DYNAMICS AND CONTROL OF FLEXIBLE GANTRY CRANE SYSTEM

Gantry crane system, a non-slewing-luffing crane system is most widely used in many work places. However, the heavier lifting capacities and the greater size of gantry crane, the vibrational motion become more significant during crane operations and it must be considered. The equations of motion of the system can be obtained by modeling the crane framework using finite element in conjuction with moving finite element method and gantry crane by using Lagrange’s equations. The combinational direct integration technique, namely Newmark- and fourth-order Runge-Kutta method is proposed to solve the coupled equations of motion.
Numerical simulation results show that the combination of flexibility of crane framework and hoist cable produces greater amplitudes and lower swing angles frequency compared to the gantry crane system with flexible hoist cable or crane framework only with respect to the rigid model. Furthermore, all the flexible models of gantry crane system have lower frequencies in the time histories of swing angles of payload with respect to the rigid model for all the parametric studies. The trends of maximum displacements of crane framework and hoist cable increase with the increase of payload mass and initial swing angle of payload. The increases are slightly linear for payload mass and nonlinear for initial swing angle of payload. Under the increase of structural damping, hoist cable stiffness, cross-sectional dimensions of crane framework and hoist cable length, the trends decrease for all the maximum displacements.
Control simulations clearly demonstrate that Zero-Vibration-Derivative-Derivative (ZVDD), Fuzzy Logic Controller (FLC) and Proportional-Integral-Derivative (PID) controllers have rough fluctuations in controlling flexible gantry crane with respect to their performances in controlling the rigid model of gantry crane. Compared to FLC and PID, ZVDD has larger steady state error.