Xu Liangfei

Water management in a self-humidifying PEM fuel cell system by exhaust gas recirculation

Efficiency and durability of proton exchange membrane fuel cell (PEMFC) are compromised by drying of the membrane and by water flooding. This paper introduces a novel water management strategy by exhaust gas recirculation (EGR). The PEM fuel cell system with cathode EGR has a simpler structure and operates at lower cost than the conventional one with an external humidifier. Based on a modified PEMFC system model with ERG description added, the water content characteristics are captured in the presence and absence of EGR, and a comprehensive EGR strategy is developed. Analysis and simulation provide insights on how to effectively implement the EGR system. The simulation results demonstrated that these adverse water content conditions in PEM fuel cells can be well handled by adopting the proposed water management strategy.

Distributed control system based on CAN bus for fuel cell/battery hybrid vehicle

A distributed control system comprising a TTCAN (Time Triggered Controller Area Network) and a J1939 CAN (Controller Area Network) is proposed for a PEM (Proton Exchange Membrane) fuel cell / Ni-MH battery hybrid vehicle. A current-regulated DC/DC (Direct Current to Direct Current converter) is used to control the output power of the fuel cell. The work of the hybrid power train is coordinated by the TTCAN network, incorporating an optimal energy management strategy and a brake energy regeneration algorithm. In order to keep the vehicle safe, another CAN network based on the SAE (Society of Automotive Engineers) J1939 protocol is designed to coordinate the work of the braking energy regeneration algorithm and the ABS. Results of the city bus in the “China typical city bus cycle” are presented.

Feedback linearization based air pressure and mass flow rate regulation for PEMFCs

In Polymer Electrolyte Membrane Fuel Cells (PEMFCs), precise regulation of air pressure and flow rate is critical to the performance and durability of fuel cell systems. This study is based on a 20-kW fuel cell engine. Based on physical interpretation and data, a nonlinear model of the cathode of the fuel cell system is presented in this paper. By utilizing the basic idea of differential geometry, the nonlinear model is further exactly linearized via coordinate transformation. Optimal controller design methodology is then adopted to construct a Linear Quadratic Regulator (LQR) for air pressure and flow rate regulation. Finally, the effectiveness of the controller is validated by the experimental results.

Electronic inertia design for in-wheel-drive system to improve off-road dynamic performance

Due to the low inertia, low damp, and high stiffness, in-wheel-drive system has vibration problems, especially under off-road conditions. Mechanical approaches such as applying additional inertia to wheels can effectively reduce the torsional vibration, however, that increases unsprung mass and brings more severe vertical vibration. In this article, electronic inertia is designed for the system to realize the same function of mechanical inertia. Joint simulation is conducted between Carsim and Matlab/Simulink, which shows that this method can suppress the torsional vibration to a satisfying level without extra cost.

Optimal Speed Pattern Generating Method for acceleration process of EVs

Electric Vehicle (EV) is an effective solution responding to the energy crisis and environment problems, and is usually used for urban traffic where the acceleration and deceleration are very common. This paper proposes a new method called Optimal Speed Pattern Generating Method (OSPG-method) to improve the economy, ride comfort and safety of the EV during acceleration. First, the OSPG-method works out the optimal speed pattern which leads to minimal energy consumption during a specific acceleration process, 20km/h to 80km/h for instance, based on the optimal control theory. The minimal energy consumption indicates the limits of energy-saving potential. Then the OSPG-method gets a serial of speed patterns and the corresponding torque decision arrays for different time limits, which indicates the acceleration intensity the driver desires. Finally the OSPG-method transfers the offline results of torque decision arrays solved by dynamic programming (DP) into accelerator pedal interpreted map, making OSPG-method possible to be applied in engineering practice easily. The OSPG-method has been simulated in an EV model, and the result shows 0.5%–2.5% energy saving compared to a typical conventional method during acceleration process. The bench test experiment is scheduled in early April. In the end, the advantages and defects of OSPG-method are discussed and the roadmap of consummating OSPG-method is proposed.