Tuesday, March 29, 2011

Maxwell Moves A Chess Piece

Earlier today we got Maxwell moving chess pieces around a bit. The gripper is still going to need some improvements for a better grasp, and the gripper control software needs some work, but:

Should be a bit more progress later this week.


A Look Inside Maxwell

Recently, I rebuilt Maxwell's base using a new design which allows the front plate to drop down for easy access to the ArbotiX2 prototype being used in Maxwell:

Here you can see the ArbotiX2 with dual 30A motor driver board. On the left is a step-up/down regulator for the Kinect, this takes 9-18VDC and outputs 12VDC@1.25A. The back area of the base is pretty much unchanged, housing the SLA battery and power terminals as seen in the initial post about Maxwell.


Wednesday, March 23, 2011

New Mech Warfare Micro Transponders

The new micro transponders are finally assembled and tested and heading out the door today!


Monday, March 21, 2011

Maxwell Gets an Emergency Stop

I had ordered the emergency stop when I bought the first round of parts for Maxwell, but I hadn't actually designed a location to attach it to on the robot. This weekend I rebuild a number of components on Maxwell, installing a new base, upgrading the torso wiring harnesses, and installing the E-stop (seen behind the arm, protected by the torso column):

The E-stop is from Digikey and is the type it latches when pressed, such that you need to twist it to release and restart the current flowing.

Maxwell's ArbotiX is powered off the USB connection, allowing all 12V power to run through the E-Stop. Pressing the E-Stop then stops all the motors and servos, while the ArbotiX continues to run and interact with the PC. On releasing the E-stop, everything comes back to life nicely.


Sunday, March 20, 2011

Sensors Hate Dark Surfaces

Previously I've mentioned my issues with the low cost Hokuyo URG-04LX-UG01, even going so far as to say that the laser in the Neato XV-11 robot was better. One of the major differences between Maxwell and his little Armadillo cousin is that on Maxwell I have mounted the laser about 6" off the ground, versus the 2" of the Armadillo. Interestingly, this has had a huge impact on performance -- our walls here in the lab are mostly white, and the laser works much better on the walls than the black base trim:

I've also found that the same black paint is on our doors, and wreaks havoc on the Kinect. The image below shows the RGB point cloud -- this is a Sunday, both doors are shut, yet invisible:

Luckily, it looks like the laser picks up the doors when close, so I won't have to worry about Maxwell driving through an invisible doorway.


Saturday, March 19, 2011

Mapping with Maxwell

I've spent a bit of time tuning the PID and cleaning up the control and feedback from the motion system on Maxwell lately. This afternoon I collected a very nice dataset and map of our lab at ILS:

As has been seen before, gmapping "shortened" the hallways (that door at the end of the hallway on the left should be about 2 meters farther down the hallway).