Robust motion control algorithm for brushless direct drive motor

Brushless direct drive motors became very popular among robot designers due to the simple mechanical structure which avoids the use of a speed reducer. Speed reducers introduce undesired nonlinear phenomena in the motion transmission, thus imposing positioning errors and uncertain control stability. With the use of the direct drive motor backlash flexibility, and friction are diminished or eliminated, while highly nonlinear load variation affecting the motor axis is not reduced. Therefore, an advanced motion control algorithm has to be applied in a control scheme. The paper introduces a robust motion control algorithm, which is derived from a sliding manifold definition and Lyapunov design introducing the perturbation estimator. The control algorithm was tested using a highly nonlinear direct driven ball and beam system. Experimental results are presented and discussed.