The Texas 4 Balancing Act

Although Milestone 3 keeps us busy with PR2 beta production and software documentation, we continue to have fun with other experiments around the office.  Our Texas 1 telepresence robot was been such a hit, that we couldn't help but tinker with its design and capabilites.  Dallas Goecker still regularly uses Texas 1 to telecommute, but his surrogate at Willow Garage was frequently incapacitated by our eager experimentation. Instead of sharing, we built a couple more.

Texas 4 is our high-speed prototype.  A touchscreen allows developers to interact directly with the robot, as opposed to doing so via the teleoperator.  This version has more powerful motors and a differential-drive configuration. With the drive wheels up front, we were able to more creatively experiment with Texas 4's capabilities.

Two of our controls engineers, Wim Meeussen and Melonee Wise, spent a day writing a dynamically-balancing controller that allows Texas 4 to balance on its two front wheels, and move about like a Segway. The robot can switch between 4-wheel drive and 2-wheel drive on the fly.  With an IMU (Inertial Measurement Unit) taped to the base, the robot self-adjusts to a pre-designated forward tilt angle whenever stability is compromised. The result was a fun sight to see around the office as well as a good experiment into the capabilities of the ROS/PR2 software platform. Wim and Melonee were able to use the same controller infrastructure they are developing for the PR2. This infrastructure allowed them to write and compile their new controller for Texas 4 without having to restart the entire system. They were also able to access many other libraries for ROS, like the filters package, which enables runtime-configurable data filtering.