## 3 Experimental Results  
The system has been validated in an indoor testbed using a mock-up as shown in Figure 8. The mock-up is a 2 m long cable suspended at 1 m above the ground. Four positions are defined, namely WP#, and prerecorded using an Opti-Track motion capture system:  
* WP1 is defined at a 6.5 m distance from the insertion point on the cable and a 2.5 m height. * WP2 is defined above the insertion point at a 2 m height (1 m above the cable). * WP3 is defined above the insertion point at a 1.3 m height (30 cm above the cable). * WP4 is defined as the insertion point on the cable. Figure 7: (**a**) Automatic installation process. The aerial robot carries the installation tool with a pre-charged diverter and approaches the power line cable. (**b**) The cable is centered in the tool while the aerial robot descends. (**c**) When the cable is in place, the linear actuator closes the clamps and pushes the diverter on the cable. (**d**) Finally, the linear actuator retracts, detaching the diverter and opening the clamps before flying out. The Opti-Track is an ultra-precise camera tracking system for providing visual feedback to the controller. The current testbed dimension is \(20\times 15\times 7\) m with high accuracy (1 mm) including 28 cameras. The high data rate translation and orientation feedback are read by the drone's controller and facilitate the semi-autonomous operation. The multi-copter autopilot controls the position using the feedback provided by the Opti-Track system. The experiments, shown in the video provided as Supplementary Material, consisted of the following phases:  
1. The pilot sends a \"Goto WP1\" command to the aerial robot, and it takes off to WP1. 2. After reaching WP1, the pilot sends a \"Goto WP2\" command, so the robot moves toward the cable, and the pilot waits until it is stabilized in that position. 3. Then, the pilot sends consecutive \"Goto WP3\" and \"Goto WP4\" commands, and the aerial robot slowly descends to the insertion point (WP4). In this position, the cable is centered in the tool and inside the clamps. 4. After WP4 has been reached, the pilot triggers the installation command, and the diverter installation tool starts its operation, automatically closing the clamps and inserting the clip on the cable. 5. When the pilot visually confirms that the bird diverter has been deployed, he/she sends a fly-up command to the aerial robot, which is finally landed. The trajectory performed during one of the trials is shown in Figures 9-14. The Cartesian coordinates are shown in Figures 9-11, and the orientation variables are plotted in Figures 12-14. The 3D trajectory of the system is also presented in Figure 15. The oscillations in the \(y\)-axis seem bigger than the other \(x\) and \(z\) axes; however, they are in  
Figure 8: (**a**) Experimental setup for validation. The aerial robot takes off to WP1. (**b**) Then, it stabilizes on WP2, 1 m above the cable. (**c**) The robot slowly descends to WP3, 30 cm above the insertion point, and (**d**) it finally reaches WP4, the insertion point. the same order. Since the motion in the \(y\)-axis is almost zero, the oscillation seems bigger than the other two. The UAV takes off and goes to WP1 from \(t=0\) s to \(t=14\) s. Then, it navigates to WP2, which is reached at \(t=27\) s. As shown in Figure 14, during this time slot, the yaw is changed to align the UAV with the cable. The pilot sends the \"Goto WP3\" command at \(t=27\) s and the \"Goto WP4\" command at \(t=33\) s. The insertion operation is then triggered at \(t=37\) s. After installing the bird diverter, the UAV flies away at \(t=40\) s.  
The yaw control would need more fine-tuning (Figure 14); however, it was intended to demonstrate that the system works even with misalignment between the tool and the power line. This has been experimentally evaluated; theoretically, the tool design (clamps and cable guide size) and the pivot joint should allow a maximum 8 cm lateral error (if it is perfectly aligned) or a maximum 20 degree misalignment (if the lateral error is zero).