• Models can be registered to CarMaker with an individual identification string. • To select and activate a model, its identification string is must to be specified in the
vehicle parameter set.
Inputs to the System
• SteerByAngle/SteerByTorque• Steering wheel angle, angle velocity (if the model is steer by angle type) • Steering wheel toque (not used by steer by angle models).
• Suspension forces to tie rod translation (left and right) • Suspension inertias to tie rod translation (left and right)
Outputs of the System
• General steer coordinate (tie rod translation) and derivatives (left and right) • Steering wheel torque required for static conditions (no accelerations). • Steering wheel angle, angle velocity (if the model is steer by torque type)
Interface structure to the steering calculation function
typedef struct tSteerIF {
tSteerBy SteerBy;/* use position or angle(in) *
* as steer input /*
double Ang;/* steer angle (in/out)*/ double AngVel;
double AngAcc;
double Trq;/* steer torque(in) *
* acting on steering wheel */
double TrqStatic; /* steer torque, required for (out) * * static conditions (no acceleration)*/
struct tSteerIFLR {
/*** Input Quantities: (Car/Driver to Steering) */ doubleFrc; /* force (external to steer system) */ doubleInert; /* inertia (external to steer system) */
/*** Output Ouantities: (Steering to Car/Driver) */ double q, qp, qpp;/* tie rod translation */
double iSteer2q;/* ratio (out) *
* steer rotation to rack translation */ } L, R; /* left, right */
Overview
Chapter 8
PowerTrain
8.1
Overview
The powertrain which acts as a global system within the CarMaker VVE is divided into a number of subsystems with well defined interfaces. In the following the basic concept of the subsystems and interfaces is described.
8.1.1
Interface Powertrain – Vehicle
This interface is responsible for the global embedding of the whole powertrain within the CarMaker VVE. As shown inFigure 8.1: the various subsystems can get input signals from ECUs or from other CarMaker modules (e. g. interaction form virtual control elements of the vehicle).
The interface of input/output quantities interacting with the Vehicle-Model is very compact. The powertrain is not interchanging many signals.
Figure 8.1: The Powertrain – Vehicle Interface ECU
Signals
Accelerator Pedal Clutch Pedal
ECU Signals ECU Signals ECU Signals Gear Selector Starter activated Ignition on/off
Engine Clutch Gearbox
TBrake2Wheel TTire2Wheel q q˙, Wheel TSupport2Vehicle P o w e r T r a i n V e h i c l e D r i v M a n
Overview
To observe and to drive the vehicle, additional output signals like the engine speed are needed and provided from the corresponding powertrain submodules.
8.1.2
PowerTrain Subsystems
The powertrain model determines the distribution of drive torque to the wheels. The power- train module can be combined with several subsystems.
A Powertrain typically consists of the following subsystems:
There are different ways to look at powertrain submodules. One is the structural view how powertrain modules are configured and connected to a complete system. This is shown in Figure 8.2.
The topmost layer is the selected powertrain model. Here a specific powertrain model is selected which is the central computation unit for the whole powertrain. This means the binding of all components and the interfacing to the Vehicle-Model and the DrivMan-Model
Model Description
Engine The ‘‘origin of all motion´´
Clutch The agent between producer and consumer of driving energy Gearbox The converter of drive torque
Figure 8.2: PowerTrain structural view PowerTrain
Engine Clutch Gearbox
E1
GenFront GenRear Gen2p2Front Gen2p2Rear Gen4WD Custom
Model 1
Custom Model 2
PowerTrain ‘Generic’ Model Library
E C GB E C GB E C GB E C GB E C GB E C GB E C GB E2 C1 C2 GB1 Custom Engine 1 Custom Engine 2 Custom Clutch 2 PowerTrain Components Library Custom Gearbox 1 Custom Gearbox 2
Overview
ponents Library is included with CarMaker and offers models for each individual compo-
nent. At this level it is also possible to add custom models to extend the library with components for special needs.
As visible inFigure 8.2the integration of custom models is seamless. As long as the spec- ified interface of each module is regarded custom modules can be mixed with standard modules as desired.
8.1.3
Interfaces of Powertrain Subsystems
The standard powertrains provided with the powertrain ‘Generic’ library are modeled as rig- id systems with five degrees of freedom. There are four wheels and the engine potentially rotating with different speeds. There has to be a differential equation for each degree of freedom in such a model. In general rotation speeds are calculated by integration of the moment-balance:
(EQ 30)
is the projected inertia of all connected parts reassessed by transmissions. These cal- culations beside others are done in the Powertrain-Module which acts as a master unit for all other powertrain submodules (seeFigure 8.3).
Another way to look at powertrain submodules is concerned with the interfacing between the powertrain modules themselves and the Vehicle-Model.Table 8.1: lists the types of quantities being exchanged between powertrain subsystems and the Vehicle-Model.
Figure 8.3 shows each powertrain subsystem and describes the required quantities exchanged between the different submodules:
Table 8.1: Notation rotation angle
angular velocity
torque from system <from> to system <to> transmission q˙˙x 1 JPro j˙ ---
∑
Tx = JProj q q˙ Tfrom→to iFigure 8.3: The PowerTrain Module Interfaces
Engine Clutch Gearbox
ECU Signals
Accelerator Pedal Clutch Pedal
ECU Signals ECU Signals ECU Signals Gear Selector Starter activated Ignition on/off TEngine TClutch2Gearbox q q˙, Engine q q˙, Gearbox iGearbox TBrake TTire TGearbox2DL q q˙, Driveshaft Powertrain- Computation q q˙, Wheel TSupport2Vehicle
Overview
Driveline Model
The driveline model transfers the torque from the gearbox output to all driven wheels. The calculation of wheel speeds and other rotation speeds is done in the computation part of this master module.
8.1.4
General Parameters
Location Parameters for configuring a powertrain are found in the parameter file for a specific vehicle under<CarMakerRoot>/Data/Vehicle/
The following parameters are used globally no matter which specific subsystem is selected. They are mandatory for all configurations and therefore listed as global parameters.
PowerTrain.Kind = KindStr
With this parameter a powertrain model is selected. The powertrain library provides the fol- lowing models:
Example PowerTrain.Kind = GenFront
PowerTrain.Kind = MyPowertrain Figure 8.4: Driveline Mode
Gearbox Driveline ECU Signals TGearBox2Driveline Σ Ti qi,q˙i TBrake TTire q q˙, Driveshaft Integration of rotation speeds q q˙, Wheel TSupport2Vehicle PowerTrain.Kind Description
GenFront standard front drive vehicle GenRear standard rear drive vehicle
Gen2p2Front front driven vehicle with rear axle hanged on Gen2p2Rear rear driven vehicle with front axle hanged on Gen4WD four wheel drive vehicle
Powertrain ’Generic’