Optimal design of ball-screw driven servomechanisms through an integrated mechatronic approach

This paper proposes a novel model-based mechatronic approach for the design of ball-screw driven servomechanisms. The proposed technique is aimed at selecting the optimal combination of electric motor and ball-screw which minimizes the motor torque, while ensuring the achievement of the prescribed dynamic performances of the closed loop system. Such performances, as well as feasibility constraints related to the component characteristics, are translated in the method as bounds in the lead – diameter space. In particular, feasible torque and speed are the constraints posed by the motor; screw critical speed, ball critical speed, service life, buckling load are those due to the ball-screw, while the controlled system performances are included through the inertia ratio and the bandwidth requirements. To this purpose, the ball-screw non-ideal characteristics are represented through models with different complexity and are accounted for in the design. A straightforward graphical approach is formulated to trade off between the many conflicting requirements and to prevent both overly conservative and undersized design, while ensuring problem solvability.