## Appendix A  
Future Automotive Systems Technology Simulator (FASTSim) was developed by NREL [53]. The modeling approach is very similar to the earlier MATLAB-based ADVISOR model but is released as a macro-enabled EXCEL file. The simulator can be used for conventional ICE vehicles, HEVs and EVs. The primary objective of FASTSim is to estimate the fuel economy, cost and performance of a vehicle with specified powertrain components over standard drive cycles. All saved vehicles are approximations of existing vehicles. Some examples of these vehicles are 2016 KIA Optima Hybrid, 2017 Toyota Prius Prime, 2016 Nissan Leaf, 2016 BMW i3 Rex PHEV, 2016 Ford C-MAX PHEV. This simulator is also free to download. The inputs of the RB EMS used by FASTSim include:  
* Battery minimum SOC;
* Battery maximum SOC;
* Level of discharge aimed at improving the fuel converter efficiency;* Level of charge aimed at improving the fuel converter efficiency;
* Speed at which the battery energy reserved to assist acceleration reaches zero;
* Percentage of usable battery energy reserved to assist acceleration;
* Speed at which the fuel converter is turned on;
* Power at which the fuel converter is turned on. The RB strategy is primarily based on the battery SOC. The operating range of the battery is limited by a specified maximum and minimum SOC. The strategy consists of three SOC zones within this range, as seen in Figure 11. The first zone is between the maximum SOC and the regenerative braking buffer (Regen Buffer). This area is calculated based on the mass and speed of the vehicle. It is the amount of battery energy reserved to capture a regenerative braking event. Similarly, the zone between the acceleration buffer SOC (Accel Buffer) and the minimum SOC is the amount of battery energy reserved to assist with accelerating the vehicle. Between the Regen Buffer and Accel Buffer, the strategy focuses on maximizing the fuel converter efficiency. There are six variables that determine the limits of the control strategy. Their influence on the engine operation is shown in the schematics below, and they are described as follows:  
* \"cs_lo_soc\": The lowest SOC corresponding to the minimum charge/discharge resistance of the energy storage system module. * \"cs_hi_soc\": This parameter should be set slightly higher than the cs_lo_soc. More specifically, it should be set to a value less than the SOC at which the either the charge or discharge resistance increases dramatically. * \"cs_charge_trq\": Defines the additional torque requested of the fuel converter to maintain an energy storage system SOC between cs_lo_soc and cs_hi_soc. * \"cs_electric_launch\": Below this vehicle speed, the vehicle will operate as a pure electric vehicle; above this speed, the fuel converter will be used as the primary power source. * \"cs_off_trq_frac\": Represents the fraction of max torque at each speed at which the engine should turn off. This parameter should be set to a value equal to the fraction of max torque at each speed at which the fuel converter efficiencies begin to drop dramatically. * \"cs_min_trq_frac\": Represents the minimum fraction of max torque at each speed at which the engine will operate when lower torque fractions are requested. This parameter is typically set to a mid to high value (0.5-0.8) in order to force the fuel converter to operate in a high torque region of its efficiency map. Once these parameters are defined, the common rule-based EMS is based on the following rules:  
1. The state of the engine (on or off) is determined by the following rules (see Figure 11):1. If the speed required is less than the electric launch speed, cs_electric_launch_spd, the engine could turn off. I.2. If the SOC is higher than its low limit, the engine could turn off. If both the requested speed is less than the launch speed and the SOC is higher than the low limit, the engine will turn off. I.3. If the torque required is less than a cutoff torque, cs_off_trq_frac fraction of the maximum torque, the engine could turn off.