On non-lidar equipped rovers, how is the width of an obstacle detected such that it can be avoided? If the ultrasonic sensors are used for obstacle detection, these sensors usually don't give data about the width. How is the width derived?

  • $\begingroup$ why do you need to calculate the width of an obstacle? ...... don't you only need to know the location of its ends? $\endgroup$ – jsotola Mar 9 '19 at 17:56
  • $\begingroup$ @jsotola Yes, but if you know the location of its ends, you'd know its width. I don't think ultrasonic sensors can give you the location of the ends of an obstacle though. $\endgroup$ – John M. Mar 11 '19 at 9:23
  • $\begingroup$ you are correct, the ultrasonic sensors cannot give you the location of the obstacle .... the sensor detects the presence of an obstacle .... the robot has to calculate the location of the obstacle within its environment .... lidar works the same way $\endgroup$ – jsotola Mar 12 '19 at 0:53
  • $\begingroup$ @jsotola But to calculate the location of the endpoints, wouldn't the ultrasonic sensors need to be rotating as Tharindu suggested? Most of the bots I've seen that use ultrasonic sensors seem to use fixed ultrasonic sensors though. $\endgroup$ – John M. Mar 12 '19 at 4:28

You may use a rotating mechanism such as a servo with the ultrasonic sensor mounted on. The ultrasonic measurements can be fused with the servo arm angle to calculate the width. Usually ultrasonic sensors have a higher field of view. This degrades the accuracy if you assume the ultrasonic wave is focused to a point. If you need more accurate measurements, you may use a mathematical sensor model to fuse the measurements.

ToF sensors have a low field of view compared to ultrasonic sensors


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