Search Results

A controller that fully utilizes the available motor capacity of an electromechanical brake to achieve high closed-loop bandwidth is proposed. The controller is developed based on the time-optimal switching curve derived from Pontryagin's Maximum Principle. The control input is scheduled using a switching surface based on the current motor velocity and position offset. Robustness to modeling errors is achieved by introducing a boundary layer in vicinity of the switching curve, reminiscent of a high gain controller. A flexible tuning procedure is also developed to aid in practical implementation, allowing a balanced choice between tracking speed and energy usage. The controller is implemented on a production-ready prototype EMB, and tested over different braking scenarios to assess the performance and robustness relative to the benchmark controllers. It is demonstrated that significant improvements in step response and dynamic tracking are obtained using the proposed approach.

A novel method for attenuation of brake judder directly at the source is proposed, utilizing an electromechanical brake to actively compensate for the variation in brake torque that causes judder. Taking advantage of the high-bandwidth closed-loop clamp force tracking performance offered by an electromechanical brake, an adaptive compensator is designed to estimate the brake torque variation (BTV), and to produce a compensating clamp force command to cancel it. The compensator is tested over fixed and varying BTV frequencies by employing a production-ready prototype EMB. It is demonstrated that significant BTV attenuation is obtained using the proposed approach.

Hybrid and fully electric vehicles are becoming more common as a response to rising fuel prices and greenhouse considerations. While the benefits of electrification on urban air quality have been studied quite widely, financial assessments of the various alternative vehicle forms are less common, particularly for Australian driving conditions. The aim of this paper is therefore to identify the scenarios under which different vehicle configurations are attractive to the vehicle owner. A Class-E conventional vehicle is compared with full-electric, plug-in hybrid, parallel hybrid, series hybrid and mild hybrid electric vehicle configurations. A simulation model of a conventional internal combustion engine based large sized car is developed and validated against experimental data. The conventional vehicle model is then systematically altered to obtain its increasingly electric variants.

The cold start emissions from gasoline fuelled vehicles are a major challenge when meeting vehicle emissions regulation. Vehicle manufacturers therefore undertake extensive design and testing of the entire exhaust and engine control systems, which is both time consuming and costly. This is particularly an issue with the growing number of control parameters in modern powertrains. This paper presents a methodology that integrates appropriate physics-based models of the engine and aftertreatment into a numerical optimisation scheme, and is proposed as a possible means of reducing this calibration effort. The methodology is demonstrated over a prescribed drive cycle by identifying the optimal spark timing trajectory that maximises fuel economy while meeting emissions constraints. The trends in the resulting control policy are explained and the results are validated where possible.

The minimisation of tail-pipe emissions and fuel consumption during cold-start can be viewed as a constrained optimisation problem involving many parameters. Examining this problem mathematically first requires an accurate and computationally practical model of the engine and exhaust system. This paper proposes such a model for use during the cold-start of a conventional spark ignition engine. This model uses as much physics-based modelling as is computationally practical for optimisation and control studies. It takes a given set of engine control inputs to simulate tailpipe CO , HC and NO emissions, and is both calibrated and validated using detailed measurements obtained on a transient engine dynamometer following the New European Drive Cycle (NEDC).

This paper proposes a new systematic procedure for model reduction of TC SI engines. The technique is based on the identification of time scale separation within the dynamics of various engine state variables. The model reduction is performed in two stages. First stage is to use dynamic properties of the engine states to obtain reduced order slow and fast time scale subsystems. Then in the second stage, physical characteristics are considered to isolate fast pressures. As a result a library of the control oriented engine models is obtained. The limitation of the reduced order models as a true representation of original model is first gauged qualitatively by the application of perturbation theory and then characterized quantitatively by means of simulations. Various assumptions under which these model reductions are applicable are presented and their validity in the context of the engine are discussed.

This paper proposes the use of support vector machines to reconstruct the indicated torque from crankshaft velocity in a six-cylinder spark ignition engine. Real-time knowledge of indicated torque is typically important for engine diagnostics, and recently, an engine idle speed controller capable of reducing the effects of cyclic combustion variability through the use of indicated torque information was proposed. While measurements of in-cylinder pressure can be used to determine indicated torque, these sensors are generally deemed prohibitively expensive for implementation in a production engine. Estimation methods, particularly traditional model based estimation, are typically computationally expensive and require independent data throughout the cylinder expansion stroke. Overlap of the expansion strokes in a six-cylinder engine complicates the problem and limits the ability of traditional model based approaches in fully reconstructing the torque production process.

A disk brake clamp force controller for electromechanical brakes (EMB) in automotive brake-by-wire systems may be obtained from a standard motion control architecture with cascaded position, speed and current control loops by replacing the outer position control loop with a force control loop. When implemented with proportional, integral and differential (PID) controllers this architecture generally performs well for standard motion control problems, but the EMB control problem is differentiated by a large operating range in which non-linear load disturbances such as friction become significant at high clamp forces of up to 30kN. This paper investigates the feasibility of a cascaded PI control architecture for an EMB with the intention of establishing a baseline standard against which the performance of future control schemes may be compared. Simulation results are presented based on an accepted EMB model.

The variability of in-cylinder combustion of gasoline at idle has been investigated previously, culminating in the development of a model relating the past and future indicated torque deviations from the mean at given engine operating conditions of intake manifold pressure, engine speed and spark advance. The developed model has the potential to be used in an idle speed control algorithm to improve vehicle noise vibration and harshness (NVH) at low engine speeds and loads. While environmental considerations have spawned the development of liquefied petroleum gas (LPG) as a viable alternative fuel, adaptation of the variability model to multipoint LPG injected automotive engines is complicated by the fact that the fuel mixture concentrations of propane and butane are subject to wide variations depending on a variety of factors including geographic location and local market pricing.

Air-fuel ratio control in gasoline engines has so far relied upon the fact that the stoichiometric air-fuel ratio of gasoline is an identified constant, largely thanks to its consistent chemical composition. In the case of Liquefied Petroleum Gas (LPG), chemical composition is subject to high variability due to geological and economic factors, amongst others. The implication of this variability is unpredictable stoichiometric air-fuel ratio of the fuel supply within any given vehicle, and ultimately degraded control of air-fuel ratio. This paper addresses the problem of stoichiometric air-fuel ratio estimation by evaluating the measurement and modeling of the relative permittivity of fuel, and also the method of iterative computation. For the estimation method proposed in this paper, simulation results are presented to demonstrate its effectiveness.

Combustion in the cylinder of a spark ignition engine, particularly under low load conditions, is subject to cycle-by-cycle variations due to factors such as mixture quality and quantity and internal exhaust gas recirculation. The major result of this phenomenon is an increase in the variability of indicated engine torque at a given engine operating point. Automotive control problems dealing with torque production at low engine loads, particularly the control of idle speed, rely on accurate information about the transfer functions of different engine subsystems, however combustion variability and the effect it has on torque production is often overlooked. In this paper we illustrate the effects that combustion variability at idle has on different transfer functions related to indicated torque, and propose new models for torque production at constant operating points.