The project EMA is funded under the national funded aerospace research program V (LufoV-1) for a period from January 2014 to March 2017.
In the future, functions of civil aircraft currently realized by hydraulic and pneumatic systems will be provided by electrical systems. This evolution shall increase efficiency as well as maintainability of future aircraft. The implementation of electromechanical actuators in primary and secondary flight control systems is in the main focus of the recent developments. One of the major challenges is to cope with increased complexity of electromechanical actuators compared to their hydraulic counterparts. Already indicated by the increased number of parts, the design of electromechanical actuators inherits the possibility to jam and thus negatively affects the reliability. Sophisticated monitoring systems are a promising approach to mitigate the risk of critical failures. Further, certification rules demanding at least two actuators are attached to one control surface to provide load path redundancy. This requirement can be easily fulfilled by hydraulic actuators by simply bypassing the hydraulic chambers of one actuator, which turns the bypassed actuator in a damper. Electromechanical actuators do not provide such an easy solution for their parallel operation. Contrary to hydraulic actuators, electromechanical ones have to be both operated in an active mode. In this configuration a phenomenon called force fight occurs, characterized by a circulating additional force carried by both actuators but in contrary direction. Force fight is the result of even small parameter differences and misalignments of the sensors of the two actuators. This additional force has no real effect in terms of accelerating the control surface or of bearing aerodynamic loads, but has to be carried by the actuators and the structure and thus decreases systems lifetime and efficiency. The control system must minimize this force fight whilst maintaining stability and good performance, but also has to reduce peak loads into the structure and shall not negatively affect the actuators lifetime.
Based on the results of completed and ongoing national and European projects, actuator and electronic technologies for electro-mechanical actuators (EMA ) of the primary flight controls (ailerons and spoilers) are developed and tested at the system level in this joint project. Objectives of the consortium are to develop the technologies and to prepare them for flight experiments. The following partners are involved in the joint project:
DLR contributes to this consortium with the organization Flight Experiments (DLR-FX), the Institute for System Dynamics and Control (DLR-SR) and the Institute of Flight Systems (DLR -FT). The DLR work share for the joint project EMA includes the development and testing of new technologies and concepts for monitoring and control of parallel-redundant electromechanical actuators for flight control of commercial aircraft. In addition, the path for the planned flight test is prepared.
For the validation of the new concepts, an existing actuator test rig for flight control systems will be adapted to the needs for tests of the specific actuators in cooperation with the company Liebherr Aerospace Lindenberg. Work is supported by the Design Organisation of DLR (DLR-FX) to take into account the policies and processes for a planned flight test up from the beginning to. In addition, possible options and necessary provisions for the integration of the actuation system in the experimental aircraft ATRA of DLR with the goal of a technology flight demonstration will be evaluated.
The focus of the scientific work of DLR is the development of control and failure detection strategies for EMA technologies with a special focus on the redundant operation of the actuators. Here the force fight compensation is especially critical in an active-active configuration of the actuators. New monitoring, control and condition monitoring concepts for EMA in active-active configuration are developed and their applicability demonstrated by means of test with the use case of a representative EMA for aileron control of a generic single aisle aircraft (e.g. Boeing 737, Airbus A320). Existing actuator control, error detection and concepts for reconfiguration from current technology projects (eg EU Actuation 2015, RECONFIGURE) are enhanced and adapted for use in an active-active actuator configuration. DLR’s research goals are the development of certifiable control and monitoring algorithms and their demonstration in a flight test campaign. To achieve this, exhaustive testing at system test rigs of the control and monitoring system and the real hardware will be conducted during the project to demonstrate the maturity of the system. A special test rig will be designed and built by DLR for this purpose.
The Institute of Flight Systems, Department of Safety Critical Systems and Systems Engineering, leads the work share of DLR in the joint project. The contributions of the Institute include in following topics:
The work of the Institute is based on the findings of past and current projects in the area of monitoring, control and condition monitoring of electromechanical actuators, including the projects