Volvo Construction Equipment Korea Co., Ltd.

Man Hyung Lee

Min Cheol Lee

Soon Yong Yang

An improved absolute position detection method is provided for a stroke sensing cylinder which includes a magnetic scale detecting step for obtaining a plurality of sine wave form voltages having different phases using a magnetic sensor unit in accordance with a driving operation of the cylinder. A wave form generation step is also provided for converting the sine wave form voltage obtained in the magnetic scale detection step into a square wave form and generating a triangle wave form having the same period as the thusly converted square wave form. A first absolute position value detection and stroke direction judging step is then provided for judging a first absolute position value and stroke direction of the cylinder using a pair of square and triangle wave forms generated in the wave form generation step. Lastly, a second absolute position value computation and storing step is provided for computing and storing a second absolute position value having a predetermined value based on the first absolute position value. The method of the present invention is directed to detecting a magnetic flux change of a magnetic scale using a plurality of magnetic sensors. The magnetic scale is disposed along the cylinder rod and includes at least one different magnetic scale processing period contained within a regularly protruded and recessed portion. Signal-processing is achieved using a microprocessor and a 1/N-dividing counter. The thusly signal-processed wave forms are counted and an absolute position and stroke direction is determined.

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Kumjung-ku, South Korea

Man Hyung Lee