Abstract
To allow the hoisting motor drive system of a crane to track a load torque quickly, a linearization method was used to transform a motor nominal dynamics model into two decoupled linear rotor speed and flux linkage subsystems. The method based on the theory of differential geometry was a precise feedback method. Two active disturbance rejection controllers (ADRCs) with identical structures were designed for the rotor speed and flux linkage subsystems. The extended state observer of the ADRC could estimate the unmodeled dynamics of the motor, the variation of motor parameters due to heating, and the unknown disturbances of the motor system to determine the total disturbances of the system. A closed-loop system with ADRC and an open-loop system were compared. The motor's full-load starting time was reduced by about 50%. When the motor operated smoothly at different load rates and the rated load was suddenly applied, the electromagnetic torque fluctuation range did not exceed 20 N·m. The rotor flux was always stable at the reference value. The motor speed decreased, but the amount of decrease did not exceed 7 rad/s. The closed-loop system had a significant energy-saving effect during the motor's starting process. The power saving rate was about 55%-59% if the motor started with a light load. The power saving rate could reach 71% if the motor started with a heavy load. The ADRC system could accurately estimate the unknown model of the rotor speed and flux linkage subsystems, and adapt to parameter variations of the motor stator and rotor resistance in the range of ±10%.
Highlights
A crane is an important type of logistics equipment to realize material handling mechanization in factory workshops or warehouses, railway freight yards, port wharfs, and other locations [1], [2]
As a main factor of improvement in the energetic efficiency of the crane, particular attention should be paid on the hoisting motor drive system [9]
In part II, we described a condition where a multi-input multi-output (MIMO) affine nonlinear system could be linearized
Summary
A crane is an important type of logistics equipment to realize material handling mechanization in factory workshops or warehouses, railway freight yards, port wharfs, and other locations [1], [2]. Unlike local linear approximations using Taylor series expansions, nonlinear feedback linearization does not ignore any higher-order nonlinear terms in the linearization process, so the linearization is accurate and global Using this nonlinear feedback linearization method, the coupled and complex nonlinear control system of an AC induction motor is transformed into two completely decoupled and simple second-order subsystems: linear rotor speed and flux linkage. The nonlinear feedback linearization method was used to transform the complex, nonlinear, and coupled nominal motor dynamics model into two simple, linear, and decoupled subsystems: rotor speed and flux linkage. Two ADRC controllers with identical structures were designed for the two subsystems, which allows the motor to start quickly and shortens the transition process of the electromagnetic torque when the motor is suddenly loaded. In parts VII and VIII, important conclusions were drawn through experimental study
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