Simulating a Motor in Dynamic Simulation

[Anonymous]

I am trying to simulate a motor that has a torque of 60 Nm in the dynamic simulation environment. I have a spring that is connected to the joint to resist this motion. My goal is to extend the spring to a certain point, using the motor, then unload the force of the motor so that all of the energy built up by the spring brings the rotating shaft downward.

I have tried creating a torque, but it doesn't seem to work that well. I have also tried the imposed motion option on my revolute joint. Does any one have any thoughts on this issue? See the attached image to get an idea of what I am talking about. Thanks,

RB

[Anonymous]

Also what is the best way to measure torque on a joint using the output grapher? Thanks,

RB

[Anonymous]

A couple of thoughts here on your mechanism:



- what type of electric motor are you using? I'm assuming DC.



- you don't want to stall your motor. If you have a DC motor, the current thru the motor is the greatest when it is stalled. You will most likely burn out your motor.



- you can't backdrive your motor as fast as you want the spring to travel.





I would recommend looking at a cam system, similar to a trigger on an old fashioned revolver. Oversize your motor so that it has >2 time the torque required at stall. Gear it appropriately for the speed you want to load the spring.

[Anonymous]

I should have made myself more clear. The motor will not stall, there will be a disengaging mechanism in place to ensure that no force or backlash is exerted on the motor when the spring is released. I have figured out how to simulate this in inventor after some trial and error. Any thoughts on how to measure torque at a specific joint?

[Anonymous]

find the joint you want to measure and then plot the moment on the graph, see attached pic for more info

[jean-yves.machillot]

Hi Berryrr,
in Dynamic Simulation, to relax an action, you have to use the Input Grapher (berryrr_0.png).

Depending if you drive a load (force & torque) or an imposed motion, you have different solutions :
- "Free" option of a sector (berryrr_1.png).
Note for an imposed motion, it is not possible to "restart" the motion : if a sector is free then all the following sectors are free too.

- "Freeing condition" of a sector for an imposed motion : if the Driving force reaches a certain value then the imposed motion is stopped and the joint is released (berryrr_2.png). The Driving force is the value in the degree of freedom which is needed to imposed the motion taken in account all the dynamic of the system (masses, inertia, forces, springs, gravity, etc).
Note for a load (force & torque) the condition is an "Application condition" : the load is applied if ...

berryrr_3.png to illustrate the "freeing condition".

To complete the answer from Josh : the Moment vector of a joint gives the global moment but you have to select the Z component to have only the action around the Z axis, which is the rotation axis in a revolution joint. In my simple example, "U_imposed" (from Driving force) is equal to Moment.

Hope it gives ideas to simulate your mechanism.
Thanks
JYves