White Paper: Test & Measurement
Testing Powertrain on an Electric Formula SAE Car
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The Italian Formula SAE team, E-Team Squadra Corse, has participated in the SAE Formula Student competition since 2008. The 2022/23 season saw a drastic change for the team. They switched from the combustion category to the electric category in the SAE Formula Student competition. Two axial flux motors replaced the well-known internal combustion engines. Switching the powertrain from ICE to electrical proved to be a tough challenge.
To support this change and improve the engine, the powertrain and electronic teams worked together. They installed and monitored all the vehicle's electronic and electrical devices. To switch to an electric car, they also had to change the rear chassis of the single-seater. This change allowed them to attach the new powertrain and battery pack.
The team collaborated with Dewesoft to acquire, process, and analyze test data to clarify the consequences of this change on the car's behavior.
The testing gave the Formula SAE team valuable insights into the car’s electrical and mechanical performance and helped them solve a key reliability issue. The data also allowed the team to validate their electrical and mechanical models, identifying both strengths and areas for improvement, guiding their next steps.
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Overview
The document outlines the development and analysis of an electric vehicle (EV) prototype by the E-Team Squadra Corse, focusing on their transition from internal combustion engines to electric powertrains for their Formula SAE car. This shift emphasizes sustainability and innovation in motorsport.
Key highlights include the vehicle's design, which features a hybrid chassis and a powerful propulsion system, specifically the EMRAX188 HV motor. The team utilized advanced data acquisition tools from Dewesoft to monitor and analyze various electrical and mechanical parameters during testing. This collaboration allowed for precise signal acquisition, enabling the team to identify and address performance issues effectively.
During testing, the team observed abnormal vehicle behavior characterized by jolting and power loss, particularly during the Siena endurance test. The analysis revealed that excessive noise from the inverters exceeded safety limits for both AC and DC currents, triggering the inverters' internal safety systems to cut power. This issue was linked to suboptimal pre-tensioning in the transmission chain, which caused noticeable "tugging" during operation.
To resolve these problems, the team focused on optimizing the engine control system. They adjusted controller parameters and increased the inverters' switching frequency from 6 kHz to 14 kHz, effectively raising the unipolar PWM control frequency from 12 kHz to 28 kHz. This adjustment shifted the harmonic spectrum to a range that naturally reduced noise, preventing the system from exceeding safety limits and eliminating power cuts.
The document also discusses the electrical analysis conducted during tests, which involved comparing average electrical power, accelerator pedal signals, vehicle speed, and line currents. This comprehensive analysis helped isolate the moments of anomaly and provided insights into the vehicle's performance.
Additionally, the document touches on the vehicle dynamics division's efforts to develop accurate vehicle models using commercial software like Adams Car. These models incorporate various degrees of freedom related to vehicle dynamics, allowing for better predictions of performance and behavior.
Overall, the document highlights the E-Team Squadra Corse's commitment to innovation, sustainability, and performance optimization in their electric vehicle project, showcasing their technical expertise and collaborative efforts in the field of motorsport engineering.