Thomas Leroy

Control-oriented time-varying input-delayed temperature model for SI engine exhaust catalyst

This paper proposes a model for the internal temperature of a SI engine catalyst. The modeling approach is grounded on a one-dimensional distributed parameter model, which is approximated by a time-varying input-delay system whose dynamics parameters (time constant, delay, gains) are obtained through a simple analytic reduction procedure. Following recent works, the distributed heat generation resulting from pollutant conversion is shown here to be equivalent to an inlet temperature entering the system at a virtual front inside the catalyst. The gain of this new input introduces a coupling to account for the conversion efficiency. Relevance of this model is qualitatively supported by experimental data.

Towards real-time optimal energy management of HEV powertrains using stochastic dynamic programming

This paper is concerned with the control of hybrid electric vehicles. In the vast literature on the subject, focus is put on the minimization of the fuel consumption. To do so, the deterministic optimal control theory is intensively used. The major concern regarding this approach is the need for driving conditions to be known in advance. In this paper, we suggest to consider the driving cycle as a stochastic process, and make use of the stochastic dynamic programming (SDP) to design the power load sharing. We formulate a weighted criterion to minimize fuel consumption and allow for drivability conditions at the same time. The resulting control law may easily be implemented online as a static mapping function of the powertrain state. We provide simulation results based on a parallel HEV case study. We use statutory cycles to build a database of randomly generated cycles. This allows to assess the relevancy of this approach by comparing optimal fuel consumption (using deterministic programming), for each cycle, to the score obtained via the SDP framework. These preliminary results show that the SDP is a promising control tool to overcome the drawbacks inherent to the classical approaches.

Prediction-based trajectory tracking of external gas recirculation for turbocharged SI engines

This paper addresses the trajectory tracking problem of intake burned gas rate for Spark Ignited engines. We propose a simple linear time-varying input delay model of this dynamics, where the delay is represented by an implicit integral equation involving the past values of the input. We extend some recent results from the literature to design a novel predictor-based controller and compare the merits of the proposed technique with the ones of previous works from the literature. Simulation results stress the relevance of this preliminary work and directions of future work are provided.

Stochastic Dynamic Programming based Energy Management of HEV's: an Experimental Validation

Abstract This paper addresses an experimental validation of an energy management strategy on a parallel Hybrid Electric Vehicle (HEV). The strategy under consideration is based on Stochastic Dynamic Programming. The control law (determining the torque split between the engine and the motor) is computed off-line by solving an infinite horizon optimization problem. It results in a time-invariant state feedback controller function of vehicle acceleration and velocity, battery state of charge and engine state. This controller is first validated in simulation and then implemented in the vehicle electronic control unit. Experimental results highlight the good behavior of the control strategy. During a 35 km urban route, the strategy succeeds in regulating the battery state of charge and judiciously uses the powertrain.

Practical delay modeling of externally recirculated burned gas fraction for Spark-Ignited Engines

In this chapter, the authors provide an overview and study of the low-pressure burned gas recirculation in spark-ignited engines for automotive powertrain. It is shown, at the light of supportive experimental results, that a linear delay system permits to capture the dominant effects of the system dynamics. The modeled transport delay is defined by implicit equations stemming from first principles and can be calculated online. This model is shown to be sufficiently accurate to replace a sensor that would be difficult and costly to implement on commercial engines.

Estimation of the distributed temperature of a SI engine catalyst for light-off strategy

This paper proposes a model for the internal temperature of a SI engine catalyst, aiming at designing a prediction-based light-off strategy. Due to its elongated geometry where a gas stream is in contact with a spatially distributed monolith, the system under consideration is inherently a distributed parameter system. This paper advocates an approach which is based on a one-dimensional distributed parameter model, coupled with an advection-diffusion equation accounting for the distributed heat generation resulting from pollutant conversion. Following recent works, this heat supply is shown here to be equivalent to an inlet temperature entering the system at a virtual entry point inside the catalyst. This new input has a static gain depending on the state of the system, which introduced a coupling. Taking advantage of the low-pass filter characteristic of the system, an estimate of this model is designed and results into a time-varying input-delay system whose dynamics parameters (time constant, delay, gains) are obtained through a simple analytic reduction procedure. A corresponding prediction-based light-off strategy is proposed and illustrated in simulations exploiting experimental data.

Impact of Driveability Constraints on Local Optimal Energy Management Strategies for Hybrid Powertrains

Abstract The paper deals with the issue of energy management in hybrid electric vehicles, considering possible solutions for addressing the power split in real-life conditions. The focus is on the comparison between two local optimal on-line energy management strategies: Stochastic Dynamic Programming (SDP) and Equivalent Consumption Minimization Strategy (ECMS). First, results of fuel consumption for simulation on 100 random driving cycles for the two strategies, tuned for best fuel consumption, are provided. Then, some driveability considerations, regarding engine utilization profile and dwell time, are made. The results of the simulation of the two strategies incorporating driveability constraints are discussed, showing a substantial change of situation with respect to the initial case.

Trustworthy Estimation and Control of Engine Knocking Level for Transient Operation

The contribution of the paper is to propose a knock controller based on the estimation of the distribution quantile of the knock intensity measures. Despite the quantile estimation randomness, the corrections undertaken by the controller are moderated by the level of confidence in the quantile estimation. This strategy offers a fast and stable control ensuring a better compromise between the engine efficiency and the prevention of knock phenomenon. The design of the controller stabilizes the engine torque and is suited for engine transient operations.

Control-Oriented Input-Delay Model of the Distributed Temperature of a SI Engine Exhaust Catalyst

This chapter aims at showing how a particular class of input delay ordinary differential equations, in which the time- and input-dependent delay is defined through an implicit integral equation, can be used to model accurately the internal temperature of a Spark-Ignited engine catalyst. The modeling approach is grounded on a one-dimensional distributed parameter model, which is approximated by a time-varying first-order delay system whose dynamics parameters (time constant, delay, gains) are obtained through a simple analytic reduction procedure. Following recent works, the distributed heat generation resulting from pollutant conversion is shown here to be equivalent to an inlet temperature entering the system at a virtual front inside the catalyst. The gain of this new input introduces a coupling to account for the conversion efficiency. Relevance of this real-time compliant model is qualitatively supported by experimental data.

Boost Pressure Control of Twincharger Diesel Engines

Abstract This paper addresses the boost pressure control of twincharger equipped Diesel engines. The variable geometry turbine and the supercharger by-pass are the two control inputs of the system. A static and dynamic analysis of the system is performed, highlighting a decoupling of the dynamics between the turbocharger and the supercharger. This allows the control problem to be reduced to two SISO problems. Consequently, the focus is put on controlling the boost pressure using the supercharger by-pass, the turbocharger control strategy remaining as-is. The proposed control strategy is based on a feedback linearization, using a physical model of the engine airpath. Experimental results stress the relevance of the approach.