EXTRA EXCAVATION CONTROLLER OF SHIELD EXCAVATOR

PURPOSE:To enhance the accuracy of extra excavation by grasping the difference between each of the aimed values of the angle at which extra excavation is started or the like and its actual actuation value per rotation of a copy cutter, and changing the timing of switching of a solenoid selector valve at the next rotation according to the difference. CONSTITUTION:The signal of a synchro transmitter 10 for converting the angle of rotation of a copy cutter 4 to an electric signal is input to a controlling calculator 20 by an A/D converter 19. A signal from a stroke sensor 11 for detecting the absolute value of jack stroke is input to the calculator 20 by an A/D converter 18. The aimed values of the angles at which extra excavation is started and completed and the stroke of extra excavation are input from an external controller to the calculator 20 and the difference between each aimed value and its actual actuation value is grasped at the calculator 20 and signals indicative of expansion and contraction or stopping of a hydraulic jack 5 are output to a sequencer 22 according to the difference. A solenoid selector valve 15 is controlled according to the signal of the sequencer 22.