## 3 Simulation Model of the Drive and Transmission Mechanism
### Numerical Calculation of the Mechanical Efficiency of the ZF 6 HP 260 Gearbox  
Thanks to the created complex model, it is possible to analyze not only the torques and revolutions but also the significant number of other outputs, for example, power, efficiency, fuel consumption, inertia or traction characteristics. As the efficiency is the most complex parameter of the ZF 6 HP 260 gearbox, which was also obtained analytically, this part of the research was focused on the comparison of the gearbox efficiency at individual gears, obtained using the numerical and analytical method.  
Figure 7: Complex model of the drive and transmission mechanism of the Iveco LMV 4 \(\times\) 4 M65 vehicle.  
During the verification of the simulation model, it was not necessary to implement any element of automation of internal or external simulation inputs. The external simulation input in this case can be represented by the driver's demand for power either in the form of the required fuel supply or in the form of the accelerator pedal position. For the purpose of the comparison of the values of mechanical efficiency \(\eta\), driving forces \(F_{1}\), powers \(P\) and dynamic factors at the particular gears, the scenario of full fuel supply (\(T=1\)) was chosen. In this case, the second external input of manual gear shifting also remained, which is achieved by the activation or deactivation of the related gearbox control components (B\({}_{1}\), B\({}_{2}\), C\({}_{1}\), C\({}_{2}\) and C\({}_{3}\)) at an adequate time (Figure 8).  
Also, for this complex model of the drive and transmission mechanism of the Iveco LMV 4 \(\times\) 4 M65 vehicle, it can be concluded that the acceptable deviation \(\Delta_{max}\) between the values obtained analytically and numerically is \(\leq\)1%.  
As it was mentioned above, the simulation involves a number of sensors for various parameters. Sensors detecting the values of the powers transmitted in particular components of the drive and transmission mechanism model were used to determine the values of the mechanical efficiencies of the vehicle's transmission at particular gears (1-6) according to the relation (12):  
\[\eta=\frac{T_{2}\omega_{2}}{T_{1}\omega_{1}}=\frac{P_{2}}{P_{1}} \tag{12}\]  
The mechanical efficiency of the transmission \(\eta\) can therefore be defined as the ratio of the powers at the gearbox output and input. That is the reason why the power sensor \(P_{1}\) was placed on the input shaft of the gearbox and the power sensor \(P_{2}\) was placed on the output shaft of the gearbox.  
From the power characteristics at the particular gears shown in Figure 9, it can be seen that mechanical losses occur in the gearbox model. The calculated values of the mechanical efficiency of the ZF 6 HP 26 gearbox at the particular gears can be seen in Figure 10.  
Figure 8: Input signals controlling the operation of the gearbox model control elements.  
These values can be subsequently used to verify the functionality and accuracy of the gearbox model by comparing them with the values obtained analytically.  
To verify the functionality of the complex model of the drive and transmission mechanism of the Iveco LMV 4 \(\times\) 4 M65 vehicle, the average values of torques, powers, tractions, dynamic factors and related characteristics were compared.