Special General Motion in ADAMS

[Saleh abbasi]

Hello, I have a problem in describe a motion in this body, i want rectangular body have a vibration in direction that I draw. I try to create this with using general motion or planar joint, part can translate in X,Y and rotate in Z, but also must always have this vibration in y direction of body. in general motion we have two markers. reference is in ground and the other is in center of body. I try to write this in motion :
x = displacement : A*sin(w*time)*sin(AZ(part_marker,ground_marker))+ DX(part_marker,ground_marker,ground_marker)
y = displacement : A*sin(w*time)*cos(AZ(part_marker,ground_marker))+ DY(part_marker,ground_marker,ground_marker)
the body can rotate in Z axes and for vibration Vector perpendicular to body I decomposition with AZ() function (Z angle).
I used DX and DY for free translation motion in these directions, but i got this error in simulation :
A probable cause is an over-specification of initial velocities of bodies.
Please specify fewer initial velocities and try again
ERROR: Simulation failure detected.

 

[GregLocock]

It is not clear how the mechanism is constrained.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[Saleh abbasi]

I try to simulate this Model :

PZT(Piezoelectric) is actuator of this robot. I try to create Vibration in direction that draw in previous image with general motion. robot can translate in X and Y direction(Global) (Y direction is free for any jumping and etc.) and can rotate about Z axes (model in XY plane). Vibration always is in normal of the body (normal to PZT plane). so how can i create this vibration? as I said for free translation I try to insert DX and DY in function, but simulation failed.
After create robot and insert this motion correctly, how can find resonance of legs? legs is connect with revolute joint and have torsion spring.

 

[GregLocock]

Sorry pretty pictures don't really help. Use wireframe. Forcing a deflection won't give modes, you need to use Linear.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[Saleh abbasi]

for better describe of my problem:
define markers:

define motion from markers:

simulate and errors in two step size (1e-5(or bigger) and 1e-6), varval(41) is A*sin(wt):

I cant find any redundant constraint in model.
Also when in motion insert X direction motion free I get this error in 2 other simulates:

Base ( piezo(orange part) and base are fixed that could see in first image). Base and leg have a revolute joint and torsion spring. legs have a contact force with plane (plane fixed with ground). in previous I write function for motion with reference to ground that have this error:
A probable cause is an over-specification of initial velocities of bodies.
Please specify fewer initial velocities and try again.

 

[GregLocock]

You can't get modes with Contact. So the legs are sprung against the marker 114 block, and are restrained by the ground.

This is massively redundant and very hard for the solver to deal with. What I would suggest you do is add damping to the torsion springs, and build the model with the legs clear of the base. So the first thing the model will do is drop the legs into some sort of equilibrium. You may need to stuff around with the contact statement to get an intital solution.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[GregLocock]

Incidentally if the ground is fixed and the block is fixed then there can be no motion.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[newbie_user]

It might be worth checking "Settings - Units". Maybe degrees are indicated instead of radians?
And the entry “varval (41)....” It's also confusing. The number itself cannot be a variable.

 

[Saleh abbasi]

varval(41) is vibration (A*sin(2*pi*f*time)), and don't have any problem in simulate.
Does changing units in a simulation affect the solution method used by the solver?
in this case legs is solid, but for better simulation we also try simulate flexible legs too, that legs fixed in base instead of using torsion spring.
I'm looking for another software that can simulate these methods. Do you know another software that can do these two methods? my dimensions in model is small and i must insert this motion in model correctly. also this software must have user define function for friction(I want insert anisotropic friction, in adams we can do this in contact force and insert it by programming).