Workshop 20
Hatchback IV
• Workshop Objectives
– In Workshop 19 - Hatchback III, you determined the approximate force
needed to close the lid. Now, you are part of a group of design engineers for
the Mazda MX-6 hatchback. Your goal is to make the model more realistic
and ensure that it meets the following criteria:
• Lid opens completely in less than 4 seconds.
• Requires less than 210 N to close the lid.
• Takes no more than 3.0 sec to close the lid.
• Software Version
– Adams 2018
• Files Required
– Saved file from Workshop 19 or Hatchback_3_completed.cmd
– located in exercise_dir/mod_19_hatchback_3/completed
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© 2018 MSC Software Corporation
• Problem Description
– In this workshop you will use the model saved in Workshop 19. Recall the
parts of this model are constrained as follows:
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© 2018 MSC Software Corporation
• Suggested Steps.
1. Import file and de-activate the Motion on the Revolute Joint.
2. Create an SFORCE to close the lid.
3. Modify the SFORCE to a Step Function and run a simulation.
4. Add a sensor.
5. Test that the sensor works properly.
6. Modify the spring preload.
7. Modify the spring stiffness.
8. Modify the closing force function to the Maximum value.
9. Create design variables.
10.Modify the springs to reference the design variables.
11.Optimize the design.
12.Optional tasks
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Step 1. Import File and De-active the Motion on the Revolute
Joint
To start the workshop:
a. Start Adams View, and set the directory to
exercise_dir/mod_20_hatchback_4
b. From the directory
exercise_dir/mod_19_hatchback_3, import
the file you saved from the previous workshop.
c. If you need a fresh copy of the model, then import
hatchback_3_completed, from the directory
exercise_dir/mod_19_hatchback_3/
completed.
To deactivate the motion:
d. Select the Motions:closing_motion, and then
select (De)activate.
Alternative way: Locate the motion on the revolute
joint, l_shortarm_rev, right click and select the
Motion:closing_motion, and then select
(De)activate.
e. Disable Object Active.
f. Click OK.
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© 2018 MSC Software Corporation
Step 2. Create an SFORCE to Close the Lid
Lid_sforce_ref
a
In Workshop 19 - Hatchback III,
you used a motion to close the lid.
In this workshop, to make this
model more realistic you will
replace the motion with a
perpendicular force to close the lid
To create an SFORCE:
a. From the ribbon Forces, select
the Single-Component Force.
b. Use the following parameters to
create the force.
• Run-time Direction: Body
Moving
• Construction: Pick
Feature (select the lid).
• Location: sforce_ref,
marker on the lid.
• Direction: y direction of
sforce_ref
c. Rename the SFORCE to
closing_force.
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© 2018 MSC Software Corporation
Step 3. Modify the SFORCE to a Step Function and Run a
Simulation
To modify the SFORCE to a Step
Function:
a. Pick the SFORCE closing_force and
select Modify, then in the Modify
Force dialog make sure the Define
Using is set to Function.
b. For the Function enter STEP(time, 4,
0, 4.2, -247). Note: 247 N is the
approximate force needed to close the
lid, as you calculated in Workshop 19 Hatchback III.
To Run a Simulation:
c. Run a 7-second, 100-step simulation
to verify that the force closes the lid.
Because you’re not activating or
deactivating any motions during the
simulation, you can run a simple
interactive simulation.
d. After running the simulation you will
see that this approximate force is not
large enough to close the lid.
To Modify the SFORCE Step Function:
e. In the Modify Force dialog, change
the SFORCE to have a maximum
value of 300 N; the new function is
STEP(time, 4, 0, 4.2, -300).
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© 2018 MSC Software Corporation
Step 4. Add a Sensor
b
When using an SFORCE, there is
no constraint stopping the rotation
of the lid beyond the closed
position. To add a sensor to stop
the lid at the closed position:
a. From the ribbon Design
Exploration, point to Create a
New Sensor.
b. Create a sensor based on the
measure, shortarm_rotation,
by filling in the dialog box as
shown to the right.
c. Click Apply to create the
sensor, and leave the dialog
box open.
a
c
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Step 5. Test that the Sensor Works Properly
To test that the sensor is working
properly:
a. Run another simulation to verify
that the sensor works as
expected.
b. Why does the sensor stop the
simulation when the lid doesn’t
appear to be fully closed?
_________________________
_________________________
_________________________
_________________________
c. Back in the Create sensor
dialog box, select Generate
Additional Output Steps at
Event.
d. Click OK to make this
modification to the sensor.
e. Rerun the simulation.
a
c
d
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Step 6. Modify the Spring Preload
Because the force required to
close the lid is greater than the
design criteria, you need to modify
the spring preload. To Modify the
spring preload:
a. Click on the left_spring, and
select modify. In the Modify a
Spring-Damper Force dialog
box, change the Preload from
550 to 400.
b. Repeat step a for the
right_spring.
c. Run a simulation
• Notice that the sensor was
triggered at time 3.5e-3,
meaning that instead of
having the hatchback open,
it dropped past the closing
position because the
springs were not strong
enough to open the lid.
d. For each spring modify the
preload again to be 470.
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Step 7. Modify the Springs Stiffness
Because the force required to
close the lid is greater than the
design criteria, you need to modify
springs stiffness. To modify the
springs stiffness:
a. Click on the left_spring and
select modify. From the Modify
a Spring-Damper Force dialog,
change the stiffness
Coefficient to .10 N/mm
b. Repeat step a for the
right_spring.
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© 2018 MSC Software Corporation
Step 8. Modify the Closing Force Function to the Maximum
Value
A value of 210 N is the maximum
force that can used to close the lid,
as defined in our design criteria
from the problem statement.
To modify the Closing Force
Function to the maximum value.
a. Click on the closing_force,
and select modify. Change
the STEP function for the
closing_force SFORCE to
have a maximum value of
210N; the function should now
look like this: STEP(time, 4, 0,
4.2, -210).
b. Run a simulation.
c. While the springs now open the
lid, the closing force is still not
large enough.
a
a
b
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Step 9. Create design variables
Creating design variables in your
model will help to speed up the
design iteration process. To create
design variables:
a. From the ribbon Design
Exploration, select Create a
Design Variable.
b. Create a design variable for the
preload on the spring. Change
the name to
.hatchback.preload.
c. For the units select force.
d. For the standard Value enter
460.
e. For the Value Range by select
Absolute Min and Max
Values
f. For the Min. Value enter 300
g. For the Max. Value enter 600
h. Click OK to create the variable.
i. Using the chart below, repeat
the above steps for the
stiffness and damping design
variables.
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© 2018 MSC Software Corporation
Step 10. Modify the Springs to Reference the Design Variables.
Modify the springs to reference
design variables:
a. Click on the left_spring and
select Modify. In the Modify
Spring-Damper Force dialog
box, right click in the
Stiffness textbox and select
Parameters>Reference
Design Variable.
b. From the Database
Navigator select the
Stiffness Variable.
c. Click Ok and the variable
appears in the Stiffness
Coefficient textbox.
d. Repeat Step a through c for
the damping coefficient and
the preload.
e. Click OK to make the
modifications.
f. Repeat steps a through e for
the right_spring.
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© 2018 MSC Software Corporation
Step 11. Optimize the Design
To optimize the design:
a. Use model tree, expand
Design Variables.
b. Select the appropriate design
variable from the list.
c. Modify the Standard Value of
the design variable.
d. Click Apply to make the
change and leave the Modify
Design Variable dialog box
open.
e. Simulate the model to see the
results of the modification.
f. Continue steps a through e
until the lid opens and closes
as required.
g. Note: There could be many
parameter combinations that
would meet the design criteria.
Try a few different values to get
a feel for the sensitivity of each
parameter.
h. Save the model. Exit Adams
View, unless you wish to
continue with the optional
tasks.
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© 2018 MSC Software Corporation
Step 12. Optional Task
Save your work before performing these tasks. Do not save your work
after performing these tasks. If you must save the model after performing
these tasks, give the model a different name.
To run an optimization to find a set of values that
meet the criteria of the problem statement.
a. Import the custom macro
/misc/optimization_optional_task.cmd
.
b. Note: This custom macro creates
measurements, a design variable, a simulation
script, and constraints needed to run this
optimization. It also modifies your optimization
settings and the values of your design variables
to allow for the model to quickly optimize.
c. From the ribbon Design Exploration, select
Design Evaluation Tools.
d. Complete the dialog box as shown to the right.
e. select Optimizer.
f. Complete the solver Settings dialog box:
•
For the category select Optimization
•
Set Algorithm to OPTDES: SQP.
•
Click Close.
g. Click Start.
h. Note: Several sets of values will meet the
design criteria. Further investigation is needed
to determine the optimal design.
i. Select the tool Create tabular report of
results.
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© 2018 MSC Software Corporation
Step 12. Optional Task (Cont.)
j. Adams View automatically
updates the standard values for
each design variable to the
values found during the
optimization process.
k. For this problem, the values
that you receive from the
optimization are very sensitive
to the starting points of the
design variables. If time
permits, try to modify the
starting values of the design
variables and run the above
optimization again. Did you find
an optimal value? What went
wrong?
l. Hint: Did the lid even open?
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Workshop 20, Review Questions
1. Which parameters were most sensitive to meeting the design criteria?
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2. How did the design variables help to speed the iteration process?
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Answer Key
• Answer Key for Workshop 20
– Question 1: Preload must be above 460 N to open the lid. Higher damping values
increase the amount of time needed to close the lid. Higher stiffness values increase
the resistance in closing the lid.
– Question 2: It allowed for easy manipulation of the spring parameters. Changing the
design variables changed the parameters for both springs at the same time.
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