The effect of sensor/actuator asymmetries in haptic interfaces

Haptic interfaces enable us to interact with virtual objects by sensing our actions and communicating them to a virtual environment. A haptic interface with force feedback capability will provide sensory information back to the user thus communicating the consequences of his/her actions. The quality and complexity of these interactions is dependent on how the interface is designed. When designing a haptic interface, one must choose how many sensors and how many actuators will be used. In particular we are now seeing interfaces which have more sensors than actuators. This "asymmetry" in sensor/actuator utilization provides for a higher dimensionality of action than sensory feedback. It is a tempting avenue for devices design due to the low cost of introducing more sensors. Yet, while this can enable more rich exploratory interactions, the lack for equal dimensionality in force feedback can lead to interactions which are energetically non-conservative. in this paper we provide a preliminary view of the properties of such "asymmetric" sensor/actuator designs. We address the design and rendering tradeoffs of these systems and introduce a framework for device analysis.