State estimation, positioning and anti-swing robust control of traveling crane-lifter system

Under different loading conditions, the over-head cranes may experience a wide range of model parameters variation. A robust control strategy is developed to achieve the high positioning accuracy, short transportation time and suppression of swing angle for an uncertain over-head crane system. Over-head crane is modeled as a three degrees of freedom system and control problem is investigated for two cases: a system with a single control input (the force on trolley) and a system with two control inputs (the force on trolley and the torque on lifter). Regulator and observer systems are designed. To achieve the tracking objectives, an optimal robust controller is designed based on μ-synthesis with DK-iteration algorithm. Perfect positioning and suppression of swing angle are achieved in shorter time when both control inputs are applied. Moreover, in this case, less control inputs resulted in smaller oscillations, in comparison with the case when only the force is exerted on the trolley.