AVIEW: initial conditions for a manipulator with stiffness

[kenkenken]

I am using ADAMS view 12.0, Im trying to do a simulation of a manipulator. The manipulator holds a heavy payload, and they are connected by bushing. I set the initial conditions that are rotation displacements for each joint, and if I run the simulation for 0.2sec, the joint rotate unexpextedly due to the stiffness by the bushing connected with the heavy payload, so I can not make an expected initial pose. In the case of rigid connection, there is no problem. How can I solve this problem?.

Thank you in advance.

 

[GregLocock]

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.