Adams car question

[babias]

Looks like the motion ratio is quite non-linear. Try using the complete formula for calulating the wheel rate which takes into account motion ratio non-linearities:
Kwheel = Kspring x MotionRatio^2 + Fspring x dMotionRatio/dWheelTravel

Compare this to the Adams calculated wheel rate - should be a lot closer.

This is the result using the complete formula with respect to the output of adams:

I have also compared the MR computed as square root of the stiffness ratio and the one evaluated with the slope of the spring displacement with respect to the wheel travel:

Your description was out, you have a continuously increasing wheel rate. In theory that rate curve should just be a straight line with zero gradient. Your spring length plot says the MR is about 0.6, so the wheelrate should be around 84 N/mm

According to the output of adams the wheel rate drops in the final part of the wheel travel

[Tim.Wright]

This is the result using the complete formula with respect to the output of adams:

For the orange line in this plot, did you use the static motion ratio or the instantaneous motion ratio at each point?

What is your definition of motion ratio - dSpring/dWheel or dWheel/dSpring?

Actually, can you post your matlab code? Will be way easier.

[babias]

This is the result using the complete formula with respect to the output of adams:
https://i.ibb.co/kBTdVsX/KW-comp.png

For the orange line in this plot, did you use the static motion ratio or the instantaneous motion ratio at each point?

What is your definition of motion ratio - dSpring/dWheel or dWheel/dSpring?

Actually, can you post your matlab code? Will be way easier.

Here I have used the MR in static position and the rate of change of the MR with respect to wheel travel. The MR (IR in the matlab code) is dSpring/dWheel because it is evaluated as the rate of change of spring length with respect to the wheel travel.
This is the code (input data is directly exported from adams):

IR=diff(nsl_ride_spring_datadisplacement_front)./diff(WheelCenterVerticalTravelvertical_left);
IR_stat=abs(IR(51)); %IR at 0 wheel travel
dIR=diff(abs(IR))./diff(WheelCenterVerticalTravelvertical_left(1:102));
for i=1:100
KW(i)=KS*IR_stat^2+nsl_ride_spring_dataforce_front(i)*dIR(i)
end

[Tim.Wright]

Update your code so it uses the motion ratio of each operating point. The it should match the adams wheel rate almost perfectly

[babias]

Wow, I have always thought that that definition was with the static value of motion ratio. Now it works!


Thank you very much for your help!