Research On Torsional Oscillation In AC Servo System

In industry, separated mechanical components are combined and work togetheraccordingly through mechanical shafts. Since the stiffness of the shaft is finite which resultto torque transfer delay through the shaft, especially with flexible shafts. Thus, the speed ofboth ends of the shaft are different, the bandwidth of the system is limited by shaft torsionaloscillation. Based on the relative research on the shaft torsional oscillation both from homeand abroad, the design and of high performance servo system are deeply discussed and anotch filter is utilized to suppress the oscillation in the servo system. The research mainlycontains4parts, as the follows.Part1includes chapter1and2. In this part, the developing history of AC servo systemis briefly concluded and the torsional oscillation in servo system is raised up which is alsothe target of this thesis. And research on methods to suppress the oscillation from home andabroad are summed up and compared. Then, the mathematic model of Permanent MagnetSynchronous Motor(PMSM) and vector control strategy are described in detail. Also, thecurrent loop and speed loop of the control system are analyzed. In addition, the influence ofPI parameters have on performance of the control system are described in detail.Part2contains chapter3. In this part, the shaft torsional oscillation in servo system isanalyzed deeply, the mathematic model of the two mass load is built up, the transfer functionthe bode diagram of the load model is obtained. Based on the magnitude-frequency diagram, thenotch filter is proposed to eliminate the poles of the transfer function thus to suppress thetorsional oscillation. Then, the method to design the notch filter and way to realize the programis given. Also, two methods to acquire the oscillation frequency are contrasted.Part3contains chapter4and5. In this part, the simulation platform of the servo systembased on the AC motor Vector Control is built up to simulate the performance of both thecontrol system and the notch filter. Also, based on the equation of motion, the load inertidentification is simulated to calculate PI parameters.Part4includes chapter6and7. In this part, the hardware and software of theexperimental platform, which contains design of main power source, periphery circuit of theDSP controller, and the absolute position encoder, are briefly described. Also the sum up ofthis thesis is given in the end.