In the above block diagram, the ref

In the above block diagram, the reference is a step input with step size 0.6 m and the control objective is to accurately move the work piece to the desired point of0.6m.The current amplifier block is to produce an appropriate current for the motor to work, and in the motor block it converts the current to appropriate torque. The input to the ball screw model is the resultant torque produced by the motor and it avoids the friction produced ,so that as a disturbance we considered a coulomb friction, the torque produced by coulomb friction is subtracted by the motor torque to applied to the ball screw model. The output of the ball screw model is the angular velocity ,for converting the rotational motion to the linear motion we are introducing a conversion ratio at the output of the ball-screw model .An integrator is placed at its output to make the output a measurable quality means a velocity to a displacement, we are using an integrator. The output of the integrator is a saturation, it is for bringing the output to a required limit.