Brouwer, I., "Cost-Performance Tradeoffs in Haptic Hardware Design." M.A.Sc. Thesis, University of British Columbia, 2004. Supervised: MacLean, Hodgson
The objective of this research was to determine whether low performance haptic hardware leads to the same surgical task performance compared to more expensive hardware in a virtual reality surgical simulator for laparoscopy. VR surgical simulators are currently being introduced in leading teaching hospitals around the world. While they provide great potential for improvement over current laparoscopic skills training methods, a major barrier to large-scale acceptance is their high cost. Therefore this study is performed to determine whether a reduction in quality and therefore cost can be obtained without affecting surgical task performance. To perform user test at different levels of haptic quality, we developed software that can introduce friction, cogging, force saturation, inertia, and backlash into the haptic loop, simulating the characteristics of less expensive hardware on a high-end haptic interface. This software avoids the need for an expensive hardware redesign, while it allows varying the different parameters on a continuous scale, independent from each other, and within a realistic range. In a pilot study expert surgeons performed a clip application (2 participants) and a dissection task (3 participants) on commercial haptic hardware and VR laparoscopic software. Each surgeon performed the task(s) 3 times under 5 different settings while forces and kinematic data were recorded. Two settings were picked from the ones mentioned above; the other three consisted of the unaltered high fidelity setting, zero force feedback, and a combination of force saturation, cogging, friction, and inertia. We compared tissue-interaction forces, velocities, tool-tip path lengths, and completion times between the high fidelity setting and each of the other 7 settings. At a significance level of 0.05 a Friedman test showed that only the no force feedback condition was significantly different from the high fidelity condition in applied 95 percentile forces. In the clip application task both 50 percentile, and 95 percentile forces were significantly different in the no force feedback condition compared to high fidelity. None of the other settings showed significant differences in any of the performance measures. These preliminary results suggest that low performance components can be used in haptic hardware for laparoscopy without affecting task performance, potentially creating a significant cost reduction.