Browse Search Popular Register Upload Rules User list Login:
Search:
Car Wheel Friction

Image:
screenshot of the scene

Author: s_noonan

Group: Technical

Filesize: 21.4 kB

Date added: 2017-02-17

Rating: 5

Downloads: 364

Views: 119

Comments: 4

Ratings: 1

Times favored: 0

Made with: Algodoo v2.1.0

Tags:

Scene tag

The intention of this scene is to show a different method for coding wheel friction. It is not intended to be an improvement over The Linkages scene.

up/down for accelerator/brake. left/right for steering.

Notes:
1. This scene is written from the tire's point of view.
2. The code in all the tires is the same.
3. The only difference in the tires is that some have _driven = true and some have _driven = false.
4. This rear wheel drive car can be converted to a front wheel drive or 4 wheel drive by changing the tires' _driven properties.
5. The speed setting knob acts as accelerator and brake.
6. _maxPower in the speed setting knob hinge determines the engine max power.
7. This scene does not use Kilinich's K-Wheels.
8. u and v are the tire's local x and y coordinate system.
9. The code takes into account the angle of the friction force when braking.
10. The code assumes that tire side friction is 10% of the friction force when "peeling out". This is because the relative velocity between the spinning tire and the road is unknown.
11. Tires turn red when slipping.

Rev A: Steering returns to center when released.
Last edited at 2017/03/12 11:54:27 by s_noonan
Please log in to rate this scene
edit
Similar scenes
Title: air braking wheel
Rating: 5
Filesize: 54.43 kB
Downloads: 343
Comments: 0
Ratings: 1
Date added: 2009/12/05 20:38:10
Made with: Phun
Rating: rated 5
download
Title: Single Wheel Car; Tri-C-Engine
Rating: 5
Filesize: 79.56 kB
Downloads: 312
Comments: 0
Ratings: 1
Date added: 2012/02/13 02:52:21
Made with: Algodoo v2.0.2 Edu
Rating: rated 5
download
Title: Friction Clutch
Rating: 7
Filesize: 108.77 kB
Downloads: 400
Comments: 0
Ratings: 3
Date added: 2008/11/28 21:20:52
Made with: Phun
Rating: rated 7
download
Title: Hummer
Rating: 5
Filesize: 0.89 MB
Downloads: 387
Comments: 1
Ratings: 1
Date added: 2016/01/15 22:59:57
Made with: Algodoo v2.1.0
Rating: rated 5
download
Title: Can anyone figure this out?
Rating: 5
Filesize: 50.8 kB
Downloads: 220
Comments: 2
Ratings: 1
Date added: 2019/05/22 15:18:30
Made with: Algodoo v2.1.0
Rating: rated 5
download
Title: A wheel.
Rating: 5
Filesize: 418.96 kB
Downloads: 76
Comments: 0
Ratings: 1
Date added: 2020/02/20 15:19:51
Made with: Algodoo v2.1.0
Rating: rated 5
download
This scene is a response to:
Title Author Rating Downloads Comments Date added
Car with Stat/Dyna Friction The Linkage 6.4 (4 votes) 896 3 2017/02/12 18:28:52
show grid
The car appears to be riding on the background, but the Algodoo background has no physical properties, so how do you calculate traction between the tires and the background (if that's what you are doing)? :s

Interesting scene! :tup:
Initially the idea of using dynamic and static friction for a scene like this started when faytree wanted to improve drifting scenes. The idea that I had was using a heavily modified K-Wing (or scripting one myself for that matter) to simulate side forces, and a thruster pointing up front for traction. i couldn't figure out how to calculate the side forces to simulate zero slip so i just scrapped it.

I noticed that your method and mine have the same amount of lag. Do you use vel instead of totImp3?

Also, "The code assumes that tire side friction is 10% of the friction force when "peeling out". This is because the relative velocity between the spinning tire and the road is unknown." How would you calculate the maximum side force in real life, then? I searched some but i couldn't find anything concrete about this
Q: Do you use vel instead of totImp3?
A: Yes.

Q: How would you calculate the maximum side force in real life, then?
A:

Ffv = u * N * Vv / (Vu^2 + Vv^2)^0.5

where

Ffv = tire sideways friction force
u = coefficient of sliding friction
N = normal force
Vv = tire sideways velocity
Vu = tire relative forward velocity

Details:

If the wheel is slipping, and has a normal force = N, and has a dynamic coefficient of friction = u, then the friction force Ff = uN, but you already knew that. The friction force vector in the forward direction of the tire Ffu, and the friction force vector opposing sideways movement of the tire Ffv must add up vectorially to the total friction force Ff which is in the direction of the relative movement between the tire and the road. So, if you know the relative velocity angle (theta) with respect to tire forward movement (u direction), then Ffu = Ff * cos(theta) and Ffv = Ff * sin(theta). Notice that if Vv = 0, then theta = 0, and Ffv = 0. In real life peeling out, Vu can be read on the speedometer or it can be calculated by wheel RPM * 2 * pi * wheel radius. Vv might be calculated by measuring the sideways tire movement per unit time on a high speed video.

So, if a car is peeling out, then it should be easy to push the car sideways if you push over the spinning wheels. This also means that if you slam on your brakes while going 60 mph, then a mild crosswind can push you sideways.
Last edited at 2017/02/18 10:03:09 by s_noonan
Xray,

Q: How do you calculate traction between the tires and the background?
A: I assume a normal force and coefficient of friction. The max traction force is Ff = uN. For acceleration, the actual traction force is calculated from the accelerator power setting. Since power equals force times velocity (P = F * V), and the power and velocity are known, I can calculate the force, F = P / V. If F > Ff then F = Ff and the car is peeling out else F = P / V. F is the force applied to the forward thruster. For the side thruster, a side force proportional to side velocity is applied, up to a max of Ff, except when peeling out, then the side force is limited to 0.1 * Ff. Braking works in a similar (reverse) manner, except in that case the relative velocity is known and Ffu and Ffv are calculated.