Study On Control Of The Load Swing And Positioning Systems For Cranes

Overhead cranes and gantry cranes are important material handling machinery in modern industrial production. They are widely used to allocate and transport products in production workshop, to stack containers at the ports and to load and unload logs in forest zones. In operation process of Cranes, the load will produce oscillations due to the dolly and cart changing their motion states. This will lower the crane hoisting operation efficiency and safety.This paper did the dynamics analysis of overhead cranes and gantry cranes’ hoisting process and put forward some control schemes according to the dynamic characteristics of the system. It has practical significance in the respect of improving the crane productivity and the operation safety. The main research contents are as follows:(1)Conduct the mechanical analysis of cranes as a whole and establish a mathematical model of the hoisting process of cranes using Lagrange equation when the dolly and cart are moving at the same time. The analysis results show that the swing of load in the dolly and carts’ running plane are uncorrelated. It’s enough to establish a system model when only cart is moving. Do the linear processing on the model and come to a conclusion that the system is critical stable state and has an oscillation.(2)Conduct the simulation test of dynamic characteristics of the system with MATLAB/Simulink software. The simulation result shows that the load is forced to do the swing from starting phase towards braking phase and its speed change periodically. The main factors of positioning are the weight of load and the rope length. It need a long time for the load to eliminate swing by the damping effect of air resistance and the wire rope damping after the cart braking to stop.(3)Use the theory of PID control and fuzzy logic control to study the swing and positioning control mechanism, then do the simulation test according to the two methods:both PID control and fuzzy control systems can let the load reach the target displacement following the cart and eliminate swing fast. While both have their shortcomings:PID control has a large overshoot and the restrict effect of biggest pendulum angle is not enough. Fuzzy control can’t eliminate the steady-state error and it’s hard to guarantee the stability. On this basis, combine the PID control and fuzzy control composing the self-tuning fuzzy PID control system. Simulation tests result show that this control system regulates fast as the common fuzzy control system does and it make the biggest pendulum angle smaller. Swing time of load become further shorter. It also has a good robustness towards the load weight and the rope length.