Human Velocity Control of Admittance-Type Robotic Devices With Scaled Visual Feedback of Device Motion

An admittance-type robotic manipulator is a nonbackdrivable device whose motion is controlled to move in response to a user-applied force, typically with velocity proportional to force. This study characterizes the ability of ten human subjects to accurately and precisely control the velocity of such a device, using force applied by the index finger, as the user is provided visual feedback of device motion and a target velocity on a display. The admittance, the velocity, and the visualization scale factor are varied in a full factorial design, with parameter levels representative of microsurgery/micromanipulation tasks. The results indicate that: visual scaling has no effect, for the levels tested; low velocity at high admittance results in reduced precision and accuracy; high velocity at low admittance results in reduced accuracy; and an admittance-dependent velocity exists at which accuracy is maximized. The results suggest that gain scheduling will result in improved performance.