WORKSHOP 9 BRAKE SYSTEM II

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.

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.

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.

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

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_3103  .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.

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?

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.

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.

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

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.

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?

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).

WORKSHOP 9 – BRAKE SYSTEM II

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.