Experimental modal analysis, DDS system identification, and forecasting compensatory control of a color laser printer.

Abstract

This dissertation presents a structural vibration analysis, a system identification, and an active vibration control of a mechanical structure based on the experimental modal analysis, the dynamic data system (DDS), and the forecasting compensatory control (FCC) methods. This approach was applied to a color laser printer which occasionally produces a blurred image presumably caused by structural vibrations. By applying the experimental modal analysis technique with both the conventional frequency response function method and the DDS method, it has been identified that the main structure of the color laser printer has three dominant modes under 1,000 Hz, and the laser scanning motor has three excitation frequencies very close to those dominant modes. This strongly indicates possible structural resonance. The experimental modal analysis results were also used to decide where the actuator and the sensor need to be placed to achieve the maximum control efficiency. The DDS method has been applied successfully to identify the system dynamics between the exciter and the sensor locations. The estimated models were used in the development of controllers. In preliminary experimental tests, a linear quadratic (LQ) controller combined with the DDS model was used to control the printer structural vibrations due to impulse and random excitations. The variance of acceleration response of the first mode at 308 Hz was reduced by 46%. The FCC method was used to control the structural vibrations. However, in the simulation and experiment, the control input frequently went into saturation because the FCC method needed a large control force. A new generalized FCC (GFCC) method has therefore been developed by incorporating the concept of the prediction horizon and a weighting function on control command in the object function. The stability robustness of this GFCC method due to the parameter perturbation is also analyzed. The GFCC has been shown very effective in both simulation and experiment. In the control of the beam's first mode at 15 Hz, a 81% variance reduction of random displacement response was achieved. For the vibration control of two modes at 15 and 88 Hz, random displacement response was reduced by a 67%.