Controlled Impedance Test Apparatus for Studying Human Interpretation of Kinesthetic Feedback

Many feedback control systems, especially those for complex applications, involve humans in the control loop. Visual information traditionally has been presented to human controllers who make manual responses (i.e., via keyboard, joystick, or other interfaces). To expand system bandwidth, other information channels can be presented so human operators. Kinesthesis, the perception of body positions and forces, represents an attractive supplementary form of human-machine communication, since the limbs (e.g., an operator's hand) can be used both for input and output of information in the control loop. Although psychophysical studies have measured perception of isolated mechanical properties, limited work has been conducted to study human kinesthetic abilities in the context of control. The research described here assesses judgement of coupled properties, including the superposition of linear stiffness, damping, and inertia. Quantitative perception of these properties may depend upon correct models of the mechanical system with which a user interacts. Similarly, perception of fundamental mechanical properties may be influenced by system delays (on the order of magnitude of human reaction time). This paper describes both an apparatus for understanding kinesthetic interaction with mechanical systems and an approach for studying human perception of mechanical properties.