High EM-Speeds in Simulation of 21-Ton EV Truck with 2-speed AMT using Virtual Vehicle Composer.

Question

Rohit Pujari 2023-8-25

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https://ww2.mathworks.cn/matlabcentral/answers/2013032-high-em-speeds-in-simulation-of-21-ton-ev-truck-with-2-speed-amt-using-virtual-vehicle-composer

回答： Pratyush 2024-2-8

Hello everyone,

I am currently working on a simulation for a 21-ton Electric Vehicle (EV) truck using the Virtual Vehicle Composer. The truck is equipped with a 2-speed Automated Manual Transmission (AMT). However, I'm encountering an issue where the Electric Motor (EM) speed is reaching very high values, approaching 20,000 rpm, which seems unrealistic (In the Results EM speed is in rad/s and Torque is in Nm)

Specifications:

Vehicle Weight: 21 tons
Gear Ratios for AMT:
1st Gear: 12.52
2nd Gear: 5.39
Final Drive Ratio: 3.32
Tire Radius: 0.513 m

For context, when using lower gear ratios of 3 (for 1st gear) and 2 (for 2nd gear) with a final drive ratio of 3.32, the simulation works fine without any issues. However, for this specific application of 21-ton truck, higher gear ratios are essential to ensure sufficient torque delivery, especially during initial accelerations and when hauling heavy loads.

I have followed the drive cycle and ensured that upshifts occur at 42 kph and downshifts at 21 kph. For the high-speed part of the drive cycle, the vehicle speed is 83 kph, and it's mostly in 2nd gear. Despite this, I'm observing these extremely high EM speeds.

I've attempted to trace back through the simulation and calculations to identify the source of the issue, but I'm currently stuck. I'm hoping someone with experience in this tool or similar scenarios can provide some insights or suggestions on what might be causing these high EM speeds and how to resolve it.

Any help or guidance would be greatly appreciated. Thank you!

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Answer 1

Pratyush 2024-2-8

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https://ww2.mathworks.cn/matlabcentral/answers/2013032-high-em-speeds-in-simulation-of-21-ton-ev-truck-with-2-speed-amt-using-virtual-vehicle-composer#answer_1404826

Hi Rohit,

To resolve the issue of high Electric Motor (EM) speeds in your 21-ton EV truck simulation with a 2-speed Automated Manual Transmission (AMT), consider the following steps:

Ensure the gear ratios are correctly implemented in the simulation.
Confirm that the simulation shifts gears at the correct vehicle speeds (42 kph for upshifts, 21 kph for downshifts).
Review the EM's speed-torque and power curves to ensure the simulation reflects the EM's realistic operating ranges.
Implement strategies to prevent the motor from exceeding realistic operating conditions.
Revisit the simulation's assumptions, including vehicle mass, aerodynamic drag, rolling resistance, and tire dynamics.

Hope this helps.