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Navigating a Linked Body in Motion Simulation Environment

Experimenter
Experimenter

Hello dears, after my long study on a complex mechanism in motion simulation (NX7.5) now I have a blind-alley. I tried to solve it myself but I could not.

 

The motion I try to get may be described as from a conveyor to another conveyor. My mechanism accepts products from feeding conveyor, processes on them and put them on the outgoing conveyor. In order to represent a fully realistical simulation, I have to use many many 3D contacts but this is very hard to be applied and very hard to solve my computer limitedly skilled.

 

So I have to manually describe the motion for the product. Namely I will navigate the part by describing the rotations around several axis, translations along the several axis. Even the rotations and translations may be simultaneous.

 

But any of the joints is not proper for such a movement. Because the linked body (my product) should make a displacement along an axis (i.e. X-axis), then should make a rotation (i.e. Z-axis). So I can not use joints-drivers.

 

I think there may be 2 possible solutions to describe the positions:

 

1- If I can design a special joint with some DOF, then I can move the linked body by drivers. I will free all the DOFs (X, Y, Z, RX, RY, RZ) and I will use function manager in driver object. Ofcourse I have to be able to select this special joints for the driver object.

 

2- If there is already any other function that I couldnt discover yet, I can use it Smiley Happy

 

I tried to make this movements in MCD environment but even in MCD I couldnt. Because I have to put both "sliding" and "hinge" joints. Also I have to do this motion in "motion simulation" because I did everything in this environment till now.

 

Thanks.

 

4 REPLIES
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Re: Navigating a Linked Body in Motion Simulation Environment

Siemens Valued Contributor Siemens Valued Contributor
Siemens Valued Contributor

In NX7.5 Motion Simulation, there is no driver for spherical joint DOF, neither driver for the Link body DOF itself.

Say you want to move a component. There is a workaround to drive its several DOFs by using dummy Links (small mass, small principal Inertia, null cross Inertia) . These links are connected as a chain that ends by the component. For example, in the case you mention, to drive one translation and one rotation of a component:

-  A dummy link1 to ground with slider joint and driver

- A link including the component, connected to the dummy link1 via a revolute joint and driver.

- The slider joints moves as well the component. So the component movements are controlled in translation and rotation.

 

Then use function to 'sequence'. You may need to use IF and/or STEP function.

For describing movements that are all kinematically defined (preferably), you can also explore Solutions type Articulation and/or Spreadsheet Run. With these solutions, the dirver displacements and rotations are very well controlled. These solutions are often used.

Hope it helps,

Gilles

Gilles Dubourg
Product Manager – Simcenter 3D Motion
Product Lifecycle Management
Siemens Industry Software SAS
gilles.dubourg@siemens.com
www.siemens.com/plm

Re: Navigating a Linked Body in Motion Simulation Environment

Experimenter
Experimenter

Hello Gilles, firstly thank you very much for your reply.

 

I tried to describe movements that are all kinematically defined via SpreadSheet solution.

 

I can "only" translate the part with slider joint along X-Axis and with parameters in spreadsheet. Also I can "only" rotate the part around Z-Axis with revolute joint and with parameters in spreadsheet.

 

But the thing I want to do is that moving the part by many parameters. It means I have to rotate and translate the part simultaneously; like "Spiderman" in the air. When I put "both" joints revolute and slider then the solver fails. So I need any other kind of joint, or I should directly control the link instead of joint.

 

Please condider that I work in dynamical environment.

 

What do you advice?

 

Thanks again...

Re: Navigating a Linked Body in Motion Simulation Environment

Experimenter
Experimenter

Hello Gilles, moreover I have to drive the part by 3 or 4 different DOF. It means Tr.X, Tr.Z, R.Y, R.Z.

 

Indeed the movement compares to a CNC programme with absolute coordination for a milling tool/machine.

 

I want to drive the "4 or 5 link" fully kinematical while all other mechanism (150 link) is working fully dynamical.

 

The spreadsheet should be similar to attached. But the driven object should be the link itself. I think "standard revolute and slider" joints will always prevent my movement.

Re: Navigating a Linked Body in Motion Simulation Environment

Experimenter
Experimenter
Hello Gilles,

Thank you very much for offering the way of "dummy links". So I can get all of the DOFs for my link and I can move the component by a driver defined by "XY Table" in which X is time and Y is displacement.