Research On On-line Torque Observation Utilizing Instantaneous Speed Of GDI Engines

Real-time estimation of internal combustion engine brake torque is the basic requirement of dynamic torque coordination control of hybrid powertrain system.However,it is difficult to estimate engine torque,as indicated torque is difficult to measure directly,and friction torque based on MAP calibration changes as engine operates.This article proposed a real-time observation method of brake torque from instantaneous engine speed,which can be used in precise control of brake torque of the engine in hybrid powertrain systems.First,an angle-domain crankshaft dynamic model with disturbance factor is established,which described the relationship between instantaneous speed and brake torque,indicated torque and friction torque in time-varying process.Based on the detailed analysis of the uncertainties in the modeling of the crankshaft dynamic model,a disturbance factor parameter are proposed to compensate for the deviation introduced by the simplification process of the crankshaft dynamic model.In order to effectively identify the disturbance factor parameter and the engine’s moment of inertia,an identification window selection method was proposed.The compression stroke was selected.Through experimental research,the angle range of model parameter identification is further confirmed.A load torque observation method based on cumulative identification of disturbance factors is proposed.Second,an adaptive observation method for indicated torque is proposed.On one hand,a dynamic angular velocity compensation is used to improve the accuracy of indicated torque observation.On the other hand,a disturbance observer is introduced to actively observe the load torque and disturbance factors,to reduce the computational burden of the indicated torque observation algorithm,and further to improve the dynamic response characteristics of torque observations.The dynamic response characteristics and steady-state accuracy of the torque observation algorithm are verified,and the observation accuracy of the indicated torque is 96.1%.The effective observation of the indicated torque not only provides the basis for engine throttle opening control and optimization of ignition angle,but also lays the foundation for friction torque model identification and brake torque estimation.Third,a real-time correction method for friction torque is proposed,and an instantaneous observation algorithm for brake torque is further presented.A friction torque polynomial regression mean model is established.Combined with the indicated torque of the observation,the parameters of the regression mean model are identified.The friction torque is corrected in real-time,and the brake torque is further extracted from the load torque.The results showed that the observation accuracy of the effective torque can reach 95.8% or more,which can be used in the output torque control of the engine in the hybrid powertrain system.Lastly,to meet the requirement of real-time brake torque observation,an ECU software and hardware architecture is proposed.An on-line brake torque observation implementation method based on multi-core parallel scheduling is proposed.The torque observation algorithm is evaluated on an ECU.The hardware-in-the-loop test shows that the torque observation task execution time is 3.2ms,the steady-state absolute deviation is 3.47% on average,and both can meet the real-time requirements of the torque observation algorithm.