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Simulate the force applied to open the bus luggage compartment by MotionView

I am working on a project for a course, which is to simulate the force to open the bus luggage compartment. Initially, I used motion to control the joints, and the model worked well. However, after I switched to using force, the model stopped working. Can anyone help me explain why this happened? And what would be the solution to fix it? Below, I will describe my model.

The luggage compartment is attached with 4 bars mechanism and 1 piston. The hinge joints are rotational, and the piston is connected to both the ground body and the luggage compartment via two ball joints. I have attached the simulation file below. Thank you in advance!!!

force.mdl

motion.mdl

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Accepted answers

GTT Adam

Hi @hoangthuy324,

I took a peak at your model and I see there are several points that look misaligned:

It is likely that due to this misalignment the system is actually kinematically bound.

The reason that the Motion-based model functions but the Force-based model does not is that the Motion is a constraint that will apply any amount of torque necessary to complete the intended displacement. In this case, if we look at the applied torque by the Motion, we can see that it applies quite a lot to overcome this kinematic restriction:

It also features discontinuities in the torque curve to break through various constraints.

To improve the results of both models, I would recommend that you improve the position of the points so they are mirrored and thus will not bind the system. For example, p_0 left and p_0 right show the following locations:

Left: -1929.9280, -1108.5930, 549.1950

Right: -3378.00, -1106.1340, 550.4910

For this point pair, set the Y and Z locations to be identical. Completing the same modifications on the remainder of the points will likely make the model function smoothly.

Tip: Point pairs mirror about the XZ axis. To achieve symmetry in the model, creating this about the XZ plane and not the YZ plane would allow you to use symmetrical points, bodies, and joints.

Hope this helps!

Adam Reid

All comments

GTT Adam

Hi @hoangthuy324,

Can you describe how your model is 'no longer working'?

Is the simulation failing to solve, or is the new Force entity not strong enough to open/close the compartment?

Hope this helps!

Adam Reid

hoangthuy324

Hi,

The simulation run well at the both cases without any failure. But I dont know why the joints that dont work when applying force. Please check the attached files for more detailed if you have time

Thank you very much

hoangthuy324

Hi @GTT Adam

The simulations run well at both cases without any failure. But i dont know why joints dont work why applying force. Please check the attached files for more detailed if you can.

Thank you very much!!

GTT Adam

Hi @hoangthuy324,

I took a peak at your model and I see there are several points that look misaligned:

It is likely that due to this misalignment the system is actually kinematically bound.

It also features discontinuities in the torque curve to break through various constraints.

Left: -1929.9280, -1108.5930, 549.1950

Right: -3378.00, -1106.1340, 550.4910

For this point pair, set the Y and Z locations to be identical. Completing the same modifications on the remainder of the points will likely make the model function smoothly.

Tip: Point pairs mirror about the XZ axis. To achieve symmetry in the model, creating this about the XZ plane and not the YZ plane would allow you to use symmetrical points, bodies, and joints.

Hope this helps!

Adam Reid

Christopher_Fadanelli

Hi @hoangthuy324 ,

Going off of @GTT Adam post. We have a great free online eLearning where you can go over MotionView and it's modeling capabilities. The example used is a four bar mechanism ;) . You can check it out here: Introduction to MotionView.

Best,

Christopher Fadanelli

hoangthuy324

I've adjusted my model based on your suggestion, and it works!!!

Thank you very much.