초록 ▼

A magnetic scale formed by arranging a non-magnetic material at a predetermined pitch in the direction of motion of a piston rod, and a pair of magnetic sensors which output two sine waves with a phase difference of 90°corresponding to the pitch of said magnetic scale, are provided. The peak voltage

A magnetic scale formed by arranging a non-magnetic material at a predetermined pitch in the direction of motion of a piston rod, and a pair of magnetic sensors which output two sine waves with a phase difference of 90°corresponding to the pitch of said magnetic scale, are provided. The peak voltages of the sensor output at each pitch of the magnetic scale are updated and stored. Center voltages are computed from the peak voltages at each pitch, and a coarse displacement is computed based on the result of comparing the center voltages and sensor outputs. Correction coefficients of the sensor outputs are computed from the peak voltages and center voltages, and the sensor outputs are compensated based on these correction coefficients. A fine displacement is then computed by an inverse trigonometric function from the two corrected signals, and a displacement signal is output by adding the coarse displacement to the fine displacement.

대표청구항 ▼

An apparatus for detecting the displacement of a piston rod in a cylinder comprising: a magnetic scale comprising a non-magnetic material embedded in the piston rod with a predetermined pitch interval in the direction of motion of said piston rod, a pair of magnetic sensors positioned to output two

An apparatus for detecting the displacement of a piston rod in a cylinder comprising: a magnetic scale comprising a non-magnetic material embedded in the piston rod with a predetermined pitch interval in the direction of motion of said piston rod, a pair of magnetic sensors positioned to output two sine waves with a phase difference of 90°with respect to the pitch interval of said magnetic scale, means for updating and storing the peak voltages output by said sensors at each pitch interval of the magnetic scale, means for computing a center voltage of the oscillation from said peak voltages at each pitch interval, means for computing a coarse displacement from the result of comparing said computed center voltages and said sensor outputs, means for computing correction coefficients of said sensor outputs from said peak voltages and said center voltages, means for compensating said sensor output signal from said correction coefficients to produce two compensated signals, means for computing and outputting a fine displacement signal from an inverse trigonometric function using said two compensated signals, and a displacement computing means for outputting a displacement signal comprising means for adding said coarse displacement to said fine displacement signal, said peak voltage updating and storing means comprising means for memorizing the peak voltages output by the sensors over the entire stroke of the piston rod.