# Collaborative Robotics: Enhance Maintenance Procedures on Primary Flight Control Servo-Actuators
## 2 Experimental Setup  
The experimental campaign has been held in the hydraulic laboratory of the Lufthansa Technik Components Innovation department. The HyDiag entry and exit tests, the robot feature extraction sequence, and the adjustments have been performed using the setup reported in Figure 2a, whose main subsystems are schematized in Figure 2b. Figure 2: (a) Test bench used for testing new maintenance procedures on EHSAs using a UR10 collaborative robot; (b) Schematic overview of the setup adopted during the experimental campaign. The unit under test has been mounted on a fixture inside the hydraulic bench, while the UR10 collaborative robot is on a movable work cart outside of it. Besides allowing a fast and straightforward setup, it simulates the working environment of the current production line. Moreover, by using a reconfigurable work cart, it has been possible to efficiently evaluate several robot positions with respect to the test bench. Due to the toxicity and corrosive properties of the oil used by servo-actuators and the high pressures involved in the maintenance process, the entire task requires mitigating the hazards for the operator. A protective plexiglass bulkhead, positioned around the work cart, allows for meeting all the safety requirements and a proper movement of the robot. This configuration, according to [18], would be labelled as \"coexistence\" of the industrial manipulator and the human operator rather than a real collaboration. However, the use of a cobot is mainly justified to assure the technician's safety, during his interaction with it, in the test campaign. Since safety is of primary importance in human-robot applications [19], in addition to the safety measures provided by Universal Robots, two protection devices have been implemented:  
* Safeguard stop: additional button located on the work cart and wired to the UR10 control unit. It is used to pause the robot program without activating the joints brakes as for the emergency stop button. Once released, the robot returns to perform the task from where it was stopped;
* Signal light: a signal tower with LEDs lights of different colours is used to inform the operator about the current status of the robot program: normal operating condition, paused, or anomaly detected. In addition to the safety features, the choice of a collaborative robot has been mainly driven by its high flexibility. These machines can share their workspace with the human operator without protective cages or fences. This, together with a compact and lightweight design, allowed for positioning the robot on a movable work cart, which can be easily reconfigured according to specific needs, resulting in low setup costs. The possibility to quickly change its mounting configuration, together with joints ranges of \(\pm 360^{\circ}\), and an intuitive programming language, also allowed adapting the UR10 to repair and test different types of servo-actuators, making it the right manipulator for rapid feasibility studies. Figure 3 reports, as an example, the different components of a servo-actuator object of regulation and adjustments. To do so, the UR10 has been equipped with wrenches and screwdrivers, stored in a warehouse on the work cart. Their modular design allows the robot to autonomously handle the tool change, leading to a fully automized test procedure. Figure 3: (**a**) Focus on the main components of a servo-actuator to be adjusted by the UR10 collaborative robot; (**b**) Tool mounted on UR10 tool flange consisting of a 2D camera, a force-torque sensor, and a customized wrench built via additive manufacturing. Nevertheless, since each unit requires different adjustments, additive manufacturing has been adopted to build customized tools. Fused Deposition Modeling (FDM) has been used to produce the camera, tool holders, and the tool head reported in Figure 2(b), while the adapters, which directly interact with the EHSA, have been purchased in metal.