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Hi guys, I need your help!

I'm simulating the translation of an arm actuated by a pneumatic cylinder (constant force) whose movement is stopped by a limit switch.

How can I simulate the limit switch to stop the motion of the translating arm keeping the force acting on the piston (as happens in reality), avoiding the penetration of bodies (see the attached .gif)?

 

I'm not interested in "Collision detection" button, since after this forced has stopped, I want another force to start acting on another body.

Thank you all!

 

CK40.gif

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Hello,

You have several ways to do this.

1) You could use a template including a fix joint when certain distance is achieved (the computation of the system can be done using a sensor)

https://altairhyperworks.com/hwhelp/Altair/2019/help/ms/topics/solvers/ms/understand_seq_sim_intro_t.htm

2) You can add contact between the bodies as it happens in the real life I guess.

https://altairhyperworks.com/hwhelp/Altair/2019/help/ms/topics/solvers/ms/3d_mesh_to_mesh_contact_sim_intro_r.htm

https://altairhyperworks.com/hwhelp/Altair/2019/help/tutorials/mv-1012.pdf

3) You could add a second force with a impact function to limit the movement (analog to use contacts)

4) You could include a bistop function on the joint providing a range that the joint can translate.

https://altairhyperworks.com/hwhelp/Altair/2019/help/ms/topics/solvers/ms/bistop.htm?zoom_highlightsub=bistop

 

Best regards,

Felipe.

 

Chris Coker likes this

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On 6/21/2019 at 8:57 PM, Felipe M Leila said:

Hello,

You have several ways to do this.

1) You could use a template including a fix joint when certain distance is achieved (the computation of the system can be done using a sensor)

https://altairhyperworks.com/hwhelp/Altair/2019/help/ms/topics/solvers/ms/understand_seq_sim_intro_t.htm

2) You can add contact between the bodies as it happens in the real life I guess.

https://altairhyperworks.com/hwhelp/Altair/2019/help/ms/topics/solvers/ms/3d_mesh_to_mesh_contact_sim_intro_r.htm

https://altairhyperworks.com/hwhelp/Altair/2019/help/tutorials/mv-1012.pdf

3) You could add a second force with a impact function to limit the movement (analog to use contacts)

4) You could include a bistop function on the joint providing a range that the joint can translate.

https://altairhyperworks.com/hwhelp/Altair/2019/help/ms/topics/solvers/ms/bistop.htm?zoom_highlightsub=bistop

 

Best regards,

Felipe.

 

Thank you Felipe,

 

Bistop function should fit perfectly.

May I ask you why the effect of the bistop function is cancelled when the compliance of the joint (where the bistop function is applied on) is activated?

 

Thank you

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Are you saying the model doesn't run when you change the joint from non-compliance to compliant?

 

OR are you saying the BISTOP is active, but not creating any reaction forces.

 

It's possible that the references you are using to define the BISTOP are removed when changing the JOINT type from non-compliant to compliant.

 

It's also possible that the torsional rate of the bushing it too high to allow the BISTOP to function as expected, i.e. it's not rotation enough, due to the stiffness of the bushing.

 

Investigating the .log file for any warnings when model behavior has changed, is always a good first step.

 

Chris

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9 hours ago, Chris Coker said:

Are you saying the model doesn't run when you change the joint from non-compliance to compliant?

 

OR are you saying the BISTOP is active, but not creating any reaction forces.

 

It's possible that the references you are using to define the BISTOP are removed when changing the JOINT type from non-compliant to compliant.

 

It's also possible that the torsional rate of the bushing it too high to allow the BISTOP to function as expected, i.e. it's not rotation enough, due to the stiffness of the bushing.

 

Investigating the .log file for any warnings when model behavior has changed, is always a good first step.

 

Chris

The BISTOP is active, but not creating any reaction forces.

Anyway I solved the problem using a spring-damper element which acts only as a damper. Basically I get the same effect I had with the trans-damping of the compliant joint and the BISTOP function creates reacting forces.

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