A unique approach to optimize the gear-shift map of a compact SUV to improve fuel economy and performance 2020-01-0969
Automated manual transmission (AMT) is often preferred by the car manufacturers as an entry-level automation technology. The AMT technology can provide the comfort of an automatic gearbox at a reasonable cost impact over the manual transmission (MT). This paper explains the unique approach to define the gear-shift map of a compact sports utility vehicle (SUV) considering the unique requirements of the Indian market. The real-world measurements revealed that an aggressive shift pattern with delayed upshift and quick downshift can deliver a good low-end drivability and performance while compromising on fuel economy. Moreover, the chassis dyno measurements in the modified Indian drive cycle (MIDC) indicated lower fuel economy values. On the other hand, a shift pattern with early upshifts and delayed downshifts could help in achieving a better fuel economy while compromising on drivability and performance. Hence, a unique approach is used to derive the most optimal gear shift map for each operating gear. Gear-shift points of actual vehicle were measured in real-world operating conditions in a reference vehicle under different operating conditions (traffic, user, road) in both MT and AMT drive modes. The data was analyzed to identify the differences in the base shift map between MT and AMT. Moreover, the recorded data was analyzed to understand the effect of a specific shift map with different drivers under different traffic scenarios. With the help of a 1-D simulation tool called AVL CRUISETM, the fuel economy and performance of each gear shift pattern was calculated and compared. Based on the results, an optimized shift map was derived considering the real-world performance and fuel economy. The finalized gear shift map based on this optimization methodology was verified in the vehicle and found to be having a benefit of 8% in real-world fuel economy for a comparable performance. Hence, this approach can be used effectively to optimize the gear-shift map of any AMT vehicle.