![]() ![]() The height of the kinematic roll center affects the distribution of the weight transfer caused by both the sprung and unpsrung mass of the vehicle. The kinematic roll center is actually constantly changing based on the dynamic position of the suspension, but for now, we will just pretend it is a constant value. I will not go into the details of what a kinematic roll center is, but it is geometric certainty that is inherent in the design of the suspension (generally the control arms). ![]() Next we will incorporate kinematic roll centers into our SSWT calculations. This gives us even more accurate results for our SSWT calculations. Now that we have a sprung and unpsprung weight, the SSWT calculations now have to include 2 center of gravities, one for sprung and one for unsprung weight. The unsprung weight is the tires, springs, and suspensions (although technically some suspension components are partially sprung and unsprung, but lets keep things simple). In generally that is weight of the chassis, the body work, and everything inside the cockpit. ![]() The sprung weight is the portion of the vehicle weight that is compressing the springs. Taking it another step, you can determine the vehicles sprung (suspended) mass and unsprung (non-suspended) mass instead of just using the sum. Also now you can determine the chassis roll angle now that we he have springs. The springs and arb’s effect the the distribution of the weight under longitudinal and lateral accelerations. Now the calculations get a little more complicated, but still relatively simple. Very simple calculations.įrom here, you add in some more variables, such as springs and anti-roll bars. From this, you can determine how much load each tire should be carrying. In its simplest form, to determine SSWT, you only need to know the corner weights of the car, the front and rear track width, the center of the gravity location, and a longitudinal and lateral acceleration of the vehicle that you want to compute. And the beauty of SSWT, is that the result is generally quite accurate even if a chassis isn’t completely rigid (and they never are). SSWT is mathematical certainty given certain assumptions such as a rigid chassis. For the most part it requires very little computational power and in its simplest form does not even require iterations or loops in the code to achieve a result. Steady-state Weight Transfer (SSWT) Steady state weight transfer (SSWT) is one of simpler things to compute with respect to vehicle dynamics and computer simulations. So instead of using the all encompassing “physics” we can break it down more clearly.Īlso, please note, that I do NOT know how iRacing does it’s physics and vehicle dynamics computations, this is meant to be general, and is my understanding and experiences of how these things are done. It is my hope that this will help clarify and differentiate the different aspects. In many vehicle dynamic related discussions I see people misunderstanding one aspect of vehicle dynamics for another. Just the basics of how a race car is simulated during acceleration, braking, cornering, or any combination of the three. It will not include anything related to engines, differentials, or transmissions. This post will not include all aspects of vehicle dynamics. I have also written several vehicle dynamic simulations involing 3D kinematics and steady-state and quasi-steady state vehicle handling. ![]() I have designed and built suspension/braking/steering systems on formula cars for 5 years. This is going to be very general, but I think it will help many of us here to have a better understanding of vehicle dynamics and tire modeling and enable us to have more informed and inteligent discussions on such matters.įirst off, I am a mechanical engineer who has been racing cars in some respect for 14 years now. I am writing this in effort to explain how a vehicle dynamics simulation works. I really enjoy vehicle dynamics and tire model discussions, and I know many others here do as well. It is an old and extensive post but some way enjoyable and worth to read and contains a good bunch of basic and elemental terms to understand more advanced subjects. Here Jeremy Spiering gave us an insight view about physics and dynamics of all vehicles and how they are handled. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |