Positioning control device for a fluid powered cylinder

摘要

A coil assembly including primary coils (A1-D1 ) disposed at predetermined locations axially spaced from one another and secondary coils (A2-D2) corresponding to these primary coils is fixed at one end of a cylinder (1). A piston rod (21) is slidably disposed through a space in the coils. Rings (21b) made of magnetic substance are provided on the rod with a predetermined axial interval therebetween. Each of the primary coils is excited with one of AC signals which are out of phase with one another and an output signal which is electrically phase-shifted in accordance with the position of the rod is obtained as a sum of output signals from the secondary coils. Piston rod position data is obtained by measuring the amount of the phase-shifting and is utilized for positioning control of the cylinder. The velocity and acceleration of the movement of the rod are detected and the amount of overrun is estimated in accordance with the detected velocity and acceleration to effect the most accurate positioning control. Each time the positioning is completed, the amount of overrun is corrected to improve the accuracy of a next positioning control.