1st ICAI 2020

International Conference on Automotive Industry 2020

Mladá Boleslav, Czech Republic

arrangement, two differentials when using one motor per axle, no mechanical differentials needed in our case). Based on our vehicle simulations, we proposed the use of four water-cooled permanent magnet synchronous motors. Every motor with peak values of power 17 kW and torque 96 Nm. We proposed the optimal gear ratio for reduction gearbox around 12. We were looking for a suitable reduction gearbox, but we did not find the optimal solution. Currently offered gearboxes for this type of electric vehicles were either expensive or heavy. For this reason, we decided to develop and manufacture our own single-speed reduction gearbox. It allowed us to fulfil our, more specific, requirements. For example, to keep the development and manufacturing cost low, we decided to design the gearbox with using of some parts from Škoda Auto MQ200. Specifically, we used selected gears and shafts from Škoda Auto gearbox. We designed the gearbox in such way so one type of gearbox could be used for all four corners of the vehicle. The main challenge of the gearbox design was to consider possible opposite rotation of input shaft. Input shaft of the gearbox in internal combustion engine vehicles always rotates in one direction (due to the rotation of crankshaft). When using one type of gearbox for all four corners, two gearboxes always rotate in the opposite direction to those on the other axle. By the need to design one gearbox to both sides of each axle of the vehicle we had to solve that axial forces (reactions of the interaction between helical gears) can act in both directions with the same magnitude. We had to find a way how to transfer these loads on the bearings inside the gearbox without making it unnecessarily complicated. Another challenge was to ensure sufficient lubrication. When using four identical gearboxes, there are two upside down to the other two. During the design process we used a lot of symmetry. The proposed drivetrain is shown in the Figure 2.

Figure 2: Designed drivetrain for TUL modular platform

Source: own elaboration (2019)

2.1.2 Chassis design concept of TUL modular platform The modular platform chassis consists of hydro-pneumatic suspension system and four wheel steering system. Both these advanced systems allow the vehicle to drive in difficult terrain conditions, thus ensuring safety for cargo or vehicle equipment.

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