Ultrasonic Distance Sensor

These range sensors test how close you are to an object by using sonar waves. These will bounce off an object and the time it took for the wave to get back to the sensor is used to calculate the distance from the object. These come in all distances and strengths but can be fairly accurate at a far lower price than Lidar.

Sensor Overview

Obstacle Detection: Detects the nearest obstacle in a cone. Although the detection area is significantly larger than IR and 1D lidar, the ultrasonic sensor still only measures the distance to the closest object. Maximum detection range is about 15 feet.

Ideal operating conditions: No sources of external ultrasonic noise present.

Sensor Pros:

• Data is easily processed, allowing the use of cheaper microcontrollers
• Inexpensive
• Good detection range and update rate

Sensor Cons:

• Ultrasonic emissions can echo, causing the receiver to pick up “ghost” data
• Similarly, complications can arise if multiple ultrasonic sensors are used since receivers can pick up emissions from other sensors. Some effort may be required to coordinate the emit/receive measurement times for each sensor.

Selecting an Ultrasonic Sensor

Here is a comparison of beam detection patterns between sensors in the LV-MaxSonar-EZ line:

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The beam patterns are shown as viewed the top, though they would look similar viewed from the side as well. The patterns are generated by keeping the sensor at a fixed location (the bottom center of each grid, facing up) and a dowel of varying diameters is moved in at progressively further distances from the sensor until the dowel is detected. By tracking the points where the dowel is detected and lost by the sensor, the beam pattern profile is generated. Each column is a different ultrasonic sensor model, and a different diameter test dowel is used for each row of the table. Note that the sensors are all able to detect larger dowels from further distances away and thus have larger beam detection patterns on the lower rows. Conversely, they can only see smaller dowels at close distances and have smaller detection patterns on the upper rows where smaller dowels are used.