Setting up Initial-Velocity Analyses
In Adams Driveline, a control subroutine (
CONSUB) called from the
.acf File sets the initial longitudinal velocity of the vehicle automatically before a dynamic simulation is performed. You specify the initial velocity in the Submit Analysis dialog box. If the tires in the model use standard tire subroutines, the initial rotational velocity of the tires is also automatically set.
All parts constrained to the tire along the rotational axis automatically inherit the initial velocity of the tire. If a part with an initial rotational velocity is not constrained to another part along the rotational axis, the second part will not inherit the initial rotational velocity from the first part. For example, suppose you have a drive shaft consisting of an inner and an outer shaft. The two shafts might be connected to each other with a rotational spring damper, which is a force-based connection (not a constraint). A way around this problem is to temporarily constrain all rotational parts along the rotational axis while Adams is calculating the initial velocity. Before you submit the dynamic
Analysis, you must remove (deactivate) all temporary constraints.
All Adams Driveline components available in the
Template Builder automatically include a rotational constraint (if needed). This constraint is a point motion (a motion between two markers) named ic_motion and it is set to zero and deactivated by default. All ic_motions in the model are also automatically added to a group named lock_array.
When you submit an analysis, Adams Driveline activates all ic_motions and stores their Adams IDs in a solver array named lock_array.
In the .acf file, a second Adams Driveline-specific CONSUB is called after the regular Adams Car CONSUB. This CONSUB first performs an initial-condition velocity analysis and then deactivates all ic_motions found in the Solver array lock_array. After the initial-condition velocity analysis is run, all parts have a longitudinal and rotational velocity according to the initial velocity of the vehicle and tires. The next line in the .acf file could be a dynamic simulation command.
Restrictions
Note the following when running the Initial Velocity Analysis:
■If you do not use a standard tire subroutine, the Adams Car CONSUB will not recognize the tire as a wheel part; therefore, no initial rotational velocity will be given to the tires. In this case, you must manually add an initial rotational velocity to the wheel part. If you use Adams Driveline ride tires, the initial rotational velocity of the wheels is set automatically when the tires are created.
■If you build a model with standard Adams Car components, Adams Driveline will not automatically create the ic_motion. You can create the ic_motion in the Template Builder by selecting the Driveline Components menu, pointing to Advanced, and then selecting IC Motions Create.
■Currently, the procedure of setting initial rotational velocity only works for Adams Driveline-specific analyses. This is due to the specific set-up macro being called from a submit macro.
■If you manually specify initial rotational velocity on two parts that are constrained to each other, Adams Driveline will calculate the average initial rotational velocity and use it for both parts (and all parts constrained to them).
■If you are driving the model with a motion active during the initial condition analysis, the motion velocity will overwrite all initial rotational velocities set on parts constrained by the motion.