The filters discussed here are tested during a short walk with a positive obstacle at the end. The signal of the infrared sensor that intercepts a positive obstacle is plotted in Fig. 12 in which we show the features of the three filters implemented. As it is possible to note there are no substantial differences between them. For all of the filters, a reduction of the smoothing degree gives an increment of the error band, vice versa, an increment of the smoothing degree gives unacceptable time delays. To remain the limit of 1 s delay we obtained an error band of roughly 20 cm. The error band gives the threshold under which no signal is sent to the vibrating motor and the half part of it represents the numeric value of the parameter e defined in Section 2.4. From this simple test we can notice that all the low-pass filters have the same results in terms of error band and reactivity with the presence of obstacle. The filter that we choose for our devise is the simple moving average. This chose is due only for simplicity of implementation and of calibration of the moving average.