Solving Traction & Friction Issues with Car Simulation

In summary: If you have a stationary object and apply a force to it, you'll find that the object will start to move. Now, if you apply the same force to the object while it's in motion, you'll find that the object keeps moving, but at a slower pace. This is because the object is using the energy of the motion to overcome the resistance of the stationary object. In summary, tires always have slip when rolling, but the amount of slip depends on the amount of traction force needed.
  • #1
synMehdi
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Hi, I'm simulating the behavior of a car and I have some troubles with the tires. Specially with slip when the car is accelerating.
I've seen many documents over the internet and I understood 2 main things: Wheel slip is necessary to accelerate & the coefficient of friction depends on the slip.
To model a Tyre I'm using Pacejka magic formula which describes the relation between the coefficient of friction and the slip.
If I put torque (car speed=0 & wheel speed=0) in the wheel, there is no slip initially and no force to push the car. The wheel will slip due to the torque, and friction will occur which accelerates the car.This will eventually decrease slip. At some point an equilibrium will occur.
Am I right?
If my torque is bigger than the maximum force of the Pacejka formula (around slip=8%), Am I going to diverge?because friction will decrease when slip increases after that point.
I don't feel that this is what occurs in real life or maybe I didn't understand the wheel model.
 
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  • #2
Wheel slip would take away from acceleration.
 
  • #3
Can you please further explain what do you mean?
If I simply apply the Pacejka model and my understanding of it. If my torque is bigger than the traction force. I will end having no vehicle acceleration and only wheel acceleration.
 
  • #4
pseudochaos said:
Wheel slip would take away from acceleration.
Not necessarily. Think of how clutch slip is used to maximize acceleration of a racing car...
 
  • #5
In an automobile drivetrain the slip at start to prevent instant slip at the wheels or motor stalling at start is provided by either the slipping of the clutch or the the liquid coupling between the engine and the transmission.
 
  • #6
Acceleration is due to the friction force between tyre and ground. Simple F=ma.

However the friction force depends on the coefficient of friction. Usually this is either the coefficient of static friction (no wheel slip) or kinetic friction (wheel slip). Usually the coefficient of static friction is higher than that of kinetic friction.
 
  • #7
As slip increases, the traction force also increases up to a point (Extremum on the next image). That is the normal range for a normal drive. The slip you need, depends on the traction force you need (between 0 and Extremum).

pacejka_curve.jpg

If you reach a wheel torque that can produce a traction force greater than the maximum force, then the «extra» torque is converted into wheel acceleration, which leads to the slip increasing beyond Extremum. Because the traction force decreases with slip at this point, it just means wheel acceleration increases. At some point, the traction force does stabilize (Asymptote).

But because there is a traction force, there is also a vehicle acceleration (as long as there is no opposing forces), although it is not as high as if you had the complete wheel torque converted to traction force.

It is actually the same principle as static and kinetic friction:

Static_kinetic_friction_vs_time.png

Yes, tires always have slip when rolling. There is nothing better than extreme cases to demonstrate the point:

 
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FAQ: Solving Traction & Friction Issues with Car Simulation

1. What is car simulation and why is it used?

Car simulation is a computer program that simulates the behavior of a car in various driving conditions. It is used to test and analyze the performance of a car, including its traction and friction, without having to physically drive it. This allows for more efficient and cost-effective research and development.

2. How does car simulation help solve traction and friction issues?

Car simulation uses mathematical models and algorithms to accurately simulate the behavior of a car on different road surfaces and under various driving conditions. By adjusting parameters such as tire type, weight distribution, and suspension settings, the simulation can help identify and optimize the factors that affect traction and friction, leading to better performance and handling of the car.

3. What are some common traction and friction issues that can be solved with car simulation?

Some common issues include understeer (when the front tires lose grip and the car fails to turn), oversteer (when the rear tires lose grip and the car spins out), and wheel slip (when the tires lose grip and spin faster than the car is moving). These issues can be caused by factors such as tire type, road conditions, and vehicle weight and distribution.

4. Can car simulation be used for all types of cars?

Yes, car simulation can be used for all types of cars, including passenger cars, sports cars, and commercial vehicles. The simulation can be customized to mimic the specific characteristics and performance of different types of cars, making it a versatile tool for solving traction and friction issues.

5. Are there any limitations to using car simulation for solving traction and friction issues?

While car simulation is a powerful tool, it is not a complete replacement for real-world testing. The simulation is only as accurate as the data and assumptions used to create it, so it is important to constantly validate and refine the models. Additionally, factors such as weather conditions and driver behavior may not be fully captured in the simulation, so real-world testing is still necessary for a comprehensive analysis of a car's performance.

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