Phantom Robotic Manipulandum
A set of PHANTOM haptic interface devices (Sensable Devices, Inc.) is available to allow studies of motor adaptation to an external manipulandum. The PHANTOM is a lightweight two-link robotic arm, which can be driven by torque motors to create forces in three dimensions. The arm contains encoders from which the position of the tip and its derivatives can be computed at a high enough rate to generate movement-contingent forces at greater than 1200 Hz.
Three models of PHANTOM are available in the laboratory. The PHANTOM Desktop device can deliver up to a 7.9 N force in a workspace of 16 x 12 cm horizontally and 12 cm high. The PHANTOM 1.5 Premium can deliver up to a 8.5 N force in a workspace of 38 x 28 cm horizontally and 19 cm high. The PHANTOM 3.0 provides 3 degree of freedom sensing and force generation, with maximum translational force of 22 N in a work space of 83.8 x 58.4 cm horizontally and 40.6 cm vertically. These devices encompass the range of movements made with just the wrist and hand to the whole arm and body, in children and adults.
An important feature of the PHANTOM is that when the motors are programmed for zero force, the arm is a minimal dynamic load (45g, 75 g and 159g apparent mass at tip; 0.06 N, 0.04 0.2N backdrive friction ) and is statically balanced throughout the workspace. The PHANTOM apparatus is mobile, which allows us to transport the set-up to off-site locations for testing subjects in clinic, school or home settings. The laboratory maintains a library of software for scripting experiments involving the PHANTOMS and other stimulation and recording hardware and for analyzing the data.