# Collaborative Robotics: Enhance Maintenance Procedures on Primary Flight Control Servo-Actuators
###### Abstract  
Electro-Hydraulic Servo-Actuators (EHSAs) are mainly used to command primary flight control surfaces in military and commercial aircraft. Since these devices are crucial for vehicle stability and maneuverability, a correct assessment of their health status is mandatory. Within this framework, a joint research project (HyDiag), held by Politecnico di Torino and Lufthansa Technik AG (LHT), aims to provide a more efficient and reliable procedure to determine the operating conditions of the EHSA. A smart and automatic sequence, able to extract several health features of the Unit Under Test (UUT), has been developed and integrated. The present paper discusses the implementation of a collaborative robot, equipped with a vision system and customized tools, for both health features extraction, and maintenance tasks on unserviceable servo-actuators. The main challenges related to the automation of such complex tasks in a real working environment are highlighted, togetherwith the advantages brought by the proposed approach. The paper also presents the first results of an ongoing experimental campaign. Specifically, it reports the enhancements of the maintenance procedures using collaborative robotics and possible future developments. collaborative robotics; automatic maintenance; diagnostics; electro-hydraulic servo-actuators; Industry 4.00000-0000-0000-0000-0000-0000-00000-0000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-000000-000000-000000-000000-00  
of maintenance tasks, which require a level of flexibility that makes the coding of the operation itself hard. By focusing the attention on maintenance applications, it is possible to identify two main branches:  
* Ordinary maintenance: it involves routine operations, mainly related to Planned Preventive Maintenance (PPM) procedures, to replace specific components on a machine to prevent a failure;
* Extra-ordinary maintenance: performed after a failure has occurred, when the component is not in a nominal operating condition anymore. Since complex components, such as a flight control servo-actuator, can be affected by several failure modes, it is required to set up an adaptive maintenance procedure. This level of flexibility increases the overall complexity of the application, making it difficult to be entirely handled by a robot. According to [5], when the environmental variability increases, there is a trend to move from autonomous to teleoperated manipulators. This shift in the paradigm of robotics is justified by the requirement of taking advantage of the flexibility, and intelligence of the human operator. This trend is confirmed by several studies [6; 7; 8; 9; 10] in which different types of robots have been successfully used, mainly, for inspection purposes rather than for repairing the damage. This work describes the implementation of a UR10 collaborative robot from Universal Robots. The aim is to optimize extra-ordinary repair procedures on electro-hydraulic servo-actuators. According to [11; 12], an efficient health-assessment methodology would bring benefits to aircraft reliability and availability, and reduce maintenance costs. The aim is achieved by a combination of advanced diagnostics and prognostics algorithms [13; 14]. In addition to the health-assessment software, an industrial manipulator has been adopted to support maintenance procedures [15; 16]. The importance of this research has been analyzed and proved to be profitable by [17], where the amount, and the costs, of Shop Load Events (SLEs) of several servo-actuators, in a period of 15 years, have been examined. The actual maintenance procedures, adopted by LHT and reported in Figure 1a, could be upgraded to a new process schematized in Figure 1b. Electro-hydraulic servo-actuators are not subjected to scheduled maintenance. In case of failure, the unserviceable unit is dismounted from the aircraft and shipped to the test field.