2.3.Development of Absolute Position DetectingCylinderFigure 6 shows a bucket arm of hydraulic excavator inwhich the absolute position detecting cylinder is installed.Sensor assembly is mounted on the head of cylinder andmagnetic scaled piston rod with grooves pattern is replacedwith a normal piston rod.We analyze the Hall sensor signals according to velocityof the cylinder in order to design the absolute positiondetecting algorithm. Figure 7 shows the amplified voltagewaveforms of two Hall sensors. After passing the datumregions, the amplitude and distortion of Hall sensor signalare increased as speeding up of stroke. The distortion iscaused by the magnetic gradient.