Cost-performance trade-offs in haptic interface design

Abstract

This projects aims at establishing guidelines to design the most cost-effective haptic hardware for laparoscopic surgery simulation.

Background and motivation

VR technology has advanced significantly in the past decade. Technology for haptic interfaces has advanced to such an extent that the market has segmented into two groups: high-end devices costing over US$10,000, and low cost devices averaging approximately US$100. The high-end devices are developed for, amongst other areas, haptic research and surgical simulation, while the low-end devices are produced mainly for the PC video game industry, and more recently are appearing as OEM components of complex interfaces, such as automobile cockpit controls.

This price gap can be explained partly by the disparity in production size and complexity among categories. A significant price reduction is achieved by only generating simple force profiles. This makes it possible to build all controller hardware into the device itself, and then only maintain low bandwidth communication between the device and the computer.Differences in design objectives are another cause of the price gap. Gaming interfaces are designed to merely convey the sense of a force event or texture, thereby allowing the use of inexpensive components. However, the design objective in interfaces for laparoscopic surgery simulation is to render forces accurately enough to match or exceed the limitations of human force perception. Whether such high standards for laparoscopic surgery simulation are actually needed has not yet been demonstrated. Arguments can be made to the contrary. Research in multimodal perception shows that in many contexts we rely more on vision than touch to judge quantities such as size, shape and position. In judging stiffness in the face of contradictory cues, the perceptual system may discard haptic information altogether. Since a force feedback haptic interface can make up a large part of the cost of a laparoscopy simulation station, it is important for surgical educators to know how improvements in haptic rendering will relate to improvements in training effectiveness.

Platform with varying haptic quality

We developed a platform devised to explore the impact on task execution in a virtual environment of the quality, and therefore cost, of the system’s haptic hardware. This platform is a complex haptic interface in which hardware quality can be varied in simulation. Software intercepts the position and force signals between the haptic hardware and the virtual environment software, and alters them to supply the effect of increased friction, cogging, backlash, inertia and/or lower force output. All parameters of the introduced effects can be set independently or in combination and on a continuous scale; a primary contribution is the creation of haptically realistic effect models that are stable in combination on complex hardware. For more details please see the ICRA 2004 paper.

Results

User tests are currently underway. This page will be updated when our final results are available.

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