Tacsac: A Wearable Haptic Device with Capacitive Touch-Sensing Capability for Tactile Display

This paper presents a dual-function wearable device (Tacsac) with capacitive tactile sensing and integrated tactile feedback capability to enable communication among deafblind people. Tacsac has a skin contactor which enhances localized vibrotactile stimulation of the skin as a means of feedback to the user. It comprises two main modules—the touch-sensing module and the vibrotactile module; both stacked and integrated as a single device. The vibrotactile module is an electromagnetic actuator that employs a flexible coil and a permanent magnet assembled in soft poly (dimethylsiloxane) (PDMS), while the touch-sensing module is a planar capacitive metal-insulator-metal (MIM) structure. The flexible coil was fabricated on a 50 µm polyimide (PI) sheet using Lithographie Galvanoformung Abformung (LIGA) micromoulding technique. The Tacsac device has been tested for independent sensing and actuation as well as dual sensing-actuation mode. The measured vibration profiles of the actuator showed a synchronous response to external stimulus for a wide range of frequencies (10 Hz to 200 Hz) within the perceivable tactile frequency thresholds of the human hand. The resonance vibration frequency of the actuator is in the range of 60–70 Hz with an observed maximum off-plane displacement of 0.377 mm at coil current of 180 mA. The capacitive touch-sensitive layer was able to respond to touch with minimal noise both when actuator vibration is ON and OFF. A mobile application was also developed to demonstrate the application of Tacsac for communication between deafblind person wearing the device and a mobile phone user who is not deafblind. This advances existing tactile displays by providing efficient two-way communication through the use of a single device for both localized haptic feedback and touch-sensing.

Modal Analysis of Liquid Hybrid Bearing in the Spindle System of High-Speed Roll Grinder

Mode analysis of liquid hybrid bearing in the spindle system of high-speed roll grinder whose grinding wheel linear velocity is 80 m/s is carried out by means of finite element analysis method, and the vibration vulnerable areas of the liquid hybrid bearing are found out near the static pressure oil cavities and the diversion groove, and the former 6 orders natural frequencies are gained, furthermore, each order vibration mode is mainly presented as torsion deformation. Therefore, in order to avoid resonance vibration, the bearing should keep away from the resonance vibration frequency region in the course of practical working, and its dynamic performance can be enhanced by optimizing the structure or improving the material property of the bearing, thus, theoretical supports for developing the liquid hybrid bearing in the spindle system of high-speed roll grinder are provided.

Adaptive Composites with Embedded Shape Memory Alloy Wires

Pre-strained martensitic Shape Memory Alloy wires embeddedz into a composite material act against the stiffness of the host material if they are heated above their retransformation temperature, biasing their strain recovery. As a result, recovery stresses are generated in the composite, leading to a shift in resonance vibration frequency if the wires are placed along the neutral axis of a composite beam. Guidelines for quantification of the effects produced, as a function of SMA wire composition, volume fraction, level of pre-strain, and of host material stiffness are not available yet. In order to investigate the governing mechanisms of activation, adaptive composite materials based on Kevlar fiber reinforced epoxy matrices have been produced by embedding thin Shape Memory Alloy wires, 150 microns in diameter, during processing in an autoclave. A mold was specially designed to pre-strain the SMA wires and prevent their recovery during the cure cycle. Values of the degree of activation in the composite materials, in terms of maximal recovery force and of the corresponding maximal resonance vibration frequency shift will be presented as a function of the stiffness of the host material and SMA volume fraction. Preliminary guidelines for the optimization of these materials will thus be given.