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Problem: Continuing from the last example where you worked on the construction of the Lift Mechanism, add the proper constraints and joint motions to your model, as shown in the figure below, and successfully run a simulation of your model. Note: If you need assistance on a step, just click on it for more information. Note: Click on images to enlarge.
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1) Click on Open an existing database.

2) Under File Name, browse to the folder where your model is located, and then click OK.

3) Then locate the bin file that contains your model, lift_mech, and click Open.

1) From the Joint toolbox, select Fixed.

2) Under Construction, make sure 2 Bod-1 Loc, Normal to Grid are selected.

3) Then select the Base as the First Body and the Ground as the Second Body, and then select the Midpoint of the Base as the Location. A Lock icon should appear indicating that you have done this process successful. It may be easier to change the view to Wireframe to complete this process.

4) Note: Because of the scale of the model you will need to zoom in to see the Lock icon, if you wish to make the scale of the Lock Icon larger, right-click on Joint:JOINT_1 and then go to Appearance and then increase the Icon Scale to 15 and click OK.

1) From the Joint toolbox, select Revolute.

2) Under Construction, make sure 2 Bod-1 Loc, Pick Feature are selected.

3) Then select the Mount as the First Body and the Base as the Second Body, and then select the Midpoint of the Mount as the Location. Then select the Global Y-Direction as the axis of rotation. A Hinge icon should appear indicating that you have done this process successful.

4) Note: Because of the scale of the model you will need to zoom in to see the Hinge icon, if you wish to make the scale of the Hinge Icon larger, right-click on Joint:JOINT_2 and then go to Appearance and then increase the Icon Scale to 15 and click OK.



1) From the Joint toolbox, select Revolute.

2) Under Construction, make sure 2 Bod-1 Loc, Normal To Grid are selected.

3) Then select the Shoulder as the First Body and the Mount as the Second Body, and then select the Anchor Marker of the Shoulder as the Location. A Hinge icon should appear indicating that you have done this process successful.

4) Note: Because of the scale of the model you will need to zoom in to see the Hinge icon, if you wish to make the scale of the Hinge Icon larger, right-click on Joint:JOINT_3 and then go to Appearance and then increase the Icon Scale to 15 and click OK.



1) From the Joint toolbox, select Translational.

2) Under Construction, make sure 2 Bod-1 Loc, Pick Feature are selected.

3) Then select the Boom as the First Body and the Shoulder as the Second Body, and then select the Midpoint of the Boom as the Location. Then select the Global X-Direction as the axis of rotation. A "Translational" icon should appear indicating that you have done this process successful.

4) Note: Because of the scale of the model you will need to zoom in to see the Hinge icon, if you wish to make the scale of the "Translational" Icon larger, right-click on Joint:JOINT_4 and then go to Appearance and then increase the Icon Scale to 15 and click OK.

1) From the Joint toolbox, select Revolute.

2) Under Construction, make sure 2 Bod-1 Loc, Normal To Grid are selected.

3) Then select the Bucket as the First Body and the Boom as the Second Body, and then select the Midpoint of the Boom as the Location. A Hinge icon should appear indicating that you have done this process successful.

4) Note: Because of the scale of the model you will need to zoom in to see the Hinge icon, if you wish to make the scale of the "Translational" Icon larger, right-click on Joint:JOINT_5 and then go to Appearance and then increase the Icon Scale to 15 and click OK.

1) Check model topology by constraints by going to the Status bar and then right-clicking on the Information tool stack. Then select the Model Topology by constraints tool and check to see if everything is constrainted properly.

2) Perform a simulation to visually see if everything is constrainted correctly.

1) First, add a motion to the Mount-to-Base joint by going to the Motion Driver tool stack and then select Rotational Joint Motion.

2) Under Speed, enter 360d*time.

3) Then select the Mount-to-Base revolulte joint (JOINT_2) to apply.

4) Now add a motion to the Shoulder-to-Mount joint by entering -STEP(time,0,0,0.10,30d) in the Speed Box.

5) Then select the Shoulder-to-Mount revolute joint (JOINT_3) to apply.

6) Now we will add a motion for the Boom-to-Shoulder joint. Under the Motion Driver tool stack, select Translational Joint Motion.

7) Enter -STEP(time,0.8,0,1,5) for the Speed.

8) Then select the Boom-to-Shoulder translational joint (JOINT_4) to apply.

9) Lastly, we will add a motion to the Bucket-to-Boom joint. Once again under the Motion Driver tool stack, select Rotational Joint Motion.

10) Under Speed enter 45d*(1-cos(360d*time)).

11) Then select the Bucket-to-Boom revolute joint (JOINT_5) to apply.

1) Check to see if the functions were properly entered for each joint by going to Modify and then Impose Motion and checking the Function. Also right near the joint and check the motion by going to right-clicking on the Motion then Modify and checking the Function(time). If the function box does not have the correct function enter it and click OK.

    For example, for the Mount-to-Base joint you can right-click on Joint:JOINT_2 and then click on Modify

2) Then, click on Impose Motion.

3) Then make sure that the Function textbox contains 360d*time, then click OK.

4) Now right-click on Motion: MOTION_1 and click on Modify.

5) Make sure that the Function(time) textbox contains 360d*time, and click OK.

6) Repeat for all joints and motions.

7) Once you have done that, check the model topology by constraints by going to the Status bar and then right-clicking on the Information tool stack. Then select the Model Topology by constraints tool and verify if the joint motions have been applied properly.

1) Simulate the model for 5 seconds and 500 steps and observe the results.

    • In this example, we learned how to apply constraints and joint motions to a model.
    • We learned how to use step functions and how to implement them in joint motions.