Chapter 7 is devoted to the basic and existing in present-day vehicles, power train modeling, and simulation. Generally, there are series and parallel hybrid power trains. In both cases, the role of the internal combustion engine and its dynamic modeling is significant. The two aspects of modeling should be considered. The one devoted to the energy distribution, the second to the local internal combustion engine’s control. For the Internal Combustion Engine (ICE) the dynamic modeling method is proposed. Using the simulation of the well-determined map of the ICE can be accepted. In the practical application of a series power train, it is necessary to consider different control strategies of the internal combustion engine’s operation. The most significant are the “constant torque” and the “constant speed” control method. The other important problem, because the Internal Combustion Engine’s (ICE) generator unit is a strong nonlinear object, is the modeling of the permanent magnet generator, connected by the shaft with the ICE. As for the common parallel hybrid power train, two of its types were, in dynamic modeling, tested by simulation. One of them is the hybrid power train equipped with an automatic (robotized) transmission. Generally, it is possible to state that this transmission can be used as the Automatic Manual Transmission (AMT) or the Dual Clutch. The second one is the split sectional hybrid power train and is the most simple solution. The Hybrid Split Sectional Drive (HSSD) applied in an urban bus is also presented.
Top1. The Internal Combustion Engine As A Primary Energy Source: Dynamic Modeling
Modeling of the Internal Combustion Engine (ICE) is generally a difficult task. The best solution for hybrid drive design is using engine-operating maps, which are possible to obtain after special laboratory bench-tests. The typical (simplified) engine-operating map is shown in Figure 1 (Szumanowski, 2006; Szumanowski, & Hajduga, 2006; Szumanowski, Hajduga, & Piórkowski, 1998b).
Figure 1. The illustration of the internal combustion engine ICE operating map in the shape of static engine characteristics - its output shaft torque versus shaft angular velocity
It is clear that the Internal Combustion Engine’s (ICE) operating points in its hybrid drive design should be in the area of its lowest fuel consumption. The proper design process of the hybrid power train should include simulation of the internal combustion engine’s operation related to its map. The result of the simulation can be illustrated by internal combustion engine operating points on the map. However, it is not complete information because only the location range of internal combustion engine operating points is known, and the time frequency of these operating points when appearing, is unknown. However, it is possible to indicate it, using only dynamic Internal Combustion Engine (ICE) modeling and simulation.
The alterations of an internal combustion engine’s momentary power, torque and angular velocity during vehicle driving should be determined. Certainly, the power of load shaft (
) can be computed, according to torque (
) and angular velocity (
) values:
The mathematical models worked out in previous chapters are necessary for this computation. These models need adequate configuration, according to analyzed power train architecture. Additionally, according to block equations set, for example using the Matlab Simulink program, the control functions of the hybrid power train should be considered. This means that only by simulation of the whole power train, can the Internal Combustion Engine (ICE) operating points be designed.
The engine’s downsizing means that internal combustion engine power, in the case of the hybrid power train, can be decreased, during downtown or urban traffic. Two types of internal combustion engine should be analyzed - gasoline and diesel. The comparable emissions of the gasoline internal combustion engine are higher (especially CO2) than a diesel engine, but the gasoline engine does not emit constant particles. Of course, the low power of the gasoline engine can limit the value of ‘on line’ emissions. The other difference is in the moment of inertia values. The gasoline engine’s inertia is lower than in comparable diesel engines, and is more sensitive to the load dynamic changes of torque at output shafts.
The modeling of the thermal combustion engine is very complicated, because the object is strongly nonlinear. For this reason, the approximation functions depicted by the high stage of polynomial or by a set of ‘spline’ functions are practically useless for simulating the drive system, consisting of a few mechanical-electrical components.
The based-on real data, obtained from laboratory tests, generic, dynamic, internal combustion engine ICE modeling approach is, for example, proposed (Haltori, Aoyama, Kitada, Matsuo, & Hamai, 2011; Zhong, 2007). The basis for dynamic engine modeling is experimental data in the form of static, internal combustion engine torque versus its output shaft angular velocity characteristics, as shown in Figure 2.