13858158.ppt

ADM701, Workshop 9, March 2013
Copyright© 2013 MSC.Software Corporation
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WORKSHOP 9
LIFT MECHANISM II

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• Workshop Objective
– In this workshop, you will use the model you previously built in (Workshop 8-
Lift Mechanism I) and create joints.
• Optional:
– If you’d like a challenge, add the following joints and motions without going
through the detailed steps presented on the following slides.
• Rotational motion to the mount-to-base joint.
D(t) = 360d*time
• Rotational motion to the shoulder-to-mount joint.
D(t) = STEP(time, 0, 0, 0.10, 30d)
• Translational motion to the boom-to-shoulder joint.
D(t) = STEP(time, 0.8, 0, 1, 5)
• Rotational motion to the bucket-to-boom joint.
D(t) = 45d*(1-cos(360d*time))
– Otherwise, continue by following the detailed instructions.

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• Software Version
– ADAMS 2013
• Files Required
– Use directory exercise_dir/mod_08_lift_mech_1
• Tips before you start
– Use the figure on slide 3 to find out what type of constraints you need.
– Simulate the model at regular intervals to check the constraints.
– Rename joints as soon as you create them.
– Adjust icon sizes whenever necessary (see Set up the working environment on
slide 7 of Workshop 8 - Lift Mechanism I.)

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• Problem Description
– Use the diagram below for the placement of the joints.

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• Suggested Steps
1. Import model and construct constraining parts.
2. Verify and simulate.
3. Add joint motion.
4. Run simulation and export.
5. Perform optional tasks.

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Step 1. Import Model and Constrain Parts
To import model:
a. From the Welcome dialog box, select Existing Model.
b. Set the Working directory to
exercise_dir/mod_09_lift_mech_2.and uncheck Use
File Directory as Working Directory.
c. Find and select the model file which you completed in the
previous workshop from the directory
exercise_dir/mod_08_lift_mech_1,
d. If you need a fresh copy of the model, select and opens
the command file, lift_mech_I_completed.cmd, from the
directory
exercise_dir/mod_08_lift_mech_1/completed.
In this section, you’ll constrain the parts that you created in
the previous workshop. To constrain the parts:
a. Use the Fixed joint tool to fix the base to ground.
b. Constrain mount to base (revolute joint):
• Use the options 2 Bod-1 Loc and Pick Geometry
Feature.
• Place the joint at the mount’s cm marker.
• Select the + y-axis as the axis for the rotation.
b
a

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Step 1. Constrain Parts (Cont.)
a. Constrain shoulder to mount
(revolute joint):
• Use the option Normal To
Grid.
• Right-click to select the
cylinder’s anchor marker.
b. Constrain the boom to the
shoulder (translational Joint):
• Use the option Pick
Feature.
• Select the x-axis as the axis
for the translation.
c. Constrain the bucket to the
boom (revolute joint):
d. Use the option Normal To Grid.
• Select the end point of the
cylinder.
b
a
c

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Step 2. Verify and Simulate
To verify your model:
a. Check model topology by
constraints (from the Status
bar, right-click the Information
tool stack, and then select the
Model topology by
constraints tool) to ensure that
all the parts are constrained as
expected.
b. Perform a simulation.
c. Are the visual results of the
simulation (the animation), what
you expected?
a

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Step 3. Add Joint Motion
Add joint motions to your model:
a. Build the joint motions using the
default expressions in the
container and then modify the
expressions using the Motion
Generators, use Rotational
Joint Motion (A) for revolute
joint and translational motion
(B) for Translational Joint.
• Follow Modify dialog box
(right-click the joint, point to
the joint name, and then
select Modify).
To add joint motions:
b. Use the Rotational Joint
Motion tool to add a motion to
the mount-to-base joint such
that:
• D(t) = 360d*time
b
a
A
B

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Step 3. Add Joint Motion (Cont.)
a. Add a motion to the shoulder-to-
mount joint such that:
• D(t) = -STEP(time, 0, 0, 0.10, 30d)
• Note: By using Normal to Grid,
the motion will be opposite the
illustration in Problem statement
(by the right-hand rule). When a
motion is opposite of what you
expect, add a negative sign in
front of the expression, in the
Modify Motion dialog box.
We will discuss the specifics of the
STEP function in the next module,
Lift Mechanism III.
b. Add a translational motion to the
boom-to-shoulder joint such that:
• D(t) = -STEP(time, 0.8, 0, 1, 5)
• Note: if arm is angled downwards,
remove (-). Right hand rule.
c. Add a motion to the bucket-to-boom
joint such that:
• D(t) = 45d*(1-cos(360d*time))
c

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Step 4. Run Simulation and Export
Run a simulation:
a. Run a simulation such
that the mount achieves
one full rotation.
Save your work:
a. Save the model such
that the saved file
contains only the model
topology and not the
results (File > Export).

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Step 4. Run Simulation and Export
• While during simulation module should look like:

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Step 5. Optional Tasks
If you did not already do so as explained in the Optional tasks for Lift Mechanism I:
a. Add tires to your model using the Torus tool.
b. Constrain the tires to the base using revolute joints.

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Workshop 9, Review
• Workshop Questions
1. What are the markers that a joint refers to called?
_____________________________________________________
_____________________________________________________
2. When motion is applied to a joint, what dictates its direction (positive
versus negative)?
_____________________________________________________
_____________________________________________________
3. Are motions considered a constraint? Why?
_____________________________________________________
_____________________________________________________
4. Is it possible to determine the torque required to achieve a prescribed
motion imposed on a revolute joint? How?
_____________________________________________________
_____________________________________________________

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