Development of Absolute Position Detecting Cylinder for Automatic Excavator

There are increasingly demands for automation in heavy construction machinery because of high rate of accidents and the shortage of skilled operators. In particular, absolute position detection in each joint is very important for implementing automation of the construction machinery. In this paper, the hydraulic cylinder with magnetic sensor is developed to detect an absolute position of the stroke. And the algorithm detecting stable an absolute position in various work environments is developed. The algorithm to recognize the datum region of a repeating pattern of grooves which are manufactured on piston rod can detect an absolute position by getting only a little displacement. Finally, the performance for detecting the absolute position is evaluated in a real excavator. As the experimental result, the developed system can stably measure an absolute stroke-sensing displacement, even though the initial position error is occurred at the beginning of operation.