Paul Eduard Moraal

EGR-VGT control schemes: experimental comparison for a high-speed diesel engine

Variable-geometry turbochargers (VGTs) are employed in high-end diesel engines. These VGTs also help in controlling the trade-offs in emissions performance. Exhaust gas recirculation (EGR) is used to dilute the combustion mixture, resulting in lower peak combustion temperatures and a lower oxygen concentration and hence lower NOx emissions. In this article, we compare some of the control methodologies previously presented and some not yet presented to evaluate their benefits experimentally. We do not include any new theory. Rather we refer to other sources for the development of the controllers evaluated. We present an objective comparison of advanced control methodologies on a complex industrial problem with widespread applications. The control methodologies discussed are essentially system based, i.e., the initial controller is developed on an engine model.

Interpolation and numerical differentiation for observer design

This paper explores interpolation and numerical differentiation as a basis for constructing a new approach to the design of nonlinear observers.

Preserving stability/performance when facing an unknown time-delay

Abstract Embedded controllers executed in real-time are, frequently, subject to a time-varying delay induced by task prioritization or communication over prioritized communication networks. Depending on the microprocessor or network load the delay value may vary. The control design that is based on the worst case assumption with respect to the delay may be very conservative and fail to deliver the adequate performance. On the other hand, the price for not properly dealing with the delay is instability. In this paper some of these issues are discussed in more detail and a control scheme is proposed which combines an unknown input observer to estimate the delayed value of the input, an on-line estimation scheme for the delay and a controller that adjusts its gains as needed to preserve system stability. Some of the aspects of the proposed scheme are discussed and illustrated with simulations on an automotive example.

Decentralized and Multivariable Designs for EGR-VGT Control of a Diesel Engine

Abstract This paper is a study into the potential benefits of a coordinated EGRVGT control strategy for a high speed diesel engine equipped with EGR and a variable nozzle geometry turbocharger (VGT). Traditionally, control strategies for this problem use SISO techniques or use one actuator at a time. Since the effect of the EGR and VGT actuators is coupled through the pressure in the exhaust manifold, it can be expected that a coordinated approach will yield a performance benefit. We will investigate in this paper to what extent this claim holds true.

Intake oxygen concentration estimation for DI diesel engines

In order to reduce emissions and improve performance of internal combustion engines, it is desirable to know the oxygen concentration of the gas inducted into the engine so that the appropriate amount of fuel can be injected. This is especially true for diesel engines in which up to 50% of the exhaust gas is recirculated back into the engine. This work presents an estimation algorithm for the oxygen concentration in the intake manifold of a turbocharged diesel engine. The only quantities needed for the estimation scheme are boost pressure, fueling rate, engine speed and EGR valve lift, all of which are generally known to the engine control unit. This estimator is a first order linear dynamic model (with time varying coefficients) and asymptotically stable. Due to the unobservability of the oxygen concentration model, the speed of convergence of the estimation scheme is fixed by engine parameters, but is as fast as the phenomenon of mixing of the exhaust gas recirculated with the air in the intake manifold. Simulation studies show the effectiveness of the proposed estimator.

Modeling and identification of a current to vacuum transducer and VNT actuator

This paper describes a model for a current to vacuum transducer (CVT) in conjunction with a variable nozzle turbocharger (VNT) actuator. CVTs are commonly used in automotive applications for the control of exhaust gas recirculation valves, throttles, port deactivation devices, and variable geometry turbochargers. They are relatively cheap, however, their dynamic behavior exhibits serious nonlinearities. The model developed in this report serves to aid in the development and initial validation of control algorithms for vacuum actuated devices. The dynamics between CVT duty cycle input and VNT guide vane position are developed here from first principles and experimental data. The experimental data shown in this report were obtained from a 2.0 liter DI Diesel engine, equipped with the VNT-15 VNT from Allied Signal.

Experience from hosting a corporate prediction market: benefits beyond the forecasts

Prediction markets are virtual stock markets used to gain insight and forecast events by leveraging the wisdom of crowds. Popularly applied in the public to cultural questions (election results, box-office returns), they have recently been applied by corporations to leverage employee knowledge and forecast answers to business questions (sales volumes, products and features, release timing). Determining whether to run a prediction market requires practical experience that is rarely described. Over the last few years, Ford Motor Company obtained practical experience by deploying one of the largest corporate prediction markets known. Business partners in the US, Europe, and South America provided questions on new vehicle features, sales volumes, take rates, pricing, and macroeconomic trends. We describe our experience, including both the strong and weak correlations found between predictions and real world results. Evaluating this methodology goes beyond prediction accuracy, however, since there are many side benefits. In addition to the predictions, we discuss the value of comments, stock price changes over time, the ability to overcome bureaucratic limits, and flexibly filling holes in corporate knowledge, enabling better decision making. We conclude with advice on running prediction markets, including writing good questions, market duration, motivating traders and protecting confidential information.

A wavelet-based combustion noise meter

The combustion noise of diesel engines can be assessed by filtering in-cylinder pressure traces. In this paper, two wavelet-based methods are discussed. It is shown that the statistical properties of a noise meter based on shift-invariant wavelet transforms are improved compared to one that is based on traditional (shift-variant) wavelet transforms. The application of noise metering for pilot injection detection is also presented

Diesel Particulate Filter Regeneration: Control of Calibration?

Abstract Diesel particulate filters are an efficient means of reducing particulate emissions of diesel engines by orders of magnitude. The necessary periodical regeneration of these filter systems requires drastic changes in the engine management, notably in fuel and air path control, because the temperature levels required for regeneration are 200°-400°C above normal levels. The approach taken to address this problem is described in this paper. It is at the same time used to illustrate typical engine control challenges and explains why model-based control methods still find only limited application in powertrain control. In particular, the importance of feedforward control is stressed, leading to the question: Control or Calibration?

Preserving Stability/Performance when Facing an Unknown Time-Delay

Abstract Embedded controllers executed in real-time are, frequently, subject to a time-varying delay induced by task prioritization or communication over prioritized communication networks. Depending on the microprocessor or network load the delay value may vary. The control design that is based on the worst case assumption with respect to the delay may be very conservative and fail to deliver the adequate performance. On the other hand, the price for not properly dealing with the delay is instability. In this paper we discuss some of these issues in more detail and propose a scheme which combines an unknown input observer to estimate the delayed value of the input, an on-line estimation scheme for the delay and a controller that adjusts its gains as needed to preserve system stability. Some of the aspects of the proposed scheme are discussed and illustrated with simulations on an example automotive application.