Exploring the Dimensions of Haptic Feedback Support in Manual Control

A promising way to support operators in a manual control task is to provide them with guiding feedback forces on the control device (e.g., the steering wheel). These additional forces can suggest a safe course of action, which operators can follow or over-rule. This paper explores the idea that the feedback forces can be designed not only to depend on a calculated error (i.e., force feedback) but also on the control device position (i.e., stiffness feedback). First, the fundamental properties of force and stiffness feedback are explained, and important parameters for designing beneficial haptic feedback are discussed. Then, in an experiment, the unassisted control of a second-order system (perturbed by a multisine disturbance) is compared with the same control task supported by four haptic feedback systems: weak and strong force feedback, both with and without additional stiffness feedback. Time and frequency-domain analyses are used to understand the changes in human control behavior. The experimental results indicate that—when well designed—stiffness feedback may raise error-rejection performance with the same level of control activity as during unassisted control. The findings may aid in the design of haptic feedback systems for automotive and aerospace applications, where human attention is still required in a visually overloaded environment.