Variable frequency 60-g haptic renderer for virtual tennis simulation

We present a sub-200 grams, ungrounded haptic device to simulate tennis ball impacts in virtual tennis simulation. We previously designed a device to generate the actual impacts [Fong et al. 2010]. The new device is more expressive as we are able to control the waveform of the accelerations generated and it has a frequency response between 40Hz and 80Hz. The fiberglass based vibrating element is designed such its natural frequency is similar to a tennis racket. By using the resonance effect, we can build up very large accelerations using small solenoids in less than 10msec. It fits into a tennis racket handle and transmit the generated accelerations directly to the hand. Acceleration is the main excitation mechanism for the skin's sensory system in this case. By approximating the accelerations generated by real impacts, which are measured on the racket near the hand as well, we can achieve similar haptic sensations. Furthermore, the device does not generate loud sharp noises on actuation. Our design is similar in spirit to the Haptuator linear vibrator [Yao and Hayward 2010]. However, to generate larger accelerations, our device is mechanically stiffer, and our drive circuit employs simple MOSFET to handle more than 10A of surge current for driving the solenoids.