The 4th ACM SIGGRAPH Conference and Exhibition on Computer Graphics and Interactive Techniques in Asia
Conference 12-15 December • Exhibition 13-15 December • Hong Kong Convention & Exhibition Centre

Emerging Technologies

Ungrounded Handheld Device for Simulating High-Forces of Ball Impacts in Virtual Tennis

We present an ungrounded handheld haptic device designed for simulating the high forces of tennis ball impacts in virtual reality. It consists of three high-power push-pull solenoids, each capable of generating more than 30-g, or 30 times the acceleration due to the Earth’s gravity. They are arranged in a Y-shaped configuration. The resultant acceleration of the whole device is measured to be 25-g, compared to 40-g measured on impact of real tennis balls traveling at 20 kilometers per hour in our previous work.
When held at the centre of the Y, users can experience torques about the lateral and longitudinal axes, due to the spatial distribution of solenoids. The Y-shaped configuration also improves weight balance for better ergonomics. Our device is 21cm long, 13cm wide and weighs 428 grams. Compared to previous ungrounded devices our device is lighter and is specifically designed for fast impacts. We integrate the device with a large stereoscopic projection display with head tracking. The graphics are rendered in a spatially accurate manner, so that the user can perceive the ball flying at them and feel a strong virtual impact. The force output of each push-pull solenoid is produced by a current pulse of 16 Amperes. The magnetic latching of the push-pull solenoids to prevent them from moving during user motion is achieved using a 3% duty pulse-width modulation. The pulse frequency is 30 kilohertz, above human hearing range, to avoid a loud audible buzz. Individual solenoid accelerations are measured by attaching an accelerometer with its sensor axis along the actuation axis of the solenoid, while the resultant device acceleration is measured at the top of the device.
Preliminary user feedback indicates that the impacts generated are closer to reality than vibrating motors. This enables more realistic feedback for simulations and games involving sharp impact forces.

Wee Teck Fong, Institute for Infocomm Research
Zhiyong Huang, Institute for Infocomm Research
Farzam Farbiz, Institute for Infocomm Research
Jingting Cher, Institute for Infocomm Research
Ching Ling Chin, Institute for Infocomm Research
Susanto Rahardja, Institute for Infocomm Research