Abstract: In the sequence program (ladder circuit), in order to give a common address between contacts of the ladder circuit longitudinally and store states before and after the processing of the contact in the ladder circuit, two types of memories corresponding to addresses at the both ends of the contact are provided and a compiler for classifying the processing into the five types and a sequence execution unit for processing a machine language of the compiler are further provided so that execution can be made even if an output instruction is provided in an intermediate portion of the ladder circuit.

Abstract: Disclosed is an industrial robot of the type wherein the robot arm is directly driven by a motor. A position encoder generates a signal representative of the actual position of the arm and a manually controlled position entry switch is operable during a teaching mode. When the arm is manually moved to a desired position, a memory controller responds to the operation of the position entry device by storing the actual position signal in a memory as a target position signal, and reads the stored signal during a playback mode. A servo-control system responds to the actual position signal from the encoder and the target position signal from the memory by controlling the motor so that the actual position of the arm approaches the desired position during the playback mode. The output of the servo-control system is decreased during the teaching mode to render the arm manually movable to the desired position and is increased during the playback mode.