Research On Sliding Mode And Its Applications In AC Servo Systems

Permanent magnet AC servo technique has grown rapidly since 1980's. Because the applications of AC servomotors become more and more complex, many higher requests are offered. The servo systems are hoped to have the ability of adaptation and better performance against disturbance. Variable structure sliding mode controller has been applied gradually in the electric drives because of its advantage of robust and easy realization. The most important drawback in engineering application is the chattering caused by high frequency switching control. Based on the comprehensively deep research on the PMSM's mathematics model and control theory, in order to overcome the blight caused by parameter variant and outside disturbance, the "Variable Structure Sliding Mode "theory is adopted to realize high performance AC servo system with adaptation.The content of this research falls into the following:1. A set of research equipment of AC servo system was built up firstly. The product of AC servo motor and drives are selected as the controlled object, PC acted as the servo controller, both of them was connected with a interface board for position control. The equipment was so flexible that any servo control algorithm can be realized by the program in the computer.2. It gives a detailed comment on the present development of the AC servo system and variable structure sliding mode, and analyzes the merits and drawbacks of the applications on AC servo system of variable structure sliding mode.3. Based on the comprehensively deep research on the PMSM's mathematics model, a newly equivalent sliding mode current controller is presented used by field-oriented control, which improves the stator-current waveform of PMSM, decreases the torque ripple. The conclusion above is verified by the simulation results.4. In order to solve the chattering brought about by structure variant of controller, a design method of dynamic sliding mode in AC servo system is proposed. The control signal produces an effective chattering reduction after integrations, and the addition of the tracking error integration can eliminate the steady-state error. The simulation ofvelocity controller of AC servo system shows that the method can effectively decrease the chattering.5. Combined the fuzzy control and the sliding mode control, an approach of distance-based FSMC is presented, and provides learning algorithms to improve system performance. The results of simulation and experiments show that the method above can eliminate the chattering, robust to the parameters change and load disturbance, and realize easily.