next topic »

[on:]

My attempts to find an aftermarket Adaptive Cruise Control System for my truck ended in failure. So I have decided to build one. I have most of the programming for it complete. The only thing I'm missing is the front distance sensors. I'm guessing Radar might be the best to use, seeing that laser has issues with direct line of sight when it would come to precipitation. Sonar, from what I have read, would have problems with wind sheer.

It needs to measure distance from 50 to up to 400 ft.

Any help will be appreciated, Thanks!

[Reply #1 on:]

I'm guessing Radar might be the best to use,

The problem you're likely to find here is that most of the radar modules you can afford will be Doppler units, which can measure speed but not range.

[Reply #2 on:]

I'm looking for the same thing for a similar project.  The only viable radar sensors I've found are only sold to oem manufacturers (Bosch, Continental, TRW).  Banner engineering has some sensors that have a range of 5m ($400) - 15m ($900) but that's not long enough for ACC at high speeds.  On ebay there's an audi A7 radar sensor for like $400 but there's no data sheets so I would be lost.  Any help on this would be much appreciated.

[Reply #3 on:]

I'm guessing Radar might be the best to use,

The problem you're likely to find here is that most of the radar modules you can afford will be Doppler units, which can measure speed but not range.

Okay, I was looking up some info on Doppler units. This seems to work similar to sonar where it sends out a wave and one is returned but then measures the Doppler effect of the wave instead of just the wave response time, therefor measures velocity instead of distance. All of the Doppler units I've looked at have all been stationary. I'm assuming this may be because of the same wind sheer effect that sonar gets? Assuming it doesn't, at speed in theory, if I was closing on a vehicle in front of me I would be getting a negative velocity reading from the Doppler, so to match speeds I would have to write the program to 0. And maybe set the distance by output power/amplification? Even if it means having a static distance.

Thoughts?

[Reply #4 on:]

m assuming this may be because of the same wind sheer effect that sonar gets?

Doppler radar use RF, not audio, so isn't going to suffer wind-shear at road speeds.
However, they only give relative speed, so a relative speed of zero could mean you're tailgating the other guy, and your control would have no way of knowing.

[Reply #5 on:]

Ahh yes... but if I programmed it to take the closing speed over time and set it to = positive speed over the same amount of time taking into account the approximate deceleration rate of my vehicle I could put the vehicle back to the edge of the Dopplers range limit, therefor keeping a safe distance, depending on what the range limit is... but then what happens if a vehicle turns in front of me going the exact same speed, it wouldn't know to slow down because the only change it would have seen would have been a very very fast spike in speed if it could even notice at all. Soooooo..... I'm guessing to keep this under/at budget I may want to consider using laser and working around the problems that come up with that system.