SECTION 4 Driveline Analyses

Topics Covered Driveline Analyses Setting up initial conditions Dropped Clutch Impulse Torque Ramp Torque Step Torque RPM Sweep Torque/Throttle Tip In- Tip Out Torque Rock Cycle Torque – Loadcase Bench test Static Loadcase

Setting up Initial-Velocity Analyses Adams/Driveline creates a point motion whenever you define a force-based connection between two parts. You can use this point motion to make the entire driveline behave as a kinematic system, so it can inherit the initial rotational velocity from the tires. Before running the dynamic analysis, Adams/Driveline automatically deactivates initial condition motions. Deactivating Point Motions In some instances, one or more point motions can cause the system to be over constrained. For example, when creating a clutch assembly, the friction disk is typically constrained both to the flywheel and to the pressure plate with a clutch force element, and to the hub of friction disk with a torsion spring damper. In this situation, there are three point motions but only two are needed to fully constrain the model. You can deactivate one of the point motions between the friction disk and flywheel, or between the friction disk and the pressure plate. To deactivate a point motion: Open your assembly in Adams/Driveline. From the Tools menu, select IC Motions Activity.

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.

Setting up Initial-Velocity Analyses 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.

Setting up Initial-Velocity Analyses 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.

Analyses Bench test Analysis:- A bench-test Analysis is a generic Adams/Driveline analysis in which you can specify an end time and the number of steps. Adams/Driveline assumes that you have previously set the model to perform any kind of analysis. You can use this analysis any time standard analyses (such as step torque, and ramp torque) are not exactly what you want to perform. To perform this analysis, you must first create either a full-vehicle assembly or a bench-test assembly. Dropped Clutch:- Clutch is initially disengaged and then engaged. User defines crankshaft initial velocity and torque. Alternately engine map property files can be used for given throttle position.

Analyses Impulse Torque:- Constant torque is applied after a ramp up torque. Then impulse torque with user defined magnitude and cycle length is applied after constant torque is reached. Ramp Torque:- Torque is ramped up after a constant torque Step Torque:- Step function is applied to torque input Rock cycle:- Vehicle is subjected to positive and negative engine torque. During this analysis, Adams/Driveline submits the vehicle alternatively to a positive and a negative engine torque simulating a 1st gear - reverse gear engagement. This test modifies only the direction of the engine torque. It does not shift gears. RPM Sweep:- Sweep function is applied to engine RPM. Adams/Driveline sets up the initial velocity according to the RPM values you specify. A motion drives the simulation and applies the RPM-sweep law to the driveline.

Analyses Throttle Tip In – Tip Out:- Adams/Driveline sets the throttle demand expression based on the values you specified for driving and coasting, and determines the input torque applied to the crankshaft according to the throttle position and crankshaft RPM as inputs for the engine property file. Torque loadcase :- Adams/Driveline sets the input torque according to the torque loadcase file you select. When you use a torque loadcase file, you can store an experimental torque time history in an ASCII file and then deliver that to the engine for a dynamic simulation.