commercial vehicle

I have no specific recommendations. I would start by looking in mechanical engineering texts, particularly ones published by the SAE. I would also not start with high hopes of getting a close model (you can never get an exact model). If I did get a close model, I would have very dim hopes of mathematical tractability.
Probably the most salient feature of a mathematical model of a physical system, which people often forget, is that it is a simplified description of what's going on. If you're modeling for behavior, then you won't necessarily want to model for heating in the springs over a rough road. Ditto, you wouldn't be interested (at least while analyzing behavior) about where the stress risers are that may lead to premature cracking.
In fact, in a rational engineering design process, it's not uncommon to have several different models for the same assembly -- I've been on one product design effort where I would model the central assembly for overall response to control inputs, someone would model that same assembly for the amount of flexure under vibration (both for the purpose of determining if it was rigid enough to do its job, and as input to my behavioral efforts), someone would model the assembly for its thermal characteristics, someone would model the thing for the amount of bearing drag (which results I would use), and so on. A model that tried to put that all together would have been insanely complex, and because of the complexity, far less useful than the collection of individual models.
So -- what are your design goals, and how do you want the model to help you?

Hi
I also wanted to know if most commercial vehicles using Rear wheel drive?? If yes why so??

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Most I have hired recently were front wheel drive.
So, why are we discussing this item in sci.engr.control? Is there not a more appropriate group for this question? Are you developing an Active Suspension System which requires electronic controls to operate?

What sort of commercial vehicle are you getting Paul?
If it's trucks, I'm astonished.

I'm assuming you mean trucks (US name -- lorries in the UK, I think). The ones I know of are almost all rear-wheel drive.
This is a question best answered by finding someone with immediate practical experience -- like a truck driver -- and asking.

I guess in the USA you might call them panel vans. In the UK we call them Vans or even Lutons (a slightly different style of van). They are based on lighter chassis. The same vehicle bases also come as flat-bed trucks. However, larger vehicles (HGV3 and HGV1 classes) will more than likely be rear wheel drive.
Regards
Paul E. Bennett IEng MIET Systems Engineer

Here in Brobdingnag -- uh, I mean, the US -- we call them "mini vans".
Some are, indeed, used for commercial purposes, but usually "commercial vehicle" refers to a truck of at least 1 ton capacity.

Then I guess your category points are somewhat different to the UK. We can get to the 3 tonne (HGV3) category before they get referred to as trucks at which point it begins to require a commercial vehicle licence to drive. The PSV licence starts out for lighter vehicles but that is based on the "passenger carrying for commercial gain" aspect. Because of when I got my licence to drive I am allowed to drive up to 7 tonne. Newer drivers have the limit at 3 tonne.