Chengliang Yin

Hardware-in-the-loop simulation for the design and verification of the control system of a series–parallel hybrid electric city-bus

Abstract Hybrid electric buses have been a promising technology to dramatically lower fuel consumption and carbon dioxide (CO 2 ) emission, while energy management strategy (EMS) is a critical technology to the improvements in fuel economy for hybrid electric vehicles (HEVs). In this paper, a suboptimal EMS is developed for the real-time control of a series–parallel hybrid electric bus. It is then investigated and verified in a hardware-in-the-loop (HIL) simulation system constructed on PT-LABCAR, a commercial real-time simulator. First, an optimal EMS is obtained via iterative dynamic programming (IDP) by defining a cost function over a specific drive cycle to minimize fuel consumption, as well as to achieve zero battery state-of-charge (SOC) change and to avoid frequent clutch operation. The IDP method can lower the computational burden and improve the accuracy. Second, the suboptimal EMS for real-time control is developed by constructing an Elman neural network (NN) based on the aforementioned optimal EMS, so the real-time suboptimal EMS can be used in the vehicle control unit (VCU) of the hybrid bus. The real VCU is investigated and verified utilizing a HIL simulator in a virtual forward-facing HEV environment consisting of vehicle, driver and driving environment. The simulation results demonstrate that the proposed real-time suboptimal EMS by the neural network can coordinate the overall hybrid powertrain of the hybrid bus to optimize fuel economy over different drive cycles, and the given drive cycles can be tracked while sustaining the battery SOC level.

Dynamic modelling and systematic control during the mode transition for a multi-mode hybrid electric vehicle

A smooth mode transition is critical for the driveability of hybrid electric vehicles and is difficult to achieve owing to transient intervention of torques from the engine, the electric machine and the transmission. This paper presents a systematic control strategy during transition from the motor-only mode to the compound driving mode of a multi-mode hybrid electric vehicle using one electric machine. The proposed strategy divides the mode transition process into four consecutive operating phases and employs a fuzzy gain-scheduling proportional–integral–derivative controller as feedback to adapt various non-linearities. Dynamic modelling of the vehicle system emphasizing the dynamics of the engine, the transmission, the clutches and the drive axle is conducted for validation simulation. Simulation results show that the mode transition controlled by the designed fuzzy gain-scheduling proportional–integral–derivative controller is completed in 700 ms with the vehicle jerk below 3.5 m/s3 and where the produced clutch frictional losses are only 56 J. The performance is better than those controlled by a conventional proportional–integral–derivative controller. A sensitivity study shows the proposed controller has good adaptability to disturbances caused by the changing road conditions, the uncertainties in engine system and the noise from clutch actuation.

Hardware-in-the-Loop Simulation of Robust Mode Transition Control for a Series–Parallel Hybrid Electric Vehicle

For series-parallel hybrid electric vehicles (HEVs), problems of driveability are significant and difficult to solve due to clutch engagement during mode transitions. In this paper, a robust controller was designed for a series-parallel HEV to reduce vehicle jerk during mode transitions and improve vehicle driveability. First, a linear dynamic system model of the controlled plant was obtained for robust control design. Then, the robust controller was designed based on the mu-synthesis method and solved using the discrete D-K iteration; parameter uncertainties in the system model were considered in the design process to ensure the robustness of the control system. Finally, a hardware-in-the-loop (HIL) simulation was performed to verify the proposed controller. The HIL platform was composed of a dynamometer-simulated engine, a real transmission, a virtual electric machine, and a virtual vehicle, which was constructed based on the nonlinear dynamics of tires, road, and vehicle body. The HIL simulation results showed the effectiveness of the proposed robust mode transition control.

Effective regenerative braking control for smooth stop of a hybrid electric bus

Regenerative braking is an important function for a hybrid electric bus with many stop-to-go drive conditions. Yet an accurate nonlinear model for the composite brake system in HEV and a nonlinear model-based control design for a series-parallel hybrid electric bus have not been fully studied. This paper describes the brake system with regenerative braking function, and a special brake pedal is applied in this brake system. A hybrid electric bus is inherently a nonlinear system with many uncertainties. Parameter estimation design is used to improve the effect introduced by the parametric uncertainties. The backstepping-based controller design technique is introduced with the estimated parameters, and the error dynamics is separated from the parameter adaptation. Experimental data are used for the demonstration simulation. The simulated output shows a good tracking performance of the practical braking vehicle speed, and the bus can stop at a bus station by regenerative braking. The effectiveness of the proposed controller design is illustrated with the adaptive system parameters.

A novel soft-switching bidirectional DC-DC converter with coupled inductors

This paper presents a novel topology for a non-isolated bidirectional dc-dc converter with soft-switching capability, which usually operates at a zero-voltage-switching (ZVS) condition. A non-isolated dc-dc converter combines a buck converter and a backwards boost converter into one circuit, which consists of a half-bridge power switch, an inductor, and capacitors. In order to realize ZVS conditions, the proposed converter utilizes an additional inductor coupled with the main inductor, a small inductor, and auxiliary switches and diodes. Due to ZVS, switching stress on switch components is reduced, and the reverse recovery problem of MOSFET anti-parallel body diodes is also solved. Moreover, the proposed converter can arbitrarily select the operating modes between ZVS and conventional hard-switching, so the converter can obtain the highest efficiency at almost all load ranges. The detailed theoretical analyses in each mode are presented, and a 1kW prototype is also built to verify the principles.

Experimental study on improvement in the shift quality for an automatic transmission using a motor-driven wedge clutch

Electrification technology is becoming increasingly popular in the actuation system of modern vehicles. A novel wedge-clutch-based actuation system driven by a motor is developed. The wedge clutch, which features a self-reinforcement function, can apply a large normal force on the clutch plates while requiring a small motor torque. However, the self-reinforcement feature results in a different dynamic behaviour of the vehicle driveline; therefore, careful control is needed during clutch engagement. A detailed analysis is performed to describe the different challenges of a wedge clutch in comparison with those of a conventional clutch. Based on the integrated engine and transmission control method, a new method of combined control of the motor actuation torque and the engine torque is proposed to improve the shift quality. The proposed control method is validated on a specialized transmission dynamometer by emulating the change from first-gear power to second-gear power in upshift vehicle conditions. The experimental results present how the shift quality of the wedge clutch is improved significantly by introducing the control method. Not only is the maximum transmission output torque about 25.5% smaller, but also the slipping energy is reduced by about 35.1%, which contributes to a smaller temperature rise on the clutch plates. Also, the smaller motor actuation torque has the potential to downsize the electric actuator further and to decrease its power consumption.

Design and simulation for a Series-parallel Hybrid Electric city-bus

A Series-parallel Hybrid Electric city-bus powertrain scheme was presented. On the basis of ECE drive cycle, component selecting and parameter matching of the powertrain system were implemented, and then logic-threshold power management strategy based on the optimal engine torque was developed. Furthermore, simulation models of vehicle and power management strategy were built, and vehicle kinetic performance and fuel economy were calculated by co-simulation of Cruise and Matlab/Simulink over ECE drive cycle. The simulation results indicate that the desired kinetic performances of the hybrid electric city-bus can be achieved, and its fuel consumption can be reduced by 26% compared to the prototype bus.

Economical comparison of three hybrid electric car solutions

Based on the benchmark of hybrid solutions adopted by most manufacturers in China, three hybrid electric car solutions, which are parallel system with ISG and single clutch (SCP), parallel system with ISG and dual clutches (DCP), and plug-in series system (PIS), are selected to be analyzed. A mid-size car is chosen as the baseline car for developing hybrid electric car. Based on ADVISOR software, powertrain components, such as NiMH battery, ICE, motor and transmission, vehicle controller, clutch and vehicle plant are modeled or modified with similar parameters matched for the solutions. According to different solutions, energy management strategies are developed or improved to achieve the target performance. The performances simulated and analyzed are fuel economy performance and emission performance. In addition, costs models including ownership cost, operating cost and maintenance cost during full life cycle are also presented to comprehensively evaluate the costs and performances. Results show that SCP takes less fuel economy, the fewest ownership cost and the fewest total cost during life cycle; it maybe the best solutions. The improvements on fuel economy and ownership cost of DCP are all at a medium level. PIS takes the best economy performance and emission performance, the battery is the main baffle of this solution. Fuel tax is an important factor which will seriously affect the cost.

Online Estimation of Electrochemical Impedance Spectra for Lithium-Ion Batteries via Discrete Fractional Order Model

An electrochemical impedance spectrum is one critical non-destructive approach to indicate the health status of lithium-ion batteries. This paper presents an online model-based method of estimating the electrochemical impedance spectra based on discrete fractional order model. Firstly, a discrete fractional order model (FOM) is employed to model the dynamic behavior of the lithium-ion battery, especially the diffusion kinetics. In addition, another highlight of FOM lay on its significant performance in the impedance modeling for Li-ion battery over a wide range of frequency domain. Secondly, the Levenberg-Marquardt algorithm is adopted to identify parameters of FOM recursively. Based on identification results, the electrochemical impedance spectra can be obtained by simulation. Finally, a verifying experiment is carried out based on hybrid pulse power characterization test (HPPC) mixed by EIS test. The first order and second order equivalent circuits (short as, EC1 & EC2) have been imported here as the comparison with the fractional order model. The simulation results reveal that the fractional order model can ensure an acceptable accuracy of the RMS of impedance spectra, with a maximum error being less than 0.1mohm.

Electro-Thermal Modeling and Experimental Verification for 18650 Li-Ion Cell

The lithium-ion battery is a multi-physics body, which invovles electrical, thermal and electrochemical dynamics. To enhance the understanding of battery system dynamics, in this paper, the electro-thermal coupled model is proposed for 18650 li-ion cell. The cell sizing, physical property of cell material and the cells direct resistance under different state of charge (SoC) is introduced to calculate the heat generation during charging and discharging process. Finally, the experiment is conducted and compared with the model simulation. The result indicates that the proposed model has great performance in the cell surface temperature prediction.