w(s) is the drive’s velocity expressed in the Laplace (i.e.“ s ”) domain. J is the inertia, and B is the viscous damping.Td is the disturbance imposed by constant Coulomb friction opposing the direction of travel. ‘Td’ can be represented with two parameters ( T and T ) in the Least Squares identification, where d TT when angular velocity,w > 0 and d TT when angular velocity, w > 0 . The overall inertia of the ball screw mechanism is estimated using catalogue and calculated values for different components .The values of motor and the coupling inertias are 24 mm .9 1010 kgm u and 24 mc .9 013 10 kgm u , respectively. The inertia of the ball screw is calculated assuming a cylindrical structure: