With a personal passion for ocean sailing combined with a
inclination toward technologies that cooperate with natural forces, it
seems inevitable that I would be drawn to combining lighter-than-air
forces with my technology interests. In my never-ending quest to defy
gravity with the SRV-1 Blackfin, and inspired by the work of Chris and Jordi at DIY DRONES,
I launched a project to add sensors and onboard computation to a small
indoor helium blimp. This is build log of that project, with entries in
reverse chronological order.
http://www.rcguys.com/66blimp.html, specifying the $229.95 version without motor controller. To complete the build, you need only add a battery (we recommend 850mAh 7.4V Lipoly), battery charger, and micro servo such as Hitek HS-55 or eFlight EFLRS75, along with the SRV-1 Blackfin Camera + Wifi.
When you order the SRV-1 or SVS controller, you need to specify that it is for use with the YARB blimp, and we will provide a modified version of the motor controller. If you already have the SRV-1 or SVS controller, you need to modify the radio/motor or SVS base board to double the capacity of the motor interface by piggybacking a second FAN8200 H-bridge chip, as shown here -
FAN8200 H-bridge chips can be ordered from Wright Hobbies. For additional info, email firstname.lastname@example.org
[updated February 21, 2010]
www.surveyor.com/blackfin/yarb.zip. To configure YARB for a specific network, the default IP address of 169.254.0.10 should be changed in "srv.config" to the appropriate address. Note that when YARB firmware starts, the gondola is carrying the camera upside-down, so the image is flipped. The blue down-arrow button on the console will flip the video to the right orientation.
Note also that the Google Android G1 console for YARB is available for download from code.google.com/p/srv1console/
66-inch helium envelope, fully assembled gondola with dual rotors and thrust vectoring, SRV-1 Blackfin camera with 2 lenses and 2 camera headers, 802.11bg Wifi radio, battery and charger.
For purchasing details, please visit our online store.
Google Android G1 phone. The phone's tilt sensors are used to set power differentially to the rotors, and buttons or the scroll wheel set the thrust vector servo. All communication is via the wireless WLAN or G3 phone connection, and live "FPV" (first person view) video is displayed on phone screen. Steering via the tilt sensors is very natural - it only takes a few minutes of practice to work out how much tilt is required to achieve the desired motion and steer smoothly.
The Android console for YARB (and other Surveyor robots) is an open source project, hosted by Google Code at code.google.com/p/srv1console. Google has provided a very nice development environment - Android Developer Kit. The console works with an unmodified SRV-1 Blackfin Camera with Wifi mounted to the blimp gondola.
Here are some videos of YARB in action under control of the Google Android G1 ...
Surveyor SVS (stereo vision system) controller with a pair of Blackfin cameras.
The new rig weighs about the same as the previous single-camera setup with added sensors. It is actually a bit too light, so ballast has been added using washers held in place on the Wifi antenna. There is a new simplified console that steers via 4 arrow keys for direction (up, down, left, right), the return key for reverse, and the spacebar to stop motors. Control via keyboard seems more direct than using mouse clicks, though the console will be able to steer via mouse clicks directly on the display window - this would work nicely with portable phones (iPhone, Android, etc).
Viewing of the live or archived video requires anaglyph (red/cyan) 3D glasses . Here is a short 3d stereo video clip captured from the blimp ...
It is fun to fly YARB around using stereo vision, but the real point of this exercise is to develop the functions that compute disparity between views of the two cameras in order to create a depth map. Similar to human depth perception, this enables the robot to measure distances to objects and obstacles without any additional ranging sensors (e.g. sonar, IR, laser). Work has already started to develop this capability in the Blackfin firmware.
As a quick test of the latest firmware, here is a video of YARB cruising through the front room. The big brown lump on the couch is a 150-lb Chesapeake Bay Retriever named "Tank" who refuses to be intimidated by a blimp.
Here's a new video clip -
Click here if the YouTube video isn't working -
Next step is to shift to autonomous operation.
At the moment, the sensor data is unfiltered, which allows us to get an idea of how much variation there might be. The ultrasonic data is pretty solid - the forward looking readings bounce around a bit, but the download readings are fairly consistent. However, I think we will change to a narrower beam module - probably the EZ1. Also, it would be nice to have a couple of side-looking modules to enable some degree of mapping capability.
The compass is less consistent, and it turns out that we're getting magnetic field interference from the motors when they are running. At the time I recorded the video clip below, I wasn't paying attention to the readings, but subsequent tests show that the readings are varying by as much as 15-degrees when the motors are powered. Either we will have to move the compass, or add some compensation in software.
Here's a snapshot of the gondola with the additional sensors -
The plan is to make changes in the sensors to clean up the data, and then to write a script using the onboard C interpreter to let the blimp wander around on its own, perhaps following a course based on heading. After that, we will add some logic to use the camera to lock onto an object and follow it around while maintaining altitude and avoiding collision - that will be a bit more challenging.
Here's some video captured from yesterday's test session. The caption overlay shows heading, forward distance and height above ground in inches.
I have installed an SRV-1 Blackfin camera board and radio on a 66-inch helium blimp (ordered without their motor controller for a $100 savings) - interfacing the H-bridge on the SRV-1 combo radio/motor board directly to the two prop motors and one of the Blackfin's timer channels to the servo which vectors the prop thrust. Note that we have modified the SRV-1 radio/motor board to double the capacity of the motor interface by piggybacking FAN8200 H-bridge chips, as shown here - http://www.surveyor.com/cgi-bin/robot_journal.cgi/2009/02/13#200. Helium was supplied by a local welding supply shop - Airgas. The 66-inch envelope takes approximately 16 cu-ft of helium.
Here's SRV1Console with some different buttons that control the vectoring of the props and invert the video (the Blackfin board is suspended upside-down from the blimp gondola).
Using SRV1Console's archiving feature, I captured the video feed while piloting the blimp around the hallway and front room from my office. The blimp is surprisingly easy to pilot - this was my first attempt, and I didn't break anything, though there were some close encounters. The camera's a bit out of focus in the following video and the afternoon light washes out the scene somewhat, but you get the general idea.
Next step is to add ultrasonic sensors and a compass in order to start programming some autonomous exploration. This promises to be a very interesting project.