Lludd The Wam
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The Barrett Whole Arm Manipulator (WAM) is a highly dexterous backdrivable manipulator. It's a 7 DOF arm (human-esque) with a 4 DOF hand (not-so-human-esque). For a quick overview of using the WAM see WamUsageGuide. For WAM hardware see WamHardware. For WAM software see WamSoftwareGuide. For common problems/solutions, WamProblemsAndSolutions.
The WAM has 7 DOF, 3 in the shoulder, 1 in the elbow, 3 in the wrist. 6 of the joints (3 shoulder, 1 elbow, 2 wrist) are cable driven. The last wrist joint is directly driven. Each joint has a 22bit relative position encoder, a brushless motor, a processor, and CAN interface circuitry (all packaged in a small "puck" on the back of the motor). The control PC drives the WAM by sending torque commands for each motor via the CAN bus. Since the WAM is relatively dangerous machine, it has a hardware safety system which shuts the motors down if certain safety criterion are not met (See WamSafety).
Hand Details
The hand is a 3 fingered 4-DOF gripper (1 DOF per finger, 1 DOF spread). The hand is a completely separate system from the arm - it is powered from a separate supply, communicates via serial port (instead of CAN), and all the joints are position controlled and direct driven. Each finger has two joints, but is driven by a single motor. The joints are driven through the Barrett "breakaway clutch", which selectively drives the 2 joints depending on obstacles in the way of the finger segments (See BarrettHandMechanics). The hand has Barrett strain gauges on each finger and our own custom sensors for force sensing while grasping (See HandSensors).
Computers and Software
WAM (WAM)
WAM is connected to WAM the computer we bought from Barrett in June 2008. The PC runs Ubuntu 7.04 with real time kernel patch Xenomai and PEAK-CAN driver. Barrett provides a set of C libraries that interface with the WAM and provide a lot of high level functionality, such as joint- and cartesian-space controllers (See BtSystem and BtWam). The WAM Server is a TCP/IP server (built on top of the Barrett libraries and the ROS network library) that provides a remote interface to the WAM (See WAMServer).
Planning (Lludd)
Most robot planning is done on Lludd, a Dell Precision 690 (lludd.csail.mit.edu - Lludd). It runs Ubuntu 8.04 with OpenRAVE and ODE. Lludd does robot simulation, path planning, and high level robot control.
Vision (Heimdall)
The vision system will provide object localization and tracking for the WAM control programs. It runs on a Dell Precision 690 (heimdall.csail.mit.edu - Heimdall). (See Wam Vision System)