Papers by Argyrios Zolotas
Sensors
Path planning plays an important role in navigation and motion planning for robotics and automate... more Path planning plays an important role in navigation and motion planning for robotics and automated driving applications. Most existing methods use iterative frameworks to calculate and plan the optimal path from the starting point to the endpoint. Iterative planning algorithms can be slow on large maps or long paths. This work introduces an end-to-end path-planning algorithm based on a fully convolutional neural network (FCNN) for grid maps with the concept of the traversability cost, and this trains a general path-planning model for 10 × 10 to 80 × 80 square and rectangular maps. The algorithm outputs the lowest-cost path while considering the cost and the shortest path without considering the cost. The FCNN model analyzes the grid map information and outputs two probability maps, which show the probability of each point in the lowest-cost path and the shortest path. Based on the probability maps, the actual optimal path is reconstructed by using the highest probability method. The...
Electronics
The global market for autonomous robotics platforms has grown rapidly due to the advent of drones... more The global market for autonomous robotics platforms has grown rapidly due to the advent of drones, mobile robots, and driverless cars, while the mass media coverage examining the progress of robotics and autonomous systems field is widespread [...]
Machine learning on thermographic images for the detection and classification of damage on composites
Thermosense: Thermal Infrared Applications XLIV
Electronics
Increasing levels of autonomy impose more pronounced performance requirements for unmanned ground... more Increasing levels of autonomy impose more pronounced performance requirements for unmanned ground vehicles (UGV). Presence of model uncertainties significantly reduces a ground vehicle performance when the vehicle is traversing an unknown terrain or the vehicle inertial parameters vary due to a mission schedule or external disturbances. A comprehensive mathematical model of a skid steering tracked vehicle is presented in this paper and used to design a control law. Analysis of the controller under model uncertainties in inertial parameters and in the vehicle-terrain interaction revealed undesirable behavior, such as controller divergence and offset from the desired trajectory. A compound identification scheme utilizing an exponential forgetting recursive least square, generalized Newton–Raphson (NR), and Unscented Kalman Filter methods is proposed to estimate the model parameters, such as the vehicle mass and inertia, as well as parameters of the vehicle-terrain interaction, such as...
Speed control of drive-train incorporating magnetic coupling
2020 International Conference on Electrical Machines (ICEM)
The paper presents a two-degree-of-freedom control method that exploits the spring dynamics of a ... more The paper presents a two-degree-of-freedom control method that exploits the spring dynamics of a magnetic coupling for electromechanical torque transfer. Initially, through analysis of a dynamic model and linearisation, it is shown that control parameters designed by previous reported methods can be too aggressive, and that a broader performance envelope can be obtained by linearising at around 75% of the pull-out torque. Secondly, the paper presents a method of identifying the spring dynamics without measuring the load-side position of the coupling. Finally, input shaping and the identified parameters are employed to provide a new controller design methodology. The internal model principle is used along with the proposed linearisation scheme to construct a feed-forward/feedback control scheme whose parameters are calculated to provide desired tracking and disturbance rejection characteristics. Experimental results show excellent reference tracking and load torque disturbance rejection performance, whilst reducing the possibility of pole-slipping resulting from aggressive control action.
IEEE Transactions on Industry Applications
The paper presents a high performance and low-cost design methodology for the servo control of ma... more The paper presents a high performance and low-cost design methodology for the servo control of magnetic drive-trains (MDTs) operating in direct drive mode. For the first time, this paper considers using sensitivity peaks to analyse the robustness and stability of MDT control systems. Initially, through analysis of a dynamic model, the key spring characteristic parameters with respect to operating points, are developed. It is also shown that a wider dynamic performance envelope can be achieved by linearizing the MDT model at around 60%-80% of the maximum coupling torque, as opposed to traditional linearization under zero torque conditions. Subsequently, the paper exploits the spring characteristics for a design methodology based on the are validated through simulation and experimental studies. Index Terms-Magnetic coupling, linearization, spring dynamics, two-degree-of-freedom PI, H∞ mixed sensitivity, servo control. H∞ mixed sensitivity approach to determine suitable control tivity of control effort to load disturbances and suppress overparameters. Following this, the maximum exogenous load-torque shoot for step command inputs [7]-[10], and have previously disturbance and speed reference that will not induce pole-slipping been reported for speed control of MDTs [5], [11]. However, can and optimal gains for position controllers are given to prevent be determined. Finally, preferential position reference profiles [5], [11] overlook the sensitivity peaks from speed references demand-induced speed oscillations. The proposed methodologies and load-torque disturbances to control effort; hence, [12]
Development of a thermal excitation source used in an active thermographic UAV platform
Quantitative InfraRed Thermography Journal
In this paper a systematic method via H∞ control design is proposed to select a sensor set that s... more In this paper a systematic method via H∞ control design is proposed to select a sensor set that satisfies a number of input criteria for a MAGLEV suspension system. The proposed method recovers a number of optimised controllers for each possible sensor set that satisfies the performance and constraint criteria using evolutionary algorithms
Model-based fully coupled propulsion-aerodynamics optimization for hybrid electric aircraft energy management strategy
Energy, 2022
ISA Transactions, 2021
The paper presents the first classical internal model control (IMC) design in the context of rail... more The paper presents the first classical internal model control (IMC) design in the context of railway carbody roll control. We propose a simple control approach for a recent hydraulically actuated vehicle body roll concept that offers limited carbody roll. The IMC approach addresses both preview-and nulling-type tilt setups, highlighting related benefits and limitations. The design provides a model simplification process that facilitates PI and PIDtype control structures without the need for complex optimization. A simple, yet practical, tool for the industrial rail rolling stock engineer in vehicle control design is offered. Vehicle roll performance is rigorously studied on the deterministic (curving acceleration response) and stochastic (ride quality) trade off. Simulations are performed on an in-house multibody dynamics software package employing a realistic nonlinear railway vehicle model and allow to appropriately assess the performance of preview and nulling type tilt performance. The results obtained confirm that preview tilt control offers the better tilt performance as it utilises a tilt command reference, and highlighted that nulling-type tilt performance remains at a relatively comparable level with the former.
On the issue of LQG embedded control realization in a Maglev system
2017 25th Mediterranean Conference on Control and Automation (MED), 2017
Sensor selection in control design receives substantial interest in the last few years. We dissem... more Sensor selection in control design receives substantial interest in the last few years. We disseminate work on Field Programmable Gate Array (FPGA)-based embedded software platform validating a systematic sensor selection framework and target efficient FPGA resource allocation. Sensor selection combines multi-objective optimization, Linear-Quadratic-Gaussian (LQG) control, applied to a Maglev suspension. The nonlinear Maglev model is realized on software platform forming a Hardware-in-the-loop (HIL) as an economic and reliable validation platform for the design setup. The LQG controller was modeled in fixed point, described in Verilog Hardware Description Language (HDL) and tied up with an ethernet core to form an FPGA-in-the-loop system prior to logic synthesis and FPGA place and route. The results illustrate efficient FPGA resource allocation level pertinent to extending to a core sensor fault tolerant scheme.
Robust control design for an uncertain electrostatic micro-mechanical system via loop shaping
2007 European Control Conference (ECC), 2007
This paper presents the design of a robust model-based controller coupled to a feed-forward compe... more This paper presents the design of a robust model-based controller coupled to a feed-forward compensator set-point regulation maneuvers of an electrostatic micro-mechanical actuator system (eμm-A) with uncertainty on its supporting springs. Linearised models of the nonlinear system are considered at multiple operating points for short-range maneuvers in distances smaller than the systems bifurcation point, while the feedforward compensator provides the nominal voltage. The robust controller, designed via ℋ∞ loop-shaping, handles any perturbations around these points while guarantees robustness against the switching nature of the linearized system dynamics. Moreover, the controller successfully tolerates any variation of the system's uncertain parameter. The performance of the designed controller is assessed via a number of appropriate simulation studies to prove its efficacy.
IEEE Access, 2021
This paper presents a novel security approach called Anomalous Resource Consumption Detection (AR... more This paper presents a novel security approach called Anomalous Resource Consumption Detection (ARCD), which acts as an additional layer of protection to detect cyberattacks in embedded systems (ESs). The ARCD approach is based on the differentiation between the predefined standard resource consumption pattern and the anomalous consumption pattern of system resource utilization. The effectiveness of the proposed approach is tested in a rigorous manner by simulating four types of cyberattacks: a denial-of-service attack, a brute-force attack, a remote code execution attack, and a man-in-the-middle attack, which are executed on a Smart PiCar (used as the testbed). A septenary tuple model consisting of seven parameters, representing the embedded system's architecture, has been created as the core of the detection mechanism. The approach's efficiency and effectiveness has been validated in terms of range and pattern by analyzing the collected data statistically in terms of mean, median, mode, standard deviation, range, minimum, and maximum values. The results demonstrated the potential for defining a standard pattern of resource utilization and performance of the embedded system due to a significant similarity of the parameters' values at normal states. In contrast, the attacked cases showed a definite, observable, and detectable impact on resource consumption and performance of the embedded system, causing an anomalous pattern. Thus, by merging these two findings, the ARCD approach has been developed. ARCD facilitates building secure operating systems in line with the ES's capabilities. Furthermore, the ARCD approach can work along with existing countermeasures to augment the security of the operating system layer. INDEX TERMS Anomalous resource consumption, brute-force attack, cyberattacks, denial-of-service attack, embedded systems, password attack, remote code execution, testbed.
This paper demonstrates a robust damping control design for multiple swing modes damping using gl... more This paper demonstrates a robust damping control design for multiple swing modes damping using global stabilizing signals. A multipleinput, single-output (MISO) controller is designed for a thyristor controlled phase angle regulator (TCPAR) to improve the damping of the critical interarea modes. The stabilizing signals are obtained from remote locations based on the observability of the critical modes. A damping control design based on the mixed-sensitivity formulation in Linear Matrix Inequality (LMI) framework is carried out. The damping performance of the centralized controller is examined in the frequency and the time domain for various operating scenarios. The controllers is found to be robust against varying power-flow patterns, nature of loads, tie-line strengths and system non-linearities, including saturations. Keywords— Global signals, swing mode, inter-area oscillations, FACTS, robustness, H-infinity control, LMI, model reduction.
2007 European Control Conference (ECC), 2007
In this paper a control design study of a nonlinear hydraulic actuator is presented based on the ... more In this paper a control design study of a nonlinear hydraulic actuator is presented based on the Quantitative Feedback Theory (QFT). The model is linearized around an operating point and the uncertainty in the nominal plant is quantified. Using the robust design specifications, a robust QFT controller is designed using a novel fixed structure optimization algorithm. The resulting feedback controller has low complexity and, as shown via numerous simulations, is successful in meeting the robust stability and performance specifications of the design. The design illustrates the effectiveness of the proposed algorithm in achieving tight loop-shaping for a real system of medium complexity.
IEEE Access, 2021
This paper presents a unique security approach for detecting cyber-attacks against embedded syste... more This paper presents a unique security approach for detecting cyber-attacks against embedded systems (ESs). The proposed approach has been shaped within an architectural framework called anomalous resource consumption detection (ARCD). The approach’s detection mechanism detects cyber-attacks by distinguishing anomalous performance and resource consumption patterns from a pre-determinable reference model. The defense mechanism of this approach acts as an additional layer of protection for ESs. This technique’s effectiveness was previously evaluated statistically, and in this paper, we tested this approach’s efficiency computationally by using the support-vector machine algorithm. The datasets were generated and collected based on a testbed model, where it was run repeatedly under different operation conditions (normal cases (Rs) versus attacked cases). The executed attack scenarios are 1) denial-of-service (DoS); 2) brute force (BF); and 3) remote code execution (RCE), and man-in-the-...
Refrigeration systems and HVAC are estimated to consume approximately 14% of the UK’s electricity... more Refrigeration systems and HVAC are estimated to consume approximately 14% of the UK’s electricity and could make a significant contribution towards the application of DSR. In this paper, active power profiles of single and multi-pack refrigeration systems responding DSR events are experimentally investigated. Further, a large population of 300 packs (approx. 1.5 MW capacity) is simulated to investigate the potential of delivering DSR using a network of refrigeration compressors, in common with commercial retail refrigeration systems. Two scenarios of responding to DSR are adopted for the studies viz. with and without applying a suction pressure offset after an initial 30 second shut-down of the compressors. The experiments are conducted at the Refrigeration Research Centre at University of Lincoln. Simulations of the active power profile for the compressors following triggered DSR events are realized based on a previously reported model of the thermodynamic properties of the refrige...
Group Design Project in Control Engineering: Adapting to COVID-19 Pandemic
IFAC-PapersOnLine, 2021
Group Design Project (GDP) is a common education strategy in engineering. However, due to the COV... more Group Design Project (GDP) is a common education strategy in engineering. However, due to the COVID-19 pandemic, GDP cannot be fulfilled in a typical lab condition. The paper describes an example of delivering intensive hands-on, group project-based engineering course Autonomous Vehicle Dynamics and Control at Cranfield University. The project was designed to be implemented using modern simulation tools. As a result, students have not only obtained a better understanding of the engineering areas but also learned the usage of essential engineering and IT tools. The students obtained skillsets useful in modern engineering applications, where a simulation environment could improve the quality of the system before deployment and reduce a development cost.
Sensors, 2021
Unmanned Aerial Vehicles (UAVs) that can fly around an aircraft carrying several sensors, e.g., t... more Unmanned Aerial Vehicles (UAVs) that can fly around an aircraft carrying several sensors, e.g., thermal and optical cameras, to inspect the parts of interest without removing them can have significant impact in reducing inspection time and cost. One of the main challenges in the UAV based active InfraRed Thermography (IRT) inspection is the UAV’s unexpected motions. Since active thermography is mainly concerned with the analysis of thermal sequences, unexpected motions can disturb the thermal profiling and cause data misinterpretation especially for providing an automated process pipeline of such inspections. Additionally, in the scenarios where post-analysis is intended to be applied by an inspector, the UAV’s unexpected motions can increase the risk of human error, data misinterpretation, and incorrect characterization of possible defects. Therefore, post-processing is required to minimize/eliminate such undesired motions using digital video stabilization techniques. There are num...
Electronics, 2020
Proposed is the facilitation of fault-tolerant capability in autonomous systems with particular c... more Proposed is the facilitation of fault-tolerant capability in autonomous systems with particular consideration of low computational complexity and system interface devices (sensor/actuator) performance. Traditionally model-based fault-tolerant/detection units for multiple sensor faults in automation require a bank of estimators, normally Kalman-based ones. An AI-based control framework enabling low computational power fault tolerance is presented. Contrary to the bank-of-estimators approach, the proposed framework exhibits a single unit for multiple actuator/sensor fault detection. The efficacy of the proposed scheme is shown via rigorous analysis for several sensor fault scenarios for an electro-magnetic suspension testbed.
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Papers by Argyrios Zolotas