Adams Assignments – Problem 5 – Compliance

Adams sign convention:

Steps:

-First rear multilink suspension is created

-then static load simulation is made

-first brake static load analysis is performed with 5000 newton braking force

-then x axis input variable was chosen which wheel base travel

-then y-axis input variable was chosen as toe angle

-then the brake steer curve is plotted

It showed brake steer 202 deg/m (absolute value),and the rear wheel toe out during braking.

-then traction steer simulation is made using static traction load analysis of 5000 N

-then the same x and y input variables are used as in the brake steer curve

-then the curve is plotted

It showed traction steer of 19.3 deg/m and the wheel toes out during traction

Why the brake and acceleration have both the same sign ?

-there's something called as markers for each and every single part of your suspension assembly

-The changes happening during these simulations are captured by the help of these markers

-This change is gonna be positive if increases and negative if decreases, irrespective of the sign convention in the co-ordinate system.

So adams can produce values with wrong signs

-Then a new x axis input is used to study the wheel recession during traction

-then y axis input variable is chosen

-then wheel recession during traction is plotted

The curve shows that the wheel will recess by 1 mm/KN

-Then x axis input variable is changed for the wheel recession during braking

-the y input variable is left the same

-then curve is plotted

The curve shows that wheel recession during braking is 0.544 mm/kN and it is different to the traction curve because of the point of application of the two forces as the force of the traction is applied at the wheel center while in the braking it is applied at the contact patch.

-Then cornering simulation is used for assessing lateral force compliance steer and a cornering force of 5000 newton is inputted

-then x-axis input variable is inputted

-then y-axis input variable is inputted

-Then curve is plotted

-It showed lateral force compliance steer of 0.164 deg/kn and it will cause the rear wheel to toe out producing oversteer

-then x- axis for lateral force compliance camper is left the same

-then a new y axis input variable was chosen

-then the lateral force compliance camber curve is plotted

-the curve  shows a camber compliance of 3.9 deg /kN of negative camber at the rear wheels  and this will cause understeer

-Then parallel wheel travel simulation is used to study the bump steer

-Then x axis input variable is chosen

-then y axis input variable is chosen

-then bump steer curve is plotted

The plot shows that there is a bump steer equal to 2.4 deg/m (abs value)or -2.4 and it will cause a toe out at the rear wheels which will cause over steer

2-Tuning:

It is required to change the bump steer to make the wheels have toe in of 2.6 deg/m instead of the toe out by changing the hardpoints

Original hardpoint table

-the hard point table is modified to the following

-then parallel wheel travel simulation is rerunned

-then the two plots of the original and modified are overlayed over each other

The modified plot shows that now there is+2.6 deg/m of bump steer that will make the rear wheels toe-in which will produce understeer unlike the original setup

-then the modifications to the hardpoint table was removed as it is required to change only one parameter at a time

-then the trailing arm bushing (that is attached to the frame) is changed to change the wheel recession to 500 N/mm ,this is because it has the largest effect  on wheel recession as it has the largest moment arm

original bushing curve

Original bushing data

-the bushing data is changed from the bushing file ,a new fx curve was made

Modified bushing curve

modified bushing data

-then the new bushing is inputted to the model

-then static load traction analysis was performed again

-then x axis input variable was chosen

-then y input variable was chosen

-then the curve was plotted

-the plot showed that the target 500 n/mm target was achieved with the new bushing

-Then the original bushing was restored to the model as it is required to change only one bushing at a time

-then upper control bushing was changed in order to reach the camber compliance of 0.45 deg/kn as it the bushing that has the most impact on the camber as it will produce the largest moments on  the wheel hub

-the bushing is modified

original bushing curve

original bushing data

-the bushing Fx curve was modified

modified bushing curve

Modified bushing data

-then static load lateral force analysis was performed with 5000 N cornering force

-then the x-axis input variable was chosen

-then y-axis input variable was chosen

-then the curve was plotted

-the plot shows that the target of 0.45 deg/kN was achieved.

Files:

https://drive.google.com/drive/folders/1C6729HHgjLWpiuU5tqj_9fzRyVSGxJmb?usp=sharing