Image Number 6 for United States Patent #4904115.
Method of controlling the trajectory of a shield-type tunnelling machine equipped with displacement control hydraulic rams (3), characterized in that, these rams being divided into at least three groups of rams (6A, 6B, 6C), the theoretical instantaneous flowrates of fluid to be applied to each of these groups are continuously determined (40) from the curvature characteristics and the overall rate of advance set point trajectory and these groups (7-26-27-28) are supplied with instantaneous flowrates, the values of which correspond to the theoretical values.
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