2018 年 12 巻 7 号 p. JAMDSM0125
This paper analyzes stability and tracking performance of displayed-marker-based position tracking on visual displays, such as an LCD (Liquid Crystal Display), which have been utilized in several studies about computer-human interaction systems. The tracking system dealt in this paper consists of an LCD and a target object with photo sensors that is placed on the display surface. A fiducial marker image is displayed beneath the object and the photo sensors detect the relative displacement between the marker and the object. The detected displacement is fed back to the tracking program and the program updates the marker position such that it will track the object. In general, this kind of tracking methods can suffer from display latency that arises from programs, graphic engines, and internal signal processing circuits of LCDs. This paper investigates the latency characteristics to reveal that the lag is not constant; it fluctuates with time. The paper, then, formulates the tracking system and analyzes how the lag affects the tracking stability. Then, the paper analyzes the tracking performance of two different classes of stable tracking algorithms, which are PD control and lag compensation. Based on the analyses, the paper provides a guideline on the selection of tracking algorithms, as well as tracking parameters. The analyzed results, as well as the guideline, are verified by experiments in 1-DOF horizontal motions.