create mechanism- dynamic analysis with servomotor

[leonardo-037]

Good morning.
I have a question about dynamic analysis in creo 2.0.
work as a mechanical designer and I have the following problem:
in a levers system there is a spring that acts as an input force and a panel fulcrated on the bottom and which can rotate 90 degrees starting from the vertical position. the need is that the panel in any position between 90 and 0 degrees compared to the horizontal remains in balance position. it is therefore necessary to equal the curve of the moment (sinusoidal) of the mass panel m by means of the variable force of a spring that is compressed and the system of levers.
in order to read the curve of the moment generated by the system, making sure that this is as close as possible to zero to have balance, how is it better to set the simulation in creo? I currently impose a servo motor with constant angular velocity of amplitude 1 and read the connection reaction on the same axis in which the servomotor is placed. My only doubt is the following: setting a rotation motion at constant speed does not alter the system's inertias? I would like every degree to create read the values of forces and moments by cancelling the inertias and therefore as if it were a static problem but at every corner step.

I tried to set the analysis with balance of forces but it comes out the error that the system does not have 0 degrees of freedom having left the possibility to the panel to rotate.

I hope that some of you can help me optimize the balancing method I currently use.
thanks and good day.

 

[320i S]

You better put a pattern, just descriptive, you don't understand what you want to achieve.

 

[leonardo-037]

the question is simple and theoretical / practical. any pattern would also be superfluous. I make it very simple: I have a panel of a certain height that rotates from 0 to 90 degrees compared to the horizontal with the point of rotation below. as a door (oven or dishwasher for us). to read the moment in the connection where the wheel panel must necessarily define a servomotor in I create otherwise I can not get the moment value at any moment. the question is simply this. the panel has its own mass like any other component and inserting a servo motor I will ultimately set a motorcycle law (in this case the speed of the servomotor of 1 deg/sec). As dynamic analysis, the definition of an angle velocity alters the inertia forces of the system? I would like a static reading of the moment but at every point during rotation considering that I put a spring and other components that balance the moment and keep the door in balance to each angle position. is it possible to do it in creo?

 

[320i S]

in practice you have to check/size a twisted spring, to counter the fall of a lightning bolted door below?

 

[leonardo-037]

in practice you have to check/size a twisted spring, to counter the fall of a lightning bolted door below?

First of all thank you for the time you are taking in answering my question.
basically I have to find a spring that together with a system of cinematisms balances me the moment that is generated by opening the panel from all vertical to all horizontal.
I already do so by setting a servomotor inside a dynamic analysis and then I read the value of the moment in the connection.

what I care about is to have in every point the balanced panel then moment on connection equal to zero.
Supposing that I can already reset it, I have cmq doubt that by setting a uniform rotary motion (because I put the servomotor) and analysis is dynamic, there are inertias that in reality are not there. in reality I take the panel I carry it in any position between 0 and 90 degrees, I leave it and it has to be balanced. Unfortunately I do not just do the analysis in two or three positions but at least every 5 degrees opening. I would like to avoid doing 16 static simulations. Here's the problem.
I hope this time I was clear.

 

[welcome to the machine]

"I must find a spring that together with a film system it balances me the moment that is generated by opening the panel from all vertical to all horizontal". So not a twisted spring on the fulcrum, but a variable lever-arm parallelgram that shares the spring so as to compensate for the non-linearity of the moment generated by the weight force? Perhaps so you can, but with a sic sic simpliciter spring I don't think that you can find the balance in all positions, unless you increase the system inertia with clutches, but the lady who has to open the door would get mad. . .

 

[leonardo-037]

"I must find a spring that together with a film system it balances me the moment that is generated by opening the panel from all vertical to all horizontal". So not a twisted spring on the fulcrum, but a variable lever-arm parallelgram that shares the spring so as to compensate for the non-linearity of the moment generated by the weight force? Perhaps so you can, but with a sic sic simpliciter spring I don't think that you can find the balance in all positions, unless you increase the system inertia with clutches, but the lady who has to open the door would get mad. . .

Maybe it's not clear the problem or I can't explain myself.... leave the problem of the spring alone.... My question is:
If I put a servo motor in order to read the connection reaction of the fulcrum I go or not to impose a uniform rotational motion and then to add inertia that in reality are not there? I actually put the panel every 5 degrees and must stay there. in the cad I put a servant to see the values of the moment (which for the record I have already balanced). Is there a way to read the moment without imposing an angle speed to the servo motor and without making a simulation every 5 degrees?
mine is a request on the program not on the problem I described. I have described it to better understand what my doubt came from.

Thank you.

 

[320i S]

I think your problem is up, because you're doing an analysis to get results in static, with a dynamic analysis system.
I try to throw them a slightly rough solution: from what I understand you have already balanced the system in at least a couple of points (I imagine completely open door) and inserted a force/moment of reaction to keep it in balance, try to put the force/moment of balance with -5%, you should allow you to move the panel and have the new "strength/moment of reduced balance" with the new position, at that point you just create

 

[leonardo-037]

I think your problem is up, because you're doing an analysis to get results in static, with a dynamic analysis system.
I try to throw them a slightly rough solution: from what I understand you have already balanced the system in at least a couple of points (I imagine completely open door) and inserted a force/moment of reaction to keep it in balance, try to put the force/moment of balance with -5%, you should allow you to move the panel and have the new "strength/moment of reduced balance" with the new position, at that point you just create

you are also a possible solution.... at the moment I have circumvented the problem so: I define a servo motor with an extremely low angle speed (so to have an almost static problem at every increment canceling the inertias). Obviously not to let go of the simulation too slow start the analysis always dynamic type but with a reading every tot frames corresponding to 5 degrees at a time.

 

[Hope]

Hi, leonardo,

Yes, you can do it with creo mechanism. you have to launch a "dynamic" analysis and define (and activate in the analysis) the acceleration of gravity and any friction (tendina close to that of the servomotors in the analysis panel)

create a "measure" on the hinge of your door and you can get them the binding reactions and strong moment if you defined the friction of the zipper.

alternatively for the problem you're trying to solve I would do a "force balance" analysis. Defuses into the same curtain where you selected dynamic analysis.

 

[leonardo-037]

Hi, leonardo,

Yes, you can do it with creo mechanism. you have to launch a "dynamic" analysis and define (and activate in the analysis) the acceleration of gravity and any friction (tendina close to that of the servomotors in the analysis panel)

create a "measure" on the hinge of your door and you can get them the binding reactions and strong moment if you defined the friction of the zipper.

alternatively for the problem you're trying to solve I would do a "force balance" analysis. Defuses into the same curtain where you selected dynamic analysis.

Hello and thank you for the answer.

as written some message above the analysis "force balance" I can not do it as the system has a degree of freedom. I should stop the door every 5 degrees and do an analysis. this every time I make a change. You understand the discomfort that would come out of it. When I go reading the measure, the curve of the balanced moment comes out. and here we are all happy but, my doubt is that the moment read from the cad and therefore what I go to balance from time to time is affected by an additional moment due to the dynamic of the door that has a disproportionate mass compared to the whole system. you understand and agree with me that a moving mass, because there is a servomotor that currently makes 1 deg/sec, generates inertial moment due to the inertial speed of the system.
in creo is it possible to move a component with mass in multiple points and to obtain reactions and static moments?
in my opinion the roads are two:
- one as mentioned before setting a motor that moves very slow (at that point the system has no inertia)
-or set the engine as a position and not as a speed. but this option fails the analysis at the start and I do not understand why.

Thank you.

 

[Hope]

in creo is it possible to move a component with mass in multiple points and to obtain reactions and static moments?

Yes, it is possible.

1) create two measures, the reaction on the hinge and angle position (in creo mechanism)

2) turn the analysis

3) go back to create and amounts the results obtained (it is all parametric and connected to mbd analysis)

4) enter the sensitivity analysis and draw the time-angle chart door.

every one you make a change see the updated chart. there is no need to change anything "by hand".

this from the point of view of the software.

with regard to the type of analysis, if the inertia of your door is considerable, you must switch to a dynamic analysis (without servomotors).

 

[leonardo-037]

Yes, it is possible.

1) create two measures, the reaction on the hinge and angle position (in creo mechanism)

2) turn the analysis

3) go back to create and amounts the results obtained (it is all parametric and connected to mbd analysis)

4) enter the sensitivity analysis and draw the time-angle chart door.

every one you make a change see the updated chart. there is no need to change anything "by hand".

this from the point of view of the software.

with regard to the type of analysis, if the inertia of your door is considerable, you must switch to a dynamic analysis (without servomotors).

I can answer you precisely just next Monday but I'm pretty sure your suggestion is not effective. to view the curve of the moment I have done exactly what you said. dynamic analysis with servomotor and chart reading at each point plotting the curve torque_vs_angle where Torque ed angle are two measures that I have created. remains the problem that the servomotre I set it with speed of 1 deg/sec therefore imposing a rotation to vconstant. in order to have a curve torque_vs_angle not influenced by system inertia I cannot do as you told me for two simple reasons:1- If I remove the servo motor, the panel is free to fall or return on (if the spring is undersized or oversized respectively). in any of the two cases I would have an accelerated motion as one between elastic force and weight force overlaps the other.2- if I remove the servomotor the reading of the connection reaction is less (I get a set of points all close to zero regardless of whether the system is in balance or not). I can assure you of this because I have tried several times, but only Monday I can give you feedback with an image.

Ultimately the only way to cancel the axial moment caused by inertia is to cancel the angular speed i.e. to take the panel put it in a position and calculate the reaction. increase by 5 degrees at a time and repeat the process what is very expensive to do.

 

[Hope]

If you can find the value of the measure you want (if it is) for a specific angle you can do it automatically for all other corners.

Can you confirm that to import the parameters to plot are you using the panel in image?

 

[Hope]

as written some message above the analysis "force balance" I can not do it as the system has a degree of freedom

That's not true. you can do it by activating the loadcell lock (as from image). this function serves precisely to find the value of the force that balances the system.

1- If I remove the servo motor, the panel is free to fall or return on (if the spring is undersized or oversized respectively). in any of the two cases I would have an accelerated motion as one between elastic force and weight force over the other

This is because you are doing an analysis without friction/mortization which is not realistic. if you introduce them and turn the analysis you will see that the system damps and mechanism returns you the right results.

you understand and agree with me that a moving mass, because there is a servomotor that currently makes 1 deg/sec, generates inertial moment due to the inertial speed of the system.

if you want to use the servo motor, from zero density to components and insert the weight forces on their geometric centers. This is clearly a force (you hear the word game) and I could tell you if it is effective only by selling the mechanism you are analyzing.