Research On Tactile Display Technology Of Navigation Information In The Virtual Uranban Environment

In the fast-paced society, mobility activities are getting more frequently. One challenge with this is orientation in unknown spaces. Most of the commonly used navigation devices convey information through the visual or auditory channel, but these channels are easily limited by the environmental factors, or occupied by other important tasks. Touch has been shown to be suitable for ubiquitous environments, and it needs few cognitive resources to interpret the conveyed information, releasing the necessary resource for other tasks. Therefore, in a vision-limited virtual urban environment, using tactile modality to convey navigation information can enhance the immersion of the observer, and guide movements. This thesis is supported by the Research Fund for the Doctoral Program of Higher Education of China. Some key issues of tactile navigation information display in the virtual urban environment are investigated in terms of technological means, encoding schemes, and performance evaluation.In real world environments, the multitude of spatial cues and the typically large timescale of navigation exert much influence on cognitive analysis. However, these problems can be overcome in a virtual environment by isolating the effect of tactile displays from additional cues that degrade navigation performance. A three-dimensional virtual city system is developed by VC/OpenGL to provide pedestrians with real-time navigation information. The city model of 3ds format is exported from Google SketchUp, mapped again in 3ds Max, and displayed in the OpenGL program frame. The user roams in the virtual urban scenario in the first or third person, and follows the predefined waypoints to the destination. Four different navigation messages are route attribute, intersection type, distance and heading direction, respectively. By means of navigation information, the user can navigate successfully in a strange urban environment under tactile stimuli. Meanwhile, this system offers the fixed-point bird’s view, the roaming timer, and can also save and display the user’s motion paths.According to tactile perception mechanism of the human skin, both vibrotactile and thermal tactile modalities are chosen to convey multi-dimensional navigation information. Their parameter categories are analyzed in detail to screen out the desirable parameters. Two or more perceptually distinct levels are marked out in each parameter based on message types. Vibrotactile feedback is produced by cylindrical vibrators, and the vibration wave propagation is explored theoretically; Thermal display is presented by a typical Peltier element, and thermal responses within the skin are derived by using semi-infinite body model. With respect to tactile navigation systems, three of the most commonly accepted models are Wickens’Multiple Resource Theory, Prenav and Chorems Theory, which can explain why tactile displays seem to be successful at providing information to the wearer.The general scheme of multi-tactile navigation system based on the virtual environment is proposed, with the aid of body accessories to design for wearability, such as a backpack, a waist belt and an arm band. The hardware design is introduced, and the components selection, composition principle and electrical connection relationship of navigation information acquisition module, kernel processing module, vibrotactile feedback module and thermal display module are analyzed. The wearable effect of the multi-tactile display device is implemented concretely, and satisfys the requirements of portability and mobility. The software design contains the drive program of the multi-tactile display device and the tactile training software. The drive program is developed in terms of RT-thread transplanting, navigation information acquisition and decoding programs, and thread synchronization, having the functions of acquiring and decoding multi-dimensional navigation information in real time. The tactile training software can provide the properties of training and evaluation, serving as a test platform for subsequent psychological experiments.The design concept of compound tactons is explained, and the design and identification researches of 3-parameter compound vibrotactile,4-parameter compound thermal+vibrotactile icons are carried out. The first experiment indicates that the overall recognition rate of 3-parameter compound tactons reaches up to 95.47%, and 19.70 icons can be identified correctly of all 24 tactile icons; The second experiment finds that the overall recognition rate of 4-parameter compound tactons decreases slightly, and 24.42 icons can be identified reliably of all 32 tactile icons; While the third experiment evaluates the navigation effectiveness of two tactile modes in a simple virtual urban environment. Seen from the experimental results, identify navigation information from 3-parameter vibrotactile tactons is very easy, and it appears that presenting thermal and vibrotactile stimuli sequentially does not significantly hinder interpretation of each other. Although the mean recognition accuracy of 4-parameter compound tactons is a little lower, the participants’ navigation performance is significantly better than that of 3-parameter tactons. In the fourth experiment, the overall recognition accuracy reduces to 91.86%, and 45.52 icons can be identified reliably of all 64 tactile icons. Therefore, it is feasible to convey navigation information by employing compound tactons.The design concept of transformational tactons is introduced, and the design and identification researches of 4-parameter four vibrotactile icons, one thermal+three vibrotactile icons and two thermal+ two vibrotactile icons are implemented respectively. The fifth experiment indicates that the mean identification rate for four vibrotactile transformational tactons is 74.77%, and approximately 31 icons can be identified correctly of all 64 tactile icons; The sixth experiment reports the overall recognition accuracy for one thermal+three vibrotactile icons is 85.01%, and 34 to 35 icons can be identified reliably; The seventh experiment reports that two thermal+two vibrotactile icons have a mean identification rate at 78.20%, with only 28 to 29 icons identified reliably. Results from these experients are promising, as presenting four-parameter transformational tactons does not seem to produce much confusion. While navigating in a complex virtual environment, the eighth experiment results show that the participants using one thermal three vibrotactile transformational tactons have the best overall performance by considering navigation performance and cognitive workload.