AVIEW: initial conditions for a manipulator with stiffness

Run a solution with relaxed error settings (etc) to establish equilibrium and then use that position as your final starting point.

The effect you see is real, we see it all the time on large models, so our custom pre-processor actually goes through a static convergence funnel (as it is known) every time.

In effect we assemble the car in mid air, then drop the car onto the ground from a small height and let it sort itself out, then we start testing.

MSC support probably has some articles on the subject, here's our funnel

! Static Funnel
equil/maxit=75, err=10000, imb=10000, stab=10000
con/fun=user(1010,555)
equil/maxit=75, err=1000, imb=1000, stab=100
con/fun=user(1010,555)
equil/maxit=75, err=100, imb=100, stab=10
con/fun=user(1010,555)
equil/maxit=75, err=0.1, imb=0.1, stab=0.1
con/fun=user(1010,555)
equil/maxit=75, err=1.0000e-03, imb=1.0000e-01, stab=5.0000e-02

The other solution is to work out the correct, static, geometry and then entering preloads in the bushes. Not very easy.






Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.