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Modeling and Control of Co-Surge in Bi-Turbo Engines
Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
2011 (English)In: Proceedings of the 18th IFAC World Congress, 2011 / [ed] Bittanti, Sergio, Cenedese, Angelo, Zampieri, Sandro, International Federation of Automatic Control (IFAC) , 2011, 13010-13015 p.Conference paper (Refereed)
Abstract [en]

Using a bi-turbocharged configuration makes for better utilization of the exhaust energy and a faster torque response in V-type engines. A special surge phenomenon that should be avoided in bi-turbocharged engines is co-surge, which is when the two interconnected compressors alternately go into flow reversals. If co-surge should occur, the control system must be able to quell the oscillations with as little disturbance in torque as possible. This paper presents a model of a bi-turbocharged engine based on a Mean Value Engine Model that includes a More-Greizer compressor model for surge. The model is validated against measured data showing that it captures the frequency and amplitude of the co-surge oscillation. The effect of momentum conservation in the pipes is investigated by adding this feature to the control volumes before and after the compressor. This gives a slightly better mass flow shape with the drawback of increased simulation time, due to more states and a higher frequency content in the model. A sensitivity analysis is performed to investigate which model parameters have most influence on the co-surge behavior. It is shown that the largest influence comes from the turbocharger inertia, the volumes after the compressor and the ``zero mass flow pressure ratio'' during flow reversal in the compressor. The model is used to investigate principles for control strategies to detect and quell co-surge. The detection algorithm is evaluated on measured data.

Place, publisher, year, edition, pages
International Federation of Automatic Control (IFAC) , 2011. 13010-13015 p.
Keyword [en]
Modeling, supervision, control and diagnosis of automotive systems, Automotive system identification and modelling
National Category
Vehicle Engineering
URN: urn:nbn:se:liu:diva-90922DOI: 10.3182/20110828-6-IT-1002.02338ISBN: 978-3-902661-93-7OAI: diva2:615224
2011 IFAC World Congress, Milano, Milano, Italy, 28 August - 2 September
Available from: 2013-04-09 Created: 2013-04-09 Last updated: 2014-04-11Bibliographically approved
In thesis
1. Modeling and control of actuators and co-surge in turbocharged engines
Open this publication in new window or tab >>Modeling and control of actuators and co-surge in turbocharged engines
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The torque response of the engine is important for the driving experience of a vehicle. In spark ignited engines, torque is proportional to the air flow into the cylinders. Controlling torque therefore implies controlling air flow. In modern turbocharged engines, the driver commands are interpreted by an electronic control unit that controls the engine through electromechanical and pneumatic actuators. Air flow to the intake manifold is controlled by an electronic throttle, and a wastegate controls the energy to the turbine, affecting boost pressure and air flow. These actuators and their dynamics affect the torque response and a lot of time is put into calibration of controllers for these actuators. By modeling and understanding the actuator behavior this dynamics can be compensated for, leaving a reduced control problem, which can shorten the calibration time.

Electronic throttle servo control is the first problem studied. By constructing a control oriented model for the throttle servo and inverting that model, the resulting controller becomes two static compensators for friction and limp-home nonlinearities, together with a PD-controller. A gain-scheduled I-part is added for robustness to handle model errors. The sensitivity to model errors is studied and a method for tuning the controller is presented. The performance has been evaluated in simulation, in test vehicle, and in a throttle control benchmark.

A model for a pneumatic wastegate actuator and solenoid control valve, used for boost pressure control, is presented. The actuator dynamics is shown to be important for the transient boost pressure response. The model is incorporated in a mean value engine model and shown to give accurate description of the transient response. A tuning method for the  feedback (PID) part of a boost controller is proposed, based on step responses in wastegate control signal. Together with static feedforward the controller is shown to achieve the desired boost pressure response. Submodels for an advanced boost control system consisting of several vacuum actuators, solenoid valves, a vacuum tank and a vacuum pump are developed. The submodels and integrated system are evaluated on a two stage series sequential turbo system, and control with system voltage disturbance rejection is demonstrated on an engine in a test cell.

Turbocharged V-type engines often have two parallel turbochargers, each powered by one bank of cylinders. When the two air paths are connected before the throttle an unwanted oscillation can occur. When the compressors operate close to the surge line and a disturbance alters the mass flow balance, the compressors can begin to alternately go into surge, this is called co-surge. Measurements on co-surge in parallel turbocharged engines are presented and analyzed. A mean value engine model, augmented with a Moore-Greitzer compressor model to handle surge, is shown to capture the cosurge behavior. A sensitivity analysis shows which model parameters have the largest influence of the phenomena. The compressor operation in the map during co-surge is studied, and the alternating compressor speeds are shown to have a major impact on the continuing oscillation. Based on the analysis, detection methods and a controller are proposed, these detect co-surge and control the turbo speeds to match during co-surge. The controller is evaluated both in simulation and on a test vehicle in a vehicle dynamometer, showing that co-surge can be detected and the oscillations quelled.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 28 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1590
National Category
Engineering and Technology
urn:nbn:se:liu:diva-105687 (URN)10.3384/diss.diva-105687 (DOI)978-91-7519-355-7 (print) (ISBN)
Public defence
2014-05-16, Visionen, ing 27-29, B-huset, våning 1, Campus Valla, Linköpings Universitet, Linköping, 10:15 (English)
Available from: 2014-04-11 Created: 2014-04-02 Last updated: 2014-04-11Bibliographically approved

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