The Research Of Dynamic Control During Mode-switches For Phev

Under the threat of energy and environment, hybrid electric vehicles have appearedand become a hot spot in automotive industry. Hybrid electric vehicles consist of twopower sources of an engine and an electromotor. Different energy distribution processesbetween the two sources bring several types of operating modes for hybrid electricsystems, including driving mode with an electromotor only, driving modes with an enginemainly, regenerative braking mode and hybrid braking mode. The hybrid control unitdecides the better one under the current condition. There may be power shortage becauseof different dynamic characteristics between the two power sources if they are controlledseparately in the process of mode-switches. This can cause rocking for vehicles,influencing its superior dynamic and comfort. For the braking mode-switches, because themotors and mechanical brake systems’characteristics are steady, it can keep the smoothpower transmission during the braking mode-switches by limiting changing rate of motorstorque. This paper intensively researches the coordinated control between an engine andan electromotor during driving mode switches.In the research, driving mode- switches are divided into three forms: the process ofengines cutting into driving state, such as, pure electric driving mode to driving modeswith an engine, the process of engines exiting from driving states, for example, enginedriving modes to pure electric mode, and power compensation by an electromotor. Duringthese processes, an electromotor is used to compensate the torque shortage caused byengine lag in response to meet the requirement torque in transmission input end, which iscalled dynamic coordinated control of torque for power systems. In addition, the secondtype of mode-switch has a problem of engine speed regulation. On purpose of rapidity andsmoothness of speed regulation, this paper proposes adaptive fuzzy-PID controller.In the last, simulation model is built based on MATLAB/SIMULINK platform. Bysimulating for the three types of mode switches, the results suggest that torquerequirement of the transmission input end is ensured through the toque dynamic control ofhybrid electric system, which ensured the smooth power transmission during mode switches and improve the whole electric vehicles’ride performances.