How to limit the motion of a prismatic joint

When I am modelling a prismatic joint and I start the simulation the joint just drops under gravity and falls off. How do I limit the range of its motion

Answer 1

[Sebastian Castro]

To do this, you can create a contact force that is applied to the joint based on some limits.

For a simple limit like this you can use the SimMechanics-Simscape interface blocks on the joint and connect it to a Translational Hard Stop block from the Simscape library.

For more complicated contact relationships, you may want to look at the SimMechanics Contact Library on the File Exchange.

- Sebastian

[Karthik Nagendra]

Hi, Sebastian , thanks for your answer. Appreciate it. I am new to using simmechanics can you explain a little more please. Thanks

[Sebastian Castro]

Sure. If you get the SimMechanics-Simscape interface block, your contact would look as follows. This screenshot is from R2015a:

Notice that you want to configure your joint to accept force/torque input and output velocities. This will make it connect to those interface blocks from the File Exchange entry.

Also, you'll have to play with the parameters of that "Translational Hard Stop" block such that the spring and damper are strong enough to overcome the weight of the object... but not too strong that they cause unrealistic behavior.

- Sebastian

[Karthik Nagendra]

Thanks sebastian looks like the problem is solved for now. If I need anything more will contact you

[Karthik Nagendra]

Also what component can I use to actuate the joint to give translational motion to it?

[Karthik Nagendra]

When I use a hardstop the prismatic joint stops at that point but I want it to go back to the starting position. How is that possible?

[Sebastian Castro]

You want it to move back and forth between he two limits?

[Karthik Nagendra]

Yes exactly. And I want it to move by providing a force manually

[Karthik Nagendra]

I want the blue slider to slide on the grey pillar/frame only within the dimensions of the pillar

[Sebastian Castro]

You could make a controller that measures the position of the object and moves it either up or down along the belt by applying a force.

[Karthik Nagendra]

I am unable to figure out how to create a belt drive and then add the slider on the belt and make a controller.