Sunday, March 9, 2008

Testing

With another late night push until the daylight savings time exacerbated wee hours of Sunday morning, we put Yeti up on blocks, rigged the power wiring, mounted the radio and processor boards, fixed up the remote user interface program, and held our breath as we plugged everything in.

We fired up the GUI and radio and nervously twitched as I pressed the first drive command. We knew we would be there for a while diagnosing various problems with the programming, the radio link, the motor controller or the power electronics so we were completely unprepared when it worked. I'm not sure this has ever happened before in history but we plugged it all together and it drives perfectly.

After a quick team high five, we headed home to crash for a few hours before meeting Steve to test the radar interference this morning.

We found that there was basically no radar interference from leaked EMI from the robot, even when the radar antenna was situated between the two rear wheels. The radio transmission pulses did create a clear interference line on the radar image, but that was with the transmitter located 20' from the antenna. When running this in Antarctica the antenna will be miles away from the radar and only rarely transmitting if ever.

Here's a video from testing today



Mike's been working on simulating our bearing control algorithm. This video shows the yeti following a set of GPS waypoints with noise introduced to the system:

video

Friday, March 7, 2008

On the road

With a late-night push, the team prevailed in overcoming all odds and finally wiring the rig, mounting our motors and gearboxes, and mounting the wheels. One might think this would be a simple endeavor but tight tolerances in the complex hub assembly have made us work pretty hard to get this thing put together.

Gus has been pulling some insane hours making her handmade PCB to supply houskeeping power to all of our electronics using a number of DC-DC converters. Our GPS, Sensors, signal processing board, and computer conveniently all run off different voltages, so Gus's board will feed each of those.

Kevin and I fine tuned all of our motor controllers such that the input voltage corresponds to a given motor velocity. This process was a little rough, it'll remain to be seen how well we can track a straight line when we start driving tomorrow.

This week Mike has been working on a simulation for our bearing control algorithms. We found that without any yaw-rate sensor we could get stuck in some pretty nasty looping situations where the robot's control system would force it to drive in circles. We ordered a Gyrocube that we'll be using for inertial navigation in conjunction with the GPS once we get that up and running.

Kevin tuning the motor controllers. This unassuming stack of hardware is about $5k worth of motors and controllers


Gus practicing her best coy look while assembling the hubs and gearboxes


Kevin working on the frame to get the wheels on


Gearboxes and bearing seats. Why does everything look sweeter when it's lined up?


Booyah

Saturday, March 1, 2008

Gearing up for the Final Lap

As the final week for our project approaches, we’ve been making significant strides toward the finish line. We’re working round the clock and like a well-oiled machine…or in our case, like robots.

We have finalized the designs for the enclosures, which have yet to arrive, and in their place machined plexiglass for testing. Eric spent many hours in the machine shop and using the CAD lab to layout the electronics within the enclosure…or as Eric would say, “I just spent five hours making rectilinear stuff with holes.” Kevin also kept him company helping to machine all of the spacers and angle brackets for supporting the enclosures and the electronics boards inside. Overall, the enclosures are coming together quickly and should be completely mounted on the backboards in a day or two. See the sweet picture below...



Last week, with the help of Professor Ray, we also finished up a thermodynamic model of the enclosures. At first we were a bit skeptical, but the model has proven very useful in deciding which insulation to use for our enclosures. The picture below is a prediction of the temperature inside the box in the worst case scenario: an outside temperature of -40 degrees Celsius and winds blowing at 20 mph.



The GPS is now working as well and we’ve got communication between the computer and the receiver. Unfortunately, we’re still having trouble locating satellites and so while the board has a nice blinking green LED that makes you smile…it still can’t steer the robot. We’ll give Novatel a call on Monday and hopefully they can impart their wisdom upon us.

Gus has also made some major strides in the past few days. She finished up the PCB last night after Thayer’s glorious Friday Beers and it’s now ready to ship off to a manufacturer. Next up is the copper power board, which will be machined in the shop and used for the remainder of the testing. In the spring, a PCB version of the power board will be made and used instead.

That’s it for now…But there will be plenty of updates in the days to come. Stay tuned.