How Does Infiniti's Lane Keeping Assist (Direct Adaptive Steering) Work?

Question

After commenting on this question and realizing that the system is fairly complicated, I began to wonder how exactly Lane Keeping Assist works. While having service information does help some, it doesn't answer all the questions I had about the system or gave vague descriptions of the component functions.

So in short, how does Infiniti's version of Lane Keeping Assist work?

I'm more interested in the technical aspects of the system. If the steering input is converted to an electric signal, what's the process? How does the system know that the car is drifting out of it's lane? What sensors are involved? What modules are included in the system. Are there safety backups incase the EPS system goes down?

I don't care about the logic i.e. the math behind turning x input into y output.

Answer 1

Basic answer from infinitiusa.com on Lane Departure Prevention, but here it is:

LDP uses a camera to monitor the distance between the vehicle and lane markings and, if the vehicle drifts towards the lane markers, the system first sounds a audible warning, followed by a selective application of the brakes to help move your vehicle back into its lane.

However, Lane Keeping Assist takes this a step further. Not only does it make beeping noises, it is hooked up to the power steering such that at speeds above 45 mph, it will actually turn the steering up to a couple degrees if it detects that you are moving too close to the line on either side.

It does help keep you in your lane, but don't try it on the Autoban!

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From wired.com:

Turning the steering wheel sends an electronic signal to the steering force actuator, which sends data to the electronic control unit, which forwards it to the steering angle actuator, which turns the wheels.

...then a bit later...

The system can adjust steering through electronic instead of mechanical inputs, which requires less work.

Here's a diagram of the basic setup of electric steering:

All that is left for the lane control system to do is to send an electronic signal to the electronic control unit which over-rides the manual input.

Answer 2

According to this, it's just a camera looking for pavement markings. Getting closer to one sounds the alarm, getting too close selectively applies the brakes to steer the car back. I'm guessing the front brake of the side you want to steer towards will get applied.