Gradual anisometric-isometric transition for human-machine interfaces

Human-machine interfaces (HMIs) are widely used in biomedical applications, from teleoperated surgical systems to rehabilitation devices. This paper investigates a method of control that allows an HMI to transition from anisometric to isometric mode, shifting the control input from position to force as the user´s movement is gradually reduced. Two different approaches for achieving this transition are discussed: one is based on the natural system dynamics, whereas the other involves selecting and controlling dynamics. The two approaches were implemented on a custom haptic device in a targeting task. Anisometric to isometric transitioning can potentially be used for training purposes, enabling transfer of what was learned in one mode to the other, as well as novel studies of the human sensorimotor system.