Electronic – Method required to enable a toy “vehicle” to follow a “target” wirelessly


I am trying to create a small robot toy car with the ability to follow a person around, with a range of about 50 m.

Ideally the person will be provided with a small transmitter of some kind, and the car will have a receiver which will allow it to determine the direction to the transmitter so that the car can follow the person holding it.

However, I understand that systems such as infrared require line of sight to operate, while others like WiFi are too omnidirectional to pinpoint the transmitter direction.

Is there any recommended method or system that would meet my requirement?



To elaborate, it is more for remote photo taking.
A person would hold a remote tag and trigger a command; after which the robot would seek out the person, and position itself in the same direction to take a shot.
Unfortunately GPS not not a solution as for this application is mostly for indoors. I understand RFID tags may work although i am not sure if it has sufficient directionality

Best Answer

An ultrasonic ping mechanism using 3 ultrasonic receiver transducers on the vehicle, and a single omnidirectional ultrasonic TX transducer (a piezo speaker or metal-cone ultra-tweeter would work) on the device to be followed, would yield direction and distance information, so long as something approximating line of sight (sound) could be maintained. A simplistic illustration:


simulate this circuit – Schematic created using CircuitLab

The follow-me unit generates an ultrasonic pulse at a calibrated time interval. The difference in time-of-flight of the pulse on the three RX units allows determination of relative distance from each RX, and thus spatial location via triangulation.

If there is a wall blocking one of the sound paths but not the others, this would add some uncertainty to the process, but so long as the follow-me is moving, this too can be worked around using a bit of signal processing and interpolation between known-good pulses.

If highly directional RX units are used, direction can be determined with just two units sufficiently separated from each other, but this will not allow estimation of distance, only angular direction.