E0073 Roll Center 5, Lateral load transfer by Large lateral force & acceleration - EulSeoggy Ko

The simplest mathematical modeling for calculating lateral load transfer is to consider the entire vehicle as a rigid body. In rigid body model, the entire vehicle parts are assumed to be rigid, there is no deformation, there is no relative motion between them, and they move as one unit. The first of the two indices calculated with rigid body modeling is the safety coefficient, which is the ratio of the rollover acceleration to the acceleration corresponding to the maximum grip force that the tire can generate. If the safety factor is greater than 1, the vehicle will not roll over, and the tires will slide on the ground. The second indices is the safety stability factor, which is the ratio of the rollover acceleration to the acceleration due to gravity. This value is equal to the track divided by twice the height of the center of gravity. The higher the safety stability factor, the lower the probability of rollover. The s s f of a S u v vehicle ranges from 1 to 1.2, while the s s f of a passenger sedan ranges from 1.3 to 1.6.
Non-rigid Body model considers the relative displacement between vehicle parts and the deformation of the parts. First, the center of gravity movement due to the suspension is considered. When lateral acceleration occurs, the center of gravity of the sprung mass moves horizontally around the roll center, and the center of gravity movement of the sprung mass at this time means the center of gravity movement of the entire vehicle. In addition, tire deformation is considered. Due to the centripetal force that occurs when the vehicle turns, the tire road contact surface is deformed in the direction toward the center of the turn along the lateral direction relative to the wheel center. Accordingly, the vertical line passing through the wheel center and the center of the road contact does not coincide with each other, so an overturning torque occurs in the wheel that tries to turn in the outward direction. The giyroscopic precession effect of angular momentum is also considered. All rotating parts of the vehicle have angular momentum. When the direction of the angular momentum is changed, a torque is generated in the direction of the precession in the vehicle parts that have momentum. An overturning torque occurs in all vehicle parts that turn in the same direction as the wheel, trying to turn outward.
Among the methods for calculating accurate rollover lateral acceleration, the rollover lateral acceleration calculated with a non-rigid model is naturally more accurate than the rollover lateral acceleration calculated with a rigid body modeling, considering all the effects such as the center of gravity movement due to the suspension mentioned above, tire deformation, and the giyroscopic precession effect of angular momentum. Therefore, the rollover that actually occurs is lower than the rollover lateral acceleration calculated with a rigid body modeling. Similarly, the safety factor and safety stability factor calculated above are also values calculated with a rigid body model, so their actual values are lower.

[@장숙희-y8w]

새해에도 건행하세요!

[@TheGamingHungary]

Great video! There is a small typo around 44:50 on the second figure, where omega_bi should be omega_fi, as it should be the final state instead of initial state for the standing person's rotation.

[@vehicledynamics]

Thank you very much! I'll make correction and update this video. All the comments will disappear after update. Many thanks again for your valuable comment!