Jeffrey A. Cook

Modeling of an internal combustion engine for control analysis

Recent activity in nonthermodynamic modeling of automotive internal combustion engines with spark ignition, which are inherently nonlinear, is reviewed. A fundamental nonlinear model of the engine is presented, and a linear control-oriented model is derived from the nonlinear process. Techniques for experimental verification are examined, and a practical linear engine example incorporating multirate sampling is illustrated.<<ETX>>

Individual cylinder air-fuel ratio control with a single EGO sensor

An approach to achieving uniform cylinder-to-cylinder air-fuel ratio control in the face of injector mismatch and unbalanced airflow due to engine geometry is presented. A key feature of the proposed method is that it functions well with the switching-type exhaust gas oxygen sensor commonly used in automobiles. The controller design, from modeling to experimental implementation in a dynamometer test facility, is documented. A method for achieving an extended operating region based on scheduling the sampling is described. >

An Energy Management Controller to Optimally Trade Off Fuel Economy and Drivability for Hybrid Vehicles

Hybrid vehicle fuel economy performance is highly sensitive to the energy management strategy used to regulate power flow among the various energy sources and sinks. Optimal non-causal solutions are easy to determine if the drive cycle is known a priori. It is very challenging to design causal controllers that yield good fuel economy for a range of possible driver behavior. Additional challenges come in the form of constraints on powertrain activity, such as shifting and starting the engine, which are commonly called “drivability” metrics and can adversely affect fuel economy. In this paper, drivability restrictions are included in a shortest path stochastic dynamic programming (SP-SDP) formulation of the real-time energy management problem for a prototype vehicle, where the drive cycle is modeled as a stationary, finite-state Markov chain. When the SP-SDP controllers are evaluated with a high-fidelity vehicle simulator over standard government drive cycles, and compared to a baseline industrial controller, they are shown to improve fuel economy more than 11% for equivalent levels of drivability. In addition, the explicit tradeoff between fuel economy and drivability is quantified for the SP-SDP controllers.

Nonlinear Low Frequency Phenomenological Engine Modeling and Analysis

The paper contains a bibliography and discussion of recent activity in nonthermodynamic (low frequency) internal combustion engine model development where spark advance, fuel, throttle, and exhaust gas recirculation are the elected control variables. Modeling considerations are delineated and the modeling relationship to experimental verification is discussed. Examples with explicit methods of parameter determination and dynamic validation are presented.

Improved cylinder air charge estimation for transient air fuel ratio control

Modern automobile engines require precise regulation of air-fuel ratio (A/F) to attain high catalytic converter efficiency and minimize tailpipe emissions. During engine transients, good A/F control requires, in turn, accurate estimation of the air charge entering the cylinders during each induction event. This paper describes the development and validation of a nonlinear, open-loop air charge estimator. A key feature is the inclusion of the dynamics of the mass air flow meter. The estimator was implemented on a V8 engine in a dynamometer test cell. Experimental results confirm the improved A/F control predicted by simulation. The prototype implementation was accomplished using an automatically generated high-level language control code executing in a dedicated PC and communicating via a shared memory board with the production microprocessor-based controller.

Sliding mode control for variable geometry turbocharged diesel engines

Accurate air-to-fuel ratio and exhaust gas recirculation (EGR) rate control are important for emission reduction in turbocharged diesel engines. In the paper, assuming that the diesel engine is equipped with a variable geometry turbocharger, a sliding mode controller is developed to control the turbine vanes so that, in conjunction with an EGR valve controller, stabilization of the engine variables to the desired equilibrium is achieved.

Control-Oriented Model of a Dual Equal Variable Cam Timing Spark Ignition Engine

A control-oriented engine model is developed to represent a spark ignited engine equipped with a variable cam timing mechanism over a wide range of operating conditions. Based upon laboratory measurements a continuous, nonlinear, low-frequency phenomenological engine model is developed. With respect to a fixed-cam timing engine, the VCT mechanism alters the mass air flow into the cylinders, the torque response, and the emissions of the engine. The developed model reflects all of these modifications and includes a representation of the breathing process, torque and emission generation, and sensor/actuator dynamics. The model has been validated with engine-dynamometer experimental data and can be used in powertrain controller design and development.

Torque management of engines with variable cam timing

This paper describe the variable cam timing (VCT) system which addresses both the drivability and emission performance by utilising an electric hydraulic mechanism to rotate the camshaft relative to the crankshaft in order to retard the cam timing with respect to the intake and exhaust strokes of the engine. By retarding the exhaust valve closing further into the intake stroke, more exhaust gas is drawn into the cylinder providing internal exhaust gas recirculation. In this manner, the amount of residual gas trapped in the cylinder at the end of the exhaust stroke is controlled by cam timing, suppressing NOx formation and reducing the pumping losses. Furthermore, this residual contains some unburned hydrocarbons; consequently, retaining it in the cylinder through two combustion cycles also reduces hydrocarbon emissions. In addition to the reduction of NOx and HC emissions, variable cam timing permits the engine designer to optimize cam timing over a wide range of engine operating conditions.

Incorporating drivability metrics into optimal energy management strategies for Hybrid Vehicles

Hybrid Vehicle fuel economy performance is highly sensitive to the energy management strategy used to select among multiple energy sources. Optimal solutions are easy to specify if the drive cycle is known a priori. It is very challenging to compute controllers that yield good fuel economy for a class of drive cycles representative of typical driver behavior. Additional challenges come in the form of constraints on powertrain activity, like shifting and starting the engine, which are commonly called ¿drivability¿ metrics. These constraints can adversely affect fuel economy. The benefits of including drivability restrictions in a Shortest Path Dynamic Programming (SPDP) formulation of the energy management problem are investigated for the first time. It is shown that this method yields up to 10% fuel economy improvement on a representative parallel electric hybrid when compared to a simpler instantaneous optimization formulation. This result is obtained by comparing a SPDP controller designed for drivability to a second SPDP controller, designed for fuel economy only, that uses an additional instantaneous optimization step for the incorporation of drivability. The results also quantify the tradeoff between drivability and fuel economy.

Control, Computing and Communications: Technologies for the Twenty-First Century Model T

In the early twentieth century, the Model T Ford defined the desirable, affordable automobile, enabled by new technologies in mechanics, materials, and manufacturing. Control, computing, communications, and the underlying software are the technologies that will shape the personal mobility experience of the twenty-first century. While the Model T was self-contained, the external reach of wireless communication technologies will define the boundaries of the twenty-first century automobile, which will be only one component in a large intelligent transportation infrastructure. This paper reviews advances in control for safety, fuel economy and reduction of tailpipe emissions, and new directions in computing, communication and software, including the interaction of the automobile with consumer electronic devices and the intelligent transportation infrastructure