The term open-loop system refers to any machine that does not incorporate a servomechanism. For this reason, open-loop robots are often called nonservoed robots. This type of robot depends, for its positioning accuracy, on the alignment and precision of its parts. There is no means for correcting positioning errors. The robot operates blind; it cannot compare its location or orientation with respect to its surroundings.

Open-loop systems can work faster than closed-loop, or servoed, robotic systems. This is because there is no feedback in an open-loop system, and therefore, no time is needed to process feedback signals and make positioning corrections. Open-loop systems are also less expensive than closed-loop systems. However, in tasks that require extreme accuracy, open-loop systems are not precise enough. This is especially true when a robot must make many programmed movements, one after the other. In some types of robotic systems, positioning errors accumulate unless they are corrected from time to time.

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