Research On Control Technology For Inverted Plasma Arc Cutting Power

This thesis makes a study on control technology for its research object,inverted plasma arc cutting power, which is a special electrical equipment inmaterial processing industry. It obtains system control requirements through theanalysis of the controlled object properties, and then makes the design andimplementation for the controller with cutting quality optimization as its startingpoint. In the cutting power field, the traditional control schemes can not improvethe cutting quality because they aim at the improvement of the output currentquality, ignoring the system disturbing effect due to the real-time processparameter changes, in the view of this article, a solution based on the hybridcontrol strategy is proposed.The design of the control strategy is decided by two sides: control objectivesand system features, control targets decide what like the object is controlled andsystem characteristics determine how to control it. The fundamental evaluationfor plasma arc cutting is the sheet metal cutting quality, not the cutting currentaccuracy. When the machining precision is determined, the key which affectscutting quality lies in the coupling disturbing effect for output current due to thereal-time changes of mutiple process parameters. Therefore, in order to achievethe purpose of optimizing the cutting quality, this thesis proposes a hybridcontrol strategy composed of intelligent technology deciding unit and servocontrol unit. The technology deciding unit makes overall reconstruction for thetechnology coupling with nonlinear mapping ability of RBF-NN to realize theprocess disturbance compensation; the servo control unit suppress systemdisturbance affect with fuzzy logic as its core to ensure system output waveformquality.Then we make hardware and software design for the digital control systemwith DSP TMS320LF2407A as the core, which is of high-speed and high accuracy, as to achieve the power’s digital control. Finally, this thesis makessystem simulation experiments in order to verify the effectiveness of the controlprogram. The system simulation makes verifications from mutiple angles such asdecoupling ability, dynamic characteristics, steady state characteristics,robustness with MATLAB7.1/Simulink6.3as simulation platform. Theexperimental results show that this control scheme can improve system dynamicand steady characteristics, and optimizes the cutting quality.