# Development of a Hybrid Electric Vehicle Simulation Tool with a Rule-Based Topology
## 2 Materials and Methods
### Control Strategies of the Simulation
#### 2.2.2 Rule-Based Control Strategies
\"Pm_min\", \"Pm_low\" and \"Pm_high\" are variable values based on driver inputs, and \"Pm_OP1\", \"Pm_OP2\" and \"Pm_OP3\" are calculated values that determine the combination of torque and speed of the ICE at the OPs for the generated power demand. The EV mode is mostly used to minimize the fuel consumption below Pm_OP1 (e.g., SOC_min, SOC_low or SOC_initial, depending on the power demand of the EM), and the ICE runs only to charge the battery when the SOC is lower than the threshold values set as low limitations. Above Pm_OP1, the EV mode will be limited only to cases where the SOC is high. When the SOC is below the threshold, the combination of the power sources (ICE and EM) will be used, and the operating regions of  
Figure 4: The selected engine operating conditions for serial hybrids. the ICE (OP1 or OP2) and the operating modes (ICE (GEN) + EV mode or ICE (GEN) mode) will be varied depending on the SOC. Above Pm_OP2, the system mostly runs in hybrid mode and charging mode, with maximum power coming from the ICE to minimize the discharge of battery, and very limited EV mode. The objective of the topology with multiple OPs is to keep the ICE operation in the sweet spot of relatively low fuel consumption, and further increase in demand essentially keeps the system operating in hybrid mode to maintain a reasonable level of SOC. The present study uses a 1-speed transmission concept, as less emphasis is placed on the vehicle's ability to climb and accelerate. The main lever here is the most cost-effective concept with minimal fuel consumption. The use of a higher number of gears is also possible in this simulation tool. The operating parameters can be controlled by the topology using a state-flow or a Fuzzy logic tool in the simulation. The control strategy of hybrids decides on the instantaneous power request from the different energy sources while respecting numerous constraints. For this reason, the combination of the parameters and the energy management strategies is very important for the HEV optimization for energy consumption. In this simulation, the Fuzzy logic controller is proposed. In case of a serial hybrid model, for example, the power demand, SOC and vehicle speed are generally used as the control parameters. The required power for EMs is generated by a combination of a generator for an ICE and an EM. They are very simple, conceptually, consisting of an input stage, a processing stage and an output stage. The input stage maps the parameters to the appropriate membership functions and the truth values. The processing stage invokes each appropriate rule and generates results for each, then combines the results of the rules. Finally, the output stage converts the combined results back into a specific control output value. The advantage of the Fuzzy logic is helping the user to view systematic validation of each interaction. The result of simulation shows the excellent effect of the optimal control strategy to share the required power between the ICE and the electric motor. Through the simulation, it can be proved that the fuzzy logic controller is useful for improving driving performance, and the Fuzzy logic technique is suitable for hybrid electric vehicles [17]. 3. Serial/parallel hybrid topology  
In multi-configuration hybrids, clutches or power-split gear sets make it possible to switch from one configuration to another (i.e., between serial and parallel systems). The serial/parallel configuration has a similar control topology to the one described before, for serial hybrids. The difference arises from its flexibility, which allows the mechanical connection of the ICE to the wheels in parallel hybrid mode or the combination of the power sources (the EM and the ICE with a generator) as in serial hybrid mode. The increased flexibility allows a combination of the advantages of each hybrid architecture. All nine operating modes (Section 2.2.1) are able to be used in the serial/parallel hybrid topology. Here, the vehicle acts as a serial hybrid at low speeds and as a parallel hybrid for highway cruising.