01-09-2012, 03:56 PM
Ultrasonic Sensors: How they Work and their Limitations in Robotics
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Abstract
Ultrasonic sensors are relatively simple and easy to interface with and thus are a good sensor to use in robotics. The sensor emits a sonic pulse and then waits for the returned echo reflecting off an object. The pulse is emitted by a transducer which converts between electrical, mechanical, and sonic energy(Ultrasonic FAQ). The time between the sent pulse and the returned echo is used to calculate distance. Ultrasonic sensors are not perfect and do have drawbacks. The emitted pulse has a cone shape and any object the pulse encounters will return an echo(lynxmotion.com). It is not possible to discern between small objects, such as a broomstick, and large objects such as a chair or wall for this reason as both will return an echo(Shinsel). These drawbacks can be overcome by using multiple or rotating sensors(Shinsel).
How do ultrasonic sensors work?
Ultrasonic sensors are a simple device. They send out an ultrasonic pulse and then wait for a response. When the pulse leaves the device, it travels through the air until it collides with an object, at which point an echo is reflected back. This echo is then sensed by the ultrasonic sensor. The sent pulse is anywhere from 40-200khz, but is typically in the 40-50khz range(Ultrasonic FAQ).
[attachment=33124]
Abstract
Ultrasonic sensors are relatively simple and easy to interface with and thus are a good sensor to use in robotics. The sensor emits a sonic pulse and then waits for the returned echo reflecting off an object. The pulse is emitted by a transducer which converts between electrical, mechanical, and sonic energy(Ultrasonic FAQ). The time between the sent pulse and the returned echo is used to calculate distance. Ultrasonic sensors are not perfect and do have drawbacks. The emitted pulse has a cone shape and any object the pulse encounters will return an echo(lynxmotion.com). It is not possible to discern between small objects, such as a broomstick, and large objects such as a chair or wall for this reason as both will return an echo(Shinsel). These drawbacks can be overcome by using multiple or rotating sensors(Shinsel).
How do ultrasonic sensors work?
Ultrasonic sensors are a simple device. They send out an ultrasonic pulse and then wait for a response. When the pulse leaves the device, it travels through the air until it collides with an object, at which point an echo is reflected back. This echo is then sensed by the ultrasonic sensor. The sent pulse is anywhere from 40-200khz, but is typically in the 40-50khz range(Ultrasonic FAQ).