# Dynamic Modeling and Characteristic Analysis of Articulated Steering Vehicles
## 3 Results and Discussion
### Power Train Results  
In order to validate the power train model, we recorded the torque information of the front and rear motors during the test, and the torque of the two motors was the same; thus, only the front motor is shown and compared with the simulation results in Figure 11. As it can be seen, the maximum torque was about 780 Nm during the presented test interval, and the maximum torque was about 650 Nm in the simulation, meaning that they occurred at the same time. Additionally, a large difference occurred during the slow reduction stage, i.e., at 11-17 s and 26-29.5 s. In the simulation model, the motor was considered to be a table with two parameters, the acceleration pedal and speed. The resulting torque might be slightly different from the actual characteristic of the motor. During the other stages, the simulation and test results coincided well, especially during the low-torque stages.  
Figure 11: Torque result of driving motor.  
Figure 10: Pressure results of steering system.  
Not only does the power train of an LHD vehicle provide the power of the driving and steering system, but it also provides the power of the working mechanism, which is normally powered by hydraulic oil like the steering system. Meeting the power demand is essential to the productivity of an LHD vehicle, and, thus, the power demand should be uncovered. In order to analyze the power distribution of a typical working cycle, we recorded the pressure and flow of the steering pump and working pump, and the current and voltage of the driving motor during three working cycles, in which the short-running, loading, running, dumping, and running-back processes were included.  
Then, the power of the motor and hydraulic system was calculated, and the total power was obtained via the sum of the two parts, as shown in Figure 12. For the first working cycle, during 0-30 s, the ASV was run to load the mining material, and then it transported the material to the dump point between 30 and 75 s. The model validation was performed with the data from this process. The model-based calculation results of the motor power and hydraulic steering power also indicate correctness. The dump and return processes occupied the time interval of 75-125 s.  
The data of the model validation were extracted in the interval of 30-80 s, and the power distribution is shown in Figure 12b. As it can be seen from the results in Figure 12a, the maximum power during the typical cycle varied from 260 kW to 289 kW, and the motor power accounted for a large part, about 203 kW. When the ASV loaded the material, the vehicle was driven to insert the bucket tip deeper into the pile, and the motor power was used to cover the resistance force during the process. For the interval of model validation, which is 0-45 s in Figure 12b, the maximum power was about 48 kW, and the hydraulic power was the steering power, which was less than 10 kW.  
Detailed information of the load and dump processes is shown in Figure 13a,b. For the results in Figure 13a, after the insertion of the bucket tip, the hydraulic power raised sharply due to the retraction of the bucket [26]. The motion needed to cover the stacking resistance force of the material pile. After that, i.e., the time after 23 s, the hydraulic power raised again, but it was less than 150 kW. During this process, the bucket and boom cylinders were cooperatively driven to load the material. In the dump process, the bucket needed to firstly be lifted and tilted. Then, the bucket returned to the original place with the cooperative control between the bucket and boom cylinders. Therefore, multiple fluctuations in the hydraulic power were involved. The maximum power of the dump process was less than 82 kW according to Figure 13b. After the dump process, the LHD vehicle was driven back to the load point, and the motor power and hydraulic power, i.e., the steering system, dominated in this region.  
Figure 12: Power distribution of typical working cycle: (**a**) global distribution; (**b**) power distribution in running condition.