Vibrotactile and pseudo force presentation using motor rotational acceleration

Linear vibration actuators such as the Force Reactor from Alps Electric Co. or the Haptuator from Tactile Labs Inc. are actively used to present numerous tactile sensation to the fingertip. They have high responsiveness compared with conventional eccentric rotating mass vibration motors, and are also able to produce pseudo-haptic illusions when asymmetric signals are applied. However, this type of actuator has certain design challenges, such as resonance via the spring attached to the vibration mass, and limited acceleration amplitude at low frequency because of the limited travel distance of the mass. In our study, we propose a new haptic presentation method using the rotational motor's counterforce that occurs during acceleration. We use the rotor of motor itself as the vibration mass, so the mass can move indefinitely without limitation. This paper reports on the use of a DC motor as a vibration actuator. The results show that the response time of a DC motor is about 3 ms, which is faster than current linear vibration actuators. The peak amplitude of vibration is at a low frequency (about 40 Hz). We also found that a DC motor is able to provide a rotational pseudo-force sensation. The combination of vibration and pseudo-force produced by a single motor allows a wide range of haptic presentation to the fingertips.