In this paper, a sliding mode controller is studied in the experimental control of a flexible undamped beam actuated by a DC motor and including Coulomb friction. A model of the system is described which includes a finite element representation for the beam and a representation for Coulomb friction. The model has been used in the study of closed-loop transient response of the slewing system and predicts the critical factors observed in slewing behavior. Development of the sliding mode controller is based on the nonlinear model of the system. The performance and characteristics of the controller are summarized in a simulation study. The sliding mode controller is particularly effective at eliminating the negative effects of shaft lock-up which tends to result from Coulomb friction and counteracts these nonlinear effects in the presence of modeling uncertainties. The system model includes the interaction that occurs between the DC motor and the slewing beam and a gear train that influences the motor-beam interaction. The effect of motor-beam dynamic interaction is studied for the nonlinear slewing system under sliding mode control. It is found that the motor-beam interaction continues to be an important factor in the closed-loop performance. The paper concludes with a summary of experimental results for the nonlinear control of the motor-beam system.

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