Compensation and calibration of gravitational forces in a force-feedback enabled surgical robot

The use of robots in performing various surgical procedures have seen a rapid increase in the last couple of decades, where advantages such as increased accuracy and repeatability can be realized. These systems still have various factors limiting their wide spread use, including; large costs, taking up too much space, and providing little or no force-feedback. Accurate force-feedback is not only important in providing the sense of touch to the surgeon, but also in safety and automation related procedures, and is the main focus of this paper. Specifically the interaction forces between the surgical tool and the manipulated tissues are of interest, with all other forces eliminated or compensated for. This paper introduces a robotic system for minimally invasive surgery with a novel surgical tool for force/torque sensing. The tool uses an overcoat method to eliminate force/torque corruption at the trocar, and an accelerometer for gravity compensation. The overcoat method is briefly presented, where the developed approach for gravity compensation and calibration is discussed in detail. Simulation and experimental results are presented to validate the concepts and show the successful removal of gravitational forces with good accuracies.