126 Industrial Robotics Fundamentals Copyright Goodheart-Willcox Co., Inc. necessary tasks. Digital systems can control various operations, such as position- ing and moving, clamping, and directing material flow. fl 6.4 Rotary Motion Systems An electric motor is a device that converts electrical energy to mechanical move- r ment in the form of rotary motion. Essentially, an electric motor is created by plac- ing an electromagnet, called an armature, between two permanent magnets. The north and south poles of the armature are aligned with the north and south poles of the permanent magnets. When a current is passed through the armature, it becomes magnetized and begins to rotate within the magnetic field of the perma- fi nent magnets. Rotation continues until the armature’s north pole is opposite the south pole of a permanent magnet and the armature’s south pole is opposite the magnet’s north pole, Figure 6-6. If the current through the armature is reversed, its poles will reverse, and the armature will rotate again. The rotary motion, or turning force, that is produced is called torque. The amount of torque produced by a motor depends on the strength of the magnetic fields and the amount of current fi Energy source Reference source Controlled element Control Comparator Feedback signal Reference source signal Correction signal Goodheart-Willcox Publisher Figure 6-5. The comparator and reference source in this closed-loop control system allow automatic adjustments to be made to a process while it is running. Armature Battery Permanent magnet Permanent magnet S N S S N N Goodheart-Willcox Publisher Figure 6-6. Matching magnetic poles that repel one another cause the armature to rotate in a motor.