## what are the equations of state space on open loop active suspension ?

## what are the equations of state space on open loop active suspension ?

(OP)

Hello

So I need to solve a problem on an active suspension .I dont know how to find the equations of state space on open loop

Given information

We apply F(t) force as ypou can see

z(t) is the distance of the upper spring edge from the ground

when spring length (not loaded ) = 1

F (spring) = -kδ^3 (t) δ = displacement of z(t)- z(not loaded)

F ( damper ) = - c dz(t)/dt

## RE: what are the equations of state space on open loop active suspension ?

these force create an acceleration of the mass, hence velocity and displacement.

as I remember this stuff (from 40 years ago) you get a differential equation (xdbldot, xdot, x).

"Hoffen wir mal, dass alles gut geht !"

General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

## RE: what are the equations of state space on open loop active suspension ?

F spring , F damper and weight down force

## RE: what are the equations of state space on open loop active suspension ?

## RE: what are the equations of state space on open loop active suspension ?

## RE: what are the equations of state space on open loop active suspension ?

force in the damper =-c*Dz

Net force on mass = -g-k*z+F- c*zD=m*D^2z

Using D notation because this is a typewriter.

There's probably a minus sign or two adrift in that. No D^3

Cheers

Greg Locock

New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

## RE: what are the equations of state space on open loop active suspension ?

And my problem says that F spring = - kδ^3(t)

I dont know how to turn u it to x dot

## RE: what are the equations of state space on open loop active suspension ?

Good Luck,

Latexman

## RE: what are the equations of state space on open loop active suspension ?

## RE: what are the equations of state space on open loop active suspension ?

Wow, well you cannot easily solve that algebraically. A quadratic rate curve (ie cubic force curve) for a spring is quite a feasible approximation in real life, but to solve it we use numerical solutions.

so -g-k*z*z*z+F- c*Dz=m*D^2z

where k c m and g are constants and D means d/dt

You could try Wolfram Alpha.

Cheers

Greg Locock

New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

## RE: what are the equations of state space on open loop active suspension ?

## RE: what are the equations of state space on open loop active suspension ?

Cheers

Greg Locock

New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

## RE: what are the equations of state space on open loop active suspension ?

I want to find the equation of damper ratio ζ>1 but including cubic spring

I know that for linear active (non cubic ) suspension is ζ= (c√m)/(2m√k)

but in my case that i have cubic spring do you have any idea how the equation is