Research on Gravity Compensation Method of Six-Axis Force/Torque Sensor for Orthopedic Surgical Robot

Abstract

In robotic-assisted orthopedic surgery, surgeons need to monitor the contact force between surgical tool and bone surface in real time using force sensor to ensure the safety of the surgery. In this paper, the position of the six-axis force/torque $(\mathrm{F} / \mathrm{T})$ sensor is designed between the robot flange and the surgical tool, and a gravity compensation method is proposed. This method diminishes the effect of the gravity of the surgical tool on the results of the sensor and thereby enables the sensor to more accurately monitor the contact force. Firstly, the composition of the data from the six-axis F/T sensor is analyzed. Secondly, the inclination angle of the robot base, the gravity and center on gravity of the surgical tool, and the zero point of the six-axis F/T sensor are determined using the least-squares method. Thirdly, the vibration force generated under idling has an effect on the measurement of the six-axis F/T sensor and is filtered using a moving average method. Finally, static calibration experiments, dynamic calibration experiments, and idle filtered experiments are being carried out, which successfully prove the effectiveness and accuracy of the above method for gravity compensation of surgical tools.