Howard Gordon's Posts (24)

Sort by

Yet Another Robotic Blimp (YARB)

Frustrated by difficulties in achieving adequate stability with my coaxial and quad flyers, and inspired by the efforts of Chris and Jordi with their BlimpBot project, I commenced yet another attempt to defeat gravity with a robotic entity.This new project employs a relatively inexpensive 66-inch helium blimp from RC Guys, modified for direct motor control using the H-bridge built into the radio board portion of the SRV-1 Blackfin board set. The build was pretty simple - the only real challenge was in mounting the vectoring servo in the gondola. I would guess that I have spent 2-3 hours total on the build.

I haven't yet mounted my other sensors, but wlll be adding two Maxbotics EZ0 ultrasonic ranging modules (forward and down views) and an HMC6352 compass. First, I need to work out flight controls and invert the video feed, so all testing thus far has been with the blimp tethered.

Here's the first captured (inverted) video from the tethered blimp - it's not very exciting to watch, but I am using the motors to rotate the blimp. Untethered flight should follow in the next 1-2 days.
Read more…

added duct to coaxial rotor

Big improvement in stability with the addition of a simple duct made from a sheet of 2.5mm RCF (extruded polystyrene) foam from rcfoam.com. The RCF is similar to depron that was recommended by another forum member, but somewhat more flexible and higher density. I was able to bend the RCF sheet to a 12-inch diameter, while a similar thickness depron sheet broke when bending.There is some yaw rotation at the beginning of the clip, but you can see toward the end that I got that under control, actually overshooting by a bit. Now that I have some semblance of control, it has become obvious that the current motor/prop configuration (CR2805 w/12" props) can't develop enough lift to get more than a few inches off the ground (i.e. out of ground effect), probably because there aren't enough windings on the motors (1430 rev/V), so I will have to return to the earlier CR2816 coaxial motor set, which weighs more but does have sufficient power.One other lesson which I mentioned on the forum - pre-flight inspection now includes a check that the electronics are secure. On the first test flight, the camera module worked itself loose and dropped onto the props -

Here's how things looked after I rebuilt the duct and replaced the camera (now secured with a cable tie)

Read more…

uav project update - fixed blade coaxial rotor

One of the uav projects I started last summer was a fixed blade coaxial rotor flyer that was steered by shifting battery weight in the style of the old Hiller Flying Platform . I put the project on hold while waiting for some lighter-weight brushless coaxial motors from Maxx Products (CR2805), and then got further sidetracked by the X3D-BL quad project.

This past week, I restarted the project, adding a mount for an SRV-1 Blackfin Camera board set, and writing the code to drive four servo channels - two channels for the E-flight electronic speed controllers, and two channels for the servos that gimbal the battery pack using a hobby helicopter swashplate. The servo interface is working quite well, and I have a slightly modified version of the java console used for the X3D which shifts the battery weight and controls the throttle. Horizontal translation is controlled by shifting the battery weight (as seen in the following videos), and yaw is controlled by trimming the difference in speed between the two prop motors.

In the first video, you can see how the weight shift mechanism works. However, I found that my battery pack was not producing sufficient output, so the flyer never got very far. In the second video, the battery had been replaced, but clearly some work is needed on steering. The crash at the end shortened one of the props by 0.5", but everything else was fine.




I think the basic structure is there, so the next step is to add accelerometers to aid in stabilizing attitude. I have both a 2-axis Analog Devices ADXL202E and a 3-axis LIS3LV, so I'll add one of the other. A gyro is clearly needed as well for yaw control, and I'm not yet certain which to use - I have a few with SPI interfaces that require 5V, or I might go with an analog output and use a voltage-to-frequency converter to capture the signal, since I don't have any A/D channels.

Read more…

X3D SRV1Console

After some distractions and delays, my uav projects, first described here - are back on track. Yesterday, I received the needed firmware update for the AscTec (X3D) quad - it's now possible control the quad via the serial interface with no FM transmitter in the loop. As before, the controller is an SRV-1 Blackfin Camera Board, which includes a 500MHz Analog Devices Blackfin BF537 processor with 1.3 megapixel Omnivision OV9655 camera module and Lantronix Matchport 802.11b/g radio. The firmware changes were critical for defining the quad's behavior upon loss of signal from the Blackfin.

As mentioned before, I have been working with a new quad rotor called the "X-3D-BL Scientific" from Ascending Technologies GmbH in Stockdorf, Germany, with the concept of integrating the SRV-1 Blackfin camera and radio board with the UAV flight controls. Interface is relatively simple - the X-3D-BL has a very capable onboardinertial measurement unit integrated with the brushless motor controls,so the interface between Blackfin and UAV is a simple 38kbps UART.


My original robot firmware required only minor changes, and I added flight controls to our Java console that was originally designed for a ground-based robot. The 3 columns of buttons on the left are assigned to pitch, roll and yaw control, and the buttons further to the right change or kill the throttle or initialize the controllers. The last column changes video capture resolution. The Java software has an archive capability which I exercised here -

http://www.surveyor.com/images/x3d-srv1-012808.mov

This particular video clip isn't very exciting, as I never take the quad more than 1-2 inches off the ground, but it does show the live view from the quad via the WiFi link and is 100% under control via WiFi from a remote host. There were some pretty good crashes earlier, but unfortunately I wasn't running the archiver at the time. I need to fine-tune the flight controls, and then will hopefully capture some more interesting video.

While this project is furthest along, I now have firmware for the Blackfin board that can either control the airframe via serial interface (e.g. the X3D) or 4 servo channels. The next flyer will be my "baby Hiller" coaxial fixed rotor which steers by shifting battery weight, and then I will start working with the fixed wing "Carbon Prime". It's nice to be making progress again on these projects, and now that I'm back in it, everything else feels like a distraction.
Read more…