Path guidance control for a safer large scale dissipative haptic display

The properties of dissipative haptic displays allow larger workspaces that permit a whole body interaction useful for sports, rehabilitation, and large-scale object design applications. To that end we designed and constructed the brake actuated manipulator (BAM) with 2m³ workspace. Dissipative devices are capable of simulating virtual objects through resistance analogous to active devices. However, the challenge remains for path guidance paradigms because neither impedance nor admittance control can be used to actively steer limb movements. Here we first define a new way to create and track a path during path guidance with a twinned vector field to allow bilateral motion. Using this new path definition three controllers, velocity ratio, force cancelling, and force mapping are compared with and without visual feedback. The results indicate that both force controllers provide better guidance over velocity control; the force mapping technique resulted in the smoothest limb trajectory. The presence of visual feedback was found to be a critical factor for path guidance using dissipative devices.