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Ortiz et al. Intell Robot 2021;1(2):131-50  I http://dx.doi.org/10.20517/ir.2021.09     Page 147




                                          8

                                          6                              14
                                                                           15
                                                      27                      16
                                                   31   28
                                                          26
                                          4
                                                   30  23
                                                      5
                                                          25  18
                                         y (m)  2       2   21  19   11  17
                                                      24
                                                        3    20
                                                      4
                                          0    22       1
                                                              7     13    12
                                                      29
                                          -2                   9    10
                                                            6
                                                              8
                                          -4
                                           -5     0      5      10     15      20
                                                            x (m)
                             Figure 13. Results of extended Kalman filter simultaneous localization and mapping with noises.


                                          8

                                          6                              10
                                                                           11
                                                                             12
                                          4          22
                                                   24    21
                                         y (m)  2  23  18  2          13
                                                              15    6
                                                                         7
                                          0            1  20
                                                             16
                                                                      14
                                                                   9
                                               17      19
                                          -2                              8
                                                                   5
                                                            3  4
                                          -4
                                           -5     0      5      10      15     20
                                                            x (m)
                                 Figure 14. Results of sliding mode simultaneous localization and mapping with noise.


               Figure 14 shows the results with SM-SLAM. Under the same bounded noises, SM-SLAM works very well,
               because of the sliding mode technique.


               To compare the errors, we define the average of the Euclidean errors as



                                                                                 
                                                 q
                                         1  Õ                            1  Õ
                                                                ∗ 2
                                                      ∗ 2
                                         =      (      −    ) + (      −    ) ,       =          −    ∗    (46)
                                                                  
                                                        
                                                                                       
                                                                              
                                             =1                               =1
               where       is the data number;    ,    , and    are real values for robot position and orientation; and       ,       , and
                                         ∗
                                            ∗
                                                   ∗
                                                     
                     are estimations of them. Figure 15 shows the errors of EKF-SLAM and sliding mode SLAM. Obviously,
               the errors of EKF-SLAM increase quickly. Robots have better estimation in long distances with sliding mode
               SLAM.
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