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### #ActualPochyPoch

Posted 12 September 2012 - 01:21 PM

Oh, and i have one more question that has haunted me those past days.

Knowing that marcos slipAngle formula is made to be used with car coordinates (that's why it takes angular vel, and so) to determine the lateral force the tire produce, it makes sense that this lateral force should be applied to the car directly perpendicular at wheel position.

But, i use a formula where the front/lat velocities are the real ones of the wheel. So, simply using this formula should work to determine slip angle :
var alpha  = -Math.atan2(wheelRealSideVelocity, Math.abs(wheelRealFrontVelocity));


But when it comes to applying that lateral force...
Case 1 : Should i apply the given force perpendicular to wheel, with steering producing an oriented lateral force, which will slow down the car ?
Case 2 : Or instead should i apply it perpencular to wheel attach point, regardless of steering, and then it will only make the car turn, but never slow it down ?

Case 1 example :

Case 2 example :

Everyone use its own formula and coordinate system in the examples i have found, so it is not clear to me.

For Slip Ratio, it is more obvious as we look at patch speed (wheel angular velocity) and ground speed in the direction the wheel is heading, it seems logical to have that vector acting in the wheel space, thus respecting steering angle.

But using a simplified formula with examples were it is used to apply a force directly perpendicular to car makes me have some doubts...

### #2PochyPoch

Posted 12 September 2012 - 01:21 PM

Oh, and i have one more question that has haunted me those past days.

Knowing that marcos slipAngle formula is made to be used with car coordinates (that's why it takes angular vel, and so) to determine the lateral force the tire produce, it makes sense that this lateral force should be applied to the car directly perpendicular at wheel position.

But, i use a formula where the front/lat velocities are the real ones of the wheel. So, simply using this formula should work to determine slip angle :
var alpha  = -Math.atan2(wheelRealSideVelocity, Math.abs(wheelRealFrontVelocity));


But when it comes to applying that lateral force...
Case 1 : Should i apply the given force perpendicular to wheel, with steering producing an oriented lateral force, which will slow down the car ?
Case 2 : Or instead should i apply it perpencular to wheel attach point, regardless of steering, and then it will only make the car turn, but never slow it down ?

Case 1 example :

Case 2 example :

Everyone use its own formula and coordinate system in the examples i have found, so it is not clear to me.

For Slip Ratio, it is more obvious as we look at patch speed (wheel angular velocity) and ground speed in the direction the wheel is heading, it seems logical to have that vector acting in the wheel space, thus respecting steering angle.

But using a simplified formula with examples were it is used to apply a force directly perpendicular to car makes me have some doubts...

### #1PochyPoch

Posted 12 September 2012 - 01:08 PM

Oh, and i have one more question that has haunted me those past days.

Knowing that marcos slipAngle formula is made to be used with car coordinates (that's why it takes angular vel, and so) to determine the lateral force the tire produce, it makes sense that this lateral force should be applied to the car directly perpendicular at wheel position.

But, i use a formula where the front/lat velocities are the real ones of the wheel. So, simply using this formula should work to determine slip angle :
var alpha  = Math.atan2(wheelRealSideVelocity, Math.abs(wheelRealFrontVelocity));


But when it comes to applying that lateral force...
Case 1 : Should i apply the given force perpendicular to wheel, with steering producing an oriented lateral force, which will slow down the car ?
Case 2 : Or instead should i apply it perpencular to wheel attach point, regardless of steering, and then it will only make the car turn, but never slow it down ?

Case 1 example :

Case 2 example :

Everyone use its own formula and coordinate system in the examples i have found, so it is not clear to me.

For Slip Ratio, it is more obvious as we look at patch speed (wheel angular velocity) and ground speed in the direction the wheel is heading, it seems logical to have that vector acting in the wheel space, thus respecting steering angle.

But using a simplified formula with examples were it is used to apply a force directly perpendicular to car makes me have some doubts...

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