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Incremental Nonlinear flight Control supplemented with Envelope ProtecTION techniques

Periodic Reporting for period 2 - INCEPTION (Incremental Nonlinear flight Control supplemented with Envelope ProtecTION techniques)

Reporting period: 2018-12-01 to 2020-11-30

Traditionally, and even today, aircraft (both manned and unmanned) control systems have been built upon the idea of using the model information available by the system’s dynamic behavior in order to select adequate navigation, stabilization, and control strategies. These solutions are most commonly found to be based on linear control theory, which provides the control system engineer with several different analysis tools. As most dynamic systems are nonlinear by nature, classical control solutions only guarantee the desired performance in a finite set of conditions around which the real system behaves (almost) linearly. Project INCEPTION has developed a robust FCS, capable of safe, steady and efficient aircraft control even in the presence of unprecedented actuator failures or configuration changes. It proposes to do so by a control system that is not only more robust but also more efficient than the most common strategies currently in use and by complementing it with model-adaptive and flight envelope prediction capabilities.

INCEPTION combines adaptive control schemes with incremental approaches to enable a novel class of control systems, which are independent of the considered aerial platform and can be transferred with minor modifications to various flying vehicles. By incorporating the general physical knowledge about flight system dynamics (type of the aircraft, available controls, flight envelope) together with INCEPTION’s modular control laws, the basis for platform-independent autopilot design will be therefore provided.
"INCEPTION has developed a system based on incremental dynamic modelling complemented with model-adaptive and flight envelope protection and prediction capabilities.

Baseline Controller
The new automatic flight controller developed by IST applies the Incremental Backstepping strategy for tracking the attitude of a fixed-wing aircraft. The application of the controller into two different aircraft simulators, the BOEING 747 and the TEKEVER ARS, highlighted the main advantages of the INCEPTION control strategy, including:
Reduced knowledge on the aircraft model in control synthesis.
Versatile structure, easily adaptable for different aircraft.
Increased robustness to changes in the flight condition, requiring a reduced or no scheduling strategy.
Increased safety in the case of actuation failure.

Adaptive Control
Two-Layer Adaptive augmentation for Incremental Backstepping Flight Control, which was capable to tackle possible actuator failures, was proposed and validated using simulation models of two aircraft platforms, the BOEING 747 and the TEKEVER AR5.
The first layer is responsible for detection of the possible anomalies in aircraft behaviour.
In case of an anomaly detection, the algorithm initiates the second-layer estimation determining the individual control effectiveness and provides updated information about the effectiveness matrix to the baseline controller.
The approach improves stability and tracking performance characteristics in case of actuator failure or control effectiveness uncertainty.
Such two-layer structure requires less excitation of the system, increases comfort and tracking performance.

Envelope Protections
Development of a new flight envelope protection concept ""Output Limiting with Backstepping in the Phase Plane"" which was demonstrated as a control limiting, command limiting and virtual control limiting scheme.
Development of a physical reference model which provides the reference dynamics for the control schemes investigated in INCEPTION, allowing the decoupling of the controller design and design of the handling qualities.
Relevant parts of the design was verified in a piloted simulator campaign in a Level 6 flight simulator, in flight test of a small UAV and in extensive simulation testing with both a 747 and TEKEVER AR5 UAV.

Inertial Measurement Unit
Typically, large aircraft flight controls require fiber optical gyroscopes (FOG) (to sense angular rates), and quartz servo technology (to sense accelerations), which are either heavy or expensive. MSS developed a MEMS-based IMU that satisfies the requirements of large UAVs (>150 kg) and sensor-based flight control.

Field Tests
Upon delivery of all modules and successful integration process, the controller has gone through exhaustive Software & Hardware testing and was flown in TEKEVER prototype aircraft."
Enhancement of competitiveness of European aviation market:
In short, INCEPTION aimed at developing and demonstrating the applicability of a self-reconfigurable flight control system that can autonomously reallocate control resources under unconventional and unforeseen failure scenarios. Results have shown that this original control strategy is technically sound. The approaches proposed in INCEPTION contribute to creation of basis for future flight control, which is totally in line with assumptions presented in “Flightpath 2050 Europe´s Vision for Aviation – Report of High Level Group on Aviation Research”. The feasibility study evaluated the potential for certification of this solution.

Improve Innovation Capacity:
All participants benefitted strongly from the collaboration within the project. Industrial partner evaluated the constraints of a new product. Academic partners that led the fundamental technology and theoretical development achieved fantastic results in delivery of this new concept through collaboration and joint effort, which may result in long-term cooperation in the future. Project outcomes will be used in lectures, new know&how will be applied in new research activities & industry cooperation projects, and finally, all best practices and experience will be shared in graduate courses and seminars. Testing and exploitation role that was given to the SME generated considerable know-how in advanced flight control methodologies and resulted in improvement of internal FCS testing processes and possible integration of new functionalities into the product lines. That in long-term will lead to more sophisticated products with higher quality specifications and increased market share. The INCEPTION consortium showed to be excellent team of industrial and academic partners contributing with research output and publications under European funding that meet the needs of the future European and global markets.

Enhance the safety of civil aviation:
Classical control solutions only guarantee the desired performance in a finite set of conditions around which the real system behaves (almost) linearly. However, most dynamic systems are nonlinear by nature. INCEPTION aimed at developing and demonstrating the applicability of a self-reconfigurable flight control system that can autonomously reallocate control resources under unconventional and unforeseen failure scenarios. At this stage of research, INCEPTION targeted cruise phase of flight and has shown the good performance in simulations and promising results in testing in flight. The project identified multiple occurrences from the past, where INCEPTION-like controller might have made a difference to the sequence of events that took place.
Project Picture illustrating artist's vision of the INCEPTION controller.