## Tool Description  
### General Principles  
The software described in this paper was developed using as environment LABVIEW (Laboratory of Virtual Instrumentation and Engineering Workbench), which is system engineering software for applications that requires tests, measurements, and control. The programming language is called Graphic Language (G-Language) and differs from the traditional ones because the syntax is not written but graphic. This language is able to perform multithreading spontaneously without explicit control from the programmer; consequently, it is an excellent tool for handling all the processes in parallel. In order to define a digital configuration environment that is capable of perfectly adapting to the real on-board configuration, the number of independent choices to perform is very high. As a result, the software requires several processes.  
The calculation procedure of the performance values starts with the evaluation of the incoming air mass flowrate to the engine \(\dot{m}_{air~{}eng}\).  
This quantity, expressed in kg/s, is evaluated through two different procedures:  
* by means of the evaluation of incoming air mass flow to the compressor \(\dot{m}_{air}\), which is measured if the Air Nozzle is installed;
* by means of the evaluation of exhaust gas mass flow \(\dot{m}_{exh}\), calculated using the Carbon Balance method if CO\({}_{2}\), CO and THC (Total HydroCarbon) detectors are present.  
As regards the logical functioning of the software, four consequential phases can be identified (Figure 1).  
Figure 1: Main block diagram of the software.  
During the first phase of Configuration Set Up, the software requires the user to make all the choices previously mentioned in order to generate a Set Up Environment. The latter will be used to communicate to the actual engine of the software, which is called Main, the calculations to perform and the constants and variables necessary for them; furthermore, it provides an association between the variables and the sensors detected in the network.  
The next phase requires running the parsing--that is, the association between the variables used in the Calculation Routine and the numerical values (i.e., the physical sensors) detected in the Sensor Network (SN). The user has to perform this phase manually every time.  
Once the parsing is completed, the software starts with the Data Processing phase. The Main determines the calculations to perform and the input to use, which is based on available in-use configuration information, manually inserted constant values, and variables collected by the SN. Indeed, the analysis of both classic bibliography and the Rules in Performance Calculation area allowed identifying the functions required to define the interest value in Performance Evaluation. A huge number of them can be calculated only if the Border Conditions provided by the Set Up Environment are fulfilled; otherwise, the software does not perform the calculation of those functions and proceeds to verify all the others.  
The last phase concerns the real calculation and the in-live visualization of the performance through a continuous update of the input values detected by the SN.