Adams car question

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babias
babias
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Joined: 16 Apr 2018, 13:16

Re: Adams car question

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Tim.Wright wrote:
19 Jul 2021, 23:15
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:
Image
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:
Image
Greg Locock wrote:
20 Jul 2021, 01:16
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

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Tim.Wright
330
Joined: 13 Feb 2009, 06:29

Re: Adams car question

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babias wrote:
25 Jul 2021, 17:03
This is the result using the complete formula with respect to the output of adams:
Image
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.
Not the engineer at Force India

babias
babias
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Joined: 16 Apr 2018, 13:16

Re: Adams car question

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Tim.Wright wrote:
25 Jul 2021, 17:16
babias wrote:
25 Jul 2021, 17:03
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

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Tim.Wright
330
Joined: 13 Feb 2009, 06:29

Re: Adams car question

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Update your code so it uses the motion ratio of each operating point. The it should match the adams wheel rate almost perfectly
Not the engineer at Force India

babias
babias
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Joined: 16 Apr 2018, 13:16

Re: Adams car question

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

Thank you very much for your help!