Ink Droplet Position Compensation Based On Extended State Observer

Serial printers print pictures and words through the print head's horizontal scanning motion and the print media's vertical feed motion. However, the droplet's parabolic trajectory, which is caused by the scanning motion of print head, will lead to a position error between the droplet's actual position and its expected position, and this position error reduces the print quality severely in high-speed printing. A novel method based on the extended state observer is proposed to compensate the droplet's position error in this paper. The entire process of this compensation method is as follows: a velocity estimator based on extended state observer is designed to estimate the carriage's velocity on line, then the exact firing time is calculated, thus the droplets are fired ahead of time. In this paper, firstly the carriage servo system and the velocity estimator base on extended state observer are built, and the simulation is finished, which shows that the velocity estimator could estimate the carriage's velocity perfectly with the estimating error less than 0.8%. Then the experimental system based on the extended state observer is designed. Finally, experiments are carried out on the test bench to check the compensation performance. Results indicate that when the print speed is increased to 1m/s, the average position error is limited to less than 11.2μm.