Influence of flexible spherical joints parameters on accuracy of the six-axis force/torque sensor with three-three orthogonal parallel mechanism

•A six-axis force/torque sensor with three-three orthogonal force-sensitive elements is proposed.•The stiffness matrix of a six-axis force/torque sensor based on flexible spherical joints is derived.•The force mapping matrix between the axial tension/pressure of the force-sensitive element and the generalized external force applied on the upper platform is established.•The influence of the flexible spherical joints parameters on the sensor accuracy is analyzed.