Simos Evangelou - Academia.edu (original) (raw)
Papers by Simos Evangelou
The multibody dynamics analysis software, AUTOSIM, is used to develop automated linear and nonlin... more The multibody dynamics analysis software, AUTOSIM, is used to develop automated linear and nonlinear models for the hand derived motorcycle models presented in (Sharp, 1971, 1994b). A more comprehensive model, based on previous work (Sharp and Limebeer, 2001), is also derived and extended. One version of the code uses AUTOSIM to produce a FORTRAN or C program which solves the nonlinear equations of motion and generates time histories, and a second version generates linearised equations of motion as a MATLAB file that contains the state-space model in symbolic form. Local stability is investigated via the eigenvalues of the linearised models that are associated with equilibrium points of the nonlinear systems. The time histories produced by nonlinear simulation runs are also used with an animator to visualise the result. A comprehensive study of the effects of acceleration and braking on motorcycle stability with the use of the advanced motorcycle model is presented. The results show...
2018 European Control Conference (ECC), 2018
This paper investigates energy efficiency of a series hybrid electric vehicles (HEV) that utilize... more This paper investigates energy efficiency of a series hybrid electric vehicles (HEV) that utilizes a continuously variable transmission (CVT) to connect the electric motor to the wheels. In contrast with a fixed transmission FT that employs a fixed final drive ratio, the CVT offers variable transmission ratio that can be freely controlled, so that the motor is driven more efficiently. The performance of the CVT is evaluated within an optimal control framework under an urban drive mission, which is specified in terms of the road geometry and the traveling time for the journey. Apart from the CVT operation, vehicle speed and the energy management are also simultaneously optimized by an indirect optimal control method, based on the Pontryagin’s minimum principle (PMP). The simulation results illustrate the benefit of the CVT as compared to a fixed transmission in terms of fuel economy.
This work is about controlling the geometry of the rear suspe n ion to reduce cornering weave osc... more This work is about controlling the geometry of the rear suspe n ion to reduce cornering weave oscillations associated with high performance motorcycle s operating at high speeds. The main lateral oscillations in two-wheeled vehicles are “wobble” and “weave”. The wobble mode is a steering oscillation whose frequency is normally in the ran ge6− 9 Hz and varies little with speed. The weave mode is a fishtailing motion that involves mainly ya wing, rolling and steering of the vehicle. At low and intermediate speeds it is well damped but becomes less damped as the speed increases, in straight running or under moderate lean angle conditions. The natural frequency is lower in heavier motorcycles and rises from zero at very low s peed to somewhere in the range 2 − 4 Hz. In cornering, the above lateral modes and the in-plane ty re deflections and suspension modes become coupled, as was first shown by Koenen [1]. The mot orcycle becomes prone to resonant forcing when regular road undulations ...
IFAC-PapersOnLine
In this paper, the optimal design of a multi-speed transmission system in terms of gear ratio, nu... more In this paper, the optimal design of a multi-speed transmission system in terms of gear ratio, number of gears and gear shifting strategy is investigated for a parallel hybrid electric vehicle. The design procedure starts with the optimization of the transmission configuration to identify the optimal gear ratios for a specified number of gears. In order to avoid solving a complex co-optimization problem that involves numerous control variables for hybrid powertrain energy management (EM), gear ratios and gear shifting, the gear ratio optimization is properly decoupled from the co-optimization problem, while the optimal gear shifting strategy for the optimized gear ratios is determined jointly with the powertrain EM. The separation of the co-optimization makes it possible to solve individual problems by dynamic programming (DP), which guarantees global optimality. To show the impact of optimally designed and controlled transmission on fuel savings, the fuel economy solution of the proposed scheme is compared with the traditional EM and gear shifting optimization method that applies non-optimized gear ratios. Simulation examples verify the effectiveness of the proposed methodology and show the fuel savings incurred by the configuration optimization of the multi-speed transmission system.
IFAC-PapersOnLine
Linear robust control schemes, for example the H ∞ control, are commonly utilized in the control ... more Linear robust control schemes, for example the H ∞ control, are commonly utilized in the control design of an active suspension system, with a linearized and time-invariant statespace model of the system adopted. However, the vehicle parameter uncertainties are mainly ignored and their effect on the control robustness is not investigated. In this paper, a µ-synthesisbased control scheme is synthesized for a full car with the recently introduced Series Active Variable Geometry Suspension (SAVGS), to mainly enhance the ride comfort and road holding performance, with two significant practical uncertainties in the sprung mass and the suspension damping taken into account. Numerical simulations with a high fidelity nonlinear vehicle model are performed, with the cases of the fixed and swept values of the sprung mass tested, to assess the control robustness and performance of the developed scheme against the passive suspension as well as the H ∞-controlled SAVGS. The proposed µ-synthesis control scheme is proved to be more effective for realistic applications as it is capable of maintaining the suspension performance improvement regardless of variations of system parameters associated with the uncertainties, while the H ∞ control performance tends to deteriorate when a notable deviation from the nominal values occurs.
IEEE Transactions on Vehicular Technology
IEEE Transactions on Vehicular Technology
Hybrid electric vehicles (HEVs) offer an effective solution for emissions reduction and fuel ener... more 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 twostep optimal control strategy that suitably separates the cooptimization 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.
IEEE Transactions on Industrial Electronics
IEEE Transactions on Vehicular Technology
IEEE/CAA Journal of Automatica Sinica
With most countries paying attention to the environment protection, hybrid electric vehicles have... more With most countries paying attention to the environment protection, hybrid electric vehicles have become a focus of automobile research and development due to the characteristics of energy saving and low emission. Power follower control strategy (PFCS) and DC-link voltage control strategy are two sorts of control strategies for series hybrid electric vehicles (HEVs). Combining those two control strategies is a new idea for control strategy of series hybrid electric vehicles. By tuning essential parameters which are the defined constants under DC-link voltage control and under PFCS, the points of minimum mass of equivalent fuel consumption (EFC) corresponding to a series of variables are marked for worldwide harmonized light vehicles test procedure (WLTP). The fuel economy of series HEVs with the combination control schemes performs better compared with individual control scheme. The results show the effects of the combination control schemes for series HEVs driving in an urban environment.
IEEE Transactions on Control Systems Technology
In this paper, the recently introduced series active variable geometry suspension (SAVGS) for roa... more 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.
Journal of Dynamic Systems, Measurement, and Control
This paper demonstrates the ride comfort and road holding performance enhancement of the new road... more 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 insta...
IEEE/ASME Transactions on Mechatronics
In this paper, a novel electromechanical active suspension for cars, the parallel active link sus... more In this paper, a novel electromechanical 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 rockerpushrod 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, and 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.
Control Engineering Practice
The paper introduces an advanced DC-link variable voltage control methodology that improves signi... more 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.
Control Engineering Practice, 2017
This paper explores the potential of the Series Active Variable Geometry Suspension (SAVGS) for c... more 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 ∞ 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.
IEEE Transactions on Vehicular Technology, 2016
The paper presents a DC-link voltage control scheme by which the power losses associated with the... more The paper presents a DC-link voltage control scheme by which the power losses associated with the power electronic converters of a series Hybrid Electric Vehicle (HEV) powertrain are reduced substantially. A DC-link commonly connects the three powertrain branches associated with series HEVs, presently interfaced by a three-phase rectifier, a threephase inverter and a Dual Active Bridge (DAB) DC/DC converter. Dynamic efficiency models of the converters are developed and a methodology is proposed by which the DC-link voltage is varied with respect to its default value, based on the ratio between the battery and DC-link voltages. The voltage control scheme introduced varies the phase shift between the gating signals of the two DAB converter bridges, proportionally to the ratio of converter input voltage to output voltage referred to the transformer primary. This level of instantaneous control forces the converter to operate in boost mode when the battery charges and buck mode when the battery discharges, allowing the converter to persistently avoid Hard Switching (HS) losses over its entire operating range. The control scheme is tested in simulations with a full HEV model by comparing its performance with constant voltage and unity voltage conversion ratio PI control schemes. The scheme proves most effective for vehicles with high hybridization factor, driving in an urban environment. I. INTRODUCTION S INCE 1970, the global Greenhouse Gas (GHG) emissions from transportation have increased by more than a factor of two. The contribution from road vehicles towards transportation emissions has increased over this period from 59.85% to 72.06% [1]. The HEV represents a step towards sustainable transportation, by reducing fossil fuel consumption [2]. By minimizing power loss within the HEV powertrain, power demand is reduced for a given road load, and hence the sustainable impact of this technology is enhanced. As mentioned in [3], efficiency is one of the key drivers behind the next generation of vehicles, and significant progress has been made through intelligent supervisory controllers over the past decade [4]. This paper proposes a DC-link voltage control scheme which enhances the combined efficiency of the three power electronic converters of a series HEV powertrain, in a further step towards achieving this goal.
The multibody dynamics analysis software, AUTOSIM, is used to develop automated linear and nonlin... more The multibody dynamics analysis software, AUTOSIM, is used to develop automated linear and nonlinear models for the hand derived motorcycle models presented in (Sharp, 1971, 1994b). A more comprehensive model, based on previous work (Sharp and Limebeer, 2001), is also derived and extended. One version of the code uses AUTOSIM to produce a FORTRAN or C program which solves the nonlinear equations of motion and generates time histories, and a second version generates linearised equations of motion as a MATLAB file that contains the state-space model in symbolic form. Local stability is investigated via the eigenvalues of the linearised models that are associated with equilibrium points of the nonlinear systems. The time histories produced by nonlinear simulation runs are also used with an animator to visualise the result. A comprehensive study of the effects of acceleration and braking on motorcycle stability with the use of the advanced motorcycle model is presented. The results show...
2018 European Control Conference (ECC), 2018
This paper investigates energy efficiency of a series hybrid electric vehicles (HEV) that utilize... more This paper investigates energy efficiency of a series hybrid electric vehicles (HEV) that utilizes a continuously variable transmission (CVT) to connect the electric motor to the wheels. In contrast with a fixed transmission FT that employs a fixed final drive ratio, the CVT offers variable transmission ratio that can be freely controlled, so that the motor is driven more efficiently. The performance of the CVT is evaluated within an optimal control framework under an urban drive mission, which is specified in terms of the road geometry and the traveling time for the journey. Apart from the CVT operation, vehicle speed and the energy management are also simultaneously optimized by an indirect optimal control method, based on the Pontryagin’s minimum principle (PMP). The simulation results illustrate the benefit of the CVT as compared to a fixed transmission in terms of fuel economy.
This work is about controlling the geometry of the rear suspe n ion to reduce cornering weave osc... more This work is about controlling the geometry of the rear suspe n ion to reduce cornering weave oscillations associated with high performance motorcycle s operating at high speeds. The main lateral oscillations in two-wheeled vehicles are “wobble” and “weave”. The wobble mode is a steering oscillation whose frequency is normally in the ran ge6− 9 Hz and varies little with speed. The weave mode is a fishtailing motion that involves mainly ya wing, rolling and steering of the vehicle. At low and intermediate speeds it is well damped but becomes less damped as the speed increases, in straight running or under moderate lean angle conditions. The natural frequency is lower in heavier motorcycles and rises from zero at very low s peed to somewhere in the range 2 − 4 Hz. In cornering, the above lateral modes and the in-plane ty re deflections and suspension modes become coupled, as was first shown by Koenen [1]. The mot orcycle becomes prone to resonant forcing when regular road undulations ...
IFAC-PapersOnLine
In this paper, the optimal design of a multi-speed transmission system in terms of gear ratio, nu... more In this paper, the optimal design of a multi-speed transmission system in terms of gear ratio, number of gears and gear shifting strategy is investigated for a parallel hybrid electric vehicle. The design procedure starts with the optimization of the transmission configuration to identify the optimal gear ratios for a specified number of gears. In order to avoid solving a complex co-optimization problem that involves numerous control variables for hybrid powertrain energy management (EM), gear ratios and gear shifting, the gear ratio optimization is properly decoupled from the co-optimization problem, while the optimal gear shifting strategy for the optimized gear ratios is determined jointly with the powertrain EM. The separation of the co-optimization makes it possible to solve individual problems by dynamic programming (DP), which guarantees global optimality. To show the impact of optimally designed and controlled transmission on fuel savings, the fuel economy solution of the proposed scheme is compared with the traditional EM and gear shifting optimization method that applies non-optimized gear ratios. Simulation examples verify the effectiveness of the proposed methodology and show the fuel savings incurred by the configuration optimization of the multi-speed transmission system.
IFAC-PapersOnLine
Linear robust control schemes, for example the H ∞ control, are commonly utilized in the control ... more Linear robust control schemes, for example the H ∞ control, are commonly utilized in the control design of an active suspension system, with a linearized and time-invariant statespace model of the system adopted. However, the vehicle parameter uncertainties are mainly ignored and their effect on the control robustness is not investigated. In this paper, a µ-synthesisbased control scheme is synthesized for a full car with the recently introduced Series Active Variable Geometry Suspension (SAVGS), to mainly enhance the ride comfort and road holding performance, with two significant practical uncertainties in the sprung mass and the suspension damping taken into account. Numerical simulations with a high fidelity nonlinear vehicle model are performed, with the cases of the fixed and swept values of the sprung mass tested, to assess the control robustness and performance of the developed scheme against the passive suspension as well as the H ∞-controlled SAVGS. The proposed µ-synthesis control scheme is proved to be more effective for realistic applications as it is capable of maintaining the suspension performance improvement regardless of variations of system parameters associated with the uncertainties, while the H ∞ control performance tends to deteriorate when a notable deviation from the nominal values occurs.
IEEE Transactions on Vehicular Technology
IEEE Transactions on Vehicular Technology
Hybrid electric vehicles (HEVs) offer an effective solution for emissions reduction and fuel ener... more 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 twostep optimal control strategy that suitably separates the cooptimization 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.
IEEE Transactions on Industrial Electronics
IEEE Transactions on Vehicular Technology
IEEE/CAA Journal of Automatica Sinica
With most countries paying attention to the environment protection, hybrid electric vehicles have... more With most countries paying attention to the environment protection, hybrid electric vehicles have become a focus of automobile research and development due to the characteristics of energy saving and low emission. Power follower control strategy (PFCS) and DC-link voltage control strategy are two sorts of control strategies for series hybrid electric vehicles (HEVs). Combining those two control strategies is a new idea for control strategy of series hybrid electric vehicles. By tuning essential parameters which are the defined constants under DC-link voltage control and under PFCS, the points of minimum mass of equivalent fuel consumption (EFC) corresponding to a series of variables are marked for worldwide harmonized light vehicles test procedure (WLTP). The fuel economy of series HEVs with the combination control schemes performs better compared with individual control scheme. The results show the effects of the combination control schemes for series HEVs driving in an urban environment.
IEEE Transactions on Control Systems Technology
In this paper, the recently introduced series active variable geometry suspension (SAVGS) for roa... more 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.
Journal of Dynamic Systems, Measurement, and Control
This paper demonstrates the ride comfort and road holding performance enhancement of the new road... more 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 insta...
IEEE/ASME Transactions on Mechatronics
In this paper, a novel electromechanical active suspension for cars, the parallel active link sus... more In this paper, a novel electromechanical 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 rockerpushrod 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, and 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.
Control Engineering Practice
The paper introduces an advanced DC-link variable voltage control methodology that improves signi... more 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.
Control Engineering Practice, 2017
This paper explores the potential of the Series Active Variable Geometry Suspension (SAVGS) for c... more 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 ∞ 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.
IEEE Transactions on Vehicular Technology, 2016
The paper presents a DC-link voltage control scheme by which the power losses associated with the... more The paper presents a DC-link voltage control scheme by which the power losses associated with the power electronic converters of a series Hybrid Electric Vehicle (HEV) powertrain are reduced substantially. A DC-link commonly connects the three powertrain branches associated with series HEVs, presently interfaced by a three-phase rectifier, a threephase inverter and a Dual Active Bridge (DAB) DC/DC converter. Dynamic efficiency models of the converters are developed and a methodology is proposed by which the DC-link voltage is varied with respect to its default value, based on the ratio between the battery and DC-link voltages. The voltage control scheme introduced varies the phase shift between the gating signals of the two DAB converter bridges, proportionally to the ratio of converter input voltage to output voltage referred to the transformer primary. This level of instantaneous control forces the converter to operate in boost mode when the battery charges and buck mode when the battery discharges, allowing the converter to persistently avoid Hard Switching (HS) losses over its entire operating range. The control scheme is tested in simulations with a full HEV model by comparing its performance with constant voltage and unity voltage conversion ratio PI control schemes. The scheme proves most effective for vehicles with high hybridization factor, driving in an urban environment. I. INTRODUCTION S INCE 1970, the global Greenhouse Gas (GHG) emissions from transportation have increased by more than a factor of two. The contribution from road vehicles towards transportation emissions has increased over this period from 59.85% to 72.06% [1]. The HEV represents a step towards sustainable transportation, by reducing fossil fuel consumption [2]. By minimizing power loss within the HEV powertrain, power demand is reduced for a given road load, and hence the sustainable impact of this technology is enhanced. As mentioned in [3], efficiency is one of the key drivers behind the next generation of vehicles, and significant progress has been made through intelligent supervisory controllers over the past decade [4]. This paper proposes a DC-link voltage control scheme which enhances the combined efficiency of the three power electronic converters of a series HEV powertrain, in a further step towards achieving this goal.