Ultrasonic triangulation for obstacle detection and avoidance

[WolfgangFahl]

The following user story describes how Ultrasonic triangulation might be used:

Situation
The RC vehicle is close to a tableleg by half it's max brake distance e.g. for a RC car 10cm or for a hexapod 5cm.
Two HC-SR04 in http://wiki.bitplan.com/index.php/Ultrasound_Triangulation configuration are in use based on two sensors mounted on servos as in http://wiki.bitplan.com/index.php/SG90-Servo.
Raw Sensor data shall be processed to object detection as outlined in:

Action
Detect obstacles in moving direction.

Expected Result
Functional: the table leg is detected in time.
Non-functional: Given 0.25 sine of 15 degrees it is not reasonable to expect better than 25% accuracy. With a safety margin we might end up with 35% to 50% accuracy which means stopping at a distance of 20 cm for something that might only be 10 cm away in reality.

Comment
see https://forum.arduino.cc/index.php?topic=243076.0 for precision data. 0.1-0.5cm precision per sensor. Angle accuracy: 15degrees.