Control and evaluation of a 2-D multimodal controlled-friction display

The multimodal control of a 2D controlled-Friction Device is presented. We use the Vector control method because the phase and amplitude of two vibration modes at a same frequency can be precisely set. The closed loop response time of 10 ms is achieved. The device is then associated with a finger position sensor. The algorithm of the multimodal approach is then tested. In spite of the inevitable limitations of the system - saturation of amplifiers, low sampling frequency of the sensor - low friction could be imposed under a finger while a high friction was imposed on a pre-determined position. This confirms the validity of the modal approach to create multi touch interactions