Positioning servo and controlled mechanism

Abstract

A tube bending machine includes a carriage mounted rotatable chuck for grasping and positioning a length of tube with respect to the bending head of the machine. Motion of the carriage along the bed of the machine toward the bending head and rotation of the chuck relative to the carriage are both powered by a single remotely mounted motor driving an endless chain. The chain engages a drive sprocket rotatable on the carriage and gear connected to rotate the chuck. A chuck brake and a carriage distance brake are selectively energized so that when chuck rotation is prevented, the sprocket is locked to the chain and the carriage will be driven by the chain, and when carriage travel is prevented, the chuck is rotated by the chain driven sprocket. The remote motor is connected in a primary servo system to provide a closed loop drive of either the chuck rotation or the carriage travel. A secondary closed loop brake control system is provided for each of the chuck rotation and carriage travel. The position error signal of the primary servo system is compared with a signal representing actual velocity of the chuck or carriage and a second error signal proportional to the difference between the position error and the actual velocity is employed to proportionally energize the corresponding brake.