The main aim of the HapKit was to create a form of haptic interface that allowed the user to use the speed and force that they would usually use when drumming.
The Hapkit is based upon the wire-gearing system of the Sensable ‘Phantom’ range of haptic devices. The wire gearing system has a few advantages over cogged gear systems. The advantage that is particularly usefull for haptics, is the lack of ‘cogging’, allowing a smooth interaction even when transmitting larger forces.
The HapKit had several novel features:
- The use of a magneto-rheological fluid brake to provide a stiffer drum surface (I used the same make of rotary brake later on in the DAMPER).
- The sound output was generated directly from the control signals to the motors. This means that the sound and the haptic feedback are very tightly linked – this was particularly noticable when there was a software glitch and both the sound and force-feedback would respnd to the glitch in the same way.
- Because the user interacts with a virtual drum, many things could be achieved that are impossible with a real drum. An example that was demo’d was the ability to rapidly turn the drum upside down; this was particularly fun as it tended to shoot the drum-stick out of the drum at high speed.
The HapKit has several limitations.
- The interaction occurs only in a single arc. The universal joint allows the drum stick to be moved though a wide variety of positions, however the tip will always only pass through the same arc.
- The model of the drum was very simple. A more complex model would give a greater variety of sounds.