1. WORKSHOP 9 BRAKE SYSTEM II

3. WORKSHOP 9 – BRAKE SYSTEM II
Problem statement
Make the brake system more realistic by applying a force to the pedal, representing a foot (instead of a motion), and modifying the tension in the brake cable to be nonlinear.

4. WORKSHOP 9 – BRAKE SYSTEM II
Model description
The given model is a simplified model of a brake system that currently has three parts and associated graphics, three revolute joints, one translational joint and a motion that moves the pedal with respect to time.
In addition, there is a single-component force (SFORCE) already defined, which describes a linear force between the cylinder and ground. This represents the tension in the brake cable.
You are going to remove the motion and apply a force to the pedal, where a foot would touch it.
You are going to model the force representing tension in the brake cable as a nonlinear force based on hypothetical test data.

5. WORKSHOP 9 – BRAKE SYSTEM II
Getting started
To get started:
Open a new Adams/View database.
Simulate the model:
Load the file named ‘brake2_start.cmd’ into Adams/View.
Run a Transient simulation for 1 second, 100 steps.
View the animation in Adams/View.
The model should look the same as the last workshop results.

6. WORKSHOP 9 – BRAKE SYSTEM II
Add a Vector Force (VFORCE):
To deactivate the motion and create an applied force:
Right-click the motion on the pedal-to-ground joint and select (De)activate from the pop-up menu. Then deselect the “Object Active” box. Simulate the model to ensure that the MOTION is no longer activate.
Apply a translational vector force to the pedal by selecting VFORCE from the Force palette.
Select construction parameters as “2 Bod-1 Loc”, “Pick Feature”. Specify “Custom” for Characteristic.
Select PART_10 as the first body and PART_1 (ground) as the second body.
To locate the VFORCE: right-click in the blank area of the background to bring up the Location Event dialog box. Enter the coordinates obtained in the previous workshop for the midpoint of the pedal ( {62.5, -400, 0.0}).
To select the X direction vector, point along the pedal towards “Marker_1082” and select the vector when properly aligned with the pedal. Similarly select the Y direction vector as the Z-axis of “Marker_1082” (you may have to rotate the view a little to view the Z-axis of that marker properly).
62.5,-400,0

7. WORKSHOP 9 – BRAKE SYSTEM II
Modify the VFORCE RM and expressions:
Right-click the VFORCE and Rename it to be “Brake_VForce”.
Do an Info (right-click) on the VFORCE and note that the Reference Marker is a child of PART_1. The VFORCE orientation must be related to a frame on the moving part (PART_10). This is done in the following step.
To transfer the Reference Marker to PART_10, simply right-click and rename it. For example:
.brake.PART_1.MARKER_  .brake.PART_10.MARKER_3103
This makes the VFORCE change direction with the pedal during the simulation.
Modify the X and Y force components to be “0” and Z force component to be “560”. Hit OK or Apply and then get Information on the VFORCE again. The Info Window should look like the following slide.

8. WORKSHOP 9 – BRAKE SYSTEM II
Check the VFORCE effect:
Re-run the simulation – does the system respond as expected?
Animate the system slowly in PostProcessor and note the orientation of the VFORCE: is the location and orientation constant with respect to the pedal?

9. WORKSHOP 9 – BRAKE SYSTEM II
Determine cable tension in cylinder:
Create another REQUEST for the force that the cable tension applies to the cylinder by using:
Design Exploration tab > Instrumentation Panel > Create a new Request
Use the MARKERs from the spring SFORCE to create the REQUEST – do an Info on the SFORCE to determine the MARKER names. These should be as shown in the figure.

10. WORKSHOP 9 – BRAKE SYSTEM II
Plot the spring stiffness:
Re-run the model with the new REQUEST in it.
Plot the displacement of the cylinder.
Use the plot to answer Question 1 in the Module review.
Next, plot the force applied to the cylinder versus its displacement. Use the ‘Independent Axis’ selection in PostProcessor to create the plot on the following page.

11. WORKSHOP 9 – BRAKE SYSTEM II
Note: to generate the plot above, re-run the simulation for 0.02 seconds, 100 steps.

12. WORKSHOP 9 – BRAKE SYSTEM II
Create a hardening spring force:
To make the brake cable tension a nonlinear force:
Import Test Data and create a spline element via the File -> Import dialog box.
Use the settings shown to fill out the dialog box; this will read the file ‘force_vs_disp.txt’ from file and create a SPLINE element from the data.
Note: the Independent Column Index must be set to 1 to signify that the first column is the displacement data.

13. WORKSHOP 9 – BRAKE SYSTEM II
Verify the SPLINE data:
Use: Elements -> Data Elements -> SPLINE_1 -> Modify to modify the spline element that was just created.
Use the ‘View as’ selection to display a plot of the spline: does the spline data look like a hardening spring?

14. WORKSHOP 9 – BRAKE SYSTEM II
Make the SFORCE non-linear:
Identify the spring ‘stretch’ portion of the existing function expression for SFORCE_3001: do an Info on the SFORCE element and consider the function expression. What is the ‘stretch’ portion of the expression?:
stretch = _____________________________
Incorporate this stretch into a spline expression for the force. Do this by modifying the existing function expression to be:
FUNC=-AKISPL(DM(3090,0190)-50,0,spline_1,0)-0.1*VR(3090,0190)
The expression above uses the AKISPL() function to define the force versus displacement (stiffness) relationship, and uses the original expression for damping.
Re-run the simulation and overlay the results on the previous plot (see following page).

15. WORKSHOP 9 – BRAKE SYSTEM II

16. WORKSHOP 9 – BRAKE SYSTEM II
Module review
What is the approximate steady-state displacement of the cylinder? Is this displacement more than the required 30 mm? _______________________________________________________________________________________________________________________________________________________________
What are the differences between the vector force (VFORCE) and the single-component force (SFORCE)? _____________________________________________________ __________________________________________________________________________________________________________
~28.4 mm
The VFORCE has three components for which you need to define the magnitude. The SFORCE only has one. The VFORCE uses a reference marker to define direction. The SFORCE uses line of sight. The VFORCE J marker must be a floating marker. The SFORCE J marker must be a fixed marker.