The NCSU EcoCAR 2 team has focused on the refinement and optimization of their 2013 Chevy Malibu in Year Three. The supervisory control and the sub-system controls algorithms have been refined, one of which is the regenerative braking strategy.
When the previous regenerative braking strategy was developed, it went through a validation process from Software-In-the-Loop (SIL) and Hardware-In-the-Loop (HIL) to Vehicle-In-the-Loop (VIL). After it was implemented in the vehicle, the vehicle was tested on a team-defined track to obtain data for the regenerative brake torque. This torque was analyzed at certain vehicle speeds, and the regenerative brake torque determined the regenerative current. The more current generated per second, the more energy recovered through regenerative braking. The team thought they may be able to get more efficiency by refining this process- so they did!
As shown in the “Previous Regenerative Strategy” figure, the model-predicted torque matches the measured torque from testing, which means the plant model has a high accuracy. After refining the plant model, an advanced regenerative braking strategy with an adaptive gain was developed to recover more energy. As shown in the “Refined Regenerative Strategy” figure, the measured torque in the refined regenerative strategy was higher than the predicted torque because the strategy adapted faster in real time than in simulation time.
Compared to the previous strategy, the refined strategy is 26% more energy efficient! Great job, NC State!
Categories: Under the Hood