Multi-Performance Optimal Gearshift Schedule of Stepped Automatic Transmissions Adaptive to Road Slope 2017-01-1137
For the vehicle equipped with stepped automatic transmission (SAT) that has a fixed number of gears, gearshift schedule is crucial to improve the comprehensive performance that takes into account power performance, fuel economy, and driver’s performance expectation together. To optimize and individualize the gearshift schedule, an optimization method and an improved performance evaluation approach for multi-performance gearshift schedule were proposed, which are effective in terms of reflecting the driver's expectation on different performance. However, the proposed optimization method does not consider the influence of the road slope on the comprehensive performance. As the road slope changes the load of vehicle that is different from the load when a vehicle runs on a level road, the optimized gearshift schedule without considering road slope is obviously not the optimal solution for a vehicle equipped with SAT when it runs on ramp. To this end, the influence of the road slope on the gearshift behavior has been analyzed at first, and then an optimization method which takes into account the slope resistance has been proposed. Based on that, a number of multi-performance gearshift schedules adaptive to different road slopes have been optimized. To evaluate the improved gearshift schedule optimization method, simulations of driving on ramp with fixed slope angle under 100% throttle opening, and simulations of driving under a modified driving cycle on ramps with both fixed and changing slope angles using different gearshift schedules, have been carried out. The simulation results show that the proposed gearshift schedule could improve the vehicle performance through eliminating gearshift cycle with slight but acceptable reduction of fuel economy when it runs on ramp.