This was our smoothest test to date, and as a result, our shortest. We had two primary goals:
Demonstrate that our new hardware stack works as intended
Steer a given compass course
We succeeded in both, and found that we could easily tune the steering PID loop to steer a straight course. We also had our operations streamlined to the point where there was very little standing around and figuring out what to do compared to previous tests. However there were a couple of flies in the ointment. First, my R/C controller started sounding its range alarm at what looked like a quarter mile, which was not as far as I had expected. Second, I made a coding error in the latest revision of the code that resulted in a blank GPS log, so no map trace of this test.
The ease of running this test means that we can test pretty much any weekend day that has good weather. We're working hard on getting our waypoint navigation and telemetry code working for our next test.
Since the last update, we've gotten in the water one more time (in late July) and we've made some substantial design changes. First off, here's a video of my talk at Toorcamp that Alex was kind enough to put together:
During our July launch, we discovered a pretty serious limitation in our comms -- we lose connection on the 900 MHz at anything over about a quarter of a mile. You can really see it in our composite map from our October, June, and July launches:
The placemark farther from the shore, at the top of the ramp, is our shore station for the October and June launches, while the one out on the point was our ground station in July. If you measure on the map, you will see we maxed out about a quarter mile from the shore station, which is a massive bummer. OTOH, we were able to bring the boat back to the dock under its own power in July, which was a nice change.
One of our big takeaways from this was that our system needed some major overhauling, and we decided to redo it from the ground up (again). Among other things, we decided to move the REST interface off the boat and on to a control server. This allows us to more easily use cellphone and satellite communications, since most of those systems are designed to exclude inbound communications. The biggest changes are as follows:
Remove the Arduino and go to a Beaglebone-only system. The BBB has the I/O capability to carry the whole load and it removes a major complication in the software. The difference in power consumption is not that high at the stage we are operating at today.
Add a cellphone module. We are going to be using an Adafruit Fona in the longer term, but in the shorter term, one of our supporters has promised us the use of a portable hotspot.
Replace the Wifi dongle with a Ubiquiti Nanostation. I already have the NanoStation, and this should end our odd dongle problems and provide a network access point for the onboard network. To this end, the new motherboard includes a boost converter to provide 15VDC PoE to the Nanostation.
Reconfigure the enable/stop function to be driven by a latching relay in a new power distribution box. This arrangement allows us to make the stop button enact a hard cut of all motor and actuator power.
Power distribution box with per-system power switches
Beaglebone reset switch and console accessible from outside the drybox.
New drybox and connectors. We'll be using SP-13s, since they are about the least expensive waterproof connectors available on eBay.
Add an RC input to give us finer manual control. We bought a Turnigy 9XR with an FrSky XJT/X8R radio combo. Among the nice features of this radio, it has a serial output called S.BUS, an RSSI output, and telemetry back to the shore unit. We chose this one because the 9XR's firmware is open source and it has an embarrassment of buttons, switches and knobs.
Mast-mounted omnidirectional status lights. This also neatly solves our running lights issue for longer range operations.
The control server will be in the cloud, and the boat will contact it for commands.
Use of KML as our internal representation for waypoints. This makes designing the interface super easy, since we can use a Google Maps plugin directly. The resulting files can be readily managed with github.
Our top priority right now is getting the new hardware squared away, along with its software. We're also going to try to get the next rev of the sails done before mid-September. This is especially important because I realized I made a serious math error that overestimated the necessary power of the tail by a factor of four or five. Redoing it means I can get the tail right this time.
I will also be at XOXO in a couple of weeks and at the Open Source Hardware Summit at the beginning of October -- if you are going to be there, please come say hi. Hackerboat will also have a booth at Seattle Mini MakerFaire on Sep 17-18. We'll definitely be outside, although not quite sure of where yet.
This is a bit late in coming, because Makerfaire ate my brain and there were some temporary blog issues. Toorcamp is next week and we're hoping that we can get some nice autonomous trips in while we are there.
At the end of our last episode, we had filled in the rough areas around the hatches, sanded, and primed the boat. The 'bright orange' paint looked a bit more ketchup red in the can, even after thinning for application. This, as it happens, is also the first time I've gone about thinning paint before applying it, and I'm kicking myself for only now discovering what a difference it makes.
Getting two coats of the orange paint on the boat stretched over a couple of weekends. This is because we needed to hand-sand between coats and because getting the boat outside while it's sunny turned out to be a bit of a production. At the end of painting, we even put a nice black diode stripe on the bow so we can tell what direction it's going even if it's several hundred yards away. That was a problem when we took it out last October.
That's enough talking; here are some nice pictures of the boat after we were mostly done:
Our launch last fall proved that the Hackerboat hardware was working fine (other than the GPS) but that the software needed a complete rewrite. We've been working on that for the last few minutes. Debugging is a bit on the slow side, but we anticipate being ready to get back in the water in the next couple of weeks. We will be at both MakerFaire Bay Area and Toorcamp with the Hackerboat in tow. This weekend, we're going to put some paint on the boat to it looks a bit better in preparation for the next launch and for public show. There will be pictures! But let's talk about the systems in preparation to talk about the software.
The current electronics configuration of the Hackerboat has a bit of a Rube Goldberg quality. The underlying intent is to build a system out of relatively small modules that can be added to without major hardware surgery. Here's a schematic diagram of the various bits and pieces. Dark red is power and power control, green is computers, yellow is propulsion, orange is communication, blue is sensors, and purple is non-propulsion actuators.
The first thing to notice is that we have two on-board computers -- a Beaglebone and an Arduino. The intent is that the the Arduino will handle all of the low-level real time functions while the Beaglebone handles all of the higher-level navigation, obstacle avoidance, and mission functions. Among other things, the relatively more power hungry Beaglebone can be put into a low-power sleep mode for extended periods, especially while in the open ocean. On the flip side, we can use the Linux environment and fast processor on the Beaglebone to support all manner of cool navigational modes and mission applications.
The communications is likewise a layer cake. Our ship to shore radio is a Ubiquiti 900 MHz Ethernet bridge. The shore side radio has a directional antenna built in to the radio and the ship side uses an external antenna on the mast. For internal data on the boat, we use a standard WiFi router. This means we don't have to futz with waterproof Ethernet cabling (expensive and troublesome)... and we can add new equipment to the boat for the cost of a WiFi interface.
Right now, the sensor fitout is very basic. We have an IMU/magnetometer combo for heading, a GPS for position, and start/stop buttons on the outside of the boat. We're planning to add cameras next, and of course we have the option to mount any sort of instruments we like for mission requirements later.
Next update will be painting, and after that I will get into our software architecture.