6.3.3 Setting Suspension Parameters
Before you submit a suspension analysis, you need to set the suspension parameters that ADAMS/Car uses when calculating suspension characteristics. These parameters describe the vehicle in which you wish to use the suspension. ADAMS/Car uses, for example, the parameters wheelbase, cg_height, and sprung mass to calculate the fore-aft weight transfer during braking and acceleration.
Once you set the vehicle parameters in an ADAMS/Car session, ADAMS/Car uses those settings for all suspension analyses until you reset the parameters.
To set parameters:
From the Simulate menu, point to Suspension Analysis, and then select Set Suspension Parameters.
Enter the desired parameter values, and then select OK.
6.3.4 Submitting Suspension Analyses
You submit an analysis by selecting a specific analysis from the Simulate menu and then entering the vertical wheel travel and other parameters needed to control the analysis. You can also select one or more loadcase files (.lcf) from an ADAMS/Car database. Loadcase files contain the vertical wheel travel and other parameters needed to control a suspension analysis. If you regularly perform several kinds of suspension analyses using the same ranges of travel, you should consider creating loadcase files for these. You can then submit all the analyses without having to reenter travel parameters each time. Actually, as you perform an analysis for which you did not create a loadcase file, ADAMS/Car temporarily creates one for you and deletes it after the analysis.
Note: All suspension analyses in ADAMS/Car are quasi-static equilibrium analyses.
1. Specifying Number of Steps
As you submit a suspension analysis, you specify the number of steps in the analysis. The number of steps is the number of solution steps from a lower bound to an upper bound. For example, for an opposite wheel travel analysis, if you specify five steps and -100 mm rebound and 100 mm jounce, ADAMS/Car temporarily creates a loadcase file that contains left vertical wheel displacement inputs of -100, -60, -20, 20, 60, and 100 mm and right vertical wheel displacement inputs of 100, 60, 20, -20, -60, and -100 mm as shown in figure 6.1:
Figure 6.2 Number of Inputs to Steps
2. Types of Suspension Analyses
The suspendsion analyses include:
The types of analyses that you can run on a suspension are:
(1) Wheel Travel Analyses:
A wheel travel analysis allows you to look at how the characteristics of a suspension change throughout the vertical range of motion of the suspension.
You can perform three types of wheel travel analyses, as explained in the next sections. As a minimum, all wheel travel analyses require a suspension subsystem. These analyses can also include a steering subsystem.
Parallel Wheel Travel Analysis
Opposite Wheel Travel Analysis
Single Wheel-Travel Analysis
Parallel Wheel Travel Analysis: A parallel wheel travel analysis keeps the left wheel and right wheel heights equal, while moving the wheels through the specified bump and rebound travel.
Opposite Wheel Travel Analysis: An opposite wheel travel analysis moves the left and right wheel through equal, but opposite, vertical amounts of travel to simulate body roll. The left and right wheels move over the specified jounce and rebound travel, 180 degrees out of phase with each other. You specify the parameters to define the vertical wheel travel and the fixed steer value when you submit the analysis.
Single Wheel-Travel Analysis: A single wheel-travel analysis moves one wheel, either the right or left, through the specified jounce and rebound travel while holding the opposite wheel fixed in a specified position.
(2) Roll & Vertical Force Analysis
A roll and vertical force analysis sweeps the roll angle while holding the total vertical force constant. The total vertical force is the sum of the vertical forces on the left and right wheels.
In contrast to the opposite wheel travel analysis, the roll and vertical force analysis allows the wheels to seek their own vertical position.
(3) Steering Analysis
A steering analysis steers the wheels over the specified steering wheel angle or rack travel displacement from the upper to the lower bound. A steering analysis requires a suspension subsystem and a steering subsystem.
(4) Static Load Analysis
Depending on the type of load you input, the static load analysis applies static loads to the spindle and the tire patches between the specified upper and lower load limits. A static load analysis requires a suspension subsystem.
(5) External-File Analyses
There are two types of external-file analyses: loadcase and wheel-envelope analysis.