Design and Control of Fully Flexible Valve Actuation Systems for Camless Engines

133 Pages·2012·9.29 MB·English

Design and Control of Fully Flexible Valve Actuation
Systems for Camless Engines
A DISSERTATION
SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL
OF THE UNIVERSITY OF MINNESOTA
BY
Pradeep Kumar Gillella
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE DEGREE OF
Doctor of Philosophy
Prof Zongxuan Sun, Advisor
December, 2012
© Pradeep Kumar Gillella 2012
ALL RIGHTS RESERVED
Acknowledgements
I would like to express my sincere gratitude to Prof Zongxuan Sun for introducing me to this
exciting field, providing all the resources and guiding me over the past 5 years. His commitment
to helping me develop the technical and interpersonal skills has been my greatest asset during my
entire educational experience up to this point.
Prof Rajesh Rajamani, Prof Perry Li, Prof Mihailo Jovanovich, Prof Kim Stelson and Prof James
Van de Ven for the valuable experiences gained as part of the coursework and being their teaching
assistant which has directly helped me with various research problems. Special thanks to Prof
Stelson, Prof Rajamani and Prof Mihailo for agreeing to serve as my examining committee.
FellowlabmatesXingyong,Adam,Yu,Chien-shin,Ke,Zhen,Ali,Vivek,Azrin,Virinchi,Yongsoon,
Venkat, Haink, Rachel and Henry for all the discussions, help and fun times.
Peter Zimmerman, Robin Russell, Mark Erickson and Dave Hultmann for their help at the machine
shop.
I would like to acknowledge MSI and MENET for the computational resources.
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Dedication
To my family, members of zoogang, bunboys, shadowz, dopy2k, k5boys, pongalboys and howitzers.
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Abstract
Themotivationtoimprovethefuelefficiencyandreduceemissionsoftheinternalcombustionengine
comes from the dwindling oil reserves and the increased concerns about climate change. A key
step towards realizing these improvements is to introduce flexibilities into the mechanisms used
for air and fuel management by replacing the mechanical devices with mechatronic systems. The
introductionoffuelinjectionsystemsinplaceofthecarburetorsresultedinsignificantimprovements
due to the additional flexibilities in fuel management. The traditional air management systems use
camshaft based mechanisms to actuate the intake/exhaust valves. The benefits offered by fully
flexiblevalveactuationandthelimitationsofthecamshaftbasedsystemsmotivatethedevelopment
of a “Camless valve actuation system”. Research in this area during the past two decades has
led to the development of several concepts. However, the stringent performance requirements to
ensure reliable operation and the shortcomings of the previously developed concepts has impeded
the widespread deployment of these systems. In this research, we propose to address the problem
from two perspectives. A design based solution capable of achieving fully flexible operation using
inexpensivecomponentswhilerequiringsimplifiedcontrollersisfirstintroduced. Itisfollowedbythe
development of a systematic procedure for optimizing the design of a key component in this system
to improve it performance and robustness. The second topic focuses on the implementation aspects
of a new control algorithm to enable precise tracking of the engine valve reference profile. The
effectiveness of the linear time invariant controllers based on the internal model principle for steady
state operation of the engine is leveraged to enable tracking control during engine speed transients
by extending the control framework to the time-varying setting. The challenges associated with the
time-varyingnatureofthecontrollerarerevealedandthedevelopedsolutionshelpitsimplementation
and validation on experimental hardware. The proposed framework can easily be extended to other
engine subsystems as well as other general rotational machinery.
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Contents
Acknowledgements i
Dedication ii
Abstract iii
List of Tables vii
List of Figures viii
1 Introduction 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Benefits of Variable Valve Actuation . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Camshaft-based Variable Valve Actuation . . . . . . . . . . . . . . . . . . . . . . . . 5
1.4 Camless Engine Valve Actuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.4.1 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4.2 Current State of the Art . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.4.3 Summary of the Challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.5 Overview of Research Topics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.5.1 Design based approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.5.2 Control based approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.6 Expected Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.7 Organization of the Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2 Design Optimization for the Actuator With Internal Feedback 16
2.1 System Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.1.1 System design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
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2.1.2 Working principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.1.3 Desirable performance characteristics. . . . . . . . . . . . . . . . . . . . . . . 18
2.2 Prototype Experimental Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2.1 Demonstration of flexibilities . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2.2 Identification of performance issues . . . . . . . . . . . . . . . . . . . . . . . . 21
2.3 Design Optimization Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.3.1 System dynamics modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.3.2 Model validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.3.3 Identification of the control variable . . . . . . . . . . . . . . . . . . . . . . . 24
2.3.4 Analysis of the internal feedback loop . . . . . . . . . . . . . . . . . . . . . . 26
2.3.5 Effect of the area-schedule on system performance . . . . . . . . . . . . . . . 27
2.3.6 Optimization of the Area-Schedule . . . . . . . . . . . . . . . . . . . . . . . . 29
2.4 Case Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.4.1 Area-schedules obtained from dynamic programming . . . . . . . . . . . . . . 35
2.4.2 Robustness to Parameter perturbations . . . . . . . . . . . . . . . . . . . . . 37
2.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3 Physical Design of the Spool Valve with the Optimal Area-Schedule 41
3.1 Background on Traditional Design of Spool Valves . . . . . . . . . . . . . . . . . . . 41
3.2 Spool Valves with Notches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.3 CFD Analysis of the Notch Designs. . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.4 Geometric Analysis of the Metering Section . . . . . . . . . . . . . . . . . . . . . . . 48
3.4.1 Experimental investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.5 Synthesis of Notch Designs for Arbitrary Area-Schedules . . . . . . . . . . . . . . . . 54
3.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4 Tracking Control Design for Engine Speed Transients 58
4.1 Problem Formulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.1.1 Approach 1 : Time domain control of frequency varying sinusoids. . . . . . . 60
4.1.2 Approach 2 : Rotational angle domain control . . . . . . . . . . . . . . . . . 61
4.2 Time-varying Internal Model based Controller . . . . . . . . . . . . . . . . . . . . . . 62
4.3 I/O Representation of Linear Time-Varying Systems . . . . . . . . . . . . . . . . . . 62
4.4 Generating Dynamics {1} . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.5 Plant {2} . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
4.6 Internal Model Unit {3,4} . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
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4.7 Stabilizer Unit {5} . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.7.1 Dynamic SISO unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.7.2 Parameter-dependent output gain injection . . . . . . . . . . . . . . . . . . . 75
5 Implementation of the LTV - Internal Model based Controller 84
5.1 Fixed vs Variable Sampling in Angle Domain Control . . . . . . . . . . . . . . . . . 84
5.2 Time vs Angle Domain Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5.3 Online Computation vs Storage of Controller Coefficients . . . . . . . . . . . . . . . 87
5.4 Numerical issues with the Canonical Transformation . . . . . . . . . . . . . . . . . . 90
5.5 Experimental Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.5.1 Hardware setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.6 Controller Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
5.6.1 Angle Domain Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . 101
5.6.2 Valve Event Transients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
5.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
References 106
Appendix A. Input/Output Representations (Time-varying systems) 113
A.1 Continuous-time domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
A.2 Discrete domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
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List of Tables
2.1 Parameter values for the Dynamic model . . . . . . . . . . . . . . . . . . . . . . . . 35
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List of Figures
1.1 A typical trajectory of the intake and exhaust valves . . . . . . . . . . . . . . . . . . 2
1.2 The schematic of a general camless engine valve actuation system . . . . . . . . . . . 6
1.3 Typicalcharacteristicsofthevalvereferencetrajectorycorrespondingtoanaggressive
operating condition (a) position, (b) velocity and (c) acceleration . . . . . . . . . . . 9
1.4 The new electro-hydraulic actuation system with internal feedback mechanism . . . 10
1.5 Valve reference trajectory corresponding to constant engine speed (1200 RPM) and
fixed valve event (8mm lift and 240 CAD duration), (b) the corresponding frequency
content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.6 Valve reference trajectory corresponding to an engine speed transient (1200 to 3600
RPM)andfixedvalveevent(8mmliftand240CADduration),(b)thecorresponding
frequency content, (c) representation of the signal in the rotational angle domain . . 12
2.1 Schematic of the new variable valve actuation system. . . . . . . . . . . . . . . . . . 17
2.2 Experimental demonstration of the new valve actuation system . . . . . . . . . . . . 20
2.3 Comparison of data obtained from experiments and model simulations for different
valve strategies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.4 Control Block diagram of the system . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.5 Hand tuned Area-schedules used in the simulations . . . . . . . . . . . . . . . . . . . 28
2.6 Flowchart for the area-schedule design procedure . . . . . . . . . . . . . . . . . . . . 30
2.7 Area-schedule candidates for generating the grid points for the first iteration . . . . 31
2.8 Illustration of the modified Dynamic Programming procedure . . . . . . . . . . . . . 32
2.9 Area-schedule candidates for the next iteration obtained by perturbing the optimal
area-schedule at the current iteration . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.10 Displacement of the engine valve (Lift control) . . . . . . . . . . . . . . . . . . . . . 34
2.11 Velocity of the engine valve (10 mm lift case) . . . . . . . . . . . . . . . . . . . . . . 35
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