Anti-Swing Control Of Overhead Cranes Using PID Method

Eliminating and suppressing swings of loads are very important for overhead cranes to increase their work efficiency and ensure safe operation. Utilizing automatic control methods to achieve anti-swing purpose is an efficient way to reduce the work intensity of drives and increase operation efficiency. This is also the tendency of actualizing the loading and unloading machinery automation. This dissertation investigated the anti-swing control of overhead cranes.We firstly derived the nonlinear dynamic model of the overhead crane system using the Lagrange equations of the second kind, and then made a simplification on it, obtaining the corresponding linear dynamic model. We found this model was controllable and observable, which is a foundation for anti-swing control.Secondly, in order to consider the effects of the dynamics of the suspend wire, the finite element method was employed to model the wire, and then a dynamic model of overhead cranes including wire dynamics was obtained. Comparative simulations were made for the linear model, nonlinear model and vibration model including wire dynamics. The results showed that there were lag and high-frequency vibration in the response of the system.PID controllers were utilized for both the cart position control and the load swing angle control. Parameters of the controller were optimized using genetic algorithm. For parameter-determined models PID controllers with optimized parameters could obtain good control effect.Finally, the fuzzy control theory was introduced to automatically tune the parameters of PID controller in order to adapt to the variation of the model parameters, thus forming a kind of fuzzy adaptive PID controller. Both the cart position and the load swing angle were controlled using the fuzzy adaptive controllers. Simulation results showed that this kind of PID control could achieve good effect in the swing suppression.