Model-Based Dynamic Calibration of a Multi-Actuator Gap Leveler for Heavy Plates

Abstract

A novel method to calibrate the work rolls of a precision leveler for heavy plates is proposed. During the leveling process, a sequence of bending steps is imposed on the plate by the work rolls of the leveler to eliminate flatness defects. The respective positions of the rolls define the intensity of the consecutive bends. Any deviation from the desired roll position may result in a suboptimal leveling process. Thus, an exact control of the position of the work rolls is required. Due to backlash, wear, tolerances, and elastic deformation, the roll positions cannot be determined from nominal parameters and dimensions. Therefore, the machine has to be calibrated and properly adjusted to find suitable reference positions for control. During calibration, the structure is prestressed with a suitable test force and the signals of force and displacement sensors are recorded. As a result, reference points for future control inputs are obtained. A major drawback of a frequently used calibration method for levelers is that the work rolls of multi-actuator gap levelers cannot be properly calibrated. In practice, the work rolls are manually adjusted by the maintenance personnel of the machine. In this case, backlash may cause the loaded work rolls to deviate from their intended positions. Thus, a new method to calibrate the position of the individually actuated work rolls is developed and tested.