Sliding Mode Propulsion Control Tests on a Motion Flight Simulator

This paper describes a fault-tolerant sliding-mode control allocation scheme capable of coping with the loss of all control surfaces resulting from a failure of the hydraulics system, during which time the scheme only uses the engines to control the aircraft. The paper presents tests of the scheme implemented on a six-degree-of-freedom motion research flight simulator at Delft University of Technology, using a realistic maneuver involving an emergency return to a near-landing condition on a runway in response to the failure. The simulator results show that not only does the controller provide high tracking performance during nominal fault-free conditions, this performance is also maintained after the total loss of all control surfaces. This shows the capability of the proposed sliding-mode control allocation scheme to achieve and maintain desired performance levels using only propulsion by redistributing the control signals to the engines when failures occur

Evaluation of a sliding mode fault-tolerant controller for the El Al incident

This paper presents piloted flight simulator results associated with the El Al flight 1862 scenario, using a modelreferencebased sliding mode control allocation scheme for fault-tolerant control. The proposed controller design was carried out without any knowledge of the type of failure and in the absence of any fault detection and isolation strategy. This is motivated by the fact that the flight crew were unaware of the losses of the right engines. For this reason, the control allocation scheme proposed uses (fixed) equal distribution of the control signals to all actuators (for both nominal situations and when a fault or failure occurs). This paper analyzes the scheme and determines the conditions under which closed-loop stability is retained. The results represent the successful realtime implementation of the proposed controller on a flight simulator, configured to represent a B747 aircraft. The evaluation results from the experienced pilots show that the proposed controller has the ability to position the aircraft for landing, both in a nominal scenario and in the El Al failure scenario. It is also shown that actuator faults and failures that occurred during the El Al incident can be handled directly without reconfiguring the controller

Fault tolerant sliding mode control design with piloted simulator evaluation

Copyright © 2008 American Institute of Aeronautics and AstronauticsThis paper considers sliding mode allocation schemes for fault tolerant control. The schemes allow redistribution of the control signals to the remaining functioning actuators when a fault or failure occurs. The paper analyzes the schemes and determines conditions under which closed–loop stability is retained for a certain class of faults and failures. It is shown that faults and even certain total actuator failures can be handled directly without reconfiguring the controller. The results obtained from implementing the controllers on the SIMONA research flight simulator, configured to represent a B747 aircraft, show good performance in both nominal and failure scenarios even in wind and gust conditions

Real-time implementation of an ISM Fault Tolerant Control scheme for LPV plants

Copyright © 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper proposes a fault tolerant control scheme for linear parameter varying systems based on integral sliding modes and control allocation, and describes the implementation and evaluation of the controllers on a 6 degree-of-freedom research flight simulator called SIMONA. The fault tolerant control scheme is developed using a linear parameter varying approach to extend ideas previously developed for linear time invariant systems, in order to cover a wide range of operating conditions. The scheme benefits from the combination of the inherent robustness properties of integral sliding modes (to ensure sliding occurs throughout the simulation) and control allocation, which has the ability to redistribute control signals to all available actuators in the event of faults/failures

Investigation of the Effects of Autorotative Flare Index Variation on Helicopter Flight Dynamics in Autorotation

Autorotation is a flight condition whereby the engine of a helicopter is no longer supplying power to the main rotor system, which is driven solely by the upward flow of the air moving through the rotor. For helicopters, autorotation is a common emergency procedure performed by pilots to safely land the vehicle in the event of a power failure or tail-rotor failure. In the classic analysis of dynamic stability of helicopters in powered flight, it is common practice to neglect the effect of variation of rotor angular velocity, as the rotorspeed is constant. However, this assumption is no longer justified in case of autorotative flight. Therefore, the rotorspeed becomes an additional degree-of-freedom in autorotation, giving rise to a new stability mode that couples with classical rigid-body modes. The present paper aims at understanding the role of the rotorspeed degree-of-freedom in modifying the stability characteristics in autorotation of rotor systems with different autorotative flare indexes. Results show that the helicopter dynamics are considerably affected in autorotation as a consequence of the fact that the rotorspeed degree of freedom couples with the heave subsidence mode. Therefore, autorotation requires a different control strategy by the pilot and should not be mistakenly considered only as an energy management task. Furthermore, the autorotative flare index, used to characterize the autorotative performance during the preliminary design phase of a new helicopter, provides only energy information. Indeed, this paper demonstrates that high values of this index, representative of good autorotative performance in terms of available energy over required energy, may lead to degraded stability characteristics of the helicopter in autorotation.Control & Simulatio

Design and evaluation of a taxi display with integrated data link

Aerospace Engineerin

Simulator Assessment of the Lateral-Directional Handling Qualities of the Flying-V

Flying wings are known for their limited lateral-directional stability and handling qualities. This study aims at assessing the lateral-directional handling qualities of a conceptual flying wing aircraft currently in development at TU Delft, the Flying-V, in a moving-base flight simulator. It focuses on two aspects: First assess the lateral-directional handling qualities of the bare-airframe Flying-V, and the compliance to quantitative requirements. Second, improve these handling qualities through a prototype flight control system, and assess its effect on the handling qualities and the requirement compliance. These assessments were performed both analytically and with a pilot-in-the-loop simulator experiment, in order to experimentally validate analytical findings and obtain new pilot-subjective insights. The analytical and experimental assessment for lowspeed flight conditions both show the lateral-directional handling qualities of the Flying-V to be insufficient for requirement compliance, due to a lack of pitch, roll and yaw control authority and an insufficiently stable Dutch roll eigenmode. The prototype flight control system, consisting of an adapted control allocation and a stability augmentation system, showed both analytically and experimentally to improve the control authority, stability, and handling qualities of the Flying-V. While the effect on the lateral-directional stability was sufficient for stability requirement compliance, the control authority was not sufficiently increased for maneuverability requirement compliance at low speed. Thus, if the landing speed is not increased from the current baseline, a challenge remains to improve the handling qualities of the Flying-V. An approximation of the control authority required for full requirement compliance in the low-speed flight conditions tested showed a control authority increase of over a factor four to be required in that case

Piloted Simulator Evaluation of Low-Speed Handling Qualities of the Flying-V

An improved understanding of pilot’s control behavior adaptations in response to sudden changes in the vehicle dynamics is essential for realizing adaptive support systems that remain effective when task characteristics suddenly change. In this paper, we replicate, extend, and validate the ‘adaptive pilot model’ proposed by Hess to verify its effectiveness for predicting human adaptive behavior in pursuit tracking tasks. The model relies on a Triggering function, that compares the current tracking performance to a stored nominal (pre-transition) state, and an Adaptation mechanism which determines new adapted human operator gain settings proportional to the magnitude of the off-nominal error occurrences. For model validation data from a previous experiment were used, where ten participants performed a pursuit tracking task with transitions in controlled element dynamics from a single to a double integrator, and vice versa. Overall, with an added human operator delay and participant-specific inner- and outer-loop gain adjustments, the model was found to accurately describe the measured steady-state tracking behavior for the participants in our data set. The results for the time-varying single integrator to double integrator transitions showed that the model can capture the transient control behavior of participants. However, the adaptive logic could only be tuned to activate for participants that had a pre-transition crossover frequency above 0.9 rad/s. Furthermore, the model was not able to capture the change in control behavior for transitions from a double to a single integrator. Here, as no distinct degradation in tracking performance occurs for such a transition to a more easily controlled system, the model's proposed Triggering logic will not activate. Further investigation and more experiment data are required for improving the applicability of the model's adaptive logic and to enable more accurate prediction of adaptive human control behavior

Simulator Evaluation of Flightpath-oriented Control Allocation for the Flying-V

A novel aircraft configuration, the tailless Flying-V, is examined for its longitudinal handling qualities in cruise by means of piloted simulations. The Flying-V is controlled by two aileron/elevator (elevon) surfaces on each side, and rudders on each wingtip. Two control allocation schemes were created: a conventional one where both inboard and outboard elevons deflect in the same direction, and one where the change in lift the elevons generate is countered by deploying the inboard and outboard elevons in opposite directions, allowing more direct control of the resulting flight path. The longitudinal handling qualities in cruise conditions were investigated by pilot opinion in a moving base simulator. Three experiments were conducted: a traditional pitch tracking experiment with the conventional control allocation, and a new flight-path-angle tracking experiment, using both the conventional and the flight-path-oriented control allocation. The pilots indicated the conventional pitch attitude control to have Level 1 handling qualities for the pitch control task, and Level 2 for the flight path control task. The flight-path-oriented control allocation improved the performance of the pilots during the flight-part tracking experiment, but the perceived control authority was considered too small for most pilots to consistently rate it at Level 1