Help with proper Joint to use for wheel on center pin in Dynamic Simulation

[hydrobro]

I have created a Drive Constraint for a wheel and center pin, and now i am trying to simulate using Dynamic Siumlation. After loading Dynamic Simulation I found that Inventor did not convert the constraint with 'Convert Assembly Constraints' (It is grayed out). So I am trying to manually insert a joint. Is the proper joint a spatial joint or is there a more straight forward joint to use like Sliding or Rolling Cylinder Joint. I have tried several with no success. Maybe I have been selecting the wrong surface or axis for the prompts. The wheel turns in the XY plane in assembly. The wheel and Pin are constrained in the assembly with an Insert Constraint. Losing my hair by the minute...any help?!

[MarkFlayler]

If it was for visual purposes only you do not need to run Dynamic Simulation at all. Stop making it more difficult than you originally intended. Find the constraint you added that you call Drive Constraint and right click on it to drive it and animated it out to an avi or wmv file.

[MarkFlayler]

Or if you want a photo realistic display of your animation run Inventor Studio and use Animate Constraint. Dynamic Simulation should be avoided unless you need to get forces from or off your parts. You did not express you needed this.

[hydrobro]

At first, I thought a drive constraint would do the trick. But then I realized that I need to add some balanced 'satellite' objects around the constant velocity wheel that will need to be simulated under a gravity force.

[shift1313]

assembly constraints get converted when using dynamic simulation however driven constraints dont(because they arent real relations. Inventor 09 and 10 have good simulations along with the Insert Joint function that tells you exactly what you need to select. If you select Display Joints Table, it might give you a better understanding of the joints. Spatial joint is a catch all. It will let you define what can be done in each of the 6 DoFs. rotate in 3 different axis and move in 3 different planes. From your short description i would guess the rolling joints would be what you want to use.

[shift1313]

i just thought about this a bit more. If you have an insert constraint in your assembly. all you need to do is add a motor in the dynamic simulation. I have inventor11 in front of me so things look a bit different but there should be a Torque you can add to your wheel.

 

What are you trying to get out of this? Just learn or is there something you need from this dynamic simulation? Dynamic simulation is used to see how things interact, get resultant forces from assemblies in motion etc. If you just want to see your wheel move(like mark was saying) just go into inventor studio. In there you can drive your constraints just as in the assembly and render the animation.

[hydrobro]

I am designing sort of a kaliediscopic device that will consist of a wheel driven by a constant force spring with 4 equal objects mounted on the outer edge of the wheel at each quadrant. Each of the 4 objects will be free to rotate in the same plane as spinning wheel. So as the wheel accelerates to a particular velocity, each of the 4 objects will wobble a bit due to gravity and the acceleration of the wheel. Dynamic Simulation seems to be the best way to go given the need to simulate under gravity.

[shift1313]

well then i would try to use the rolling joints. You will also be able to add springs to the mechanism. Make sure you have some sort of fixed ground plane or when you turn gravity on your object will just fall:)

[hydrobro]

Which rolling joint would you recommend using for a pin in the center hole of a wheel. Cylinder in Cylinder seems like the most appropriate, but the joint sample illustration shows the outer cylinder being much larger than the inner cylinder. Same goes for a Sliding joint with Cylinder in Cylinder.

[shift1313]

can you post a screen shot of your model? is the pin going to be fixed and is the wheel fixed except for its rotation? how many degrees of freedom do these parts have?

[hydrobro]

I can't figure out how to post a screen shot, but will try explaining what I have. My assembly is a grounded pin with one end of it flush to one face of a wheel using an Insert Constraint. I can spin the wheel using my mouse in the assembly environment which, if I understand the DOF concept correctly, the wheel has 2 degrees of freedom ( spinning in the XY plane). Is that right? When I bring the assemly into Dynamic Simulation, both wheel and pin are listed under 'Grounded' in the Dynamic Simulation' browser pane. I have been trying to manually insert a Cylinder in Cylinder joint and the prompts are cryptic to me. For example, under both Outer and Inner Cylinder in the joint definition dialog box, there are selection prompts for 'Origin' and 'X-Axis'. Origin of the cylinder or something else? When I move my cursor over the center of either cylinder, no grip, or center appears for me to select. Same goes for the X-Axis prompt. X axis of what? Do I select an edge that is parallel to an x axis somewhere else on the assembly? Do I need to define a work plane to select?

[hydrobro]

Matt, Note that the Dyanmic Sim browser panel in the screen shot does not show the Insert constraint that is defined in the assembly. Is that a problem? I deleted the angle drive constraint in the assembly, so no I can drag the wheel about the pin in Dynamic Sim. If I can only define the wheel /pin joint to get on with the rest of my simulation building.

Wheel and Pin Screen shot.pdf

[shift1313]

If you have a wheel rolling on a pin and all it can do is rotate around that pin, that is 1 degree of freedom. You have 3 planes and 3 axis of rotations. xy, xz, yz are your 3 planes. if it can move freely in those planes each one accounts for 1 dof. then you have rotation about the x,y,z axis. if it can move and rotate in all of those you have 6 dof. If it can only rotate around on axis and cannot move you have 1.

 

If this particular joint is just a wheel rotating on an axis try the Standard Joints category and the revolution joint. You have options for "in place" or "out of place".

 

let me try and work up a few screen shots for you. I have an older version in front of me but the procedure will be the same.

[shift1313]

The reason all your parts are in the grounded subset is because there are no joints setup yet. it might be easier to set things up with the parts assemble for you. Also you can also use the Select Other feature and scroll through available selections.

 

When working with a Standard Revolution joint there are 6 selections in front of you. First you need to select your pin. I selected the outter surface of my pin. It references this as the Z axis(axis of rotation). I didnt select the origin and i didnt do anything with the Xaxis just let it be wherever it wants to. For something like this its not an issue but when you are setting up something thats not round part(like a hinge) it will matter. If you let the annimation run it will show you the selection process.

 

for component 2 i selected the inner face edge of my wheel and i left the other selections. since we are dealing with round parts the origin will be setup in the center of the part automatically(as far as i know).

 

thats it. First pic is before the selection process. second pic is my first selection highlighted, third pic is the component 2 first selection.

[hydrobro]

Matt, Apparently AI 2009 does not have a revolution joint. I think the closest is called a 'spatial' joint. I have attached screen shots showing the joints available in 2009 with dialog box screen shots for cylinder in cylinder and spatial. The icon used for spatial matches your version's icon for revolution, so they might be the same. Instead of a 'z-axis' prompt, spatial has an 'entity' prompt. Do you think they are equivalent joints? Also, I assumed that if the prompt button was red, Inventor required a selection without the option to ignore as you did. I like your approach much better. Lastly, if I can rotate the wheel about the pin with the mouse in Dynamic Sim, doesn't that indicate that Dynamic Sim recognizes the 'Insert Joint' constraint that I created in the assembly between the wheel and pin? Once I successfully create a spatial or revolution joint, should I see the wheel appear in a 'Mobile Groups' category and the joint appear in a 'Standard' Joints' category listed the Dynamic Sim browser pane? I really appreciate your help, Matt!

Inventor 2009 Joints.pdf

Generic 'Spatial' Joint prompts.pdf

Cylinder in Cylinder Joint Prompts.pdf

[hydrobro]

Hi Matt,

 

I think I got the joint successfully inserted. Your instructions worked, but only after I first deleted the Insert Joint that I defined in the assembly. Apparently, assmebly joints can conflict with joints needed specifically in Dynamic Sim. I will be now working to rotate the wheel in Dynamic Sim, but for now it looks like I finally have my joint inserted with the proper Mobile Groups and Standard Joints appearing in the browser pane. Thanks much Matt!

[shift1313]

spatial is a catch all but you need to be careful and make sure you edit the joint and lock the other DOF's you dont want. It allows you to control all 6 individually.

 

I have 2010 at home but i didnt get until late last night so I didnt have the chance to play with it.

 

Usually joints that conflict will be suppressed once you enter dynamic sim. You can also suppress these joints in the assembly(so you dont have to delete them).

 

You are correct, once you insert a joint, the affected parts will move into the mobile group. Also if you click a point on your wheel and drag the mouse away you will notice an arrow that stretches out with your cursor. This is a force vector. Think about applying a force at that location and that is the direction vector(magnitude and direction).

 

if you need me to i can check out the available joints when im at my home computer later tonight.

[numberOCD]

@shift1313

Hey, I'm following your steps (far better than wikihelp FYI), and I'm stuck in a little part. I have (2) rail wheels on separate but colinear axes being driven by a long shaft with cylinder to cylinder contact on each on of the shaft. The wheels are 12"DIA and the shaft at contact is 6"DIA and I'm getting a notice that the distance between the axes is not equal to the sum of the radii. Could you help me out with this? I even wonder if I assembled incorrectly. I deleted all of the mates from the assembly as a precaution before adding the spatial joints and Cylinder on Cylinder joints. (FYI, I still have never seen the option to "Retain" the DOF, only to "Ignore" it).

 

Thanks! CraneAssembly.zip