| At present,the contradiction between economic development,energy and environment is becoming increasingly prominent,and China proposes to develop new energy vehicles as an important strategic measure to address climate change and promote green development,and then increase efforts to achieve energy conservation and emission reduction.As an important part of new energy vehicle products,plug-in hybrid vehicles can extend driving range,alleviate range anxiety,and effectively reduce carbon emissions.One of the core technologies of plug-in hybrid vehicle powertrains is the globally optimized energy management control method.Therefore,how to determine the globally optimal power output ratio of the power source during its driving is one of the key theoretical issues in the field of energy management strategy;the globally optimized energy management strategy can theoretically achieve optimal global energy consumption,but the globally optimized energy management strategy is difficult to directly apply online.Therefore,seeking an online utilization method that can be based on the globally optimized energy management strategy is one of the key application problems to promote the globally optimized energy management strategy.In view of the above problems,based on the research status of globally optimized energy management strategy,an online utilization method for globally optimized energy management based on three-dimensional convex hull is proposed in this paper.The three-dimensional convex hull is used to extract the rules of the vehicle drive mode selection method under the globally optimized energy management strategy,establish the correlation between the driving cycle working condition information and its corresponding rules,formulate the online driving mode switching rules,improve the working condition adaptability of the online switching rules,and make the vehicle drive mode selection method close to the offline globally optimized energy management control,so as to improve the energy consumption performance.This paper aims to explore a method for using globally optimized energy management laws online from the perspective of figurative geometry.The main contents of this article include:1 、 Aiming at the problem that the globally optimized energy management strategy is difficult to directly implement online,the globally optimized energy management is carried out under several driving cycles,and the law is extracted.With the help of MATLAB software platform,taking a single-axis parallel plug-in hybrid vehicle as the research object,a longitudinal dynamic model of the whole vehicle is established,and the global optimization algorithm based on the established model is realized with the cumulative fuel consumption as the optimization goal,and the global optimal energy distribution trajectory is obtained,and then the scatter information of vehicle drive mode under the three-dimensional coordinates of power source demand torque,vehicle speed and battery state of charge is extracted from the results of globally optimized energy management under different driving cycles.2、Aiming at the problem of lack of unified and rapid methods to extract vehicle drive mode switching rules under a large number of driving cycles,the threedimensional convex hull of irregular geometry is used to cover the scattered points of each type of vehicle drive mode separately,and the relationship between the threedimensional convex hull and its characteristic parameters is studied.Using the random increment method,the scatter points of vehicle drive mode corresponding to the threedimensional convex hull coordinates of vehicle power source demand torque,vehicle speed and battery state of charge under each driving cycle are quickly solved by threedimensional convex hull,and the vehicle drive mode switching rules are extracted from the perspective of concrete geometry.Then,the characteristic parameters of the threedimensional convex hull are calculated,and the approximate position,size and shape of the three-dimensional convex hull are inferred by using these characteristic parameters,and then a method for generating a three-dimensional convex hull based on the characteristic parameters of the convex hull is formed.3、In view of the poor adaptability of the rules extracted from the fixed driving cycle working conditions,and the diversity and complexity of unknown driving cycles,the three-dimensional convex hull is linked with the driving cycles.The characteristic parameters of driving cycles are selected and calculated,and then the stepwise regression analysis method and generalized regression neural network are used to establish a linear prediction model and a nonlinear prediction model with the driving cycle characteristic parameters as input variables and the convex hull feature parameters as the output,forming a convex hull feature prediction model based on driving cycle features,so that the three-dimensional convex hull can be directly generated according to the unknown driving cycle characteristics,and then the online vehicle drive mode switching rules are quickly determined,forming an online utilization method of vehicle globally optimized energy management based on threedimensional convex hull.Finally,the effectiveness of the predictive model is verified.4、By supplementing the online utilization method of vehicle globally optimized energy management based on three-dimensional convex hull,a complete online energy management strategy is formed and verified.The gear and torque distribution ratio results are extracted from the globally optimized energy management results,as a supplement to the online utilization method,combined with the online vehicle working mode switching rules,to form a complete online energy management strategy,namely the Convexhull-based strategy,and the results of other three energy management strategies are compared and analyzed,it proves that this strategy can maximize fuel economy under unknown driving cycles. |
