Papers by James Whidborne
ArXiv, 2020
In this paper, a deep reinforcement learning (DRL) method is proposed to address the problem of U... more In this paper, a deep reinforcement learning (DRL) method is proposed to address the problem of UAV navigation in an unknown environment. However, DRL algorithms are limited by the data efficiency problem as they typically require a huge amount of data before they reach a reasonable performance. To speed up the DRL training process, we developed a novel learning framework which combines imitation learning and reinforcement learning and building upon Twin Delayed DDPG (TD3) algorithm. We newly introduced both policy and Q-value network are learned using the expert demonstration during the imitation phase. To tackle the distribution mismatch problem transfer from imitation to reinforcement learning, both TD-error and decayed imitation loss are used to update the pre-trained network when start interacting with the environment. The performances of the proposed algorithm are demonstrated on the challenging 3D UAV navigation problem using depth cameras and sketched in a variety of simulat...
Chemical Engineering Journal Advances, 2021
Slugging flow is a condition caused by a liquid obstruction at the riser base. It exhibits cyclic... more Slugging flow is a condition caused by a liquid obstruction at the riser base. It exhibits cyclic behaviour. The cycle consists of a protracted time of no gas production at the riser's top, followed by the arrival of a liquid slug with a length greater than the riser height, and ultimately the breakthrough of a significant gas surge. The cycle time might range from a few minutes to a few hours, depending on the system size and flow conditions. In offshore oil production, feedback control is a practical and cost-effective way to prevent slug flow. To control the flow rate or the pressure in the pipeline, adjusting the choke valve opening on the topside facility is generally utilised as the control input. From a practical standpoint, designing a control system based on topside data rather than seabed measurements is preferable. Controlling the topside pressure alone is difficult and ineffective in reality, but combining it with the flow rate results in a more reliable control solution. Measuring the flow rate of a multiphase flow, on the other hand, is difficult and expensive. All the topside measurements-based slug control techniques was critically reviewed and necessary recommendations for enhanced control performance provided. In conclusion, this review acknowledged that slugging is a well-defined flow pattern, yet despite having been studied for several decades, current slug control methods still have robustness issues. Slug flow problems are expected to become even more intense in the future as a result of longer vertical risers driven by deep-water Exploration and Production (E&P).
IEEE Transactions on Aerospace and Electronic Systems, 2021
The problem of trajectory tracking control for a Blended-Wing-Body (BWB) large aircraft with mode... more The problem of trajectory tracking control for a Blended-Wing-Body (BWB) large aircraft with model parameter uncertainties and unknown disturbances is considered. A Linear Parameter-Varying (LPV) model is derived from the nonlinear dynamics of the BWB aircraft from which a robust linear parameter-varying controller is designed to track a desired trajectory. Using a Single Quadratic Lyapunov Function (SQLF) and an infinite number of linear matrix inequalities to be evaluated at all vertices, a pair of positive definite symmetric matrix solutions is determined via Lyapunov stability theory and linear matrix inequality technique. Furthermore, a disturbance-observer is designed to process the unknown disturbances. Considering the plant exists some model errors except for disturbances, a Radial Basis Function Neural Network (RBFNN) approximation is embedded into the SQLF LPV controller to improve tracking performances, and a composite disturbance-observer based Neural Network Single Quadratic Lyapunov Function (NNSQLF) controller can realize desired trajectory tracking of the linear parameter-varying system through regulating performance weighting functions. The closed-loop system of trajectory tracking control is proved to be asymptotically stable by using Lyapunov theory. Simulation results of forward flight speed and altitude tracking control of the BWB aircraft show that the proposed disturbance-observer based NNSQLF control can robustly stabilize the LPV system and precisely track the desired trajectory by comparing with conventional SQLF control and Parameter-Dependent Lyapunov Functions (PDLF) control, even in unknown exterior disturbances and model uncertainties. KEY WORDS: BWB aircraft; linear parameter-varying system; disturbance observer; trajectory tracking; neural network I. INTRODUCTION Blended-Wing-Body (BWB) aircraft have attracted considerable interest for their potential in delivering significant improvements in carbon emissions performance as well as reduced noise, higher speed, longer flight range, and broader internal volume compared with traditional "tube-and-wing" configurations [1]. However, the longitudinal stability of the BWB aircraft decreases as the angle of attack increases, even at small angles of attack, i.e., the lift curve shows a nonlinear increase at small angles of
Chemical Engineering Journal, 2021
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Advances in Space Research, 2021
In the presence of unknown disturbances and model parameter uncertainties, this paper develop a n... more In the presence of unknown disturbances and model parameter uncertainties, this paper develop a nonlinear backstepping sliding-mode controller (BSMC) for trajectory tracking control of a stratospheric airship using a disturbance-observer (DO). Compared with the conventional sliding mode surface (SMS) constructed by a linear combination of the errors, the new SMS manifold is selected as the last back-step error to improve independence of the adjustment of the controller gains. Furthermore, a nonlinear disturbance-observer is designed to process unknown disturbance inputs and improve the BSMC performances. The closed-loop system of trajectory tracking control plant is proved to be globally asymptotically stable by using Lyapunov theory. By comparing with traditional backstepping control and SMC design, the results obtained demonstrate the capacity of the airship to execute a realistic trajectory tracking mission, even in the presence of unknown disturbances, and aerodynamic coefficient uncertainties.
Integration of Wake Vortex Effects in Simulations of UAVs in Close Formation Flight - Bristol 2009 UAVS Conference presentation
ABSTRACT
Robust control of a glass tube shaping process
In this paper a two-degree-of-freedom (2 DOF) controller is designed for an industrial MIMO proce... more In this paper a two-degree-of-freedom (2 DOF) controller is designed for an industrial MIMO process. The design tech nique used is Discrete-Time H∞ control (via a coprime factor framework [4]) with the Method of Inequalities [7] and the pro cess is a glass tube shaping plant. The purpose of the study is to investigate the performance and robust stability char acteristics of ten different models derived from experiments carried out on the process. It is desired to control all the models with one controller, and it is shown that an accept able performance/robustness trade-off can be obtained by a loop-shaping technique built into a 2 DOF design as described in [2].
Development of unmanned flying observation robot with real time video transmission system
ABSTRACT
Drones
In order to operate safely in windy and gusty conditions, multirotor VTOL aircraft require gust r... more In order to operate safely in windy and gusty conditions, multirotor VTOL aircraft require gust resilience. This paper shows that their gust rejection properties can be improved by applying a small amount of fixed outward rotor tilt. Standard aerodynamic models of the rotors are incorporated into two dynamic models to assess the gust rejection properties. The first case is a conceptual birotor planar VTOL aircraft. The dependence of the trim and stability on the tilt angle are analyzed. The aircraft is stabilized using a pole-placement approach in order to obtain consistent closed-loop station-keeping performance in still air. The effect of gusts on the resulting response is determined by simulation. The second case study is for a quadrotor with a 10° outward rotor tilt. The aerodynamic coefficients are analyzed for trimmed station-keeping over a range of steady wind speeds. An LQR controller is used to apply station-keeping that includes integral action, and the gust responses are ...
Aerospace
This paper studies the attitude tracking control of a flexible airship subjected to wind disturba... more This paper studies the attitude tracking control of a flexible airship subjected to wind disturbances, actuator saturation and control surface faults. Efficient flexible airship models, including elastic deformation, rigid body motions, and their coupling, are established via Lagrange theory. A fast-nonsingular terminal sliding-mode (NTSM) combined with a backstepping control is proposed for the problem. The benefits of this approach are NTSM merits of high robustness, fast transient response, and finite time convergence, as well as the backstepping control in terms of globally asymptotic stability. However, the major limitation of the backstepping NTSM is that its design procedure is dependent on the prior knowledge of the bound values of the disturbance and faults. To overcome this limitation, a wind observer is designed to compensate for the effect of the wind disturbances, an anti-windup compensator is designed to compensate for actuator saturation, and an adaptive fault estimat...
A Benchtop Flight Control Demonstrator - Data and Code
Codes and data for "A benchtop flight control demonstrator"J R Duran, J F Whidborne, M ... more Codes and data for "A benchtop flight control demonstrator"J R Duran, J F Whidborne, M Carrizales Rodriguez, A PontilloInternational Journal of Mechanical Engineering EducationPublished online July 27, 2019doi: 10.1177/0306419019852688<br><br><br><b>Codes</b><br>Flight-Desk-Control-Demonstrator-master.zip - GUI on a computer programmed in JAVA - PID Controller for Arduino<br><b>Experimental Results</b>- Test open loop.xls- Test P.xls- Test PID.xls<br><b>Fluent CFD Files<br></b>windtunnel.cas<br>Windtunnel.jouWindtunnel_refine.meshdat<br><b>JavaFoil file</b>scriptJaveFoil<br><br><b>Microsoft Excel Windtunnel design worksheet</b>Wind Tunnel Design V2.xlsm<br><br><b>CATIA CAD files</b>CAD-CATIA.zip<br><b>MSc Dissertation<br></b>Duran JR. <i>Flight Desk Control Demonstrator.</i> MSc dissertatio...
Several methods for the generation of state-space equations representing the linearised and discr... more Several methods for the generation of state-space equations representing the linearised and discretised velocity-vorticity formulation of plane Poiseuille °ow are presented, with the aim of producing models suitable for feedback control. The system state is observed via boundary shear-stress measurements and controlled by boundary transpiration. The methods di®er in selection of state variables and implementation of the controlling boundary condition transpiration velocities. Streamwise and spanwise discretisation is by Fourier anal-ysis, and wall-normal discretisation by Chebyshev polynomial series. Two methods for the modi¯cation of the Chebyshev polynomial series to conform to homogeneous boundary con-ditions are presented, the second being innovative and resulting in low matrix conditioning for one test case, for which a theoretical basis is provided. The eigenvalues and eigenfunc-tions from all the resulting systems compare well with a representative reference model for
High Aspect Ratio Wing Design Using the Minimum Exergy Destruction Principle
AIAA Scitech 2019 Forum, 2019
2019 Workshop on Research, Education and Development of Unmanned Aerial Systems (RED UAS), 2019
Research into autonomous control and behaviour of mobile vehicles has become more and more widesp... more Research into autonomous control and behaviour of mobile vehicles has become more and more widespread. Unmanned aerial vehicles (UAVs) have seen an upsurge of interest and of the many UAVs available, the quadrotor has shown significant potential in monitoring and surveillance tasks. This paper examines the performance of iterative learning control (ILC) in gradient-based control that enhances a quadrotor's controllability and stability during attitude control. It describes the development of the learning algorithms which exploit the repeated nature of the fault-finding task. Iterative learning control algorithms are derived and implemented on a quadrotor in a test bench. The proposed ILC algorithms on the quadrotor model are evaluated for system stability, convergence speed, and trajectory tracking error. Finally, the performance of the proposed algorithms is compared against a baseline performance of the PID control schemes.
2016 UKACC 11th International Conference on Control (CONTROL), 2016
This paper presents the design of an inclinationand azimuth-hold controllers and their subsequent... more This paper presents the design of an inclinationand azimuth-hold controllers and their subsequent stability and performance analysis for directional drilling tools as typically used in the oil industry. Using an input transformation developed in earlier work that partially linearizes and decouples the plant dynamics of the directional drilling tool, a bilinear model of the directional drilling tool is developed and is used as the basis for Bilinear PI controller design. Results for a transient simulation of the proposed BPI controller are presented and compared with that of the PI controller of the earlier work. It is presented that BPI controller gives more consistent responses over a broader operating range compared to the PI controller. In addition, the effect of time delay on the feedback measurements with respect to the stability and performance is investigated in the simulations.
Matlab Code for State-Space System Matrices for Poiseuille Flow (mincode-version2)
ABSTRACT Matlab Code for State-Space System Matrices A,B,C and Energy Matrix Q;- This Zip File (v... more ABSTRACT Matlab Code for State-Space System Matrices A,B,C and Energy Matrix Q;- This Zip File (version2 29/8/06) contains the Matlab functions for the system matrices A,B,C and energy matrix Q for modelling linearised plane Poiseuille flow with wall-transpiration actuation and wall shear-stress measurements, which may be of use for controller synthesis. See mincode.m to begin. For academic use please acknowledge and reference via thesis: Mckernan, J. &#39;Control of Plane Poiseuille Flow: A Theoretical and Computational Investigation&#39;, PhD Thesis, School of Engineering, Cranfield University, 2006. NOT FOR COMMERCIAL USE WITHOUT PERMISSION.
Electronic tuning of a high frequency DC/AC inverter for inductive power transfer
2013 5th International Conference on Power Electronics Systems and Applications(PESA), 2013
ABSTRACT The misalignment and displacement of the coupled coils in an inductive power transfer sy... more ABSTRACT The misalignment and displacement of the coupled coils in an inductive power transfer system reduce the power efficiency and limit the amount of power that can be transferred. Coil misalignment results in the primary coil driver to operate in an un-tuned state which causes non-optimum switching operation and results in an increase in switching losses. This paper presents a novel method to electronically tune a Class E inverter used as a primary coil driver in an inductive power transfer system to minimize the detrimental effects of misalignment between the inductively coupled coils which may occur during operation. The tuning method uses current controlled inductors (saturable reactors) and a variable switching frequency to achieve optimum switching conditions regardless of the misalignment. Mathematical analysis is performed on a Class E inverter based on a piecewise linear state-space model. Experimental results are presented to confirm the analysis approach and the suitability of the proposed tuning method.
Journal of Aircraft, 2010
While operating at low airspeeds with nominal static margins, the controls on a blended-wing-body... more While operating at low airspeeds with nominal static margins, the controls on a blended-wing-body aircraft begin to saturate, and the dynamic performance gets sluggish. Augmentation of aerodynamic controls with the propulsion system is therefore considered in this research. Two aspects were of interest: namely, thrust vectoring and flap blowing. An aerodynamic model for a large blended-wing-body transport aircraft with blown flap effects was formulated using empirical and vortex lattice methods and then integrated with a Trent 500 turbofan engine model. To enhance control effectiveness, both internally and externally blown flaps were simulated. For a full-span internally blown flap arrangement using intermediate compressor flow, the amount of engine bleed and the resulting blowing coefficients were limited. However, even with a reduced bleed mass flow, the pitch control effectiveness increases by 15.9% at 85% fan revolutions per minute. For an externally blown flap arrangement using bypass air, much higher blowing coefficients can be achieved. For instance, at 100% fan revolutions per minute, there is a 44% increase in pitch control authority at low dynamic pressures. The main benefit occurs during takeoff, where both thrust vectoring and flap blowing help in achieving early pitch rotation, reducing takeoff field length and liftoff speed considerably. With central flap blowing and a limited thrust vectoring of 10 , the liftoff range reduces by 48%, and liftoff speed reduces by almost 26%.
High-Input-Voltage High-Frequency Class E Rectifiers for Resonant Inductive Links
IEEE Transactions on Power Electronics, 2015
ABSTRACT publications/rights/index.html for more information. Abstract—The operation of tradition... more ABSTRACT publications/rights/index.html for more information. Abstract—The operation of traditional rectifiers such as half-wave and bridge rectifiers in wireless power transfer applications may be inefficient and can reduce the amount of power that is delivered to a load. An alternative is to use Class E resonant rectifiers which are known to operate efficiently at high resonant frequencies and at large input voltages. Class E rectifiers have a near sinusoidal input current which leads to an improved overall system performance and increased efficiency, especially that of the transmitting coil driver. This paper is the first to investigate the use of Class E resonant rectifiers in wireless power transfer systems based on resonant inductive coupling. A piecewise linear state-space representation is used to model the Class E rectifier including the rectifying diode&amp;#39;s forward voltage drop, its ON resistance and the equivalent series resistance of the resonant inductor. Power quality parameters, such as power factor and total harmonic distortion, are calculated for different loading conditions. Extensive experimental results based on a 10 W prototype are presented to confirm the performed analysis and the efficient operation of the rectifier. An impressive operating efficiency of 94.43 % has been achieved at a resonant frequency of 800 kHz.
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Papers by James Whidborne