Design and characterization of the lateral actuator of a bimodal tactile display with two excitation directions

• Published in: Displays 2018-09, Vol.54, p.34-46
• Main Authors: Schmelt, Andreas S., Hofmann, Viktor, Fischer, Eike C., Wurz, Marc C., Twiefel, Jens
• Format: Article
• Language: English
• Subjects: Bimorph; Load model; Perception threshold; Piezoelectric; Tactile display
• ISSN: 0141-9382; 1872-7387
• DOI: 10.1016/j.displa.2018.09.002

•The approach uses coupled actuators to stimulate the finger in two directions.•This stimulation provides a better user experience than conventional approaches.•Each individual actuator requires only a round surface with a diameter of 2.3 mm.•The lateral actuator was described and designed with a comprehensive model.•The concept of the bimodal tactile display is validated by various experiments. In this paper, a bimodal tactile display used to stimulate the mechanoreceptors is proposed. The use of tactile displays to provide tactile sensations has become the object of increasing interest in recent years. Most of these displays have only one actuator type to generate the tactile perceptions and the spatial resolution of many displays is too rough for good tactile impression. Hence, for the proposed tactile display, two types of actuators for lateral and vertical (normal) excitation are combined. The resolution of the 4 × 4 array is 2.4 mm. Due to its design concept, the presented display is easily expanded. The normal actuator is based on the reluctance principle and the lateral actuator is based on the piezoelectric effect. This contribution focuses on the design and characterization of the piezoelectric actuator. The lateral actuator is mounted on the normal actuator. This has a significant impact on the design of the piezoelectric actuator. To describe the dynamics of this actuator, a Transfer Matrix Method (TMM) Model is created. The mechanical boundary condition at the connection to the normal actuator is included utilizing discrete elements. The model is validated by experiments. Using the model, the geometry of the actuator elements is designed. For performance tests, several experiments have been carried out. The behavior of the lateral actuator has been analyzed in the two end positions of the normal actuators for different load conditions. In terms of performance, the lateral actuators achieve sufficient deflection, even under high load conditions, using imitation human skin as the contact material and with a weight of 50 g. It is shown in a subject test that the lateral actuator works well under real conditions. A measurement of the combined movement has been performed using a Micro System Analyzer (MSA-100-3D) at different frequencies.