Per Andersson

Modeling of a turbocharged SI engine

Turbocharged SI engines are a major possibility in the current trend of down-sized engines with preserved drivability performance. Considering control and supervision it is favorable to have a mean value model to be used e.g. in observer design. Such models of turbo engines are similar to those of naturally aspirated engines, but there are some special characteristics, e.g. the interconnected gas flows, the intercooler, the difference in relative sizes between the gas volumes (compared to naturally aspirated engines), the turbo, and the waste gate. Here, a model is developed with a strategy to find a model for each engine component (air filter, compressor, after cooler (or intercooler), throttle, engine, turbine, waste gate, and a lumped model for the catalyst and exhaust) as they behave in an engine setting. When investigating agreement with measured data and sensitivity of possible model structures, a number of interesting issues are raised. The experiments and the model validation have been performed on a Saab 2.3 1 production engine.

Air-to-Cylinder Observer on a Turbocharged SI-Engine with Wastegate

Observers for air mass flow to the cylinder is studied on a turbocharged SI-engine with wastegate. A position change of the wastegate influences the residual gas mass and causes the volumetric effi ...

Cylinder Air Charge Estimator in Turbocharged SI-Engines

Mean value cylinder air charge (CAC) estimation models for control and diagnosis are investigated on turbocharged SI-engines. Two topics are studied; Firstly CAC changes due to fuel enrichment and secondly CAC sensitivity to exhaust manifold pressure changes. The objective is to find a CAC model suitable for control and diagnosis. Measurements show that CAC models based on volumetric efficiency gives up to 10% error during fuel enrichment. The error is caused by the cooling effect that the fuel has as it evaporates and thus increases the charge density. To better describe the CAC during fuel enrichment a simple one parameter model is proposed which reduces the CAC estimation error on experimental data from 10% to 3%. With active wastegate control, the pressure changes in the exhaust manifold influences the CAC. The magnitude of this influence is investigated using sensitivity analysis on an exhaust manifold pressure dependent CACmodel. From the sensitivity analysis it can be concluded, that the CAC is most sensitive to exhaust manifold pressure changes for low intake manifold pressures (part load). Without taking the exhaust manifold pressure into account the CAC error is approximately 5% when the wastegate is opened at part load. The exhaust manifold pressure dependent CAC model is then augmented with the charge cooling model and the total model gives precise agreement on experimental data. The resulting model is thus highly suitable for CAC estimation for control and diagnosis of turbocharged SI-engines.

Recognition of knowledge and skills at work : In whose interests?

Purpose – Work‐place learning takes place in many settings and in different ways, resulting in knowledge and skills of different kinds. The recognition process in the work place is however often implicit and seldom discussed in terms of recognition of prior learning (RPL). The aim of this paper is to give examples of how the knowledge/skills of employees get recognition in the workplace and to discuss what the consequences of such recognition processes might be.Design/methodology/approach – This paper is based on a study in two companies and two municipalities, where 21 interviews were conducted with human resource managers, team leaders and union representatives. The research questions concerned the ways skills were recognised among employees and how the logics of these actions could be understood.Findings – The findings show that both companies and municipalities have their own ways of assessing knowledge/skills, mostly out of a production logic of what is needed at the workplace. However, certain skill...

Detection of Exhaust Manifold Leaks on a Turbocharged SI-Engine with Wastegate

Emissions from modern SI-engines are reduced by a three way catalyst. However if there are leaks in the exhaust system before the catalyst emissions increase for two reasons. First the untreated emissions leak out. Second which is worse, due to waves in the exhaust system, oxygen leaks into the manifold and causes an oxygen sensor offset. The result is increased emissions as the air/fuel controller makes the engine run rich. Here a method to detect leakages in the exhaust manifold is presented. The sensors used are binary oxygen sensor(s), intake manifold pressure and temperature, and the air mass flow sensor. Injection time is also used to estimate air/fuel ratio. Experimental results are shown with measurements from a turbo charged SAAB SI production engine with wastegate.

Point-of-Care Troponin T Testing in the Management of Patients with Chest Pain in the Swedish Primary Care

Objective. To investigate the diagnostic accuracy and clinical benefit of point-of-care Troponin T testing (POCT-TnT) in the management of patients with chest pain. Design. Observational, prospective, cross-sectional study with followup. Setting. Three primary health care (PHC) centres using POCT-TnT and four PHC centres not using POCT-TnT in the southeast of Sweden. Patients. All patients ≥35 years old, contacting one of the primary health care centres for chest pain, dyspnoea on exertion, unexplained weakness, and/or fatigue with no other probable cause than cardiac, were included. Symptoms should have commenced or worsened during the last seven days. Main Outcome Measures. Emergency referrals, patients with acute myocardial infarctions (AMI), or unstable angina (UA) within 30 days of study enrolment. Results. 25% of the patients from PHC centres with POCT-TnT and 43% from PHC centres without POCT-TnT were emergently referred by the GP (P = 0.011 ). Seven patients (5.5%) from PHC centres with POCT-TnT and six (8.8%) from PHC centres without POCT-TnT were diagnosed as AMI or UA (P = 0.369). Two patients with AMI or UA from PHC centres with POCT-TnT were judged as missed cases in primary health care. Conclusion. The use of POCT-TnT may reduce emergency referrals but probably at the cost of an increased risk to miss patients with AMI or UA.

Mean-value Observer for a Turbocharged SI-engine

Abstract For air/fuel control, where the cylinder air charge (CAC) estimation is based on intake manifold pressure, it is essential to reduce the noise from measured intake manifold pressure signals while at the same time keeping the phase delays low during transients. Observers provide means of filtering without introducing large delays and therefore an observer is developed with emphasis on CAC estimation for air/fuel ratio control. It also enables model based diagnosis opportunities. The observer is based on a nonlinear mean value engine model including the intake and exhaust side together with turbine shaft speed. The observer feedback gains are determined using an extended Kalman filter. Systematic methods are presented to determine the covariance matrices for the noise and as part of that a novel method is presented to determine the state noise based on the model quality. Additional performance benefits are demonstrated when the model is augmented with one state. The observer is evaluated using real engine data with feedback from measured pressures in the intake manifold and after the intercooler. It shows very good results for CAC estimation as it suppresses intake manifold pressure noise without introducing phase delays. It also provides an accurate estimate of turbocharger speed. Therefore it is highly suitable for control and diagnosis in turbocharged SI-engines.

Consequences of high-sensitivity troponin T testing applied in a primary care population with chest pain compared with a commercially available point-of-care troponin T analysis : an observational prospective study

BackgroundThere is a demand for a highly sensitive and specific point-of care test to detect acute myocardial infarction (AMI). It is unclear if a high-sensitivity troponin assay will have enough discriminative power to become a decision support in primary care. The aim of this study was to evaluate a high-sensitivity troponin T assay performed in three primary health care centres in southeast Sweden and to compare the outcome with a point-of-care troponin T test.MethodsThis study included 115 patients who consulted their general practitioner for chest pain, dyspnoea on exertion, unexplained weakness and/or fatigue in the last 7xa0days. Troponin T was analysed by a point-of-care test and a high-sensitivity method together with N-terminal pro-B-type natriuretic peptide (NT-proBNP) and creatinine. All patients were checked for AMI or unstable angina (UA) within 30xa0days of study enrolment. Univariate and multivariate logistic regression was carried out to examine possible connections between troponin Txa0≥xa015xa0ng/L, clinical variables and laboratory findings at baseline. In addition, 21 patients with troponin Txa0≥xa015xa0ng/L and no signs of AMI or UA were followed up for 2–3xa0years.ResultsThree patients were diagnosed with AMI and three with UA. At the ≥xa015xa0ng/L cut-off, the troponin T method had 100% sensitivity, 75% specificity for AMI and a positive predictive value of 10%. The troponin T point-of-care test missed one case of AMI and the detection limit was 50xa0ng/L. Troponin Txa0≥xa015xa0ng/L was correlated to age ≥65xa0years (odds ratio (OR), 10.9 95% CI 2.28–51.8) and NT-proBNP in accordance with heart failure (OR 8.62 95% CI 1.61–46.1). Fourteen of the 21 patients, without signs of AMI or UA at baseline, still had increased troponin T at follow-up after 2–3xa0years.ConclusionsA high-sensitivity troponin T assay could become useful in primary care as a point-of-care test for patients <65xa0years. For patients older than 65–70xa0years, a higher decision limit than ≥15xa0ng/L should be considered and used in conjunction with clinical parameters and possibly with NT-proBNP.

Exhaust Manifold Pressue Estimation on a Turbocharged SI-Engine with Wastegate

The exhaust pressure can change rapidly in a turbocharged engine with wastegate. This paper presents a method to estimate the exhaust manifold pressure for diagnosis of wastegate and turbocharger on spark ignited engines. The method does not require any extra sensors in the exhaust system after the calibration. Also discussed is the development of a nonlinear model of the exhaust pressure. It is determined that estimates of the exhaust manifold pressure rely on information from an air-to-cylinder observer and a static map of stationary exhaust pressure, The paper validates the exhaust manifold pressure estimator by using a series of wastegate steps on a turbocharged Saab 2.3 l SI engine. The exhaust pressure estimation is designed for steady-state conditions and the validation shows that it works well and converges within 1 to 4 seconds.

Observer Based Feedforward Air-Fuel Control of Turbocharged SI-Engines

Abstract Air-fuel control on turbocharged (TC) SI-engines require precise prediction of the cylinder air-charge (CAC). Using an observer it is possible to both estimate the necessary system states and to provide a framework to design the necessary CAC feedforward controller. Here a mean value engine model of a TC SI-engine is used to develop an observer. The output of the observer is fed as an initial condition to a predictor which is used for feedforward of the CAC for air-fuel control. The resulting controller is experimentally validated on a SAAB 2.0 dm 3 TC engine using tip-in and tip-out transients. The results show that the excursions in Λ are less than 5%.