| Vulnerable road users(VRU),such as pedestrians,cyclists,and motorized bicyclists,account for a high proportion of casualties in traffic accidents.The research on traffic accidents and protection technologies related to VRU has become a hot spot in the automotive industry and academia.In order to reduce VRU crash injury in traffic accidents,many countries and regions have successively formulated and implemen ted VRU protection regulations and third-party assessment procedures based on in-depth investigation of traffic accidents.At the same time,in order to meet the abo ve regulations and assessment requirements,reducing VRU crash injury through vehicle structure design has become the focus of new vehicle safety development.However,the vehicle structure design is restricted by discrete variables,multi-attribute factors and uncertain factors.How to obtain the optimal vehicle front-end structure parameters within the limited development cycle brings challenges to the engineering development.In addition,with the continuous improvement of automobile intelligence,VRU injury protection device(pop-up hood,pedestrian protection airbag and front bumper airbag)also provides an effective way to improve the VRU protection performance of intelligent automobile.At present,there is still a lack of development and research on VRU injury protection device system in China.Therefore,in order to improve the safety of vehicle to VRU collision,this paper takes the vehicle front-end structure as the research object,and carries out systematic research by using simulation,optimization design and experimental methods.Starting with solving the multi-objective discrete deterministic optimization problem,this paper establishes the multi-attribute decision discrete optimization design process,Furthermore,considering the influence of uncertainty,the multi-attribute decisionmaking discrete robust optimization design method and fuzzy optimization design method are proposed,and the method is applied to the vehicle f ront-end structure design,which effectively improves the VRU protection performance.Finally,this paper puts forward the development process of VRU injury protection device,carries out subsystem experimental verification and vehicle experimental verific ation on the basis of module design and simulation,and reveals the functional principle and protection mechanism of pop-up hood,pedestrian protection airbag and front bumper airbag.The research work of this paper establishes the theoretical system of ve hicle VRU protection engineering design.The research contents are as follows:(1)The discrete optimization design method based on multi-attribute decision making and its application.In order to efficiently solve the multi-objective discrete optimization design problem in engineering,a set of multi-objective discrete optimization design algorithm based on multi-attribute decision-making is developed in this paper.In the running process of the algorithm,entropy weight method is used to calculate the attribute weight coefficient,TOPSIS method is used to convert the multi-attribute objective function into a single cost function,and the continuous orthogonal matrix is used as the optimizer to perform algorithm iteration.On the basis of verifying the effectiveness of the algorithm with two mathematical benchmark examples,the algorithm is applied to the design of vehicle front-end structure under TRLPLI to vehicle impact conditions.The experimental results show that compared with the initial design,the optimized vehicle pedestrian lower extremity protection performance is significantly improved,and the algorithm also provides a reference for other similar engineering design problems.(2)Discrete robust optimal design method based on multi-attribute decision making and its application.In order to consider the fluctuation of design variables in engineering and improve the robustness of design,a general algorithm flow of multi-objective discrete optimization design based on multi-attribute decision-making is developed in this paper.The algorithm combines Taguchi design,attribute weight calculation methods(AHP,PCA)and scheme ranking methods(TOPSIS-relative entropy,GRA).Among them,Taguchi design is used as an optimizer to execut e the program iteration process,and the necessary function evaluation is called directly in the design iteration process.The attribute weight coefficient calculated by AHP and PCA method is combined with TOPSIS-relative entropy and GRA scheme ranking method to convert multi-attribute objectives into a single measurement index for ranking.The method is applied to the structural design of the front end of the vehicle under TRLPLI to vehicle impact conditions,Flex PLI to vehicle impact conditions,head form to vehicle impact conditions respectively.The results show that the method can not only meet the design objectives,but also improve the robustness of the optimal solution in the analysis of the above cases.(3)Discrete fuzzy optimal design method based on multi-attribute decision making and its application.In order to solve the problem of fuzzy uncertainty in engineering design,a discrete fuzzy optimization design method based on multi-attribute decision-making is proposed in this paper.The method in tegrates TOPSIS ranking method and fuzzy method,and uses continuous orthogonal experiment as optimizer to deal with multi-variable and multi-level problems.The algorithm is applied to Flex PLI-UBM to vehicle impact conditions.The optimization results sho w that the knee ligament and femur bending moment of Flex PLI-UBMc are significantly reduced.At the same time,the engineering development strategies that are conducive to reducing pedestrian lower extremity injury are obtained,that is,increasing the thickness of the support beam at the bottom of the bumper,reducing the density of energy absorbing foam,increasing the thickness of the radiator grille mounting plate and weakening the front edge of the hood,which provide a reference for solving similar high-dimensional fuzzy engineering design problems.(4)Development and verification of injury protection device for VRU.In order to reduce the impact on other attributes and further improve the vehicle VRU protection performance,this paper systematically developed the VRU injury protection device from three aspects: module design,module simulation and module verification,including the pop-up hood device,pedestrian protection airbag device and front bumper airbag device.The subsystem verification results show that the performance of VRU head and lower extremity has been significantly improved.Aiming at the bottleneck of verification technology in real traffic scenarios,the pedestrian to vehicle impact verification platform and two wheeled bicycle to vehicle impact verification platform are designed and built,and the test accuracy is better than the highest accuracy requirements of vehicle collision related laws and regulations.Based on this verification platform,we carried out standing pedestrian to vehicle impact test and two wheeled bicycle to vehicle impact test.After the vehicle collision,we obtained VRU motion response and head injury indicators,and systematically verified the effectiveness of the injury protection device for VRU. |
