An inductive proximity sensor takes advantage of electromagnetic interaction that occurs between or among metallic objects when they are near each other.

An inductive proximity sensor uses a radio-frequency (RF) oscillator, a frequency detector, and a powdered-iron-core inductor connected into the oscillator circuit, as shown in the diagram. The oscillator is designed so a change in the magnetic flux field in the inductor core causes the frequency to change. This change is sensed by the frequency detector, which sends a signal to the apparatus that controls the robot. In this way, if the system is designed properly, a robot can avoid bumping into metallic objects. In some detectors, the flux change causes the oscillation to stop altogether. So-called metal detectors that people use to search for coins and jewelry at the beach are common examples of devices that employ inductive proximity sensors.

Objects that do not conduct electricity, such as wood and plastic, cannot be detected by inductive proximity sensors. Therefore, other kinds of proximity sensors are necessary for a robot to navigate well in a complex environment, such as a household or office.

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