2.3.3. Validation by dVRK

The proposed prototype has been tested on the dVRK system. The experimental protocol followed for the tasks performed with the aid of the dVRK system, and the various phases, tools, and objects used are presented below. As shown in Figure 10, an MTM from the dVRK console was used to teleoperate the instrument mounted on the PSM. The activities were carried out by three users with the support of the visual feedback of the dVRK endoscope, designed with two separate optical channels capable of recreating the most important aspect of stereopsis: binocular disparity. Inside the viewer, therefore, users followed the operations thanks to the stereoscopic vision that provided three-dimensional images of the work area [16].

**Figure 10.** Functionality demonstration. MTM from the dVRK console was used to teleoperate the instrument mounted on the PSM.

The Arduino board with the integrated proximity sensor was positioned, using the support made by a 3D printer, on the EndoWrist instrument two centimeters from the tip of the tool, as shown in Figure 11. The positioning of the board at this distance from the tip of the instrument was in line with the results obtained during the sensor calibration phase; from the characterization curve, it is possible to see that the operating area of the liver sensor occurred after two centimeters, a distance at which the sensor returned the first non-null value.

Users were asked to perform a simple transfer task; a suitably sized ball was picked up from the worktable with the ProGaspr tool supplied with the dVRK, and it was brought within eight centimeters of the liver simulation object. The sequence of images below shows the steps just mentioned in performing the task (Figure 12). Finally, the user placed the ball on the object by approaching it slowly (Figure 13). During the execution of the operations, the user was able to estimate the distance of the instrument from the object based on what could be perceived by the viewer. During the entire execution phase of the task, the proximity values read by the sensor were recorded and compared with the values visually estimated by the users.

**Figure 11.** Positioning of the sensing device prototype on the PSM tool of the dVRK system.

**Figure 12.** Three frames concerning the phases of the performed transfer task, taking the ball from the workspace and positioning it about 8 cm from the tissue.

**Figure 13.** Positioning of the ball on the object placed on the work surface.
