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     Wu. Intell Robot 2021;1(2):99-115  I http://dx.doi.org/10.20517/ir.2021.11          Page 111
                       1                                        1.5
                                                   without payload                           without payload
                      0.8                          with payload                              with payload
                                                                 1
                      0.6
                      0.4
                                                                0.5
                      0.2
                    x [mm]  0                                 y [mm]  0
                     −0.2
                                                               −0.5
                     −0.4
                     −0.6
                                                                −1
                     −0.8
                      −1                                       −1.5
                       0      0.1    0.2    0.3    0.4    0.5    0      0.1    0.2    0.3    0.4    0.5
                                        time [s]                                  time [s]
                                      (a)                                       (b)
                      0.5                                        1
                                                   without payload                           without payload
                      0.4                          with payload  0.8                         with payload
                      0.3                                       0.6
                      0.2                                       0.4
                      0.1                                       0.2
                     z [mm]  0                                φ x  [deg]  0
                     −0.1                                       −0.2
                     −0.2                                       −0.4
                     −0.3                                       −0.6
                     −0.4                                       −0.8
                     −0.5                                       −1
                       0      0.1    0.2    0.3    0.4     0.5    0     0.1    0.2    0.3    0.4    0.5
                                        time [s]                                  time [s]
                                      (c)                                       (d)
                       2                                         2
                                                   without payload                           without payload
                                                   with payload                              with payload
                      1.5                                       1.5
                       1                                         1
                      0.5                                       0.5
                     φ y  [deg]  0                            φ z  [deg]  0
                      −0.5                                      −0.5
                       −1                                        −1
                      −1.5                                      −1.5
                       −2                                        −2
                        0     0.1    0.2    0.3    0.4    0.5     0     0.1    0.2    0.3    0.4    0.5
                                        time [s]                                  time [s]
                                      (e)                                       (f)
               Figure 8. Displacement responses of the end-effector: (a)    direction; (b)    direction; (c)    direction; (d)       direction; (e)       direction; and
               (f)       direction.
               perimental measurements along previous trajectory, where the experimental data are read from the motor
               encoders. Due to the frictions and time-varying disturbance in the joints, the experimental curve profiles
               have more fluctuations and larger vibration amplitudes than the simulation ones. On the other hand, the com-
               parison shows that the differences between these two curves are small, thus, the built analytical model can be
               acceptable for dynamic analysis of the robots.
     	
