288 research outputs found
Aerobatic maneuvering of Autonomous Hybrid UAVs: Trajectory Tracking using INDI in the Control Frame
No full textUnmanned Aerial Vehicles (UAVs) are increasingly being used in various applications, which demand longer endurance, extended range, and high maneuverability. These requirements necessitate the development of effective control methods for Hybrid UAVs. In this paper, we propose an outer loop Incremental Nonlinear Dynamic Inversion (INDI) controller for Hybrid UAVs, based on an analytically derived control effectiveness to control the linear acceleration of the UAV. The control effectiveness is derived in a new frame that does not show singularities, technically allowing controlled flight at all attitudes. For trajectory tracking purposes, a Proportional Derivative (PD) controller is added. In simulation the proposed controller shows comparable results to already existing INDI controllers for hover and forward flight. When performing loop the loops it is shown that the proposed control system is able to handle high roll angles, while the already existing INDI controller crashed.Aerospace Engineerin
Hybrid UAV Attitude Control using INDI and Dynamic Tilt-Twist
No full textThe application of Unmanned Aerial Vehicles (UAVs) is increasing, much like the performance of these aircraft. A tailsitter is a type of UAV which is capable of performing vertical take-offs and landings (VTOL) and long endurance flights. During hover, the yaw control is limited due to the dynamics of these tailsitters. The generally used quaternion feedback for the attitude does not compensate for this as it describes a singular rotation. Tilt-twist is a solution to the problem as it splits the tilt (pitch and roll) from the twist (yaw). The axis of the yaw rotation is body fixed. When hovering with a pitch and/or roll angle the twist axis will be aligned with the body z-axis, instead of the desired gravitational force vector (for position control). Previous tilt-twist methods used a PID controller. This paper describes an improvement over previous tilt-twist approaches, the dynamic tilt-twist in combination with INDI. The INDI controller is designed for nonlinear systems. The dynamic tilt-twist compensates for the problem with the normal tilt-twist as test results will demonstrate. Tests are performed in a simulation and a real life test with the NederDrone hybrid tailsitter is done.Aerospace Engineerin
Hybrid UAV Attitude Control using INDI and Dynamic Tilt-Twist
No full textThe increased search for the performance of Unmanned Aerial Vehicles (UAVs) has led to an interest in hybrid concepts like the tail-sitter UAV. A tail-sitter UAV is capable of combining vertical take-offs and landings (VTOL) with efficient long-endurance forward flights. During hover, the wings do not provide lift but instead act as disturbance and limit the yaw response. Attitude control based on direct quaternion feedback does not take the differences in reaction speed for the three axes into account. Tilt-twist control has been proposed to overcome this problem as it splits the faster tilt (pitch and roll) from the slower and less important twist (yaw) and is successfully applied to quadrotor control. This paper proposes a novel tilt-twist controller based on Incremental Nonlinear Dynamic Inversion (INDI). But in tail-sitter UAVs, the lift vector can differ a lot from the tilt angle, especially when partly or fully transitioned to forward flight. To address this, a dynamic tilt-twist controller is proposed that redefines the twist according to the transition angle. Simulations and test flight tests are performed with the Neder- Drone hybrid tail-sitter to show the increased performance.Control & Simulatio
Improving the Performance of INDI Flight Control for a Quadrotor in the Ceiling Effect
No full textAs the application areas of Unmanned Aerial Vehicles (UAVs) keep expanding, new flight areas are encountered more often. Small UAVs, named Micro Air Vehicles (MAVs), even fly in areas like sewage pipes. These areas introduce new difficulties such as aerodynamic effects caused by the ground and/or ceiling. In this paper two main contributions are presented that deal with the aerodynamic effects caused by the ceiling: 1) an adaptive model describing the ceiling effect using onboard measurements, which can be altered to describe other aerodynamic effects that occur when flying in constrained spaces, 2) incorporating the adaptive model into an Incremental Nonlinear Dynamic Inversion (INDI) controller. The controller is implemented and tested onto a MAV (Crazyflie). The results have shown stability improvements for close ceiling flight. Moreover the minimal distance the MAV can fly from the ceiling is decreased using the new controller.Aerospace Engineerin
INDI Control for the ObliqueWing-Quad Plane Drone
No full textA type of UAV sharing the advantages of rotorcraft and fixed wing vehicles is the hybrid vehicle. Hybrid UAVs can take-off and land vertically and fly fast and efficient in forward flight due to the presence of a wing generating lift. However, combining the fixed wing and rotorcraft concept ends up in a multi-rotor with large dimensions when landed, and catching a lot of gust when hovering. Therefore, the oblique wing-quad plane drone has been developed which can rotate its quad arm and wing such that the wing can be aligned with the fuselage in hover. The wing can be rotated to fixed wing position during fast forward flight, stowing away one quad-arm. An INDI inner and outer loop controller has been implemented for this platform. Successful flight tests proved the feasibility of this controller and drone concept which is patent pending NL 2031701, Aeronautical Vehicle and Method of Transitioning between Flight Modes for an Aeronautical Vehicle, April 26th 2022,Control & Simulatio
Flight Control Law Design using Hybrid Incremental Nonlinear Dynamic Inversion
No full textIncremental Nonlinear Dynamic Inversion (INDI) is a sensor-based control strategy, which has shown robustness against model uncertainties on various aerospace platforms. The sensor-based nature of the method brings attractive properties, which has made it popular in the last decade. INDI globally linearizes the system by making use of control input and state derivative feedback. Despite the enhanced robustness against parametric system uncertainties compared to traditional NDI, mitigating the effects of time lag between the control input and state derivative feedback paths represents an important challenge for INDI. Past research has shown that this can be addressed by synchronizing these feedback signals, although the method remains vulnerable to unexpected measurement delays. This paper proposes a hybrid INDI approach based on complementary filtering to further mitigate this robustness issue. The approach fuses the system model and sensor measurement to generate an estimate of the angular acceleration of the system. The estimation responds rapidly to the system input thanks to the on-board model, whereas adequate accuracy in the low-to-medium frequency range is maintained by the sensor measurement. The control law is found to retain good performance in case of model mismatches and measurement delays. To demonstrate the method, a hybrid INDI-based attitude control law is designed for a nonlinear F-16 aircraft model. The robustness properties of the resulting control system are analyzed using time-domain simulations.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Control & Simulatio
Quadrotor Fault Tolerant Incremental Sliding Mode Control driven by Sliding Mode Disturbance Observers
No full textThis paper proposes an Incremental Sliding Mode Control driven by Sliding Mode Disturbance Observers (INDI-SMC/SMDO), with application to a quadrotor fault tolerant control problem. By designing the SMC/SMDO based on the control structure of the sensor-based Incremental Nonlinear Dynamic Inversion (INDI), instead of the model-based Nonlinear Dynamic Inversion (NDI) in the literature, the model dependency of the controller and the uncertainties in the closed-loop system are simultaneously reduced. This allows INDI-SMC/SMDO to passively resist a wider variety of faults and external disturbances using continuous control inputs with lower control and observer gains. When applied to a quadrotor, both numerical simulations and real-world flight tests demonstrate that INDI based SMC/SMDO has better performance and robustness over NDI based SMC/SMDO, in the presence of model uncertainties, wind disturbances, and sudden actuator faults. Moreover, the implementation process is simplified because of the reduced model dependency and smaller uncertainty variations of INDI-SMC/SMDO. Therefore, the proposed control method can be easily implemented to improve the performance and survivability of quadrotors in real life.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Control & Simulatio
Discrete-time Design and Stability Analysis for Nonlinear Incremental Fault-tolerant Flight Control
No full textIncremental control, including incremental nonlinear dynamic inversion (INDI) and incremental backstepping (IBS), is a sensor-based control framework that enhances the control robustness by exploiting sensor measurements. Although its effectiveness has been demonstrated on various aerospace systems, the explicit and quantifiable expression for the ultimate bound of the tracking error, as a function of the sampling frequency and perturbation bound, has not been presented. This issue is addressed by the discrete-time domain stability analysis of the incremental control in this paper, which allows convenient yet realistic performance assessment and parameter tuning before performing real-world flight tests. Another challenge faced by the incremental control is that its stability criterion can be violated in severe aircraft fault scenarios, such as the control reversal. Therefore, this paper proposes a discrete-time control-direction-based incremental sliding mode control, denoted as D-INDI-SMC, which has broader applicability than the state-of-the-art incremental control methods. The robustness of D-INDI-SMC against control reversal, sensing errors, model uncertainties, actuator faults, and structural damage has been theoretically proved and numerically demonstrated.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Aerospace Structures & Computational Mechanic
Incremental Nonlinear Dynamic Inversion controller - structural vibration coupling: Study of the phenomenon and the existing solutions
No full textIncremental Nonlinear Dynamics Inversion (INDI) flight controllers are sensor-based control systems, that are robust towards model uncertainty and with good disturbance rejection characteristics. These controllers show coupling effects in structural modes when implemented in specific flying vehicles with low-frequency structural motions. This paper investigates different INDI implementations, standard INDI, hybrid INDI, and notch filter placement in the INDI loop via simulation and flight tests on the Nederdrone. System identification of the structural characteristics of the vehicle and the system’s yaw dynamics are executed via ground vibration and hover flight tests. Closed-loop behaviour of theINDI inner-loop, disturbance rejection performance, and outer loop step-tracking performance was assessed with dedicated flight tests. The investigated INDI solutions show similar disturbance rejection and outer-loop step tracking performance, while the hybrid INDI solution performs a better nonlinear dynamic inversion. Index Terms—INDI, complementary filter, unmanned vehicle, flight control system structural motion couplingAerospace Engineerin
Seamless Active Morphing Wing Simultaneous Gust and Maneuver Load Alleviation
No full textThis paper deals with the simultaneous gust and maneuver load alleviation problem of a seamless active morphing wing. The incremental nonlinear dynamic inversion with quadratic programming control allocation and virtual shape functions (denoted as INDI-QP-V) is proposed to fulfill this goal. The designed control allocator provides an optimal solution while satisfying actuator position constraints, rate constraints, and relative position constraints. Virtual shape functions ensure the smoothness of the morphing wing at every moment. In the presence of model uncertainties, external disturbances, and control allocation errors, the closed-loop stability is guaranteed in the Lyapunov sense. Wind tunnel tests demonstrate that INDI-QP-V can make the seamless wing morph actively to resist “1-cos” gusts and modify the spanwise lift distribution at the same time. The wing root shear force and bending moment have been alleviated by more than 44% despite unexpected actuator fault and nonlinear backlash. Moreover, during the experiment, all the input constraints were satisfied, the wing shape was smooth all the time, and the control law was executed in real time. Furthermore, as compared with the linear quadratic Gaussian control, the hardware implementation of INDI-QP-V is easier; the robust performance of INDI-QP-V is also superior.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Aerospace Structures & Computational Mechanic
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