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Page 8 of 15                     Cui et al. Complex Eng Syst 2023;3:3  I http://dx.doi.org/10.20517/ces.2022.57


               where

                                                             2                        2
                                                         ¤
                                                                                  ¤
                                       =               −                    −            +                  
                              
                                           2                         2
                                    8(            2)         8(            1)

                                      1 =     [   +          −       ]
                              
                              
                                      2 =     [   −          −       ]
                              
               The first subsystem named as energy loss is given by
                                                      
                                     
                                     
                                                       2
                                                                    2
                                                0             0
                                     
                                         1 = 1 −    /       + 1 −    /     
                                                   
                                                                
                                     
                                                                  2
                                                                             2
                                                 0 2       0            0
                                          + 1 −       /       + 1 −    /       + (1 −    /  )          (15)
                                                               
                                                               
                                                  
                                                                       :
                                     
                                     
                                                 0
                                           3 ≤    ≤ 5
                                                  
                                     
                                     
                                     
                                                  0
                                                           0
                                                     0
                                                        0
                                                              0
                                               ≤       ,    ,    ,    ,    ,    0
                                                                     ≤      
                                     
               The second subsystem named as road feel is given by
                                                     
                                    
                                    
                                                      2
                                    
                                                                  2
                                                00           00
                                        2 = 1 −    /       + 1 −    /     
                                                   
                                                               
                                    
                                                    2
                                                                               2
                                              00             00 2       00
                                         + 1 −    /       + 1 −       /       + 1 −    /               (16)
                                                                            
                                                  
                                                              
                                                 
                                                                      :
                                    
                                    
                                                00
                                           3 ≤    ≤ 5
                                                 
                                    
                                    
                                    
                                                        00
                                                 00
                                                    00
                                                           00
                                              ≤       ,    ,    ,    ,    00
                                                                    ≤      
                                    
               The third subsystem named as steering sensibility is given by
                                                    
                                   
                                   
                                                     2
                                                                   2            2
                                   
                                              000           000           000
                                       3 = 1 −    /       + 1 −    /       + 1 −    /     
                                                                             
                                                 
                                                               
                                   
                                   
                                                                 2
                                                    2                        2
                                            000           000          000
                                        + 1 −    /       + 1 −    /       + (1 −    /  )               (17)
                                                
                                                              
                                                             
                                                
                                                                     :
                                   
                                   
                                            3 ≤    000  ≤ 5
                                                  
                                   
                                   
                                   
                                                           000
                                             ≤       ,    ,    ,    ,    ,    000
                                                              000
                                                000
                                                   000
                                                       000
                                                                    ≤      
                                   
               According to the above models, the multi-objective collaborative optimization model of EHPS is showed in
               Figure 3.
               3.2. Multi-objective optimization algorithm
               The NSGA-II algorithm has excellent global search performance and is often used in multi-objective optimiza-
               tion. Ontheonehand, theNSGA-IIintroducesanelitestrategyintheprocessofranking, whichavoidstheloss
               of non-dominated individuals in the evolution process and speeds up the convergence speed of the algorithm.
               On the other hand, the NSGA-II improves the crowded-comparison approach, which ensures the diversity of
               the next generation and enhances the global exploratory capability of the algorithm.
               The main steps of NSGA-II algorithm can be depicted as follows.
               (1) Generate the initial population    0 at random and the size of    0 is   ;
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