With a spatial haptic interface device and a suitable haptic rendering algorithm, users can explore and modify virtual geometries in three dimensions with the aid of their haptic (touch) sense. Designers of surgery simulators, anatomy exploration tools and applications that involve assembly of complex objects should consider employing this technology. However, in order to know how the technology behaves as a design material, the designer needs to become well acquainted with its material properties. This presents a significant challenge today, since the haptic devices are presented as black boxes, and implementation of advanced rendering algorithms represent highly specialized and time consuming development activities. In addition, it is difficult to imagine what an interface will feel like until it has been fully implemented, and important design trade-offs such as the virtual object's size and stability gets neglected.
Traditional user-centered design can be interpreted as that the purpose of the field study phase is to generate a set of specifications for an interface, and only solutions that cover these specifications will be considered in the design phase. The designer might miss opportunities to create solutions that uses e.g. lower cost devices since that might require reinterpretation of the overarching goal of the situation with starting point in the technical possibilities, which is unlikely without significant material knowledge. As an example, a surgery simulator designed in this thesis required a high cost haptic device to render adequate forces on the scale of human teeth, but if the design goal is reinterpreted as creating a tool for learning anatomical differences and surgical steps, an application more suitable for the lower cost haptic devices could be crafted. This solution is as much informed by the haptic material "speaking back to" the designer as by field studies.
This licentiate thesis will approach a perspective of spatial haptic interface design that is grounded in contemporary design theory. These theories emphasizes the role of the designer, who is not seen as an objective actor but as someone who has a desire to transform a situation into a preferred one as a service to a client or greater society. It also emphasizes the need for crafting skills in order to innovate, i.e. make designed objects real. Further, it considers aesthetic aspects of a design, which includes the subtle differences in friction as you move the device handle, and overall attractiveness of the device and system.
The thesis will cover a number of design cases which will be related to design theory and reflected upon. Particular focus will be placed on the most common class of haptic devices which can give force feedback in three dimensions and give input in six (position and orientation). Forces will be computed and objects deformed by an volume sampling algorithm which will be discussed. Important design properties such as stiffness, have been identified and exposed as a material for design. A tool for tuning these properties interactively has been developed to assist designers to become acquainted with the spatial haptic material and to craft the material for a particular user experience.
Looking forward, the thesis suggests the future work of making spatial haptic interfaces more design ready, both in software and hardware. This is proposed to be accomplished through development of toolkits for innovation which encapsulate complexities and exposes design parameters. A particular focus will be placed on enabling crafting with the haptic material whose natural limitations should be seen as suggestions rather than hinders for creating valuable solutions.
Stockholm: KTH Royal Institute of Technology, 2013. , vii, 49 p.
Sundström, Petra, Ph.D.
Sallnäs Pysander, Eva-Lotta, Ass. Prof.