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The conversion of rotary to translational motion in lead screw drives occurs at the meshing lead screw and nut threads. Adecreasing coefficient of friction with sliding velocity, may lead to instabilities in these drives. In this paper, a sliding mode controller is designed for a two degrees of freedom lead screw drive model. This controller has two objectives: to regulate the lead screw angular velocity to a preset value and to attenuate friction-induced vibrations. Only upper and/or lower bounds of system parameters are assumed to be known. In addition, in the development of the controller no specific model is assumed for the dependence of the coefficient of friction on the relative sliding velocity. Two modifications are applied to the basic discontinuous sliding mode controller to eliminate the inherent chattering problem and to limit thecontrolled input torque levels. Numerical simulation results are presented that show the applicability and the performance of the proposed controller.

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