Let's Make Robots!

Motion Tracking from stationary observer

Hey guys..

I have an issue at my house right now...Young hoodlums of unknown origin have been sneaking onto my property and stealing things off my deck, and animals have been getting into my garbage.

 I want to build a robot that when motion is detected with a passive ir sensor, a webcam will activate and start recording, however I want the sentry to track the movement with some precision, since the target (hoodlum or rodent) will be of different sizes.

 So my question is, do I use an PIR sensor array to track movement? How should I go about doing this?  Does anyone know any good references on motion tracking?

 sorry for all my questions I'm kinda new at this.

Thanks in advance

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pir would be too sensetive from my understading of how it works plus it wouldn't give good directional information(quadrant maybe??)....

I've found things like this that look promising when I was looking to do something similar...


you could also use a cmu-cam but thats another expensive toy....


but they are also a bit pricy... :(

You can do an array of ir sensors and recievers set up along a known intrusion path for short range intereference detection,(if the signal is broken then thats where a camera would point) but the amount that you need for a yard could be a bit much. Still...the much antiquated but still very effective, floodlight at the slightest mottion I've found works wonders plus blinds said hooligans. :)

yet another way is using a standard computer web cam... most come with software that detects motion(changes in pixil density??) and can be set to be very sensetive. I don't recall if you can get any output data and use it, but it's possible.

A web cam can be interfaced with a PC in such a way as to record and track motion...However I think it only works with Windows...havent found a Linux version yet. But you can use the Java Media Framework(JMF) to capture and perform operations on real time streaming video.

Airsoft automatic turrent



I saw some type of automatic sprinkler video, where the sprinkler would come one when motion was detected in the frame. Can't find it now though.

OMG that turrent is fantastic :) I want one!! :)
well you could also use a simple relay to active the camera if you already have one and don't want to spend money on another one

Here's a quick google search that looks like it yielded some good results.


...and you can even use the system to launch guided missiles at the perps.



I'm looking for a device that records my walking motions digitally, and can control servos to imitate my walking forces, balance etc..

You see, I've got this 'mechanical spring-loaded bipedal walking frame' that assists in the walking motion (google search "spring walker" to understand what I mean), and what I want to do with it is turn it into a autonomous walking robot.

I've been thinking that if I attached servos and a computer (brain) to it to record my walking motions, then I can get it to walk on its own...without me strapped into it, that is. But I need advice on what kind of servos (make, model) to use that's powerful enough to move the walking frame. And, also what kind of device or program would allow me to record and save my actions in such a manner that I don't have to keep sorting out the data to tell the computer "when this, do this, etc (if p then q)? Presumably there's a device out there that would do all this for me, and not too expensive? 

I figured I could utilize the info gained by IR sensors taped to the frame to help with the decision making of what king of motion to do at a given situation (i.e. that it doesn't try to clime a hill when walking on the road, or walking when it's suppost to clime, etc.) Can you advise on what IR sensors are good for this particular job?

I don't know the scale of this kind of project, or if it's too difficult to do without expert roboticists on hand, but I'd like to try anyway.

Thanks very much, hope you guys can help.

using some kind of camera to do that sounds very very very hard. why not try some sensors like gyros (but i don't really know if you can apply those to your frame) to detect how much the axles the frame is made of rotate? (then you need to find a way to store these variables on a timeline so that at the end of the experiment you can check what happened.

Yeah, a camera might not be the best method to get raw motion data that a computer can use...but if I use a stepper motor, on the other hand, I can simply send a series of pulses to the motor, and it will rotate an angle proportional to the number of pulses. In theory, if we know how many pulses have been sent, we know where the motor is, and we know the velocity of the motor is proportional to the pulse frequency. If I do the math backwards, and knew how many pulses it took to get the motor to a particular place, then I could match my walking by literally knowing how many pulses it takes to walk a certain distance and program that into a controller...However, I’ve read somewhere stepper motors do not generate much torque, and as a result, slipping can occur (i.e. where the motor turns when no pulses are given or the motor fails to turn in response to the pulses). Also, that the control electronics are somewhat more complicated to do.

Then again if I used a permanent magnet brushed DC gearhead motor, it would be better than a stepper motor, since the advantages of DC motors include: simple to drive, cheap, and relatively high power-to-weight ratio. A disadvantage is that I’d need a sensor, such as an encoder or tachometer, to keep track of the position or velocity of the motor (this would be the raw motion data I mentioned above). According to BaseOverApex (posted elsewhere), with a DC gearhead motor there is a direct link between torque & price (greater torque=higher price).

Emmm...what to do? It's starting to go over my head a little, I have to admit!