1. USING OPTIONAL SUBSYSTEMS
WORKSHOP 10
USING OPTIONAL SUBSYSTEMS

3. WORKSHOP 10 – USING OPTIONAL SUBSYSTEMS
Problem Statement
Investigate the braking performance of a truck with and without a trailer. Modify the braking system to improve braking performance.

4. WORKSHOP 10 – USING OPTIONAL SUBSYSTEMS (CONT.)
Model Description
You will use the truck_trailer database full-vehicle model that is included in the library of example vehicle databases shipped with Adams/Chassis. You will run a braking event without the trailer to set a baseline for comparison.
The front suspension of the truck trailer vehicle uses an SLA front suspension with rack and pinion steering.
The rear suspension of the truck_trailer vehicle uses a solid axle with leaf springs.
The model includes a simple-type trailer with optional rear suspension #2.
The brake optional subsystem is a simple type.

5. WORKSHOP 10 – USING OPTIONAL SUBSYSTEMS (CONT.)
Modifying the model
You will perform a braking test on a truck with and without a trailer. You will also find the effective pad radius necessary to attain the same performance with the trailer as you did without it.
Use the example vehicle database truck_trailer.vdb. First, you need to modify the model to not include the trailer to use as a baseline test.
To modify the model:
Create a new session.
Copy truck_trailer.vdb to your working directory using Database Utilities.
From the truck_trailer.vdb, load the model truck_trailer_full_sys.xml.
Now you must turn off the trailer to analyze the truck’s performance alone.
In the treeview, select truck_trailer_btt and then click the Construction Options tab.

6. WORKSHOP 10 – USING OPTIONAL SUBSYSTEMS (CONT.)
To modify the model (Cont.):
Change the Current Setting for trailer to Off.
Click Save As, then enter truck_btt.xml, and then click Yes to update references.
Select the modified system in the treeview.
In the system editor, clear the selection next to Rear Suspension #2.
Replace the default simple brake subsystem with achassis_gs_brakes.xml. You can find this file in the achassis_gs database.
Save the modified configuration file as truck_full_sys.xml.

7. WORKSHOP 10 – USING OPTIONAL SUBSYSTEMS (CONT.)
To modify the model (Cont.):
In Test mode, select Open Loop Braking and use the following parameters:
Vehicle Velocity: Kph
Brake Pedal Force: N
Step Initial Time: 1.0 sec
Step Final Time: 1.5 sec
Click Build and Run Selected Events.
In Review mode, run the animation to verify that the truck behaves as you would expect. Ignore any warning messages.
Load the plots. Use them to answer Question 1 and Question 2 at the end of this workshop.

8. WORKSHOP 10 – USING OPTIONAL SUBSYSTEMS (CONT.)
To use the complex model with the trailer:
In Build mode, load the original truck_trailer_full_sys.xml model. Remember, this model includes the trailer.
Now you must increase the trailer mass to enhance the effect.
Select truck_trailer_btt and the click the Parts tab.
Increase the mass of the trailer to 450kg (~1000 pounds). You can assume that the inertial properties of the trailer remain unchanged.
Save the body subsystem over the existing file.
Replace the current brake subsystem with the same complex model from the achassis_gs database.

9. WORKSHOP 10 – USING OPTIONAL SUBSYSTEMS (CONT.)
To use the complex model with the trailer (Cont.):
Highlight truck_trailer_full_sys in the treeview, and then save the system file over the existing file.
In Test mode, use the trailer model to run an Open Loop Braking event with the same parameters you used earlier.
View the animation to make sure it looks correct.
Overlay the plots from both events. Use the plots to answer Question 3 and Question 5 at the end of this workshop.

10. WORKSHOP 10 – USING OPTIONAL SUBSYSTEMS (CONT.)
Modifying the pad radius
Your goal is to get the same acceleration level with the trailer as you did without the trailer using the same pedal-force input. To achieve this goal, you could modify several parameters, but instead you will limit this study to the pad radius.
To modify the pad radius:
Edit the brake subsystem file for the truck_trailer_full_sys model.
In the Construction Options tab, double-click front_pad_location_method.
Change front_pad_location_method to radius and use 90mm for the left and right value.
Change rear_pad_location_method the same way. Using 90 mm is almost the same as the XYZ location setting you were previously using.
Because you modified the achassis_gs brake subsystem, you must save the new one to the truck_trailer database.

11. WORKSHOP 10 – USING OPTIONAL SUBSYSTEMS (CONT.)
To modify the pad radius (Cont.):
Click Save As, select truck_trailer for the registered database, and then enter truck_trailer_brakes_90mm.xml.
Click Yes to update references.
Select the modified model in the treeview, click Save As, and then enter truck_trailer_full_sys_90mm.xml.
Edit the brake subsystem file again. Change the radius to 100mm for the front and rear.
Click Save As, and then enter truck_trailer_brakes_100mm.xml.
Select the modified model in the treeview, click Save As, and then enter truck_trailer_full_sys_100mm.xml.

12. WORKSHOP 10 – USING OPTIONAL SUBSYSTEMS (CONT.)
To modify the pad radius (Cont.):
Edit the brake subsystem file again. Change the radius to 110mm for the front and rear.
Click Save As, and then enter truck_trailer_brakes_110mm.xml.
Select the modified model in the treeview, click Save As, and then enter truck_trailer_full_sys_110mm.xml.
Create vehicles that use 120mm and 130mm pad radius using the same procedure.
In Test mode, right-click the current event, click Copy Selected Event, and then make five copies.
Now, change the model that each event uses and modify the event name to include the pad radius used for that event.
Now you need to build and run these five events.

13. WORKSHOP 10 – USING OPTIONAL SUBSYSTEMS (CONT.)
To modify the pad radius (Cont.):
Highlight the five events, and then click Build and Run Selected Events.
In Review mode, overlay the plots from all seven events. You should get a longitudinal acceleration versus time plot similar to this:
Use the plot to answer the remaining review questions.

14. WORKSHOP 10 – USING OPTIONAL SUBSYSTEMS (CONT.)
Section Review
What is the steady-state acceleration level achieved by the truck due to a 100 N pedal force? ______________________
What caused the simulation to stop there?_______________
Tip: Review the message file (.msg) and dataset file (.adm) by right-clicking the event  name in Build mode, and then selected Edit Event Files.
What is the steady state acceleration level achieved by the truck and trailer due to a 100N pedal force? ______________
How much farther does the vehicle travel before the simulation ends?___________________________________
Answer 1: -0.63Gs
Answer 2: Sensor_1000 was triggered, and vehicle longitudinal velocity dropped below 5 mph.
Answer 3: Gs
Answer 4: 20 m

15. WORKSHOP 10 – USING OPTIONAL SUBSYSTEMS (CONT.)
Section Review
What is the difference in brake torques between the two results?___________________________________________
Does this make sense?______________________________
Between which two pad radius settings is the original truck-only acceleration curve?______________________________
Notice the different curve shape of the 130 mm radius simulation in the acceleration versus time plot. Using the other plots and the animation of this event, explain why the curve has a different shape. _________________________________________________
Does this guess-and-check method seem like an efficient way to find the necessary pad radius? _________________________________________________
Answer 5: No difference. It makes sense because the pedal force and brake system were unchanged. The only difference was the addition of the trailer.
Answer 6: Between 110 mm and 120 mm
Answer 7: The Animation shows the vehicle lose control. The plots on Page 3 show the rear tire slip ratios near 100%. The rear wheels have locked up.
Answer 8: It is not.