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.

The Design:

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:

Navigation:

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.