Banderon

I want to implement smart cruise control. Now, to do this I need a rangefinder sensor to measure the distance to the car in front. All of the sensors I've been able to find are good for a few feet at most... I need a couple of meters at LEAST.

I might use laser, but only in conjunction with the radar. Laser systems can be innaccurate for motorcycles and other such not-very-wide-and-reflective vehicles and surfaces.

Any ideas on where to find both laser and (especially) radar rangefinders?

Scouse Monkey

Just a quick one: What about digital tapemeasures that estate agents use? Normally laser i think, or adapt one of those bumper mounted ultrasonic parking thingys (that is what i was planning on hooking up to my pc eventually in case i ever let a woman drive my car!)

djmickyg

the newish merc's use a sesor at the front of the car that can mesure a few M
but good luck finding one..

Banderon

The problem with those is they're for parking. Their range doesn't cover the distance to a car ahead of you on a 70mph highway.

spectrrr

i would think you would want a couple sensors mounted on each side of the car so they could crossrefernce each other for enhanced accuracy

The Durango Kid

I think your nuts.. Hehe But good luck..

TimmyM

I think I had something like this. It used a laser for aiming then radar/sonic something else for range finding. It was lame, and about worthless outdoors, I ended up giving it way. I couldn't see it working at 70mph. Maybe for parking but I doubt it.

arkadiyp

I don't think you'll be able to get away with just one sensor, since you will not be able to cover an area in front of a car. Also you would need some FAST processing for it especially at highway speed. Also are you planning to attach it to your cruise control? Because if you are its not going to be very smart since cruise control modules can't break too well - I think in most cars if you reduce the speed for cruise and you are going faster the car will just coast until you get to that speed.

__________________
Never be afraid to do something yourself. Remember - amateur built the Ark, professionals built the Titanic.

Chairboy

First, the reason ultrasonic sensors won't work has more to do with high frequency sound propagation at 70mph then it does with range. The effective range of ultrasound in inches at speed.

Second, the original poster's intention is probably to tie the distance sensor to the brake signal line, not the actual brakes, so that all it needs to do is emulate someone tapping the brakes and, consequently, disengaging cruise control. This can alert the driver as well as, in some cases, maybe provide enough of a slow down to prevent you from rear ending a car you've been closing with that is going a couple mph slower then you.

Third, because of the limitations of sonar, the best solution (as defined as 'most reasonable and within reasonable cost') is probably one or two laser rangefinders. You could use LIDAR or shortwave low wattage radar, but it'd be somewhat more expensive. As is, you're looking at probably 200-300 dollars for a sport laser rangefinder, plus the effort of reverse engineering it to output data.

siberia37

If you knew enough or researched enough about computer vision algorithms you could do it with just a couple webcams theoritically. Here's a research paper about it.

Banderon

Siberia, I don't know much about programming computer vision algorithms, unfortunately... but that'd be damn cool. Also, I'm planning on doing this with microcontrollers, and for webcams I'd need a full OS.


Chairboy, ultrasonic/sonar units are out of the question, for the precise reason you stated. They're for very limited range, low speed applications. I'm shooting for a radar/laser combination, or just radar if it comes down to a choice.

Actually, I am planning on tieing it directly to my Cruise Control, and putting an actuator on the brake line. If the speed of the car ahead of me drops, the gas will release and the brake will apply slightly (or more than slightly if the accel of the car ahead goes into negative very rapidly) until speed is evened out, and an alert will sound if the deceleration is over a specified limit. I haven't worked out the precise way I want to program this, but I'm thinking that I'll enter values for speed vs min distance that I want the car to keep.

Sonar is out of the question. The problem with laser is that it has such a limited coverage area. Most of the cars that have smart cruise control via laser are not as effective as those with radar, and nowhere near those with both systems in place.

At the end of the day, I envision spending somewhere in the range of $1,000 for this. If it goes over a little, depending on the reasons, I might go higher.


Arkadiy... I doubt most cars with smart cruise control have only one sensor. I don't know how good a coverage you'd have that way.. and with 2 or more sensors you can zero in on the general shape of the object ahead. I was thinking of maybe even implementing the steering wheel's angle into the calculations... so when the wheel is tilted, more emphasis is given on the sensors on that side.

I wouldn't need fast processors at all. I'd just need to analyze the data from the sensors, and run them through some algorithms to determine what to do. Not too complex at all, and nothing that today's Mhz range microcontrollers can't handle.

And you're right about today's cars. All they do is disable gas so that you coast down to a lower speed. I'm not sure if smart cruise control cars are different in that they can also take the distance to the car ahead of you into account so they know when to stop with the gas. I'm not sure if any of them actually apply the brake... I doubt it.


The Durango Kid... what's so nuts about it? It's just some calculations and some I/O on a microcontroller.

The Durango Kid

Just the thought of testing it out scares the hell out of me.. What happens if you forget something and lock the crusie on? Well I guess we get no where without crash test dumbies.. Hehe that was a joke..

Banderon

lol
I'll throw in a Kill Switch just to be on the safe side.

Here's a possible layout of what can go where.

Attached Images

 

Scouse Monkey

You could always make the laser like the light on Knight Rider!!! he he

What abot the tranducers/sensors used to make speed traps? Their outputs could easily be integrated down to calculate distance and you could also include the closing speed into your program to determine the amount of braking etc - but to be honest i wouldn't go in a car with a home-made system in it! Most big manufacturers have worked on this and so far i think there has only been one car with it (a merc i think but i may be wrong)

Banderon

Most of today's newly released luxury cars come with smart cruise control. And it's not really all that complex a system. I think I could manage all this in only a couple lines of code. The most time-consuming part would probably be working out the equations I'd need to use. Good thing I'm a math major. =P

The radar guns used in speed traps are like $1,000-2,000 systems all by themselves... I don't want a full system, just a radar emitter and reciever. Same for the laser.