collision avoidance

Hi all - this is my first post so please be gentle with me.

As my first non-trivial project, I want to build a collision avoidance system into a simple ground vehicle which can negotiate object-type surfaces as well as 'ground'. I've come up with several ideas, but need some feedback on their feasibility. The vehicle won't go fast. I've had a good look at the wikis and the forums. I guess my main concerns are about server costs and lag.

- use a non-physical object with llvolumedetect on an invisible 'bumper' sticking out front.
Advantages - simple detection, low server cost(?)
disadvantages - ugly and difficult movement

- use a physical object with sensor events every second or so
Advantages - nice movement
Disadvantages - more difficult analysis of sensor results, high server cost

- maybe use a phantom physical object and switch on llvolumedetect for a moment every second or so. Does the object return to normal physics after llvolumedetect is switched off?

- maybe use a separate invisible phantom object for the bumper, which is 'pushed around' by the main physical vehicle? Server cost?

- does sensor detect an object when a part of its 'boundary box' is in the sweep, or only when its centre is in the sweep?

A volume detect prim is capable of being physical (I actually have working examples) and so I would postulate that a physical, volume-detect prim at the head of your vehicle would be the best answer. I have not tackled this problem myself, however, so I am unfamiliar with any difficulties the method might create.

There is a tutorial on lsl robotics in the wiki. It gives code examples and gothas on collision avoidance.

http://www.lslwiki.org/index.php/TutorialRobotics

Thanks for the help guys. Another wiki! Just what I need!

I had done some thought experiments on this some time ago, and I think it might be possible to attach a phantom, alpha'd object to yourself. If you create a segmented ring around yourself (like defensive shields on a sci-fi spaceship) you can detect the direction of the collision and react according to that.