Control of Camless Intake Process Part II

A model based control scheme is designed to regu late the cylinder air charge of a camless multicylinder engine for unthrottled operation The controller con sists of a feedforward and an adaptive feedback scheme based on a control oriented model of the breathing process of an engine equipped with electro hydraulic springless valve train The nonlinear control scheme is designed to achieve cylinder to cylinder balancing fast cycle to cycle response and minimization of pumping losses The al gorithm uses conventional sensor measurements of intake manifold pressure and mass air ow to the intake mani fold and intake valve duration measurement Closed loop simulation results are shown for a four cylinder engine Introduction In this paper we develop an adaptive controller for a camless engine equipped with electro hydraulic springless valvetrain The scheme amounts to control electronically the air ow into each cylinder using individual intake valve actuation This results in decoupling the driver from the engine and allows better optimization over a wide oper ating range based on pedal position and estimated torque demand Pumping losses are signi cantly reduced because conventional engine throttling is eliminated and replaced by early valve closing or valve lift control whenever nec essary Eliminating the slow intake manifold lling dy namics leads to faster breathing characteristics and can potentially increase the transient torque performance The major challenge in camless operation of a spark ignition engine is controlling the cylinder air charge rapidly and accurately based on conventional measure ments The feedback controller has to ensure regulation of the air charge trapped in the cylinders in order to be seamlessly integrated with the air to fuel ratio and spark timing control algorithms of a conventional engine man agement system Speci cally the di culty in controlling camless cylinder air charge arises from the following issues Firstly the controller has to correctly balance cylinder to cylinder variations and at the same time provide correc tion for slowly varying parameters in the engine and valve Corresponding author e mail anna engineering ucsb edu phone fax Research supported in part by the National Science Foundation under contract NSF ECS and the Departmentof Energy CooperativeAgreementNo DE FC EE matching funds were provided by FORD MO CO train components Secondly cylinder to cylinder control must be achieved using conventional engine sensors such as temperature pressure and ow into the intake mani fold The developed controller addresses these two issues It employs an adaptive feedforward scheme that regulates in dividual intake valve lift IV L and intake valve duration IV D based on mass air ow and intake manifold pres sure measurements The feedforward controller ensures fast tracking response of the cylinder air charge demand The desired cylinder air charge m that the variable valve controller must track can be speci ed by a nonlinear function of the pedal position and engine speed as shown in Figure As Figure shows the controller consists of i a feedforward controller C ii cylinder air charge esti mator and iii on line parameter estimator The adapta tion enables robust cylinder to cylinder and cycle to cycle operation it is based on the individual cylinder air charge estimation using existing intake manifold measurements Furthermore the controller minimizes pumping losses by choosing an appropriate combination of IV L and IV D Demand Map Controller C(m ,ξ) Engine Intake Valve Actuators m e Cylinder Air Charge Estimator On−Line Parameter Estimator pp