Impulse-based Control of an Impulsive Haptic Interface

In a previous paper, the authors presented the first haptic display capable of applying directly an impulse to its operator. The resulting immediate change in momentum is considered invaluable to make interactions with rigid virtual objects feel realistic. The size of the impulse is controlled by adapting the amount of momentum of a momentum wheel. At the predicted instant of contact with the virtual object, an electromagnetic tooth clutch is engaged. The axes of momentum wheel and haptic handle are connected and a real but controllable collision between the operator and the momentum wheel is realized. This paper presents some tools to improve the accuracy of the impulses realized by the device. First, a detailed investigation of the dynamic properties of the tooth clutch is included. Based on this analysis, conclusions with respect to the range of display able impulses are made. The first order adaptive windowing method (FOAW) of Janabi-Sharifi is extended to a second order form (SOAW) and used to make accurate predictions of the instant and velocity of impact. Finally, the impulse generation capability of the device is utilized in a new method to estimate the inertia of the device's interacting components. All these tools are combined and a rigid virtual wall was implemented. Experimental results confirm the quality improvement with respect to traditional virtual walls