Intelligent Gearshift Schedule Considering Road Slope Based On Multi-performance Optimization

Shift schedule is directly related to vehicle performance,and is one of the vehicle’s important research contents.Traditional shift schedule only considers optimization of a certain performance,which cannot satisfy the different driving demands.When road ramp changes,traditional shift schedule does not consider the influence of slope on gearshift performance and therefore it can not adapt to the change of road slope.The paper focused on the application of multi-objective optimization method to calculate the multi-performance integrated optimal shift schedule and the ramp schedule.The following aspects are analyzed and studied:(1)The types of automatic transmissions and shift schedule have been introduced briefly.And the current research status has been summarized.(2)Through analyzing the basic theory and the formulating method of shift schedule,evaluation function of each performance has been established.With the non-dimensional treatment,the linear weighting method has been used to establish the comprehensive evaluation function of shift schedule.BP network have been used to indentify the model of engine’s output torque and fuel consumption respectively.And dynamic weight of different proportions of the shift schedule under multi-performance integrated optimal for automatic transmission,are calculated using GA optimization algorithm.(3)The weighted ideal points and square sum method has been applied to establish the comprehensive evaluation function of multi-performance integrated optimal shift schedule,and the shift schedule with different weights for dynamic performance are calculated using GA optimization algorithm.Through comparing the upshift lines of the aforementioned two shift schedules with same combinations of weights for dynamic performance,we found that the weighted ideal points and square sum method is more suitable for calculating the multi-performance integrated optimal shift schedule,and the power performance and fuel economy of the shift schedules developed by this method have also been further verified.(4)Analysis of the effect of road ramp to the shift schedule and the reason,according to the balance between the driving force and the running resistance,find the each gear speed constraint on the ramp,combined comprehensive evaluation which established by the weighted ideal point and square sum method,shift schedule on the ramp was calculated using GA optimization algorithm.(5)A simulation-based evaluation system for shift schedule,which consists of the neural network models of engine performances,the simulation model of(automated manual transmission),the simulation model of vehicle longitudinal dynamics,the simulation model of slope recognition,the shift logic simulation model and the simulation model of HWFET-MTN test cycle,have been built usingMATLAB/Simulink/Stateflow platform.Theslope recognition model is based on the vehicle’s longitudinal dynamics,a slope recognition method by ECU memory accelerometer is proposed.The formulated shift schedule for each ramp have been evaluated through simulation experiment under the constant throttle,the simulation result show that: under the constant throttle,shift schedule for each ramp can eliminates frequently gearshifts and effectively smooth out the velocity fluctuation.The HWFET-MTN test cycle simulation result shows that the shift times of the shift schedule considering ramp is less than that without considering ramp while vehicle drives on same ramp,but its fuel consumption increases slightly.