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Chen et al. Intell Robot 2023;3:420-35  https://dx.doi.org/10.20517/ir.2023.24         Page 430

               Table 2. Comparison before and after the reduction
                                       Before         Layer reduction         Channel reduction
                Accuracy (mAP)         0.81           0.75                    0.73
                Parameters             61,523,734     1,424,654               963,752
                Inference time (s)     0.014          0.0092                  0.0057


               Table 3. Accuracy of distance measurement
                                       0.5 m       1 m         1.5 m       2 m        3 m       4 m
                1                      0.54 m      0.95 m      1.43 m      2.00 m     2.86 m    4.00 m
                2                      0.53 m      1.06 m      1.43 m      1.82 m     2.86 m    4.00 m
                3                      0.47 m      0.95 m      1.54 m      1.82 m     3.07 m    4.44 m
                4                      0.57 m      1.06 m      1.43 m      2.00 m     3.07 m    3.64 m
                5                      0.57 m      0.91 m      1.54 m      2.00 m     2.86 m    4.00 m
                Average error          0.048 m     0.062 m     0.058 m     0.072 m    0.11 m    0.16 m
                Standard deviation     0.04        0.07        0.06        0.10       0.12      0.28



























                                           Figure 11. An example image from the COCO dataset.















                      Figure 12. mAP and loss results of initial training. (A) mAP results of initial training; (B) Loss results of initial training.

               The results show that within 2 m, the average error is small; however, as the distance increases, the
               measurement error increases. This is due to the characteristics of the stereo camera, which has a smaller
               parallax for objects at greater distances, resulting in a lower resolution. Another factor is that the baseline
               was set as 10 cm to account for the convenience of carrying the camera.
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