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State of the art in tilt-quadrotors, modelling, control and fault recovery
Abstract
Research studies on quadrotors have recently drawn significant interest from academia and industry. Faults and failures handling are the major weaknesses of conventional quadrotor platforms; therefore, an innovative actuation mechanism was introduced to allow tilting the rotors. Tilting rotors of multirotor platforms provide high dexterity for flying between adjacent obstacles and assist the platforms in dealing with various failure scenarios. This paper reviews the state of the research on tilt-quadrotor platforms. Several platforms, software and hardware architectures, were discussed in the literature. Most of the latest developments were focused on conventional quadrotor modelling, combined with rotor tilting dynamics. On the other hand, controlling such platform was mainly studied using two types of controllers: Feedback Linearisation technique and Control Allocator. Recovery strategy in case of fault or failure has been covered extensively for conventional quadrotors, but very limited known work for tilt-quadrotor. This review concludes that the system dynamic modelling is relatively well covered compared to exploring new control techniques for more stringent requirements. However, recovery strategies as the main advantage of tilt-quadrotor platforms are not explored extensively and require more research attention.
... The conditions (12), (13) are equivalent to the condition below [22]: Property 1. A platform is capable of static hovering if and only if 0 0 0 ∈ int(M ) ...
... For each of these groups, the platform is first assumed to be able to achieve static hovering; therefore, for any of the above groups conditions (12), (13) can be achieved. Then we can define the conditions for each of the above groups as follows: ...
... However, note that the analysis of the dimensionality of R assumed that the corresponding platform can achieve static hovering; as shown in Eqs. (12), (13), one of the conditions for static hovering is the platform's ability to apply forces larger than its weight. Consequently, while the definitions Def (3)-(4) do not explicitly analyze the platform's set of feasible controls C , the necessary hovering ability inherently requires the analysis of the platform's actuation limits. ...
This paper presents a theoretical study on the ability of multi-rotor aerial vehicles (MRAVs) with tiltable propellers to achieve and sustain static hovering at different orientations. To analyze the ability of MRAVs with tiltable propellers to achieve static hovering, a novel linear map between the platform's control inputs and applied forces and moments is introduced. The relation between the introduced map and the platform's ability to hover at different orientations is developed. Correspondingly, the conditions for MRAVs with tiltable propellers to realize and sustain static hovering are detailed. A numerical metric is then introduced, which reflects the ability of MRAVs to sustain static hovering at different orientations. A subclass of MRAVs with tiltable propellers is defined as the Critically Statically Hoverable platforms (CSH), where CSH platforms are MRAVs that cannot sustain static hovering with fixed propellers, but can achieve static hovering with tilting propellers. Finally, extensive simulations are conducted to test and validate the above findings, and to demonstrate the effect of the proposed numerical metric on the platform's dynamics.
... The relationship [19] between roll, pitch, yaw and the angular velocities is given in Equation (18). ...
... (19)-(20), respectively. ...
Conventional quadrotors received great attention in trajectory design and fault-tolerant control in these years. The direction of each thrust is perpendicular to the body because of the geometrics in mechanical design. Comparing with the conventional quadrotor, a novel quadrotor named quad-tilt-rotor brings better freedom in manipulating the thrust vector. Quad-tilt-rotor augments the additional degrees of freedom in the thrust, providing the possibility of violating the normal direction of the thrust in the conventional quadrotor. This provides the ability of greater agility in control. This paper presents a novel design of a quad-tilt-rotor (quad-cone-rotor) whose thrust can be assigned along the edge of a cone shape. Besides the inheriting merits in agile from quad-tilt-rotor, the quad-cone-rotor is expected to take fault-tolerant control in severe dynamic failure (total loss in all thrusts). We simulate the control result in a UAV simulator in SIMULINK, MATLAB.
... with C x (s), C y (s), E x (s) and E y (s) being linear PD controllers and the error signals as in (5.14)-(5.15). The dynamics of the servomotors are neglected since, according to the results reported in the literature (see for instance [163]- [166]), it is relatively faster than that of the overall aircraft. Thus, the α(s) and β (s) angles are assumed to be instantaneously tracked. ...
One of the questions of ongoing interest for linear time-delay systems is to determine conditions on the equation's parameters that guarantee the exponential stability of solutions. In general, it is quite a challenge to establish conditions on the parameters of the system in order to guarantee such a stability. One of the effective approaches in the stability analysis of time-delay systems is the frequency domain approach. In the Laplace domain, the stability analysis amounts to study the distribution of characteristic quasipolynomial functions’ roots. Once the stability of a delay system has been proven, it is important to characterize the exponential decay rate of the solutions of such systems. In the frequency domain, this decay rate corresponds to the dominant spectral value. Recent works emphasized the link between maximal multiplicity and dominant roots. Indeed, conditions for a given multiple root to be dominant are investigated, this property is known as Multiplicity-Induced-Dominancy (MID). In this dissertation, three topics related to the MID property are investigated. Firstly, the effect of multiple roots with admissible multiplicities exhibiting, under appropriate conditions, the validity of the MID property for second-order neutral time-delay differential equations with a single delay is explored. The stabilization of the classical oscillator benefits from the obtained results. Secondly, the effects of time-delays on the stability of Unmanned Aerial Vehicles (UAVs) is exploited. In this regard, a symbolic/numeric application of the MID property in the control of UAV rotorcrafts featuring time-delays is provided. Lastly, the stabilization of a rolling balance board by means of the MID property is considered.
... The dynamics of the servomotors are neglected since, according to the results reported in the literature (see for instance [144,145,54,2]), it is relatively much faster than that of the overall aircraft. Thus, the α(s) and β (s) angles are assumed to be instantaneously tracked. ...
A recent and exciting topic within the field of autonomous aerial vehicles is the interaction with the surrounding environment via in-flight manipulation, including retrieving, transport and deployment, which unveils an enormous potential vis-a-vis industrial and service applications. In this regard, the actual thesis focuses on the conception and energy-based dynamical study of a multi-link unmanned aerial system able to perform manipulation tasks. The study of the aforementioned robotic aerial system includes the control of the flying multi-link vehicle by the sliding mode control theory and the conception of Lyapunov-based controllers alongside the application of Kalman Filters for state and disturbances estimation. The last part of the thesis is devoted to the examination of time-delays effects on unmanned aerial systems. Detailed simulation results are provided to prove the effectiveness of the overall thesis proposal.
... The summation of force required to accelerate the mass of the quad, m b and the centrifugal force of the quad body, ω b (mV b ) is equal with the gravity gR T and the total thrust from the rotors T b as shown in the ( ). here m is the mass of the drone, b is the linear acceleration of the fix body drone, ω b is the angular velocity of the fix body drone, V b is the linear velocity of the fix body drone, g is the gravity acting on the fix body drone, R T is the rotation matrix from body frame to the initial (8), and T b is the thrust of the rotors. The angular acceleration of the inertia can be obtain from (6), where J b is the inertia matrix stated in (12) and τ b is the gyroscopic forces acting on the body fixed frame Rotation matrix from the body frame to the inertial frame is stated in (7) and (8) [24]. ...
p> In this paper we focus on the overall overview of the mathematical modelling of the DJI F450 UAV quadcopter, the hardware and software system integration based on PID control system for the attitude feedback. The parameter specification of the DJI F450 is fed into the mathematical model and implement a basic PID for the system. Future research using the DJI F450 model can benefit from this observation by implementing the modelling and tune in their own variable that varies, such as the overall of their weight. The data of PID control system simulation using the quadcopter frame model type DJI F450 parameter. The mathematical model for the quadcopter modelled DJI F450 is developed using Newton-Euler method. Altitude data for the control system is obtain from the analysis data of the Simulink simulation. The simulation is done using the Simulink toolbox inside the MATLAB software. From this paper, we can more understand the step involves in making a full control system of a quadcopter. The mathematical model for other type of quadcopter model can be implemented using the steps with their own parameter and achieve fast development. </p
This paper designs the double closed-loop control system combining nonlinear disturbances observers (NDOB) and an adaptive fast nonsingular terminal sliding mode (AFNTSM) for the tracking control problem of quadrotor under external disturbances, actuator saturation and unmodeled dynamics. The NDOB-AFNTSM method avoids the singularity problem. To compensate for disturbances, an adaptive strategy estimates the unknown bound of NDOB errors and the unknown bound of disturbances. Besides, new fast reaching law shortens convergence times. The dead zone method is chosen to avoid over-estimation and system divergence. Considering actuator saturation, this paper uses an anti-saturation auxiliary compensator to compensate for unknown saturation errors. System stability is confirmed by the Lyapunov direct method. The simulation results reveal that the proposed method improves convergence speed and accuracy, which is more robuster than similar methods. Finally, two comparative studies for performance indexes in simulation demonstrate the preferable performance of the proposed method.
This paper presents a theoretical study on the ability of multirotor aerial vehicles (MRAVs) with tiltable propellers to achieve and sustain static hovering at different orientations. To analyze the ability of MRAVs with tiltable propellers to achieve static hovering, a novel linear map between the platform’s control inputs and applied forces and moments is introduced. The relation between the introduced map and the platform’s ability to hover at different orientations is developed. Correspondingly, the conditions for MRAVs with tiltable propellers to realize and sustain static hovering are detailed. A numerical metric is then introduced, which reflects the ability of MRAVs to sustain static hovering at different orientations. A subclass of MRAVs with tiltable propellers is defined as the critically statically hoverable platforms (CSH), where CSH platforms are MRAVs that cannot sustain static hovering with fixed propellers, but can achieve static hovering with tilting propellers. Finally, extensive simulations are conducted to test and validate the above findings, and to demonstrate the effect of the proposed numerical metric on the platform’s dynamics.
The current work exploits the effects of time-delays on the stability of unmanned aerial vehicles s). In this regard, the main contribution is a symbolic/numeric application of the multiplicity-induced-dominancy property in the control of unmanned aerial vehicles rotorcrafts featuring time-delays. The multiplicity-induced-dominancy property is considered to address two of the most representative aerial robotic platforms: a classical quadrotor vehicle and a quadrotor vehicle endowed with tilting rotors. The aforementioned property leads to an effective delayed feedback control design (multiplicity-induced-dominancy tuning criteria), allowing the system to meet prescribed behavior conditions based on the placement of the rightmost root of the corresponding closed-loop characteristic function/quasipolynomial. Lastly, the results of detailed numerical simulations, including the linear and non-linear dynamics of the vehicle, are presented and discussed to validate the proposal.
This paper presents the modelling and control of a single-axis tilting quadrotor unmanned aerial vehicle (UAV). The single-axis tilting of the rotors transforms the quadrotor into an overactuated system, enabling control in all 6 6 degrees-of-freedom (DOF). The development of a detailed mathematical model for single-axis tilting quadrotor UAV is presented. Thereafter, a proportional-integral-derivative (PID) controller implementation and a control-allocated sliding mode control (CASMC) implementations are investigated. Stability analysis of the proposed sliding mode controller was carried out using Lyapunov stability method. The method was validated within the MATLAB/Simulink environment, in order to generate data for comparison purposes. It was determined that the single-axis tilting quadrotor CASMC technique provides better overall performance when compared to the PID controller.
In this paper, computed torque control as one method of feedback linearization techniques is considered for an unmanned aerial vehicle (UAV) robot that has two tiltable coaxial rotors so as to realize multifunctional locomotion modes, where each rotor has 2-DOF tilt mechanism. First, a dynamical model of such an UAV robot is derived following the Newton–Euler law. Next, under the assumptions that the anti-torque of the tiltable coaxial rotors is zero and the gyro moment effect of the tiltable coaxial rotors can be ignored, a computed torque controller is derived, because the resultant model of the UAV robot can be simplified to a fully actuated model, which has six motion inputs and six generalized coordinate outputs. In addition, a control allocation problem of the system, in which the control inputs designed using the dynamical model are assigned to all motors for tilting the rotor as well as rotating it, is solvable by using a Moore–Penrose pseudo-inverse, where a coordinate transformation is used to simply the allocation problem. Finally, some simulations are demonstrated to verify the effectiveness of the computed torque control strategy for the robot.
Standard quadcopters are popular largely because of their mechanical simplicity relative to other hovering aircraft, low cost and minimum operator involvement. However, this simplicity imposes fundamental limits on the types of maneuvers possible due to its under-actuation. The dexterity and fault tolerance required for flying in limited spaces like forests and industrial infrastructures dictate the use of a bespoke dual-tilting quadcopter that can launch vertically, performs autonomous flight between adjacent obstacles and is even capable of flying in the event of the failure of one or two motors. This paper proposes an actuation concept to enhance the performance characteristics of the conventional under-actuated quadcopter. The practical formation of this concept is followed by the design, modeling, simulation and prototyping of a dual-axis tilting quadcopter. Outdoor flight tests using tilting rotors, to follow a trajectory containing adjacent obstacles, were conducted in order to compare the flight of conventional quadcopter with the proposed over-actuated vehicle. The results show that the quadcopter with tilting rotors provides more agility and mobility to the vehicle especially in narrow indoor and outdoor infrastructures.
In this work, we simulate the motion of a quadcopter when two symmetric propellers fail and the full thrust is gradually decreasing on each of the remaining propellers. Applying a control obtained in standard mode leads to the flying vehicle falling down. We pose and solve the problem of synthesizing a bounded control law that lets one land the flying vehicle. We consider numerical modeling problems that arise in the implementation of the proposed mathematical model of a quadcopter.
In this paper, stability and control of tilting-rotor quadcopters is presented upon failure of one propeller during flight. A tilting rotor quadcopter provides advantage in terms of additional stable configurations and maneuverability. Upon failure of one propeller, a traditional quadcopter has a tendency of spinning about the primary axis fixed to the vehicle as an outcome of the asymmetry about the yaw axis. This forces the quadcopter to land abandoning its mission. The tilting-rotor configuration is an over-actuated form of a traditional quadcopter and it is capable of handling a propeller failure, thus making it a fault tolerant system. In this paper, a dynamic model of tilting-rotor quadcopter with one propeller failure is derived and a controller is designed to achieve hovering and navigation capability. The simulation results showing the effectiveness of the proposed controller is presented using the translational and hovering motion.
Copyright © 2016 by ASME Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
Resumo: This paper deals with a quad rotor hovercraft provided with a mechanism based on a memory shape alloy witch allows tilting the rotors angles. Thus the thrust force vector of each propeller can assume two possible directions: perpendicular to the plane formed by the center of the rotors or tilted inwards. The performed analysis shows that with the second set the vehicle has greater stability, while with the first, there is higher agility. The vehicle's dynamics was studied both analytically and by simulations using MATLAB/Simulink in order to compare the two possible configurations. Based on the analytical study, it is shown that the internal inclination of the rotors, combined with the placement of the vehicle's center of mass below the propellers plane, allows an increase on the maximum torque applied by the controller to establish attitude. Three different scenarios were performed by simulation. In the first scenario, an initial attitude inclination was applied to the hovering Micro Aerial Vehicle (MAV) and the time until stabilization was measured. In the second scenario, with the MAV hovering, it was measured the time it takes to move vertically up to a certain altitude. The MAV with tilted rotors showed better results in the first scenario, wile the conventional configuration showed better performance in the second scenario. The third simulation revealed that the act of tilting the rotors does not change the MAV's position significantly.
Conventional quadrotor UAVs have crucial underactuation limitations. This appears in the coupling between the roll angle and the movement in y-direction, and between the pitch angle and the movement in x-direction. The quadrotor capability of hovering with either roll or pitch angle is restricted due to these limitations. In this paper, a novel design modification is proposed in order to increase the quadrotor degrees of freedom. Four additional rotations for the propellers grant overactuated system. It could be used to make either an oriented hovering without any translational movements or make horizontal movement with zero inclination angle, as followed in this work. A PID controller is used for the quadrotor control. Simulation results show the validity of the proposed control scheme.
Mobility of a hexarotor UAV in its standard configuration is limited, since all the propeller force vectors are parallel and they achieve only 4-DoF actuation, similar, e.g., to quadrotors. As a consequence, the hexarotor pose cannot track an arbitrary trajectory while the center of mass is tracking a position trajectory. In this paper, we consider a different hexarotor architecture where propellers are tilted, without the need of any additional hardware. In this way, the hexarotor gains a 6-DoF actuation which allows to independently reach positions and orientations in free space and to be able to exert forces on the environment to resist any wrench for aerial manipulation tasks. After deriving the dynamical model of the proposed hexarotor, we discuss the controllability and the tilt angle optimization to reduce the control effort for the specific task. An exact feedback linearization and decoupling control law is proposed based on the input-output mapping, considering the Jacobian and task acceleration, for non-linear trajectory tracking. The capabilities of our approach are shown by simulation results.
A systematic fault tolerant control (FTC) scheme based on fault estimation for a quadrotor actuator, which integrates normal control, active and passive FTC and fault parking is proposed in this paper. Firstly, an adaptive Thau observer (ATO) is presented to estimate the quadrotor rotor fault magnitudes, and then faults with different magnitudes and time-varying natures are rated into corresponding fault severity levels based on the pre-defined fault-tolerant boundaries. Secondly, a systematic FTC strategy which can coordinate various FTC methods is designed to compensate for failures depending on the fault types and severity levels. Unlike former stand-alone passive FTC or active FTC, our proposed FTC scheme can compensate for faults in a way of condition-based maintenance (CBM), and especially consider the fatal failures that traditional FTC techniques cannot accommodate to avoid the crashing of UAVs. Finally, various simulations are carried out to show the performance and effectiveness of the proposed method.
In this paper, the dynamic model of a tilting rotor quadcopter, i.e., a quad-rotor aerial vehicle with rotors that can tilt along one of its axes, is presented. The tilting rotor quadcopter provides the added advantage in terms of additional stable configurations, made possible by additional actuated controls, as compared to a traditional quadcopter without titling rotors. The tilting rotor quadcopter design is accomplished by using an additional motor for each rotor that enables the rotor to rotate along the axis of the quadcopter arm. This turns the traditional quadcopter into an over-actuated flying vehicle allowing us to have complete control over its position and the orientation. In this paper, a dynamic model of the tilting rotor quadcopter vehicle is derived for flying and hovering modes. The model includes the relationship between vehicle orientation angle and rotor tilt-angle. Furthermore, a PD controller is designed to achieve the hovering and navigation capability at any desired pitch or roll angle. The dynamic model and the control design is verified with the help of numerical studies.
This paper presents the design and modelling of a novel multi rotor actuation approach. In order to increase the agility and reliability of the multi-rotors, the novel concept seeks to fuse 3 main actuation mechanisms, namely, gyroscopic torques, thrust vectoring and differential thrusting. The design of a novel quadrotor implementing the Dual Axes Tilting concept is presented. A detailed modelling of the new actuator suite, which includes the development of the gyroscopic equations for the propellers, the characterisation of the propeller aerodynamics and the dynamic identification of both the motors and the servomotors, is described. Finally, the results of the simulation model are compared with those of the real vehicle by conducting experiments on a test rig. On the light of the results it can be stated that the simulation model is representative of the dynamics of the real vehicle.
This paper proposes a novel strategy to improve the performance and fault tolerance of multi-rotor vehicles. The proposed strategy uses dual axis tilting propellers and thus enables three different actuation mechanisms, namely, gyroscopic torques, thrust vectoring and differential thrusting. Unlike the conventional quadrotor, the proposed strategy offers a wider range of control torques by combining the three actuation mechanisms. Conventional quadrotors cannot be reconfigured if one of rotors fails. However, the proposed strategy is still able to reconfigure the vehicle with complete failure of one rotor and a pair of adverse motors. In order to prove this concept, a dual axis tilting UAV is first designed and prototyped. Next, a mathematical representation of the prototyped vehicle is modelled and verified using experiments. Then, a control system is developed based on a PD controller and pseudoinverse control allocator and validated through tests on a rig and flight tests. The tests show that the vehicle is faster than a conventional counterpart and that it can resist the failure of two rotors. Finally, this paper suggests how to lead further substantial improvements in performance.
This paper proposes a magnetic compass fault detection method for GPS/INS/Magnetic compass integrated navigation systems.
The fault is assumed to be caused by the hard iron and soft iron effect and modeled as an abrupt change in the magnetic compass
output. In order to detect the fault, a test statistic related with only azimuth error measurement is determined. When a fault
is detected, the GPS/INS/Magnetic compass integrated navigation system is changed into a GPS/INS integrated navigation system
mode. In order to show the validity of the proposed method, computer simulation and van testing are carried out. The simulation
and van test results show that the proposed navigation system gives more accurate outputs than the GPS/INS/Magnetic compass
without the proposed method.
KeywordsFault detection–GPS/INS/magnetic compass–magnetic compass fault.
This paper presents recent work concerning a small tiltrotor aircraft with a reduced number of rotors. After several attempts, the final design consists of two propellers mounted laterally. The direction of the thrust can be redirected by tilting the propellers laterally and longitudinally. A theoretical analysis of this mechanism proves its effectiveness and the experimental results show that this aerodynamical configuration is very promising. A model of the full birotor dynamics is also presented in this paper and a controller based on the backstepping procedure is synthesized performing also an autonomous flight.
This paper considers the question of using a nonlinear complementary filter for attitude estimation of fixed-wing unmanned aerial vehicle (UAV) given only measurements from a low-cost inertial measurement unit. A nonlinear complementary filter is proposed that combines accelerometer output for low frequency attitude estimation with integrated gyrometer output for high frequency estimation. The raw accelerometer output includes a component corresponding to airframe acceleration, occurring primarily when the aircraft turns, as well as the gravitational acceleration that is required for the filter. The airframe acceleration is estimated using a simple centripetal force model (based on additional airspeed measurements), augmented by a first order dynamic model for angle-of-attack, and used to obtain estimates of the gravitational direction independent of the airplane manoeuvres. Experimental results are provided on a real-world data set and the performance of the filter is evaluated against the output from a full GPS/INS that was available for the data set.
This paper addresses the problem of attitude and heading restitution for a VTOL UAV. We describe an observation strategy to restitute the complete attitude matrix of the vehicle starting from Inertial Measurement Unit (IMU) and magnetometers. This study is a part of the development of the ducted fan UAV designed by Bertin Technologies. First, a measured orientation matrix is calculated from both inertial vectors which are the gravity and the earth magnetic field. Then, an estimated orientation is built by integrating gyroscopic readings, and corrected by the measured one. Nonlinear observation techniques are used to design a nonlinear estimator of the orientation matrix and an adaptive filter of the gyroscope's bias which ensure the convergence of the observer. Such an observer is as ecient as classical Extended Kalman Filtering based observers, and easier to implement in real time. Simulations are proposed to illustrate the concept. Copyright c ∞ 2005 IFAC
Autonomous vehicle navigation with standard IMU and differential GPS has been widely used for aviation and military applications. Our research interesting is focused on using some low-cost off-the-shelf sensors, such as strap-down IMU, inexpensive single GPS receiver. In this paper, we present an autonomous vehicle navigation method by integrating the measurements of IMU, GPS, and digital compass. Two steps are adopted to overcome the low precision of the sensors. The first is to establish sophisticated dynamics models which consider Earth self rotation, measurement bias, and system noise. The second is to use a sigma Kalman filter for the system state estimation, which has higher accuracy compared with the extended Kalman filter. The method was evaluated by experimenting on a land vehicle equipped with IMU, GPS, and digital compass.
This paper presents recent work concerning a small tiltrotor aircraft with a reduced number of rotors. The design consists of two propellers which can tilt laterally and longitudinally. A model of the full birotor dynamics is provided, and a controller based on the backstepping procedure is synthesized for the purposes of stabilization and trajectory tracking. The proposed control strategy has been tested in simulation
A Small Autonomous Underwater Vehicle Navigation System (SANS) is
being developed at the Naval Postgraduate School. The SANS is an
integrated Global Positioning System/Inertial Navigation System
(GPS/INS) navigation system composed of low-cost and small-size
components. It is designed to demonstrate the feasibility of using a
low-cost strap-down inertial measurement unit (IMU) to navigate between
intermittent GPS fixes. The present hardware consists of a GPS/DGPS
receiver, IMU, compass, water speed sensor, water depth sensor, and a
data processing computer. The software is based on a 12-state
complementary filter that combines measurement data from all sensors to
derive a vehicle position/orientation estimate. This paper describes
hardware and software design and testing results of the SANS. It is
shown that results from tilt table testing and bench testing provide an
effective means for tuning filter gains. Ground vehicle testing verifies
the overall functioning of the SANS and exhibits an encouraging degree
of accuracy
Conventional unmanned aerial vehicles, quadrotor have a plethora of applications for civilian and military purposes. Quadrotors as the name implies usually have four input variables (fixed rotors) which are used to drive six outputs (i.e., 3 translational and 3 rotational motions), and this leads to coupling between motions. Tilt- rotor quadrotors are more versatile because they have more input variables to independently control its orientation and position without coupling. In this paper, a decentralized backstepping control approach is used to generate a new set of inputs capable of independently and simultaneously achieve decoupling of motions while rejecting wind disturbances. The tiltrotor quadrotor dynamic is first decentralized to achieve six subsystems, then controller inputs for each subsystem are generated via Lyapunov based backstepping method whereby the controller parameters are optimized by Differential Evolution (DE) technique. This system exhibits robustness capability because it is able to reject external disturbances.
A secure control system is of great importance for unmanned aerial vehicles, especially in the condition of fault data injection. As the source of the feedback control system, the Inertial navigation system/Global position system (INS/GPS) is the premise of flight control system security. However, unmanned aerial vehicles have the requirement of lightweight and low cost for airborne equipment, which makes redundant device object unrealistic. Therefore, the method of fault detection and diagnosis is desperately needed. In this paper, a fault detection and diagnosis method based on fuzzy system and neural network is proposed. Fuzzy system does not depend on the mathematical model of the process, which overcomes the difficulties in obtaining the accurate model of unmanned aerial vehicles. Neural network has a strong self-learning ability, which could be used to optimize the membership function of fuzzy system. This paper is structured as follows: first, a Kalman filter observer is introduced to calculate the residual sequences caused by different sensor faults. Then, the sequences are transmitted to the fault detection and diagnosis system and fault type can be obtained. The proposed fault detection and diagnosis algorithm was implemented and evaluated with real datasets, and the results demonstrate that the proposed method can detect the sensor faults successfully with high levels of accuracy and efficiency.
A class of abstract aerial robotic systems is introduced, the laterally bounded force vehicles, in which most of the control authority is expressed along a principal thrust direction, while along the lateral directions a (smaller and possibly null) force may be exploited to achieve full-pose tracking. This class approximates platforms endowed with noncollinear rotors that can modify the orientation of the total thrust in a body frame. If made possible by the force constraints, the proposed SE(3)-based control strategy achieves the independent tracking of position-plus-orientation trajectories. The method, which is proven using a Lyapunov technique, deals seamlessly with both underactuated and fully actuated platforms, and guarantees at least the position tracking in the case of an unfeasible full-pose reference trajectory. Several experimental tests are presented that clearly show the approach practicability and the sharp improvement with respect to state of the art.
A quadrotor which has four actuators becomes an active object research in the area of identification, control related to each formation to cover certain area such as in the surveillance mission. The performance of the quadrotor is determined, one out of several possibilities, by the working condition of each actuators. Therefore, the states of healthiness of the actuators should be monitored. In other words, if there is an actuator fault signal, it should be isolated immediately. In this paper, a detection filter is proposed to solve actuator fault signal isolation on the quadrotor in hovering motion since the detection filter can generate decoupled detection space which corresponds to each actuator fault signal if mutually detectable requirement is satisfied. The result shows that mutually detectable requirement is satisfied by adding a virtual actuator vector and detection filter gain is succesfully calculated so that decoupled detection spaces can be obtained.
This paper examines the problem of designing a module for the detection and isolation of faults affecting quadrotors' actuation subsystem. Furthermore, differently from other diagnosis scheme available in literature, in this paper (not necessary small) environmental disturbances are also taken into account. In particular, this paper proposes a new two-steps strategy, based on the NonLinear Geometric Approach, for fault detection and isolation: in the first step, the application of the NonLinear Geometric Approach leads to coordinate changes able to highlight new systems affected by the wind and by a part of all possible faults; the second step exploits wind estimators designed on the equations of the new systems found at the end of the step one. These estimators are combined to generate a residuals set structured for fault detection and isolation. Simulation results demonstrate and validate the performance and the capabilities of the proposed fault detection and isolation algorithm.
Equipped with four actuators, quadrotor Unmanned Aerial Vehicles belong to the family of underactuated systems. The lateral motion of such platforms is strongly coupled with their orientation and consequently it is not possible to track an arbitrary 6D trajectory in space. In this paper, we propose a novel quadrotor design in which the tilt angles of the propellers with respect to the quadrotor body are being simultaneously controlled with two additional actuators by employing the parallelogram principle. Since the velocity of the controlled tilt angles of the propellers does not appear directly in the derived dynamic model, the system cannot be static feedback linearized. Nevertheless, the system is linearizable at a higher differential order, leading to a dynamic feedback linearization controller. Simulations confirm the theoretical findings, highlighting the improved motion capabilities with respect to standard quadrotors.
Autonomous unmanned air vehicles (UAVs) are critical to current and future military, civil, and commercial operations. Despite their importance, no previous textbook has accessibly introduced UAVs to students in the engineering, computer, and science disciplines--until now. Small Unmanned Aircraftprovides a concise but comprehensive description of the key concepts and technologies underlying the dynamics, control, and guidance of fixed-wing unmanned aircraft, and enables all students with an introductory-level background in controls or robotics to enter this exciting and important area. The authors explore the essential underlying physics and sensors of UAV problems, including low-level autopilot for stability and higher-level autopilot functions of path planning. The textbook leads the student from rigid-body dynamics through aerodynamics, stability augmentation, and state estimation using onboard sensors, to maneuvering through obstacles. To facilitate understanding, the authors have replaced traditional homework assignments with a simulation project using the MATLAB/Simulink environment. Students begin by modeling rigid-body dynamics, then add aerodynamics and sensor models. They develop low-level autopilot code, extended Kalman filters for state estimation, path-following routines, and high-level path-planning algorithms. The final chapter of the book focuses on UAV guidance using machine vision. Designed for advanced undergraduate or graduate students in engineering or the sciences, this book offers a bridge to the aerodynamics and control of UAV flight.
Quad tilt rotor Unmanned Aerial Vehicle (UAV) solves the problem of underacuated system in general quadrotor UAV. The quad tilt rotor UAV can control position and attitude independently by tilting directions of propellers. However, the flight control system in a wide range of attitudes has not been discussed yet, e.g. a UAV flying and hovering with a 90 [°] pitch angle and can flip over when the range of the tilting motor rotates wide enough. In this paper, we present the attitude transition flight control system for pitch angles ranging 0 [°] to 90 [°] since flight condition with a 90 [°] pitch angle significantly differs from that in a conventional quadrotor UAV flight, and then adequate control system and sufficient experimental validation are necessary for stable flight in a wide range of attitude conditions.
This paper presents and implements a method to detect actuator faults (loss of effectiveness) for a quadrotor unmanned helicopter (known as the Qball-X4) altitude control. Fault model is presented with the first principle physical modeling method. Mathematical model is further adjusted based on the grey-light-box scheme to adjust the model parameters and reduce model uncertainty of the Qball-X4. The Kalman filter is used for the fault detection and state estimation purpose with integration of a LQ (linear quadratic) technique based controller for controlling the altitude of the Qball-X4. The benefit of using this method is that it is robust to the process and measurement noises. The method is implemented and experimentally tested in the platform of the Qball-X4 helicopter.
Standard quadrotor unmanned aerial vehicles (UAVs) possess a limited mobility because of their inherent underactuation, that is, availability of four independent control inputs (the four propeller spinning velocities) versus the 6 degrees of freedom parameterizing the quadrotor position/orientation in space. Thus, the quadrotor pose cannot track arbitrary trajectories in space (e.g., it can hover on the spot only when horizontal). Because UAVs are more and more employed as service robots for interaction with the environment, this loss of mobility due to their underactuation can constitute a limiting factor. In this paper, we present a novel design for a quadrotor UAV with tilting propellers which is able to overcome these limitations. Indeed, the additional set of four control inputs actuating the propeller tilting angles is shown to yield full actuation to the quadrotor position/orientation in space, thus allowing it to behave as a fully actuated flying vehicle. We then develop a comprehensive modeling and control framework for the proposed quadrotor, and subsequently illustrate the hardware and software specifications of an experimental prototype. Finally, the results of several simulations and real experiments are reported to illustrate the capabilities of the proposed novel UAV design.
In recent years quadrotor unmanned aerial vehicles are being used in various different studies. A regular quadrotor has fixed rotors. This inability to tilt its rotors lead to limited success in trajectory tracking due to controlling 6 DOF systems only with 4 input parameters. There are some studies on tilt rotor and tilt-roll rotor quadrotors that can compensate for versatile conditions. Some of these proposed quadrotors are able to hover and position hold at user defined desired angles unlike regular quadrotors. This study presents the design and control of a novel quadrotor system that can tilt its rotors independently so that it can adaptively update its rotor angles and speeds to compensate for more chaotic and realistic scenarios. After deriving the mathematical model, the designed control algorithms are explained by comparing with the latter studies' abilities. Proposed quadrotor with adaptive control is compared with regular and non-adaptive tilt-roll rotor type multicopters, in various simulations. The results show that the proposed design has clear advantages in certain situations, especially when environmental limitations and hardware inconsistencies and inefficiencies exist.
This paper presents a nonlinear H-infinity control law for underactuated mechanical systems with input coupling. Apart from the controlled degrees of freedom (DOF), the proposed controller considers the dynamics of the remaining DOF in the cost variable, which allows to stabilize them. The underactuated mechanical system is normalized to obtain a diagonal inertia matrix allowing to weigh with various criteria different DOF. This controller is applied to the quadrotor helicopter to perform path tracking, whose mechanical structure has been modified in order to obtain coupling between longitudinal and lateral movements with roll and pitch motions. Simulation results in presence of aerodynamic disturbances, structural and parametric uncertainties are presented to corroborate the effectiveness and the robustness of the proposed controller.
Quadrotors have a great potential for transportation, commercial and military applications. In this paper, a quadrotor design is proposed for manned application. The design decouples all motions by allowing each rotor to tilt in two directions about its fixed frames. This modification improves the stability and safety of the quadrotor and gives it more maneuverability and robustness. The model is presented along with a proposed operator control panel. Several flight scenarios are also simulated to illustrate the superiority over conventional manned air vehicles.
Fault-tolerant Control Systems reports the development of fault diagnosis and fault-tolerant control (FTC) methods with their application to real plants. After an introduction to fault diagnosis and FTC, a chapter on actuators and sensors in systems with varying degrees of nonlinearity leads to three chapters in which the design of FTC systems is given thorough coverage for real applications: (i) a winding machine typifying a subsystem in various sheet and film processes; (ii) a hydraulic three-tank system representative of those used widely in chemical plants; and (iii) an active suspension system demonstrating application in whole large-scale systems by splitting into subsystems.Actuator and sensor faults are accommodated within the control-law design and the integration of fault diagnosis models in the FTC systems described. Commentary is given on the recent results presented. Critical failures â the loss of system observability from total loss of a sensor and of controllability from complete loss of an actuator â are considered. Linearized systems around an operating point and nonlinear systems are discussed and illustrated. A complete simulation platform of the three-tank system, in closed-loop, with or without actuator and sensor faults, is provided for the use of the reader via download from www.springer.com/978-1-84882-652-6.With its emphasis on real application, Fault-tolerant Control Systems makes an important contribution to the literature on FTC and will be of significant assistance to practicing control engineers with problems of this nature to solve. The book will also be of use to academic researchers and graduate students interested in FTC, bringing to their attention the need to adapt their methods for implementation and suggesting ways in which this can be done.
In this work we present a novel concept of a quadrotor UAV with tilting propellers. Standard quadrotors are limited in their mobility because of their intrinsic underactuation (only 4 independent control inputs vs. their 6-dof pose in space). The quadrotor prototype discussed in this paper, on the other hand, has the ability to also control the orientation of its 4 propellers, thus making it possible to overcome the aforementioned underactuation and behave as a fully-actuated flying vehicle. We first illustrate the hardware/software specifications of our recently developed prototype, and then report the experimental results of some preliminary, but promising, flight tests which show the capabilities of this new UAV concept.
The use of unmanned aerial vehicles (UAVs) for military, scientific, and civilian sectors are increasing drastically in recent years. The quadrotor platform has been used for many applications and research studies, as well. One of the limiting factors that prevents further implementation of the quadrotor system into applications, is the way quadrotor moves. It needs to tilt along the desired direction of motion. By doing this it can have necessary acceleration towards that direction. But tilting has the undesired effect of moving the onboard cameras' direction of view. This becomes an issue for surveillance and other vision based tasks. This study presents the design and control of a novel quadrotor system. Unlike previous study that uses regular quadrotor, this study proposes an alternative propulsion system formed by tilting rotors. This design eliminates the need of tilting the airframe, and it suggests superior performance with respect to regular quadrotor design. The mathematical model of the tiltable-rotor type quadrotor and designed control algorithms are explained. Various simulations are developed on MATLAB, in which the proposed quadrotor aerial vehicle has been successfully controlled. Comparison of the proposed system to regular quadrotor suggests better performance.
Standard quadrotor UAVs possess a limited mobility because of their inherent underactuation, i.e., availability of 4 independent control inputs (the 4 propeller spinning velocities) vs. the 6 dofs parameterizing the quadrotor position/ orientation in space. As a consequence, the quadrotor pose cannot track an arbitrary trajectory over time (e.g., it can hover on the spot only when horizontal). In this paper, we propose a novel actuation concept in which the quadrotor propellers are allowed to tilt about their axes w.r.t. the main quadrotor body. This introduces an additional set of 4 control inputs which provides full actuation to the quadrotor position/orientation. After deriving the dynamical model of the proposed quadrotor, we formally discuss its controllability properties and propose a nonlinear trajectory tracking controller based on dynamic feedback linearization techniques. The soundness of our approach is validated by means of simulation results.
Quadrotors have recently become a focus of research in Unmanned Aerial Vehicle (UAV) and flying robots applications. However, controlling the quadrotor dynamics is noticeably complex as the conventional quadrotor is underactuated. Some of the quadrotor motions are coupled with others which makes it impossible to achieve all the desired maneuvers. In this paper, a novel quadrotor design is proposed. The design increases the number of inputs from four in conventional quadrotors to twelve by allowing each rotor to tilt in two directions about its fixed frames. This addition aims to separate the quadrotor motions and give it more maneuverability and robustness. The model of the new design is introduced and several flights are simulated to show the superiority over conventional design.
Unmanned aerial vehicles (UAVs) offer an incomparable means of gathering intelligence and carrying out missions without needing an onboard human pilot. The benefits are considerable in terms of cost, efficiency, and reduced pilot risk.
In order to complete a mission efficiently and with a high level of safety and security, the following key design points must be met:
• the flight control system must be robust against the aircraft’s model uncertainties and external disturbances;
• an efficient fault detection and isolation (FDI) system should be capable of monitoring the health of the aircraft; and
• the flight control and guidance system should be reconfigurable depending on actuator fault occurrence or aircraft damage, and should be able to avoid obstacles.
Fault-tolerant Flight Control and Guidance Systems addresses all of these aspects with a practical approach following three main requirements: being applicable in real-time; highly computationally efficient; and modular. The text provides:
• an overview of fault-tolerant flight control techniques;
• the necessary equations for the modeling of small UAVs;
• a complete nonlinear FDI system based on extended Kalman filters; and
• a nonlinear flight control and guidance system.
The book is written in a didactic style with many figures and diagrams making it suitable not only for academic researchers and practicing engineers but also graduate students working in the fields of fault detection techniques and the automatic control of UAVs.
Supervision, health-monitoring, fault detection, fault diagnosis and fault management play an increasing role for technical processes and vehicles, in order to improve reliability, availability, maintenance and life-time. For safety-related processes fault-tolerant systems with redundancy are required in order to reach comprehensive system integrity. This book gives an introduction into the field of fault detection, fault diagnosis and fault-tolerant systems with methods which have proven their performance in practical applications. It guides the reader in a structured tutorial style: supervision methods, reliability, safety, system integrity and related terminology; fault detection with signal-based methods for periodic and stochastic signals; fault detection with process model-based methods like parameter estimation, state estimation, parity equations and principal component analysis; fault diagnosis with classification and inference methods; fault-tolerant systems with hardware and analytical redundancy; many practical simulation examples and experimental results for processes like electrical motors, pumps, actuators, sensors and automotive components; end-of-chapter exercises for self testing or for practice. The book is dedicated to graduate students of electrical, mechanical, chemical engineering and computer science and for practising engineers.
The report contains a condensed description of the X-19 V/STOL technology. The broad categories discussed include in Section I a review of the developments leading up to the X-19 program. Sections II through VI are devoted entirely to the propellers and the considerations involved in design. The radial force principle is postulated in Section II. Interference effects on the wings due to the propellers are discussed in Section III. The propeller aerodynamic design in hover and cruise is presented in Section IV. Section V is devoted to the structure and control mechanisms of the propeller. Section VI relates to the use of propellers as in airplane control device. The tandem wing principle is discussed in Section VII, covering stability, control, and drag. Section VIII is devoted solely to ground effects. The wind tunnel research activity leading up to the X-19 is presented in Section IX. The structural loads in hover, transition and cruise are discussed in Section X. Section XI presents information pertinent to landing procedures in hover or cruise in the event of power failure. A summary of the flight test program is given in Section XII, including aircraft and hardware performance characteristics. Finally, Section XIII is devoted to a general discussion and assessment of the aircraft's unorthodox features.
Development of a dual axis tilt rotorcraft UAV: modelling, simulation and control
- P S Gasco
Cogging torque reduction in brushless dc motor by shaping of rotor magnets and modifying stator slots
- Man Doss
Quad tilt rotor vertical take off and landing (VTOL) unmanned aerial vehicle (UAV) with 45 degree rotors
- A Quader
- Abd Hm
- I Allateef