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Force control of flexible catheter robots for beating heart surgery

Recent developments in cardiac catheter technology promise to allow physicians to perform most cardiac interventions without stopping the heart or opening the chest. However, current cardiac devices, including newly developed catheter robots, are unable to accurately track and interact with the fast moving cardiac tissue without applying potentially damaging forces. This paper examines the challenges of implementing force control on a flexible robotic catheter. In particular, catheter friction and backlash must be compensated when controlling tissue interaction forces. Force controller designs are introduced and evaluated experimentally in a number of configurations. The controllers are based on the inner position loop force control approach where the position trajectory is adjusted to achieve a desired force on the target. Friction and backlash compensation improved force tracking up to 86% with residual RMS errors of 0.11 N while following a prerecorded cardiac tissue trajectory with accelerations of up to 3800 mm/s2. This performance provides sufficient accuracy to enable a wide range of beating heart surgical procedures.