Multi-Performance Optimal Gearshift Schedule of Stepped Automatic Transmissions Adaptive to Road Slope

Paper #:
  • 2017-01-1137

Published:
  • 2017-03-28
Abstract:
With respect to the stepped automatic transmission (SAT) having a fixed number of gears, gearshift schedule is crucial to improve the comprehensive performance of vehicle that takes into account power performance, fuel economy, and driver’s performance expectation together, as it determines the timing when a SAT should be shifted from a certain gear position to another one. To optimize and individualize the gearshift schedule, our previous work proposed a multi-performance gearshift schedule optimization method and an improved performance evaluation approach, which are effective in terms of reflecting the driver's expectation on different vehicle performance by assigning different value to the weights in the performance evaluation function. However, the proposed optimization method does not consider the influence of road slope on the gearshift performance. As the road slope changes the load of vehicle that is different from that when a vehicle runs on a level road, the optimized gearshift schedule without considering the road slope is obviously not the optimal solution for a vehicle equipped with SAT when it runs on ramp. To this end, in this investigation the influence of the road slope on the gearshift behaviour has been analyzed, and then a modified optimization method which takes the slope resistance in the constraints of the gearshift optimization problem has been proposed. Based on that, the multi-performance gearshift schedules adaptive to different road slopes have been optimized. To evaluate the improved gearshift schedules, simulation of climbing hills having different slopes with 100% throttle opening, and simulation under a modified driving cycle, using different gearshift schedules have been carried out. The simulation results show that the improved gearshift schedules could improve the vehicle performance when it climbs hills, and meanwhile the comprehensive performance of vehicle still could represent different driver's intention. The paper will be organized as follows. Section 1 will discuss the research background. Section 2 will introduce the multi-performance optimal gearshift schedule briefly. Section 3 will analyze the influence of road slope on the gearshift performance. Section 4 will describe the improved gearshift schedule optimization method considering the road slope, and show some optimization results for a prototype vehicle equipped with an 5-speed automated manual transmission (AMT). Section 5 will discuss the simulations corresponding to different fixed slopes and corresponding to a modified driving cycle. The paper will conclude with Section 6.
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