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Modeling and control of actuators and co-surge in turbocharged engines
Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
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.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1590
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-105687DOI: 10.3384/diss.diva-105687ISBN: 978-91-7519-355-7 (print)OAI: oai:DiVA.org:liu-105687DiVA: diva2:709572
Public defence
2014-05-16, Visionen, ing 27-29, B-huset, våning 1, Campus Valla, Linköpings Universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2014-04-11 Created: 2014-04-02 Last updated: 2014-04-11Bibliographically approved
List of papers
1. Model-Based Throttle Control using Static Compensators and Pole Placement
Open this publication in new window or tab >>Model-Based Throttle Control using Static Compensators and Pole Placement
2011 (English)In: Oil & gas science and technology, ISSN 1294-4475, E-ISSN 1953-8189, Vol. 66, no 4, 717-727 p.Article in journal (Refereed) Published
Abstract [en]

Model-Based Throttle Control using Static Compensators and Pole Placement - In modern spark ignited engines, the throttle is controlled by the Electronic Control Unit (ECU), which gives the ECU direct control of the air flow and thereby the engine torque. This puts high demands on the speed and accuracy of the controller that positions the throttle plate. The throttle control problem is complicated by two strong nonlinear effects, friction and limp-home torque. This paper proposes the use of two, simultaneously active, static compensators to counter these effects and approximately linearize the system. A PID controller is designed for the linearized system, where pole placement is applied to design the PD controller and a gain scheduled I-part is added for robustness against model errors. A systematic procedure for generating compensator and controller parameters from open loop experiments is also developed. The controller performance is evaluated both in simulation, on a throttle control benchmark problem, and experimentally. A robustness investigation pointed out that the limp-home position is an important parameter for the controller performance, this is emphasized by the deviations found in experiments. The proposed method for parameter identification achieves the desired accuracy.

Place, publisher, year, edition, pages
Institut Francais du Petrole, 2011
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-73743 (URN)10.2516/ogst/2011137 (DOI)000297969200015 ()
Available from: 2012-01-12 Created: 2012-01-12 Last updated: 2017-04-19
2. Wastegate Actuator Modeling and Model-Based Boost Pressure Control
Open this publication in new window or tab >>Wastegate Actuator Modeling and Model-Based Boost Pressure Control
2009 (English)In: Proceedings of the 2009 IFAC Workshop on Engine and Powertrain Control, Simulation and Modeling / [ed] Antonio Sciarretta and Paolino Tona, 2009, 87-94 p.Conference paper, Published paper (Refereed)
Abstract [en]

The torque response of an engine is important for driver acceptance. For turbocharged spark ignited (TCSI) engines this is tightly connected to the boost pressure control, which is usually achieved with a wastegate. A challenging scenario is when the throttle is fully open and the load is essentially controlled by the wastegate. First a model for the pneumatic wastegate actuator and air control solenoid is developed. The wastegate model consists of three submodels; the actuator pressure, the static position, and an additional position dynamics. A complete engine model is constructed by including the actuator model in a Mean Value Engine Model (MVEM) for a TCSI engine. This model describes the transient boost pressure response to steps in wastegate control inputs. The subsystems and complete MVEM are validated on an engine test bench and it explains the overshoot seen in the step responses. The model is used to study the system response and give insight into the dominating phenomena and it points out that the engine speed is important for the response. Further, for each speed it is sufficient to model the system as a second order linear system, that captures an overshoot. A controller consisting of a mapped feedforward loop and a gain scheduled feedback loop is developed together with a tuning method based on the IMC framework for the feedback loop. The controller and tuning method is shown to achieve the desired boost pressure behavior both on the complete MVEM and on real engines. The experimental validation is carried out both in an engine test cell and in a vehicle.

Keyword
Engine modeling, engine control, turbocharging, internal model control, PID
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-50769 (URN)10.3182/20091130-3-FR-4008.00012 (DOI)978-3-902661-58-6 (ISBN)
Conference
2009 IFAC Workshop on Engine and Powertrain Control, Simulation and Modeling, November 30th - December 2nd, Paris, France
Projects
LINK-SIC, MOVIII
Available from: 2009-10-14 Created: 2009-10-14 Last updated: 2014-08-27Bibliographically approved
3. Modeling and validation of a boost pressure actuation system, for a series sequentially turbocharged SI engine
Open this publication in new window or tab >>Modeling and validation of a boost pressure actuation system, for a series sequentially turbocharged SI engine
2013 (English)In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 21, no 12, 1860-1870 p.Article in journal (Refereed) Published
Abstract [en]

An actuation system for flexible control of an advanced turbocharging system is studied. It incorporates a vacuum pump and tank that are connected to pulse width modulation controlled vacuum valves. A methodology for modeling the entire boost pressure actuation system is developed. Emphasis is placed on developing component models that are easily identified from measured data, without the need for expensive measurements.The models have physical interpretations that enable handling of varying surrounding conditions.The component models and integrated system are evaluated on a two stage series sequential turbo system with three actuators having different characteristics.Several applications of the developed system model are presented, including a nonlinear compensator for voltage disturbance rejection where the performance of the compensator is demonstrated on an engine in a test cell. The applicability of the complete system model for control and diagnosis of the vacuum system is also discussed.

Place, publisher, year, edition, pages
Elsevier / International Federation of Automatic Control, 2013
Keyword
Engine; Turbocharger; Vacuum system; Solenoid valve; Nonlinear compensator
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-103723 (URN)10.1016/j.conengprac.2013.01.004 (DOI)000329017200022 ()
Available from: 2014-01-24 Created: 2014-01-24 Last updated: 2017-12-06
4. Modeling and Control of Co-Surge in Bi-Turbo Engines
Open this publication in new window or tab >>Modeling and Control of Co-Surge in Bi-Turbo Engines
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, Published 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
Keyword
Modeling, supervision, control and diagnosis of automotive systems, Automotive system identification and modelling
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:liu:diva-90922 (URN)10.3182/20110828-6-IT-1002.02338 (DOI)978-3-902661-93-7 (ISBN)
Conference
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
5. Co-Surge in Bi-Turbo Engines: Measurements, Analysis and Control
Open this publication in new window or tab >>Co-Surge in Bi-Turbo Engines: Measurements, Analysis and Control
2014 (English)In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 32, 113-122 p.Article in journal (Refereed) Published
Abstract [en]

In parallel turbocharged V-engines, with two separate air paths connected before the throttle, an oscillation in the flow can occur.If the compressor operates close to the surge line, typically during low speed and high load, and a disturbance alters the massflow balance, the compressors can begin to alternately go into surge. This phenomenon is called co-surge and is unwanted due tohigh noise and risk for turbocharger destruction. Co-surge is measured on a test vehicle in a chassis dynamometer and the systemanalyzed and modeled using a mean value engine model. The investigation shows that the alternating compressor speeds have animportant role in the prolonged oscillation. A reconstruction of the negative flow from measurements is made and compared tosimulation results, showing similar amplitudes, and supports the model validation. A new co-surge detection algorithm is presented,suitable for a pair of sensors measuring either mass flow, boost pressure or turbo speed in the two air paths. Furthermore, a newcontroller is proposed that uses a model based feedforward for the throttle, together with wastegate actuation to force the compressorspeeds together and improve balance at the recovery point. This has shown to be sufficient with moderate to high pressure ratiosover the throttle, only for zero or very low pressure drop the use of bypass valves are necessary. The advantage of not opening thebypass valves is a smaller drop in boost pressure which also reduces the torque disturbance. The performance of the controller is evaluated both in simulation and in the test vehicle.

Place, publisher, year, edition, pages
Elsevier, 2014
Keyword
Compressor surge, surge detection, surge control, engine modeling, engine control
National Category
Control Engineering
Identifiers
urn:nbn:se:liu:diva-105686 (URN)10.1016/j.conengprac.2014.08.001 (DOI)000344435200009 ()
Available from: 2014-04-02 Created: 2014-04-02 Last updated: 2017-12-05Bibliographically approved

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Output format
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