# A Framework for Communicating and Building a Digital Twin Model of the Electric Car
## 1 Introduction
* Hardware-in-the-loop (HiL)--uses actual physical connections to the embedded processor, such as inputs and outputs and actuators or a communication interface; used for verifying if the controller works stably and how it responds in real time to changing signals. * Vehicle-in-the-loop (ViL)--last step before full road testing; complete vehicle system; used for testing real-world scenarios with a virtual environment. Differences between the simulation methods are presented in Table 2. Depending on current characteristics, progress, and requirements of the project, some of these methods can be used. Each method has a specific approach and provides unique feedback. The MiL method is virtual while ViL is real and provides the best accuracy but is also expensive. ViL simulation should be used for complex systems, such as the advanced driver assistance system (ADAS), which is crucial to safety. In the case of less complicated car systems, such as wipers or smart keys, more virtual methods are used, such as MiL, SiL, or HiL [33; 34]. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline
**Category** & **Dimensions** & **Comment** \\ \hline Digital twin interaction & Specifies whether there is only one DT or multiple DTs and describes how they collaborate. \\ \hline Hierarchy & This dimension provides information about the rank of collaborating DTs. \\ \hline Connection mode & The connection between a DT and a physical object. \\ \multirow{4}{*}{Integration [29; 30]} & \(\bullet\) Digital model—there is no automated data exchange form, and it is carried out manually. \\ \multirow{2}{*}{[29; 30]} & \(\bullet\) Digital shadow—automated data flow from the physical object to the DT. \\ \multirow{2}{*}{Useer focus} & \(\bullet\) Digital twin—automatic data exchange in both directions. \\ \hline User focus & DT can be useful for an individual user, a department, a company, or several organizations. \\ \hline Collaboration & There are DTs established for different organizations, there is data exchange between them, and they can have similar purposes or work independently. \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._In addition to the dimension of the Fourth Industrial Revolution, i.e., integration, communication, and interaction standards, there is an advanced combination of virtual and real tools and tests that improve the efficiency of electric cars. A study [39] shows that the well-to-wheel (WTW) efficiency of diesel ICEV ranges from 25-37%. However, in the case of an EV powered by renewable energy, the overall efficiency ranges from 40-70%. An overview of areas where the energy efficiency of EVs can be improved is discussed in [40]. Tests include various methods, such as the following:  
* Regenerative braking--a simulation test proved that the regenerative braking logic saved approximately 30% of energy consumption compared to a vehicle without recuperation [41]. * Battery efficiency--different speed profiles were tested on a chassis dynamometer with VW e-Up. The question concerned the impact of speed on energy consumption and battery performance [42]. * Energy management system--data from vehicles were sent to the cloud via 4G LTE network. Real-time vehicle performance was consistent with the cloud computing status. Based on these calculations, an ID-VIL simulation was performed to evaluate possible decisions to minimize costs and battery life loss [43]. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**AspectMethod** & **MiL** & **SiL** & **PiL/FiL** & **HiL** & **ViL** & **Test Drive** \\ \hline Software simulated model & ✓ & ✓ & ✓ & ✓ & & \\ \hline Control simulator & & ✓ & & & & \\ \hline Embedded processor & & ✓ & ✓ & ✓ & ✓ \\ \hline I/O, communication & & & & ✓ & ✓ & ✓ \\ \hline Real conditions & & & & & & ✓ \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Characteristics of different simulation methods.