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Enhancements to the planar active handrest

The Planar Active Handrest (PAHR) is a large workspace assistive device that improves user precision manipulation. The PAHR is restricted in its use, because it does not rotate in the horizontal plane, which limits the workspace size and reduces user comfort. This paper evaluates an improved device, the Enhanced Planar Active Handrest (E-PAHR), which allows lateral/medial rotation of the upper arm. Under the E-PAHR design, the desired hand position can be obtained with redundant arm and device configurations. As such, we gave consideration to controller input choices and resultant device motions that are available. Three experiments evaluated the controller designs to select the most effective method to control our device. We conclude that a rotational DOF (degrees of freedom) allows the E-PAHR to better follow the kinematics of a user's planar arm movements while allowing skill level equal to the PAHR, with reduced user force input and lower perceived exertion.