Ungrounded handheld device for simulating high-forces of ball impacts in virtual tennis

We present an ungrounded haptic device for use in virtual reality tennis, with three push-pull solenoids arranged in a Y-shaped configuration as shown in Figure 1. When held at the centre of the Y, users can experience strong torques due to the spatial distribution of solenoids. We increase the resulting acceleration of the haptic device [Fong et al. 2010] from 14g, or 14 times of gravity, to 25g, and omit the real racket to allow for multiple solenoids at a similar weight. Compared to ungrounded devices such as the Torque-Bar [Swindells et al. 2003], which weighs 1050 grams, and iTorqU [Winfree et al. 2009], which weighs 833 grams, our device weighs 428grams. Our device can generate sharp impacts due to use of fast acting solenoids, compared to slower-acting changes of inertia used by above mentioned devices. We integrate the device with a large stereoscopic projection display with head tracking. The graphics is rendered in a spatially accurate manner, so that the users can perceive the virtual ball flying at them and feel the virtual impacts.