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This paper presents a detailed model of a novel electropneumatic valve actuator for both engine intake and exhaust valves. The valve actuator's main function is to provide variable valve timing and variable lift capabilities in an internal combustion engine. The pneumatic actuation is used to open the valve and the hydraulic latch mechanism is used to hold the valve open and to reduce valve seating velocity. This combination of pneumatic and hydraulic mechanisms allows the system to operate under low pressure with an energy saving mode. It extracts the full pneumatic energy to open the valve and use the hydraulic latch that consumes almost no energy to hold the valve open. A system dynamics analysis is provided and followed by mathematical modeling. This dynamic model is based on Newton's law, mass conservation, and thermodynamic principles. The air compressibility and liquid compressibility in the hydraulic latch are modeled, and the discontinuous nonlinearity of the compressible flow due to choking is carefully considered. Provision is made for the nonlinear motion of the mechanical components due to the physical constraints. Validation experiments were performed on a Ford 4.6 l four-valve V8 engine head with different air supply pressures and different solenoid pulse inputs. The simulation responses agreed with the experimental results at different engine speeds and supply air pressures. [DOI: 10.1115/1.4000816] Keywords: automotive systems, powertrain systems, camless valve actuation, hydraulic and pneumatic system model

This paper presents experimental investigation results of an electric variable valve timing (EVVT) actuator using linear parameter varying (LPV) system identification and control. For the LPV system identification, a number of local system identification tests were carried out to obtain a family of linear time-invariant (LTI) models at fixed engine speed and battery voltage. Using engine speed and battery voltage as time-varying scheduling parameters, the family of local LTI models is translated into a single LPV model. Then, a robust gain-scheduling (RGS) dynamic output-feedback (DOF) controller with guaranteed H∞ performance was synthesized and validated experimentally. In contrast to the vast majority of gain-scheduling literature, scheduling parameters are assumed to be polluted by measurement noises and the engine speed and battery voltage are modeled as noisy scheduling parameters. Experimental and simulation results show the effectiveness of the developed approach. [ABSTRACT FROM AUTHOR]

State-feedback gain-scheduling controller synthesis with guaranteed performance is considered in this brief. Practical assumption has been considered in the sense that scheduling parameters are assumed to be uncertain. The contribution of this paper is the characterization of the control synthesis that parameterized linear matrix inequalities (PLMIs) to synthesize robust gain-scheduling controllers. Additive uncertainty model has been used to model measurement noise of the scheduling parameters. The resulting controllers not only ensure robustness against scheduling parameters uncertainties but also guarantee closed-loop performance in terms of H2 and H∞ performances as well. Numerical examples and simulations are presented to illustrate the effectiveness of the synthesized controller. Compared to other control design methods from literature, the synthesized controllers achieve less conservative results as measurement noise increases. [ABSTRACT FROM AUTHOR]

This paper presents a model of an electric variable valve timing (EWT) system and its closed-loop control design with experimental validation. The studied EWT uses a plane-tary gear system to control the engine cam timing. The main motivation of utilizing the EWT system is its fast response time and the accurate timing control capability. This is critical for the combustion mode transition control between the spark ignition (SI) and homogeneous charge compression ignition (HCCI) combustion, where the engine cam timing needs to follow a desired trajectory to accurately control the engine charge and recompression process. A physics-based model was developed to study the characteristics of the EWT system, and a control oriented EWT model, with the same structure as the physics-based one, was obtained using closed-loop system identification. The closed-loop control strategies were developed to control the EWT to follow a desired trajectory. Both simulation and bench test results are included. [ABSTRACT FROM AUTHOR]

Modern spark ignited (SI) internal combustion engines maintain their air-to-fuel ratio (AFR) at a desired level to maximize the three-way catalyst conversion efficiency and du-rability. However, maintaining the engine AFR during its transient operation is quite challenging due to rapid changes of driver demand or engine throttle. Conventional tran-sient AFR control is based upon the inverse dynamics of the engine fueling dynamics and the measured mass air flow (MAF) rate to obtain the desired AFR of the gas mixture trapped in the cylinder. This paper develops a linear quadratic (LQ) tracking controller to regulate the transient AFR based upon a control-oriented model of the engine port fuel injection (PFI) wall wetting dynamics and the air intake dynamics from the measured air-flow to the manifold pressure. The LQ tracking controller is designed to optimally track the desired AFR by minimizing the error between the trapped in-cylinder air mass and the product of the desired AFR and fue I mass over a given time interval. The performance of the optimal LQ tracking controller was compared with the conventional transient fuel-ing control based on the inverse fueling dynamics through simulations and showed improvement over the baseline conventional inverse fueling dynamics controller. To vali-date the control strategy on an actual engine, a 0.4 I single cylinder direct-injection (DI) engine was used. The PFI wall wetting dynamics were simulated in the engine controller after the DI injector control signal. Engine load transition tests for the simulated PFI case were conducted on an engine dynamometer, and the results showed improvement over the baseline transient fueling controller based on the inverse fueling dynamics. [ABSTRACT FROM AUTHOR]

A multi-input-multi-output (MIMO) sliding mode control scheme was developed with guaranteed stability to simultaneously control air-to-fuel ratio (AFR) and fuel ratios to desired levels under various air flow disturbances by regulating the mass flow rates of engine port-fuel-injection (PFI) and direct injection (DI) systems. The sliding mode control peiformance was compared with a baseline multiloop proportional integral differential (PID) controller through simulations and showed improvements. A four cylinder mean value engine model and the proposed sliding mode controller were implemented into a hardware-in-the-loop (HIL) simulator and a target engine control module, and HIL simulations were conducted to validate the developed controller for potential implementation in an automotive engine. [ABSTRACT FROM AUTHOR]

This paper applies integrated system modeling and control design process to a continuously variable valve timing (VVT) actuator system that has different control input and cam position feedback sample rates. Due to high cam shaft torque disturbance and high actuator open-loop gain, it is also difficult to maintain the cam phase at the desired constant level with an open-loop controller for system identification. As a result, multirate closed-loop system identification becomes necessary. For this study, a multirate closed-loop system identification method, pseudo-random binary signal q-Markov Cover, was used for obtaining linearized system models of the nonlinear physical system at different engine operational conditions: and output covariance constraint (OCC) controller, an H2 controller, was designed based upon the identified nominal model and evaluated on the WT test bench. Performance of" the designed OCC controller was compared with that of the well-tuned baseline proportional-integral (PI) controller on the test bench. Results show that the OCC controller uses less control effort and has significant lower overshoot than those of PI ones. [ABSTRACT FROM AUTHOR]

This paper presents a detailed model of a novel electropneumatic valve actuator for both engine intake and exhaust valves. The valve actuator's main function is to provide variable valve timing and variable lift capabilities in an internal combustion engine. The pneumatic actuation is used to open the valve and the hydraulic latch mechanism is used to hold the valve open and to reduce valve seating velocity. This combination of pneumatic and hydraulic mechanisms allows the system to operate under low pressure with an energy saving mode. It extracts the full pneumatic energy to open the valve and use the hydraulic latch that consumes almost no energy to hold the valve open. A system dynamics analysis is provided and followed by mathematical modeling. This dynamic model is based on Newton's law, mass conservation, and thermodynamic principles. The air compressibility and liquid compressibility in the hydraulic latch are modeled, and the discontinuous nonlinearity of the compressible flow due to choking is carefully considered. Provision is made for the nonlinear motion of the mechanical components due to the physical constraints. Validation experiments were performed on a Ford 4.6 l four-valve V8 engine head with different air supply pressures and different solenoid pulse inputs. The simulation responses agreed with the experimental results at different engine speeds and supply air pressures. [ABSTRACT FROM AUTHOR]

Engine downsizing and down-speeding are essential in order to meet future U.S. fuel economy (FE) mandates. Turbocharging is one technology to meet these goals. Fuel economy improvements must, however, be achieved without sacrificing performance. One significant factor impacting drivability on turbocharged engines is typically referred to as "turbolag." Since turbolag directly impacts the driver's torque demands, it is usually perceptible as an undesired slow transient boost response or as a sluggish torque response. High throughput turbochargers (TC) are especially susceptible to this dynamic and are often equipped with variable geometry turbines (VGT) to mitigate some of this effect. Assisted boosting techniques that add power directly to the TC shaft from a power source that is independent of the engine have been shown to significantly reduce turbolag. Single unit assisted turbochargers are either electrically assisted or hydraulically assisted. In this study, a regenerative hydraulically assisted turbocharger (RHAT) system is evaluated. A custom-designed RHAT system is coupled to a light duty diesel engine and is analyzed via vehicle and engine simulations for performance and energy requirements over standard test cycles. Supplier-provided performance maps for the hydraulic turbine, hydraulic turbopump were used. A production controller was coupled with the engine model and upgraded to control the engagement and disengagement of RHAT, with energy management strategies. Results show some interesting dynamics and shed light on system capabilities especially with regard to the energy balance between the assist and regenerative functions. Design considerations based on open-loop simulations are used for sizing the high-pressure accumulator. Simulation results show that the proposed RHAT turbocharger system can significantly improve engine transient response. Vehicle level simulations that include the driveline were also conducted and showed potential for up to 4% fuel economy improvement over the FTP 75 drive cycle. This study also identified some technical challenges related to optimal design and operation of the RHAT. Opportunities for additional fuel economy improvements are also discussed. [ABSTRACT FROM AUTHOR]