrong way to the destination.
We made a few software changes for the 2nd run, that were hastily implemented, and prevented Odyssey from even getting off the starting line…so we had to forfeit our second run.
Our third run was the best of all. We navigated away from the starting line correctly, made the correct turns to navigate down the starting ramp, and out onto the course. We navigated correctly about half way to the destination cone, got near the grove of trees, and lost the GPS signal. The dead-reckoning code that was supposed to take over to keep Odyssey on track, had a bug in it (of course). So, he ended up navigating a path perpendicular to the destination. Our obstacle avoidance was working flawlessly. We successfully circumnavigated a flower bed, and many plants without driving into them. Odyssey finally got a good GPS signal again, turned around and started heading back to the destination, but by then it was too late. Another bug in the code caused him to stop dead in his tracks about 1/2 way to the destination. The run was good enough to take 2nd place (the silver medal) in the competition.
Lots of excitement! We are definitely looking forward to doing this contest again in the future. I guess several other clubs are talking about holding Robo-Magellan contests, so it will be nice to have more opportunities to compete with our platform. Either way, we will be there next year in Seattle for the 2005 Robo-Magellan.
Here are the vital stats on the F-14 Tomcat:
|Constructed from plans designed by Matt Halton in the UK.|
|Blew the plans up to 123% original size so the plane could accept 90mm fans.|
|All balsa sheeted construction with tissue-dope covering.|
|Twin Schubeler DS-51-3PH 90mm fans. Obtained via ShredAir.|
|Twin Hacker B50-10XL brushless motors. Obtained from ICARE in Canada.|
|Twin Schultze 80bo speed controllers.|
|SpringAir 305 retracts|
|44 x Sanyo CP-1700 cells|
|NOT YET FLOWN! Almost complete!|
Here is the construction sequence for the Tomcat:
Here is the initial layout of the fuse formers. One of the other early Tomcat builders pulled the fuse parts into Autocad, and laser cut fuse parts. These fuse parts are now being sold by Jet Hangar Hobbies. Saved me lots of time in front of the scrollsaw.
I have the formers together now, and part of the bottom sheeting applied, plus my initial ductwork fitting. I am using stiff paper card for the ducts.
Here is my early fitting of the GX parts that form up the inlet ramps, and wing glove area.
Here is the glove rough sheeted, but not yet sanded. Notice the fuselage sheeting is starting to come together at this point too.
In order to bend ductwork out of heavy card, I made some duct forming tools out of some dowels and some of the duct punch-outs from the fuse formers.
I reinforced the ductwork in places where it still seemed weak with some strips of 3/4 oz./in. glass cloth and epoxy resin.
Most of the ductwork is in here, and I have some of the fuse sheeting complete. The duct transitions are held together with a bead of thick CA glue.
The motors and speed controllers showed up from ICARE. It took awhile to get them (about 2 months), but it was well worth the wait.
I have most of the bottom sheeted, and the nose wheel is test fitted into place.
Sheeting the bottom of the plane goes VERY slowly. I used 3/8″ strips of balsa, and planked the bottom with them. I used aliphatic resin to glue the strip into place, which has a slow (30 min) curing time. It’s slow going, but I end up with a much better, and sand-able finish than doing it using CA glues.
Took me well over a month of evening and weekend gluing to sheet the bottom of the plane. Here it is, starting to fill now and sand. I use lightweight wall putty to fill in the cracks and divots.
Whoops! Problem. The sheeting doesn’t line up right with the fuselage edge. Notice the lip. I had to break this joint loose, and re-glue it with a shim in place to hold it out so it would be flush with the 3/32″ balsa planking I was using.
Here I have started planking the turtle-deck area to get ready to work on the cockpit.
Working on the inlet ramps here, and completely sheeting the wing gloves. Lots more filling and sanding to be done. My arm is sore at this point.
Nose gear is now permanently mounted into the plane. I built up a mount out of spruce, plylite, and epoxied the gear mount down using carbon fiber laminate.
Main gear now mounted into the plane also using spruce mounts, reinforced with carbon fiber laminates.
Carving a nose out of pink foam. I cut a foam blank from the per-plan 2d pattern, and made a 3d foam blank. It took me 5 tries to get the blank the right shape. What a huge mess I made! Pink foam all over the garage.
After some initial shaping, I mounted the pink foam blank on the plane, and sanded to shape. A little bit of wall putty to fix the tip of the nose, and the transition, and then I was able to cover the nose with 1/2oz. glass cloth and resin. A little wet sanding later, and my nose is looking permanent. Here is a photo of the recently sanded nose, pre-glassing.
Starting to look like a Tomcat now!!!
Another eZoner, Admiral Red, worked up these beautiful wing templates using Compufoil and Autocad. He emailed me a DXF file, and I printed them out, and cut wings from the design. Here are my freshly cut ribs laid out on the printout, ready to construct a built-up wing.
Here are the wings, single-sided.
Time to make a REALLY strong set of wing spars. I was guessing the AUW of the plane would be over 12 pounds. I knew I needed them to be bulletproof. I laminated together pieces of maple, with lite-ply in an I-beam formation using 2 hour epoxy.
Here is a spar being test fitted into the wing.
More test fitting.
Wings are finished and ready to go!
Lets put them on the plane and see what she looks like!
Here is my initial cockpit decking, with some rubber pilots sitting in their seats.
Carved some radar, and cockpit instrumentation out of pink foam.
Gluing the canopy on. Pilot is really in there now!
Starting to construct the taileron boxes. I built, tabbed, interlocking ply pieces that contoured to the shape of the rear of the plane.
Here is the first one, glued into place with a test servo in there. I ultimately went with larger servos than this, but it was a good test fit.
Here they are all mounted. I have some real control surfaces finally.
Time to mount the fans, and tailcones. Look at those nice, pink foam tailcones covered in light glass. I turned them on a drill-press and used a piece of 80 grit sandpaper to shape them.
Mounted the rudder servos and the control rod tubes, as well as the pneumatic air tank for the retracts.
Time to build a battery mount. The tray is made out of 3/32″ birch ply with velcro straps to hold the batteries down. This system has worked quite well in other planes, and I trust it fully.
Here is a battery pack. 44 cells of CP-1700. 2kw of power ready to ride!
Starting to sheet the FOA area so the wings tuck into place.
Time to build the main hatch out of balsa, and getting it all puttied up to sand.
Covered the hatch with 1/2oz. glass cloth and resin to make it nice and strong.
Wing sweep area all done. Ready to start thinking about how I am going to mechanically sweep those wings!
Here is a jackscrew I bought from Janeco through the back of an AMA magazine.
Initial bench testing suggests that with a 9v supply, this jackscrew can supply 20 pounds of force. Here I have it hooked up to a fish scale to measure power.
My initial attempt at building a bell-crank to make the jackscrew work. I am having all kinds of problems getting the wings to sweep evenly with my bellcrank. I ultimately ended throwing this design away, because the uneven sweep issues. Another Tomcat builder in the UK, has built a promising jackscrew system using a programmed PIC and limit switches specifically designed for this Tomcat design. Here is a link to his website, for photos, and even a QuickTime Movie of the jackscrew working in his plane: http://www.freenetpages.co.uk/hp/geoff.sim/
I am very concerned that the wing pivots will be strong enough. So, I obtained some aircraft composites to reinforce them. Carbon-fiber-nomex, reinforced with kevlar cord to keep the nomex from delaminating.
After fooling with the jackscrew for over a month….I have put it aside. Here is my backup plan. 2 quarter scale servos. 12 pounds of torque, each!
Here they are mounted in the plane for some tests. I need to make some aluminum servo horns that are longer than these so I can get the total sweep out of the servos. This is where I am at currently, although some more work is going to be required to finish.
I have remounted them more securely now. I have carbon fiber rods going to the wings. I hoped to complete the maiden flight under this setup.
Oh wow! What a mean looking pair. Someone parked a small carrier air group in my driveway!
All sanded, covered with tissue, dope and sanding sealer. Then, primed with a basecoat of white, oil, primer.
First coat of ghost grey is now on her. I used Testors model masters, oil paint, thinned, and shot through an airbrush. It’s a mess to clean up, but man does it go on smooth.
Tails and cockpit area now painted black. Here it is, test fitting.
Made home-made graphics using Photoshop, and lots of pictures of real Tomcats.
Whoops! I messed up. I mounted the skids on the plane backwards, and had to rip them off. Bummer, I messed up my new paint already.
Here they are…mounted correctly. Oh well…it’s the bottom…less people will see the color issues. I thought I would add a tailhook as long as I was working down there.
Here she is…initial paint and decals applied.
LATEST UPDATE: I am still working on the wing sweeping mechanism. I started out with one jackscrew I bought via the AMA magazine, and it was powerful, but slow, and difficult to mount because it would need a bellcrank. Another Tomcat builder in the UK, has built a promising jackscrew system using a programmed PIC and limit switches specifically designed for this Tomcat design. Here is a link to his website, for photos, and even a QuickTime Movie of the jackscrew working in his plane: http://www.freenetpages.co.uk/hp/geoff.sim/
For now, I have settled on using some huge 1/4 scale servos. Here is my current setup I hope to complete the maiden flight under:
Video Clip: Tomcat Wing Sweep (Windows) - 885k – Video of the Tomcat wings sweeping. This is a short clip of the wings moving forward and back under the power of the wing-sweep servos.
Total Construction Time = Countless Hours – I started this project over a year ago, and it still is not done. Each photo at different phases of the construction represents many hours of work. This is easily the most difficult plane I have ever built, but it’s well worth it!
Here are the vital stats on the Schreiner F-18:
|Schreiner F-18 kit from Schreiner/Savex in Germany. Dieter from ShredAir in Oregon was able to import the kit for me.|
|Twin Schubeler DS-51-3PH 90mm fans. Also obtained via ShredAir.|
|Twin Hacker B50-15L brushless motors. Obtained from ICARE in Canada.|
|Twin Schultze 55bo speed controllers.|
|SpringAir 305 retracts|
|44 x Sanyo CP-1700 cells|
Unpacking and construction sequence:
The plane came in a huge box via airfreight from Germany. It showed up about a week before Christmas. Here is what it looked like when I unpacked the box, and started looking at the parts. Notice the big box in the background on the floor.
The parts were well made. The entire plane came pre-painted with lots of nice detail.
One of the most difficult parts of making EDF jets is the inlet duct forming. This kit comes with pre-formed inlet ducts, that are very well made.
The outlet ducting is similarly well constructed.
Taileron bearings are pre-installed.
Interior of the plane is bare. You need to scratch-construct the entire interior yourself. So although this plane is an ARF on the outside….it is definitely not an ARF on the inside.
Notice the detailing of the paint and decaling.
Here is what it looks after press-fitting all the parts together out of the box.
The construction started out by obtaining the missing parts…fans, motors, batteries..etc. The plane was difficult to get, the fans were almost equally difficult to aquire. These fans are also made in Germany by Schubeler Jets. They are 90mm fans, made out of carbon fiber, and are literally functional pieces of artwork.
This plane needs lots of cells. I chose to go with the 4/5 sized, sub-C cells, the Sanyo CP-1700. I did some motocalc calculations running a 90mm fan, with a Hacker B50-15L, and came up with 22 cells per motor. By going with the 4/5 sized cells, I was able to save 16 oz (a whole pound!) of battery weight over using standard sub-c’s.
The Schreiner F-18 is not designed to carry landing gear. It is designed to be a trolly-launched, belly flopper that you land on a grass surface. Since I wanted to be able to ROG, I cut holes in the bottom, and made these landing gear mounts. I mounted SpringAir 305 retracts in the plane, and used 1oz glass cloth, and epoxy resin to mount the gear into the airplane.
I made a custom fan mount out of 1/16″ lite-ply, with a basswood base. The fans are each cradled in one of these mounts.
The fans are secured to the mounts, using high-temp RTV, and the ductwork is held to the inlets and outlets using duct-tape.
Here is a shot of the battery tray mounted in the plane, with batteries in-place.
Here is a bottom view of the retract, mains. The cutouts were made into gear doors that close when the gear is retracted.
Since the plane was designed to be a belly flopper, it needs LOTS of angle of attack when rolling on the ground. The first flight was less than successful because I did not have enough AOA. I couldn’t get off the ground and crashed into the grass off the end of the runway. There is excellent video of the first flight attempts in the video library.
Here it is…all finished and ready to fly. WOW!
Total Construction Time = 6 months. The interior of the plane is completely custom made by hand. It took quite a-lot of trial and error to get everything to fit just right. It took close to 3 months to get the initial kit from the time I ordered it. It was approx. 1 year from the time I ordered it until I was ready for a maiden flight. Schreiner F-18 Videos
|Schreiner F-18 First Flight Attempt My first flight attempt of the Schreiner F-18 was less than successful. My landing gear was too far back, and not enough AOA on the wings.|
|Schreiner F-18 First Actual Flight (QuickTime) 10 meg – A few more takeoff run attempts, and it flies! Yay!|
|Schreiner F-18 Half-Moon Bay Flight Here is some footage of the flight at the Half-Moon Bay e-Fly during the Summer 2002. Good long flight movie, however, I still have yet to capture a good landing on video. Watch and see.|
|Schreiner F-18 Landing Mishap I lengthened my nose strut even more, for more AOA, and now I have some problems with ground control. I had a rough landing, clipped the safety fence at the field and tore the nose off the plane. Nothing a bit of lite glass and resin can’t fix….DOH!|
(03/27/05) – Flameout takes the Silver medal in firefighting at the 2005 RoboGames
(03/21/04) – Flameout takes the Bronze medal in the firefighting event at the Robolympics!
(10/29/03) – Flameout takes 2nd place at the Seattle Robothon
I built the first version of this fire-fighting robot, by taking Bob’s well designed base for the tabletop challenge, and bolting on a top platform with all the necessary fire-fighting gear. It’s first debut was at the 2003 Seattle Robothon, sponsored by the Seattle Robotics Society. All the additional sensors were a challenge to get debugged in-time for the event.
Bob and I got the hardware all debugged the night before we had to leave for Seattle, and I literally wrote most of the software on the airplane. The first time the robot set its wheels in an actual house, was the morning of the contest. All the software was written by looking at a printout of the map of the house on the airplane, and guessing at what the right thing to do would be. Anyway, amazingly, we took 2nd place in the competition! WOW! It was a-lot of last-minute stress to get everything working properly, but well worth the stress to participate in a fire-fighting competition for the first time.
Here is “FlameOut” looking for the fire at the event. I figured it was either going to put the flame out….or Flame-Out itself. I have to mention that only one robot…the one that got first place actually put the candle out. There was a good-sized crowd of spectators on-hand to see the fire-fighting robots in Seattle.
Both fire-fighting robots uses the same board stack Bob and I developed for the tabletop, with one additional board, specific for reading the fire-fighting sensors. The fire board reads the Hamamatsu flame sensor board, as well as the Eltec Pyroelectric sensor, deals with the servo sweeps, of the pyro is mounted to, and then distills all this info down to a digestible form for the main PIC to process. The motion control code is almost identical to the tabletop challenge, except that there are walls to avoid, and obviously, a flame to try and find. The onboard relay circuitry is hooked up on this robot, so I can power up a fan motor and blow out the flames when the robot finds the fire.
Bob has been dreaming of doing robot fire-fighting for years. He has built a fire-fighting house to practice strategy. Hopefully we can find a place to set it up where the winter weather won’t wreck it, and then we can practice more fire-fighting. After the Seattle Robothon, I pulled the firefighting gear off the robot, in order to re-use the base for the tabletop challenge. I designed a different base for doing cooperative swarm work, that I decided would make an excellent firefighting base. I bolted all the firefighting hardware onto this new base.
This 2nd revision of the base, is what I entered into the firefighting competition at the 2004 Robolympics, where it won the Bronze medal!
I learned many new lessons about how to make a fast, efficient firefighter at the Robolympics. I hope to leave this robot set-up in it’s current configuration so I can just improve upon the software for the next robot firefighting event.
RoboGames 2005 Firefighting Competition:
Here are video clips of many of FlameOut’s first two runs:
|FlameOut – First Run|
|FlameOut – Second Run|
Here I am on the left at the 2005 RoboGames accepting the Silver medal for FlameOut. Yes, the Gold medal was won by another member of the Home Brew Robotics Club, Tony Pratkanis. His robot Solenopsis Invicta, ran the house flawlessly, and with good time. Oh, and did I mention he is 13 years old? He put us all to shame with his well designed firefighter.