help build a follow me car using cheap components

we need to build a car that follows some kind of transmitter a person can hold wherever he goes.. we had the idea of using ultrasonic transmitters and receivers but don't quite know how to execute, what component to buy and how to program them.. using GPS would've been ideal if it were in a large range and we weren't short on money so it's out of the plan.. i read somewhere that a sharp IR proximity sensor would work but still need some details on how exactly it would do so.. if you can help with any of these or have other suggestions please do

Google says watch this video.

Sara_EA:
we need to build a car that follows some kind of transmitter a person can hold wherever he goes.

You mean a full size car, like the sort that you would drive on the road ?

Stick some IR leds on the leader, servo sweep an IR detector on the car like a shark, and write the code.

I may be wrong but it sounds like "school project" to me. I assume small RC car, controlled obstacle free environment.

The hard part I think is the "follow" sensor, not sure how to go about that. You need to measure two things: direction and distance from vehicle to beacon. Of course the car is supposed to follow, not bump into the beacon carrier, so there needs to be some sense of distance between the two.

Both are not trivial. Distance could be done by using an ultrasonic range finder, and basically considering the beacon holder as obstacle (s/he would be the only obstacle in the room, and anyway be an obstacle in the direction of the beacon).

Direction is a harder one. I don't have suggestions for this.

When you have that the vehicle control is quite simple. Turn into the direction of the signal, move forward.

See video link in reply #1. It shows how they used ultrasonics for direction.

Put the IR transmitters on your belt. Limit the vertical view of the receiver. It will drive up to you and stop when it can no longer see the transmitter. It will be slightly jerky following a slow walk but it will work.

vinceherman:
See video link in reply #1. It shows how they used ultrasonics for direction.

I didn't watch the whole thing , but the concept seems to be to use two ultrasonic rangefinders with overlapping field of view. These sensors have a relatively narrow field of view (about 30 degrees) and a key operating principle is to drive the motors to keep the followed object in the overlapping area of the two sensors and at a pre-determined range.

I've attempted to illustrate the concept in the following figure. The yellow (red) pie slice represents the field of view and range covered by one HC-SR04. A simple operating concept based on the sectioning the sensor returns into over/under target range and overlapping/non-overlapping returns is shown by the text pointing to the various areas of the figure.

hcsr05follow.PNG

    • As an aside the proliferation of video as a "how-to" medium annoys me, but maybe that's just the cranky old guy in me. Written and illustrated monographs tend to be better distilled to the essentials. Note that's not intended as a criticism of vinceherman who has posted a useful link from which I've learned something.

Follow-me car using cheap components....

String?

INTP:
Follow-me car using cheap components....

String?

LOL

...R

Those ultrasonic sensors may work indeed - as long as you don't walk to the side too fast (including sharp turns), and stay within about 3m from the car, and there is no second object in range (e.g. a wall).

But it will work as proof of concept, whether it's good enough depends on the other project specifications.