Parameters. Version 1.0 6/18/2008 1

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1 Warning: Remember to change your working directory before you begin this lesson. If you do not, Adams may not work correctly. Also remember to move everything you wish to keep from the working directory before you log off. See the Opening Files tutorial for more information. Parameters ADAMS/Car models have parameters that allow you to specify properties for various subsystems such as anti-roll bar stiffness and max steer angle. On the front suspension subsystem you can specify the camber and toe angle for the tires. To view the parameters that can be modified click Adjust>Parameter Variable>Table. To view different subsystems click the dropdown menu and select the desired subsystem (screen shot). To make changes simply enter new values and click OK to apply. Version 1.0 6/18/2008 1

2 Subsystems The brakes and engine are primarily parameter values. A look at the FSAE subsystem file fsae_4w_brakes.sub shows the available parameters. Notice that the brake system does not have inertia. You will have to add inertias to the wheels. Version 1.0 6/18/2008 2

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4 The powertrain mechanical properties are parameters that can be modified. Version 1.0 6/18/2008 4

5 Analysis Parameters Prior to running suspension and full-vehicle analysis you must setup the vehicle parameters. The parameters provide the rest of the information required to simulate the vehicle that are not specified by the model. An explanation table of the setup parameters is found at the end of this document. To find the definitions for the setup parameters for suspension or full-vehicle analyses as well as other helpful information open the help file and search setup parameters. To modify the parameters for suspension analysis click Simulate>Suspension Analysis>Parameters. Version 1.0 6/18/2008 5

6 When the Suspension Analysis:Setup Parameters window appears enter the appropriate values and click OK. Version 1.0 6/18/2008 6

7 To modify the parameters for full-vehicle analysis click Simulate>Full-Vehicle Analysis>Parameters. When the Full-Vehicle Analysis: Setup Parameters window appears enter the appropriate values and click OK. Version 1.0 6/18/2008 7

8 To see the see the help file on analysis setup parameters search setup parameters in the help file. Click on either Full-Vehicle Analysis: Setup Parameters or Suspension Analysis Setup Parameters. Version 1.0 6/18/2008 8

9 Full-Vehicle Analysis: Setup Parameters The Driving Machine, when operating in closed-loop mode, must know a series of vehiclespecific parameters to correctly scale the output values. For the option: Full-Vehicle Assembly Do the following: Select the assembly for which you want to set parameters. Steering Ratio Enter the dimensionless ratio between the steering wheel angle and the road wheel angle. You can obtain this value by running a steering analysis on the front suspension and steering assembly. Rack Ratio Max Front Brake Torque Max Rear Brake Torque Brake Bias (% Front) Enter the rack ratio (angle/length) between the steering hand wheel and the rack displacement expressed in SI units. This parameter influences the response of the controller only when driving by force/displacement. Enter the maximum torque, expressed in model units, representing the torque generated for the front axle under maximum brake demand, also expressed in model units. Enter the maximum torque, expressed in model units, representing the torque generated for the rear axle under maximum brake demand, also expressed in model units. Enter the front-to-rear dimensionless ratio. Brake bias can be computed as Max Front Brake Torque / (Max Front Brake Torque + Max Rear Brake Torque). Version 1.0 6/18/2008 9

10 Suspension Analysis: Setup Parameters For the Do the following: option: Suspension Assembly Tire Model Select the suspension assembly you want to analyze. The menu lists all suspension assemblies currently open in your session. Select one of the following: User Defined Property File If you set Tire Model to User Defined, ADAMS/Car enables the following two options: Tire Unloaded Radius Enter a value for the unloaded radius. Tire Stiffness Enter a positive number that defines the tire stiffness at the input position of the suspension assembly. If you set Tire Model to Property File, ADAMS/Car enables the following option: Tire Property File Wheel Mass Enter a tire property file. Tips on entering file names in text boxes. Enter a positive real number that defines the mass of the wheel part. Sprung Mass Enter the mass of the vehicle supported by the suspensions. For most vehicles, the sprung mass is about 90% of the total unloaded vehicle mass. CG Height Wheelbase Enter a positive number for the vertical distance from the contact patch to the center of gravity (center of mass) of the sprung mass. Enter a positive number that describes the longitudinal distance between the front and rear wheel centers. Drive Ratio Select a number that defines the percentage of the total driving force applied to the front wheels: For a front suspension, use a setting of 100 to define a pure front-wheeldrive setup and a setting of 0 to define a pure rear-wheel-drive setup. For a rear suspension, use a setting of 0 to define a pure front-wheel-drive setup and a value of 100 to define a pure rear-wheel-drive setup. Version 1.0 6/18/

11 For an all-wheel-drive vehicle, the drive ratio might be, for example, 60. Brake Ratio Select the percentage of the total braking force applied to the front wheels. The brake ratio is often called brake bias and is constant. The value defines the proportion of braking force between front and rear axles. For a rear suspension with a constant front/rear proportion of 60/40, this value will be set to 60. If you set Tire Model to Property File, ADAMS/Car enables the following option: Select to view property file information. By default, your template-based product displays this information in the Information window, but you can choose to display the information in a text editor. Learn about: The Information window Displaying files in a text editor Warning: Remember to change your working directory before you begin this lesson. If you do not, Adams may not work correctly. Also remember to move everything you wish to keep from the working directory before you log off. See the Opening Files tutorial for more information. Version 1.0 6/18/