Research on Load's Tracking Control for Crane's Motor Driving System

In order to control a crane motor to real-time track the abrupt load torque with a given rotational speed for the motor driving system, the equivalent moment of inertia and equivalent load torque on the rotor of the hoisting mechanism and the dynamic equation of the motor driving system were derived through equivalent conversion. Then a system of synchronous rotating coordinates was constructed according to rotor flux linkage orientation, and a vector variable frequency control system for tracking load torque was designed based on the slip angle frequency. The results of a case study show that the starting time of the close-loop control system with no load was 0.34 s faster than that of the open-loop system, the motor could start stably, and the difference of electromagnetic torque's peak value was 148 Nm between the open-loop system and the close-loop control system. In addition, the electric power consumption of the motor in the close-loop control system was less than that in the open-loop system; especially at the motor's starting stage, the motor peak power of the open-loop system was 2.5 times that of the close-loop control system. In brief, under the designed close-loop control, the motor could save about 50% energy during the starting stage and about 30% during the stable running stage.