发动机调速史密斯预估定量反馈控制

对于电机后置式及地面耦合式混合动力系统,在其换挡过程中,可以通过电机补偿动力中断,因此调节发动机转速与AMT变速箱转速匹配可以实现平顺的换挡过程。针对发动机调速特性引入基于定量反馈理论与史密斯预估器结合的控制方法。首先,在AMESim中搭建自然进气发动机高保真模型,并通过速度特性验证保证模型的合理性;其次,基于机理建立发动机线性模型,并且分段辨识得到参数的不确定范围,从而将非线性系统用具有参数不确定性的线性模型表示;然后,通过频域分析优化得到一组最佳的史密斯预估器模型,用以补偿发动机进气-扭矩过程不确定延迟;最后,结合史密斯预估器与定量反馈理论设计得到发动机调速SP-QFT鲁棒控制器,从而保证系统在参数不确定情况下的鲁棒稳定性及跟踪性能要求。仿真结果表明:所设计的SP-QFT控制器满足设计要求,相比于基本QFT控制器及PID控制器,有效提高了发动机速度调节的控制精度及响应速度。

Smith Predictive Quantitative Feedback Engine Speed Control

For hybrid electric vehicles with traction motors installed behind transmission, traction motors can compensate the torque interrupt during gear shifting. Thus engine speed is adjusted to achieve the speed synchronization with AMT so that shifting smoothness is guaranteed without disengaging clutch. Quantitative feedback theory (QFT) combined with Smith predictor (SP) was adopted to achieve engine speed control. Firstly, a high realistic model of naturally aspirated gasoline engine was established in AMESim and the speed characteristic was validated to guarantee the reasonable features. Secondly, the engine nonlinear model was identified under piecewise working conditions so that several linear models with regions of parametric uncertainty were achieved. Thirdly, an optimized Smith predictor model was selected based on two criteria in frequency domain so as to deal with the intake to torque uncertain time delay. Finally, based on quantitative feedback theory, an engine speed SP-QFT robust controller was designed to guarantee the robust stability and reference tracking. The simulation results showed that the step responses between the minimum and maximum speeds were of 0.75% overshoot, 0.7s settling time and 6r/min steady state error which met the demands of performance requirements of the synchronizer engagement during gear shifting of AMT and obviously improved the system dynamic characteristics compared with QFT controller and PID controller. Moreover, the simple form of SP-QFT controller is convenient to implement in engineering.