DESIGN OF THE BALL SCREW MECHANISM FOR OPTIMAL EFFICIENCY

This paper develops theories for evaluating the efficiency of the ball screw mechanism and additionally, for designing this mechanism. Initi ally, a quasi-static analysis, which is similar to that of the early w ork in this area, is employed to evaluate efficiency. Dynamic forces, which are neglected by the quasi-static analysis, will have an effect on efficiency. Thus, an exact theory based on the simultaneous solutio n of both the Newton-Euler equations of motion and the relevant kinema tic equations is employed to determine mechanism efficiency, as well a s the steady-state motion of all components within the ball screw. How ever, the development of design methods based on this exact theory is difficult due to the extensive computation necessary and thus, an appr oximate closed-form representation, that still accounts for the ball s crew dynamics, is derived. The validity of this closed-form solution i s proven and it is then used in developing an optimum design methodolo gy for the ball screw mechanism based on efficiency. Additionally, the self-braking condition is examined, as are load capacity consideratio ns.