Limits of the Tactile Display Developed
The main limitation of the developed system is the inability to represent trajectories with curvature radii lower than 30 mm. However, considering the available tactile devices, which allow for a free hand and continuous surface exploration, the proposed system can be considered as a major improvement in terms of range of curvatures
Fig. 7.4 Qualitative results of users preliminary tests
Discussion and Users Test that can be rendered. Furthermore, the device has been developed in order to be able to render smooth surfaces, which are those that most need a tactile evaluation performed in a free-hand modality.
Another limit of the developed system is the fact that it is not capable of representing discontinuity. However, it is worth mentioning that at the moment there are no free-hand shape displays that can represent discontinuity. Usually this kind of evaluation is performed by using a point-based force feedback device. In order to interact with such device, the user has to hold a tool as a stylus, which allow punctual exploration, but not a natural, free-hand exploration.
The representation of the shape of products by means of trajectories could be considered as a limit of the proposed solution. However, as mentioned at the beginning of this book the Tactile Display has been developed with the aim of supporting designers in a typical modality they use for exploring and evaluating the quality of surfaces. Specifically, it has been observed that designers during the exploration of the shape of a product slide their hands along a trajectory. So the limitation regarding the use of trajectories for shape rendering is not related to the operational principle, but to the modality implemented for selecting the appropriate cutting plane, which is the new starting reference point, required for obtaining the trajectory. Whenever the designer intends to change the trajectory to explore, he/she needs to select a new cutting plane. To overcome this limitation, it will be studied, as mentioned in Sect. 9.1 about future works, a solution based on the same operational principle proposed by the Tactile Display, but able to render spatial 3D surfaces.