A bottom rail for a vehicle trailer. According to the invention, two insulated metal electrodes assembled as a cylinder are inserted into the root canal until electric contact with the fragment to be extracted. Then, an image is obtained by the imaging system placed in defocus conditions. A method 90, 200 of control of the system provides interventions 203, 204, 205, 206 at different levels 92, 94, 96, 98 of control, ranging from mass flows 35 to work of a compressor 50, heat from a heater 70, and a predictive processing 215 of feedback 217 for controlling commands 216 algorithmically. Moreover, candidate pixels to be averaged with the pixel to be filtered is selected from the pixels of the selected mask to better maintain the details of the image, and a weight is applied to improve the calculation speed of the averaging operation.