Abstract: According to the deficiency of performance of the traditional six-axis force sensor based on Stewart platform structure on decoupling and stiffness, a pre-stressed six-axis force sensor with dual layers is designed and developed, and the static calibration of the sensor is carried out. The proposed six-axis force sensor uses cone-socket type spherical joint instead of the traditional one, which reduces the friction torque of spherical pair effectively and eliminates the commutation impact force for the measuring limbs compressed all the time, so the overall stiffness is improved. Based on screw theory, the mapping of the applied external force and the axial force of measuring limbs of the sensor is derived, and then the measuring principle of the pre-stressed six-axis force sensor is described. Analysis of static decoupling and measurement error of the sensor is conducted by using linear least squares calibration method, and the calibration matrix and error matrix are deduced. The prototype of the dual layers pre-stressed six-axis force sensor was manufactured and the static calibration is performed. The experimental result shows that the maximum nonlinearity error in all the directions of the sensor prototype is less than 1.17%, and the maximum interference error is less than 1.82%, which indicates that the developed six-axis force/torque sensor possesses high measurement accuracy, and can be used for the industrial production which requires higher six-axis force measurement.

Key words: Dual layers, Pre-stressed, Six-axis force sensor, Spherical joint, Static calibration