79 results found
Arif J, Rehman-Shaikh MA, Evangelou S, Comprehensive Technology Qualification Process for Subsea Electronics Assemblies, IEEE Transactions on Industrial Electronics, ISSN: 0278-0046
Evangelou S, Rehman-Shaikh MA, Comprehensive energy efficiency analysis of series hybrid electric vehicles with dual-phase-shift-controlled DC-DC converter, Journal of the Franklin Institute, ISSN: 0016-0032
Yu M, Cheng C, Evangelou S, et al., 2020, Robust control for a full-car prototype of series active variable geometry suspension, 2019 IEEE 58th Conference on Decision and Control, Publisher: IEEE
The Series Active Variable Geometry Suspension (SAVGS) which has been recently proposed shows promising potential in terms of suspension performance enhancement, limited power consumption and so on. In this paper, the control aspects of a full-car prototype with the front axle retrofitted by the SAVGS, which is developed to validate the practical feasibility of the novel mechatronic suspension, are addressed. Two 12 Vdc batteries and one DC/AC inverter constitute an independent power source that supplies the overall embedded mechatronic system, with two AC rotary servo motors driving the single links (in the SAVGS) at two front corners, respectively.A robust control scheme, with an outer-loop H-infinity control and an inner-loop actuator velocity tracking control, is synthesized to enhance the vehicle ride comfort and road holding performance. Numerical simulations of the full-car prototype, withthetypical road events of a 2 Hz harmonic road, and a speed humptested, are performed. Nonlinear simulation results provide the potential suspension performance improvement contributed by the SAVGS and the power usage in the batteries, which will be compared in the future with the upcoming experimental testing results of the prototype on-road driving.
Chen B, Li X, Evangelou S, et al., 2020, Joint propulsion and cooling energy management of hybrid electric vehicles by optimal control, IEEE Transactions on Vehicular Technology, ISSN: 0018-9545
This paper develops an optimal control methodology for the energy management (EM) of a series hybrid electric vehicle (HEV) with consideration of ancillary cooling losses, to minimize fuel consumption. Both engine and battery thermal management (TM) models are integrated into the HEV powertrain model as they interact with each other during operation. By collecting all components for propulsion and cooling, a control-oriented model is established, which enables the joint EM and TM optimization problem to be solved simultaneously. Experimental driving cycles are utilized to reveal the impact of the cooling losses on the fuel economy under different driving circumstances. The case study shows the effectiveness of the proposed strategy in finding the optimal power sharing of the hybrid powertrain with consideration of both propulsion and overall cooling requirements. Moreover, a benchmark method based on separately optimized EM and conventional thermostat and PI controlled cooling systems is introduced to verify the solution quality of the proposed approach. It is demonstrated that the proposed method outperforms the benchmark by 0.7%-2.49% in terms of fuel economy, depending on the driving scenarios.
Chen B, Evangelou SA, Lot R, 2019, Series hybrid electric vehicle simultaneous energy management and driving speed optimization, IEEE/ASME Transactions on Mechatronics, Vol: 24, Pages: 2756-2767, ISSN: 1083-4435
The energy management (EM) and driving speed co-optimization of a series hybrid electric vehicle (S-HEV) for minimizing fuel consumption is addressed in this article on the basis of a suitably modeled series powertrain architecture. The paper proposes a novel strategy that finds the optimal driving speed simultaneously with the energy source power split for the drive mission specified in terms of the road geometry and travel time. Such a combined optimization task is formulated as an optimal control problem that is solved by an indirect optimal control method, based on Pontryagin's minimum principle. The optimization scheme is tested under a rural drive mission by extensive comparisons with conventional methods that deal with either speed optimization only or EM strategies with given driving cycles. The comparative results show the superior performance of the proposed method and provide further insight into efficient driving.
Chen B, Evangelou S, Lot R, 2019, Hybrid electric vehicle two-step fuel efficiency optimization with decoupled energy management and speed control, IEEE Transactions on Vehicular Technology, Vol: 68, Pages: 11492-11504, ISSN: 0018-9545
Hybrid electric vehicles (HEVs) offer an effective solution for emissions reduction and fuel energy savings. The pursuit of further improvements in their energy efficiency has led to the two fundamental optimization challenges of vehicle speed and powertrain energy management (EM), which are inherently coupled. This paper examines the vehicle speed and powertrain EM co-optimization problem for fuel economy for a series HEV following a prescribed route with expected traveling time. In order to overcome the computational burden of a large scale optimal control problem (OCP), this work presents a novel two-step optimal control strategy that suitably separates the co-optimization problem on the basis of involving the characteristics of the HEV powertrain power split and losses in the speed optimization step without an explicit use of a powertrain model. A benchmark method that simultaneously solves the optimal driving speed and the energy source power split is introduced, which is used to show the solution quality of the proposed approach. It is illustrated that the proposed method yields a driving speed solution close to the benchmark method, and additionally it outperforms the benchmark fuel economy, with much higher computational efficiency. The simplicity and effectiveness of the proposed two-step approach make it a practical and implementable EM control strategy.
Yu M, Evangelou S, Dini D, 2019, Position control of parallel active link suspension with backlash, IEEE Transactions on Industrial Electronics, Vol: 67, Pages: 4741-4751, ISSN: 0278-0046
In this paper, a position control scheme for the novel Parallel Active Link Suspension (PALS) with backlash is developed to enhance the vehicle ride comfort and road holding. A PALS-retrofitted quarter car test rig is adopted, with the torque flow and backlash effect on the suspension performance analyzed. An elastic linear equivalent model of the PALS-retrofitted quarter car, which bridges the actuator position and the equivalent force between the sprung and unsprung masses, is proposed and mathematically derived, with both the geometry and backlash nonlinearities compensated. A position control scheme is then synthesized, with an outer-loop H∞ control for ride comfort and road holding enhancement and an inner-loop cascaded proportional-integral control for the reference position tracking. Experiments with the PALS-retrofitted quarter car test rig are performed over road cases of a harmonic road, a smoothed bump and frequency swept road excitation. As compared to a conventional torque control scheme, the newly proposed position control maintains the performance enhancement by the PALS, while it notably attenuates the overshoot in the actuator’s speed variation, and thereby it benefits the PALS with less power demand and less suspension deflection increment.
Li X, Evangelou S, 2019, Torque-leveling threshold-changing rule-based control for parallel hybrid electric vehicles, IEEE Transactions on Vehicular Technology, Vol: 68, Pages: 6509-6523, ISSN: 0018-9545
A novel rule-based control strategy is proposed for the energy management of parallel hybrid electric vehicles (HEVs): the torque-leveling threshold-changing strategy (TTS). In contrast to the most commonly used heuristic electric assist control strategy (EACS) that is designed based on the load following approach, the TTS proposes and applies the new fundamental concept of torque leveling. This mechanism operates the engine with a constant torque when the engine is active, thus ensuring the engine works at an efficient operating point. The TTS additionally extends and uses a design concept that has previously been proposed in the context of series HEVs, thethreshold-changing mechanism, to operate the HEV in a chargesustaining manner. By exploiting this new set of design principles for parallel HEVs, the TTS realizes energy source control sharing behavior that is reminiscent to optimization-based methods. To show its effectiveness, the TTS is implemented to a through-theroad (TTR) HEV and benchmarked against two conventional control strategies: Dynamic Programming (DP) and the EACS. The results show that the TTS, despite its simplicity, is able to deliver comparable fuel economy as the global optimization approach DP and thus achieve significant improvement compared to the EACS. In addition, to facilitate real-time application, a simplified version of the TTS (STTS) is also developed, which is able to deliver similar performance as the TTS but is more simple to implement in practice.
Moreno-Ramirez C, Tomas-Rodriguez M, Evangelou S, Effects of interconnected suspension systems on the in-plane dynamics of sport motorcycles, Symposium on the Dynamics and Control of Single Track Vehicles
The effects of interconnected front and rear suspension systems on the in-plane dynamics of sportmotorcycle is investigated. The interconnected suspension mathematical description is presentedand included in a high-fidelity motorcycle model. The suspension behaviour under road step bumpinputs is studied for different values of stiffness and damping interconnection coefficients. Optimalvalues of interconnection coefficients are proposed for the current motorcycle model. Finally, theoscillating dynamics of the motorcycle at straight running conditions is studied through its normalmodes.
Yu M, Arana C, Evangelou S, et al., 2019, Quarter-Car Experimental Study for Series Active Variable Geometry Suspension, IEEE Transactions on Control Systems Technology, Vol: 27, Pages: 743-759, ISSN: 1063-6536
In this paper, the recently introduced series active variable geometry suspension (SAVGS) for road vehicles is experimentally studied. A realistic quarter-car test rig equipped with double-wishbone suspension is designed and built to mimic an actual grand tourer real axle, with a single-link variant of the SAVGS and a road excitation mechanism implemented. A linear equivalent modeling method is adopted to synthesize an H-infinity control scheme for the SAVGS, with the geometric nonlinearity compensated. Simulations with a theoretical nonlinear quarter-car indicate the SAVGS potential to enhance suspension performance, in terms of ride comfort and road holding. Practical features in the test rig are further considered and included in the nonlinear model to compensate the difference between the theoretical and testing behaviors. Experiments with a sinusoidal road, a smoothed bump and hole, and a random road are performed to evaluate the SAVGS practical feasibility and performance improvement, the accuracy of the model, and the robustness of the control schemes. Compared with the conventional passive suspension, ride comfort improvements of up to 41% without any deterioration of the suspension deflection are demonstrated, while the SAVGS actuator power is kept very low, at levels below 500 W.
Luo C, Shen Z, Evangelou S, et al., 2019, The Combination of Two Control Strategies for Series Hybrid Electric Vehicles, IEEE-CAA JOURNAL OF AUTOMATICA SINICA, Vol: 6, Pages: 596-608, ISSN: 2329-9266
Shabbir W, Evangelou S, 2019, Threshold-changing control strategy for series hybrid electric vehicles, Applied Energy, Vol: 235, Pages: 761-775, ISSN: 0306-2619
This paper proposes a new set of design principles to classify and design rule-based control strategies for the powertrain energy management of series hybrid electric vehicles. The design principles proposed consider the two most established rule-based control strategies for series hybrid electric vehicles, the Thermostat and the Power follower control strategies, and also an optimization-based control strategy, the Equivalent consumption minimization strategy, in terms of the mechanisms they employ to ensure charge sustaining operation and fuel efficient driving. Thus, the work then reflects upon the most effective design principles and derives a novel and superior rule-based control strategy for series hybrid electric vehicles that is claimed to outperform all the existing rule-based schemes in terms of fuel economy: the optimal primary source strategy (OPSS). The OPSS is implemented and then compared on a high fidelity hybrid electric vehicle model to Thermostat, Power follower and Equivalent consumption minimization strategies, as well as to a recently developed rule-based control strategy, the Exclusive operation strategy. As compared to conventional rule-based control strategies, the OPSS is found to deliver significantly improved fuel economy and which is remarkably close to that achieved by the optimization-based Equivalent consumption minimization strategy, while the design of the OPSS is simple and robust as compared to optimization-based strategies. The impressive performance is partly attributed to the recent improvements in engine start stop system technology. It is also shown that the battery is operated in a more steady manner, with a lower depth of discharge, consequently reducing battery degradation.
Cheng C, Evangelou S, 2019, Series active variable geometry suspension robust control based on full-vehicle dynamics, Journal of Dynamic Systems, Measurement, and Control, Vol: 141, ISSN: 0022-0434
This paper demonstrates the ride comfort and road holding performance enhancement of the new road vehicle series active variable geometry suspension (SAVGS) concept using an H∞ control technique. In contrast with the previously reported work that considered simpler quarter-car models, the present work designs and evaluates control systems using full-car dynamics thereby taking into account the coupled responses from the four independently actuated corners of the vehicle. Thus, the study utilizes a nonlinear full-car model that represents accurately the dynamics and geometry of a high performance car with the new double wishbone active suspension concept. The robust H∞ control design exploits the linearized dynamics of the nonlinear model at a trim state, and it is formulated as a disturbance rejection problem that aims to reduce the body vertical accelerations and tire deflections while guaranteeing operation inside the existing physical constraints. The proposed controller is installed on the nonlinear full-car model, and its performance is examined in the frequency and time domains for various operating maneuvers, with respect to the conventional passive suspension and the previously designed SAVGS H∞ control schemes with simpler vehicle models.
Li X, Evangelou SA, Lot R, 2019, Integrated management of powertrain and engine cooling system for parallel hybrid electric vehicles, 2018 IEEE Vehicle Power and Propulsion Conference (VPPC), Publisher: IEEE
In this work, a supervisory control strategy is pro-posed for parallel hybrid electric vehicles (HEVs). The controlstrategy is based on the equivalent consumption minimizationstrategy (ECMS) but it also considers the power consumedby the engine cooling system to optimize the overall fueleconomy of the vehicle. To verify its effectiveness, the proposedcooling-sensitive ECMS is implemented on a through-the-road(TTR) HEV, after the mathematical model of the TTR HEV isdeveloped based on power flows, and engine thermal dynamicsis also included. Simulations are performed with different drivecycles, and the results show that the cooling-sensitive ECMS isable to improve the fuel economy by 2.7% compared to thebaseline ECMS. Furthermore, it is shown that cooling-sensitiveECMS operates in a charge-sustaining manner provided thatthe equivalence factors are optimally selected.
Lopes DR, Evangelou SA, 2019, Energy savings from an Eco-Cooperative Adaptive Cruise Control: a BEV platoon investigation, 18th European Control Conference (ECC), Publisher: IEEE, Pages: 4160-4167
Chen B, Evangelou SA, 2019, Truncated Battery Power Following Strategy for Energy Management Control of Series Hybrid Electric Vehicles, 18th European Control Conference (ECC), Publisher: IEEE, Pages: 738-743
Luo C, Shen Z, Evangelou S, et al., 2018, A Control Strategy Combined Thermostat Control with DC-Link Voltage Control for Series Hybrid Electric Vehicles, 21st IEEE International Conference on Intelligent Transportation Systems (ITSC), Publisher: IEEE, Pages: 294-299, ISSN: 2153-0009
Yu M, Arana C, Evangelou S, et al., 2018, Parallel active link suspension: a quarter car experimental study, IEEE/ASME Transactions on Mechatronics, Vol: 23, Pages: 2066-2077, ISSN: 1083-4435
In this paper, a novel electro-mechanical active suspension for cars, the Parallel Active Link Suspension (PALS), is proposed and then experimentally studied. PALS involves the introduction of a rotary-actuator-driven rocker-pushrod mechanism in parallel with the conventional passive suspension assembly, to exert an additional controlled force between the chassis and the wheel. The PALS geometric arrangement is designed and optimized to maximize the rocker torque propagation onto the tire load increment. A quarter car test rig with double wishbone suspension is utilized for the PALS physical implementation. Based on a linear equivalent model of the PALS quarter car, a conservative and an aggressive robust H∞ control schemes are synthesized separately to improve the ride comfort and the road holding, with different levels of control effort allowed in each of the control schemes. Simulations with a theoretical nonlinear model of the PALS quarter car are performed to evaluate the potential in suspension performance enhancement and power demand in the rocker actuator. Experiments with a harmonic road, a smoothed bump and hole, and swept frequency are conducted with the quarter car test rig to validate the practical feasibility of the novel PALS, the ride comfort enhancement, as well as the accuracy of the theoretical model and of a further nonlinear model in which practical features existing in the test rig are identified and included.
Yu M, Evangelou S, Dini D, 2018, Control design for a quarter car test rig with parallel active linkSuspension, 2018 Annual American Control Conference (ACC), ISSN: 2378-5861
In this paper, a recently proposed novel vehicle suspension of Parallel Active Link Suspension (PALS) is adapted on a quarter car test rig. Control strategies with the PALS are studied and synthesized for ride comfort and road holding performance enhancement. A linear equivalent model of the PALS-retrofitted quarter car is derived, with geometric nonlinearity compensated. A linear control scheme is then synthesized, with an outer-loop H-infinity control and an inner-loop actuator torque tracking. Nonlinear simulations with the model of the PALS-retrofitted quarter car test rig are performed over typical road profiles, including 2 Hz harmonic road, smoothed bump and hole, and ISO random road. Results are discussed to evaluate the potential of the PALS-retrofitted quarter car test rig in ride comfort and road holding performance enhancement, as well as the power consumption in the actuator.
Li X, Nazemi A, Evangelou SA, Real-time Adaptive Heuristic Control Strategy for Parallel Hybrid Electric Vehicles, the 44th Annual Conference of the IEEE Industrial Electronics Society
Chen B, Evangelou SA, Lot R, 2018, Impact of Optimally Controlled Continuously Variable Transmission on Fuel Economy of a Series Hybrid Electric Vehicle, European Control Conference (ECC), Publisher: IEEE, Pages: 576-581
Chen B, Evangelou SA, Lot R, Fuel efficiency optimization methodologies for series hybrid electric vehicles, 2018 IEEE Vehicle Power and Propulsion Conference (VPPC), Publisher: IEEE
This paper provides an overview of various opti-mization formulations that can lead to improved fuel economyfor a series hybrid electric vehicle (HEV). The relevance andimprovement to the current state-of-the-art are discussed. Theformulated optimal control problems (OCP) consist of twoindividual optimization challenges: vehicle speed optimizationand powertrain power-split optimization. These OCPs can bemerged leading to a practical and global problem, where allthe aspects are optimized simultaneously for a prescribed routeand traveling time. Alternatively, the global problem can beapproximated by solving individual OCPs, one for each aspect,in steps and combined a posteriori. The optimal solutionsin each case are investigated and compared by simulationexamples to expose the trade-off between optimality of fueleconomy achieved by global optimization and reduction incomputational complexity and hence practicality of the two-step solution approximation.
Yu M, Evangelou SIMOS, Dini DANIELE, Chassis Leveling Control with Parallel Active Link Suspension, 14th International Symposium on Advanced Vehicle Control
Li X, Evangelou SA, Load-following Threshold-changing Rule-based Strategy for Energy Management of Parallel Hybrid Electric Vehicles, The 14th International Symposium on Advanced Vehicle Control
Chen B, Evangelou S, Lot R, Impact of optimally controlled continuously variable transmission on fuel economy of a series hybrid electric vehicle, European Control Conference (ECC) 2018, Publisher: IEEE
This paper investigates energy efficiency of a serieshybrid electric vehicles (HEV) that utilizes a continuouslyvariable transmission (CVT) to connect the electric motor tothe wheels. In contrast with a fixed transmission (FT) thatemploys a fixed final drive ratio, the CVT offers variabletransmission ratio that can be freely controlled, so that themotor is driven more efficiently. The performance of the CVTis evaluated within an optimal control framework under anurban drive mission, which is specified in terms of the roadgeometry and the traveling time for the journey. Apart fromthe CVT operation, vehicle speed and the energy managementare also simultaneously optimized by an indirect optimal controlmethod, based on the Pontryagin’s minimum principle (PMP).The simulation results illustrate the benefit of the CVT ascompared to a fixed transmission in terms of fuel economy.
Moreno Ramırez C, Tomas-Rodriguez M, Evangelou SA, 2018, Dynamic analysis of double wishbone front suspension systems on sport motorcycles, Nonlinear Dynamics, Vol: 91, Pages: 2347-2368, ISSN: 0924-090X
In this paper, two alternative front suspension sys-tems and their influence on motorcycle nonlinear dynamicsare investigated. Based on an existing high-fidelity motor-cycle mathematical model, the front end is modified to ac-commodate both Girder and Hossack suspension systems.Both of them have in common a double wishbone designthat varies the front end geometry on certain manoeuvringsand, consequently, the machine’s behaviour. The kinemat-ics of the two systems and their impact on the motorcycleperformance is analysed and compared to the well knowntelescopic fork suspension system. Stability study for bothsystems is carried out by combination of nonlinear dynami-cal simulation and root-loci analysis methods.
This paper studies the trajectory tracking problem for the nonlinear model of a scooter and presents a robust H∞ controller based on measurements of the tracking errors, the roll angle, the yaw angle and the steering angle. The study first introduces the full nonlinear model developed in Autosim which has 12 degrees of freedom. This is far more complex than a simple bicycle model and provides a good description of the scooter. Then a robust H∞ controller based on the linearization of the nonlinear model is designed. Finally, the effectiveness of the controller is verified by means of two case studies.
Yu M, Evangelou SA, Dini D, 2017, Model Identification and Control for a Quarter Car Test Rig of Series Active Variable Geometry Suspension, 20th IFAC World Congress, Publisher: Elsevier, Pages: 3376-3381, ISSN: 1474-6670
In this paper, a quarter car test rig is utilized to perform an experimental study of the singlelinkvariant of the Series Active Variable Geometry Suspension (SAVGS). A nonlinear model of the testrig is identified with the use of a theoretical quarter car model and the rig’s experimental frequencyresponse. A linear equivalent modeling method that compensates the geometric nonlinearity is alsoadopted to synthesize an H-infinity control scheme. The controller actively adjusts the single-linkvelocity in the SAVGS to improve the suspension performance. Experiments are performed to evaluatethe SAVGS practical feasibility, the performance improvement, the accuracy of the nonlinear model andthe controller’s robustness.
Evangelou SA, Rehman-Shaikh MA, 2017, Hybrid electric vehicle fuel minimization by DC-DC converter dual-phase-shift control, Control Engineering Practice, Vol: 64, Pages: 44-60, ISSN: 1873-6939
The paper introduces an advanced DC-link variable voltage control methodology that improves significantly the fuel economy of series Hybrid Electric Vehicles (HEVs). The DC-link connects a rectifier, a Dual Active Bridge (DAB) DC-DC converter and an inverter, interfacing respectively the two sources and the load in a series HEV powertrain. The introduced Dual Phase Shift (DPS) proportional voltage conversion ratio control scheme is realized by manipulating the phase shifts of the gating signals in the DAB converter, to regulate the amount of DAB converter power flow in and out of the DC-link. Dynamic converter efficiency models are utilized to account for switching, conduction, copper and core losses. The control methodology is proposed on the basis of improving the individual efficiency of the DAB converter but with its parameters tuned to minimize the powertrain fuel consumption. Since DPS control has one additional degree of freedom as compared to Single Phase Shift (SPS) voltage control schemes, a Lagrange Multiplier optimization method is applied to minimize the leakage inductance peak current, the main cause for switching and conduction losses. The DPS control scheme is tested in simulations with a full HEV model and two associated conventional supervisory control algorithms, together with a tuned SPS proportional voltage conversion ratio control scheme, against a conventional PI control in which the DC-link voltage follows a constant reference. Nonlinear coupling difficulties associated with the integration of varying DC-link voltage in the powertrain are also exposed and addressed.
Arana C, Evangelou SA, Dini D, 2016, Series active variable geometry suspension application to comfort enhancement, Control Engineering Practice, Vol: 59, Pages: 111-126, ISSN: 1873-6939
This paper explores the potential of the Series Active Variable Geometry Suspension (SAVGS) for comfort and road holding enhancement. The SAVGS concept introduces significant nonlinearities associated with the rotation of the mechanical link that connects the chassis to the spring-damper unit. Although conventional linearization procedures implemented in multi-body software packages can deal with this configuration, they produce linear models of reduced applicability. To overcome this limitation, an alternative linearization approach based on energy conservation principles is proposed and successfully applied to one corner of the car, thus enabling the use of linear robust control techniques. An H∞ controller is synthesized for this simplified quarter-car linear model and tuned based on the singular value decomposition of the system's transfer matrix. The proposed control is thoroughly tested with one-corner and full-vehicle nonlinear multi-body models. In the SAVGS setup, the actuator appears in series with the passive spring-damper and therefore it would typically be categorized as a low bandwidth or slow active suspension. However, results presented in this paper for an SAVGS-retrofitted Grand Tourer show that this technology has the potential to also improve the high frequency suspension functions such as comfort and road holding.
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