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SATIN System: Issues and Problems to Solve

This Section described the SATIN system that has been developed in the context of the EU-funded project IST-FP6 SATIN, and the issues and problems outlined and subsequently addressed in the present research. The research presented in this book is the natural prosecution of the SATIN project. In actuality, having as a starting point the knowledge and know-how acquired during the project by the researchers at the KAEMaRT group, it has been possible to identify the limits of the system, and to define the research path to follow in order to develop an innovative and novel system, much performing and better usable than the previous one.

The SATIN project consists of a working station for the evaluation of and interaction with virtual prototypes of products. It is mainly made up of: (1) a tactile interface, (2) a stereoscopic visualization system, (3) a system for sound rendering.

The tactile interface consists of a flexible strip placed in the space by two MOOG- HapticMaster devices [1]. The strip imitates the bend typically used by designers to perform style evaluation of physical mock-ups of concept products.

A 3D visualization of the surface is superimposed on the physical model by means of a retro-projected stereoscopic visualization system. This consists of a DLP projector, a mirror, a half-silvered mirror and a rear-projection screen (Fig. 3.3). The projector is located in a position that is above and on the back with respect to the haptic system (C). This position allows the user to stand in front of the visualisation system without the problem of creating a shadow with her/his head, thus occluding the image projected by the projector. The display system is also designed in a way that its components do not interfere with the haptic workspace (A). So, the user can freely move her/his hands within the interaction space, and is able to interact with the system by grabbing and manipulating the physical interface (F), which is positioned under the half-silvered mirror.

The two haptic devices (D) are positioned under the visualisation system. The stereo image deriving from the projector is reflected on the mirror positioned on top of the layout (G). The image is projected straight to the overhead projection plane,

Concept of 3D visualisation system which is a rear-projection screen

Fig. 3.3 Concept of 3D visualisation system which is a rear-projection screen (H) that has been previously angled in order to correct the distorted image. The user sees the mirrored image in the virtual plane where the 3D image is created through the half-silvered mirror (I).

This configuration offers good image visualisation and also allows us to control the sense of depth. If the rear-projection screen is located near to the half-silvered mirror the user perceives the virtual object near as well; if the rear-projection screen is located far from the half silvered mirror the user perceives that the virtual object is far as well. A frame (B) supports the components and a platform (E) is used to accommodate the users height. All the components are equipped with regulation systems. These allow us to easily relocate and adjust the position and orientation of the virtual image plane (L).

In order to increase the perception of the 3D image, the user is provided with stereoscopic glasses. These glasses are tracked so that the projected image is always coherent with the orientation of the users point of view. This tracking has been made possible by using the Opti-Track system [2], which is provided with three cameras, placed on the upper part of the whole structure.

The tactile system is made up of a flexible strip that is bended and twisted (Figs. 3.4 and 3.5) so as to be able to render a portion of a virtual surface, which physically represents the digital model of the product. In order to obtain the desired deformation, the strip is moved by relative servo-actuated mechanisms. They control the strip by means of parallel equidistant sectors, which correspond to the control points of the rendered surface (Figs. 3.6 and 3.7).

The SATIN system is extremely innovative. However, it has some limits, which make difficult its effective adoption in a design studio. By analysing the criticalities of the system, it is possible to identify issues related to:

  • • Size;
  • • Costs;
  • • Customization;
  • • Rendering performances.

Size. The system is bulky and it is difficult to move it from a place to another one. The big size of the system is due to:

Bending system of tactile device

Fig. 3.4 Bending system of tactile device

Twisting system of tactile interface

Fig. 3.5 Twisting system of tactile interface

Control points of the tactile interface

Fig. 3.6 Control points of the tactile interface

  • The necessity to use a structure for the displacement of the mirrors of the retro- projection system;
  • The need of using frames for the correct spatial placement of the tracking system;
  • The presence of the two MOOG-HapticMaster devices, which are cumbersome.

Costs. The entire system is very expensive from an implementation point of view. This is due to:

  • The use of the MOOG-HapticMaster devices for positioning the tactile interface;
  • The need of semi-reflective mirrors for the development of the visualization system, which are very expensive;
Prototype of the tactile interface

Fig. 3.7 Prototype of the tactile interface

• The big size of the frame, which is made up of expensive modular elements.

Customization. The system, as it has been conceived, results to be poorly flexible in terms of implementation and adaptability to the users needs. The system is not only a fixed working station requiring a big amount of space, but it has also limitations related to the use of the tactile interface, which is composed by eight modules in standard configuration. It has been, indeed, conceived to be partially customized for what concerns its size. However, it presents limitations due to the relative nature of the actuation systems. In order to customize the length of the strip, according to the kind of the surface to render, it is necessary to add or remove some modules of the strip itself. This is first of all an activity that requires effort and time. Moreover, it is not possible to add an infinite number of modules because, after a certain number, the system will not be able to sustain its weight.

 
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