TABLE OF CONTENTS There are a wide variety of sensors used in mobile robots (Figure 6.1). Some sensors are used to measure simple values like the internal temperature of a robot s electronics or the rotational speed of the motors. Other, more sophisticated sensors can be used to acquire information about the robot s environment or even to directly measure a robot s global position. We classify sensors using two important functional axes:
proprioceptive/exteroceptive and
passive/active.
Proprioceptive sensors measure values internal to the system (robot); for example, motor speed, wheel load, robot arm joint angles, and battery voltage.
Exteroceptive sensors acquire information from the robot s environment; for example, distance measurements, light intensity, and sound amplitude. Hence, exteroceptive sensor measurements are interpreted by the robot in order to extract meaningful environmental features.
Passive sensors measure ambient environment energy entering the sensor. Examples of passive sensors include temperature probes, microphones, and CCD or CMOS cameras.
Active sensors emit energy into the environment, and then measure the environmental reaction. Because active sensors can manage more controlled interactions with the environment, they often achieve superior performance. However, active sensing includes several risks: the outbound energy may affect the very characteristics that the sensor is attempting to measure. Furthermore, an active sensor may suffer from interference between its signal and those beyond its control. For example, signals emitted by other...
