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Modeling and Optimal Control of Heavy-Duty Powertrains
Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Heavy duty powertrains are complex systems with components from various domains, different response times during transient operations and different efficient operating ranges. To ensure efficient transient operation of a powertrain, e.g. with low fuel consumption or short transient duration, it is important to come up with proper control strategies. In this dissertation, optimal control theory is used to calculate and analyze efficient heavy duty powertrain controls during transient operations in different applications. This is enabled by first developing control ready models, usable for multi-phase optimal control problem formulations, and then using numerical optimal control methods to calculate the optimal transients.

Optimal control analysis of a wheel loader operating in a repetitive loading cycle is the first studied application. Increasing fuel efficiency or reducing the operation time in such repetitive loading cycles sums up to large savings over longer periods of time. Load lifting and vehicle traction consume almost all of the power produced by a diesel engine during wheel loader operation. Physical models are developed for these subsystems where the dynamics are described by differential equations. The model parameters are tuned and fuel consumption estimation is validated against measured values from real wheel loader operation. The sensitivity of wheel loader trajectory with respect to constrains such as the angle at which the wheel loader reaches the unloading position is also analyzed. A time and fuel optimal trajectory map is calculated for various unloading positions. Moreover, the importance of simultaneous optimization of wheel loader trajectory and the component transients is shown via a side to side comparison between measured fuel consumption and trajectories versus optimal control results.

In another application, optimal control is used to calculate efficient gear shift controls for a heavy duty Automatic Transmission system. A modeling and optimal control framework is developed for a nine speed automatic transmission. Solving optimal control problems using the developed model, time and jerk efficient transient for simultaneous disengagement of off-going and engagement of in-coming shift actuators are obtained and the results are analyzed.

Optimal controls of a diesel-electric powertrain during a gear shift in an Automated Manual Transmission system are calculated and analyzed in another application of optimal control. The powertrain model is extended by including driveline backlash angle as an extra state in the system. This is enabled by implementation of smoothing techniques in order to describe backlash dynamics as a single continuous function during all gear shift phases.

Optimal controls are also calculated for a diesel-electric powertrain corresponding to a hybrid bus during a tip-in maneuver. It is shown that for optimal control analysis of complex powertrain systems, minimizing only one property such as time pushes the system transients into extreme operating conditions far from what is achievable in real applications. Multi-objective optimal control problem formulations are suggested in order to obtain a compromise between various objectives when analyzing such complex powertrain systems.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2016. , 27 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1771
Keyword [en]
Powertrain, transmission system, optimal control, modeling for control
National Category
Control Engineering
Identifiers
URN: urn:nbn:se:liu:diva-128002DOI: 10.3384/diss.diva-128002ISBN: 978-91-7685-748-9 (print)OAI: oai:DiVA.org:liu-128002DiVA: diva2:928666
Public defence
2016-06-17, Visionen, Ingång 27, B huset, Campus Valla, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2016-05-30 Created: 2016-05-16 Last updated: 2016-05-31Bibliographically approved
List of papers
1. Modeling and optimal control of a wheel loader in the lift-transport section of the short loading cycle
Open this publication in new window or tab >>Modeling and optimal control of a wheel loader in the lift-transport section of the short loading cycle
2013 (English)In: Elsevier IFAC Publications / IFAC Proceedings series, ISSN 1474-6670, Vol. 46, no 21, 195-200 p.Article in journal (Refereed) Published
Abstract [en]

Abstract Optimal control of a wheel loader operating in the short loading cycle is studied in order to investigate the potentials for fuel consumption reduction while maintaining acceptable production rates. The wheel loader is modeled as a system with five states and three control inputs including torque converter nonlinearities. The torque converter is modeled with no lockup enabling power transmission in both directions. The geometry of the wheel loader boom and the demanded force in the lift cylinders during lifting are used to ensure that the in-cylinder pressure remains below component’s limits. The lift-transport section of the short loading cycle is divided into four phases due to discontinuities in the gearbox ratios and fuel consumption is calculated in each phase. Time optimal and fuel optimal transients of the system and the power consumption in each and every component is presented showing the dominance of the torque converter losses compared to the other components especially in the time optimal solutions. It is shown that introducing path constraints on the maximum lifting speed of the bucket due to limitations in hydraulic pumping speed moves the diesel engine operation towards higher speeds in order to maintain the lifting speed. Trade-off between fuel optimal and time optimal transients is calculated which is found to be in agreement with the results of experimental studies.

Keyword
Multi phase optimal control, wheel loader model, short loading cycle, torque converter
National Category
Vehicle Engineering Other Mechanical Engineering
Identifiers
urn:nbn:se:liu:diva-128706 (URN)10.3182/20130904-4-JP-2042.00083 (DOI)
Conference
7th IFAC Symposium on Advances in Automotive Control, September 4th-6th, Tokyo, Japan
Available from: 2016-05-30 Created: 2016-05-30 Last updated: 2017-11-30Bibliographically approved
2. Optimal control of wheel loader operation in the short loading cycle using two braking alternatives
Open this publication in new window or tab >>Optimal control of wheel loader operation in the short loading cycle using two braking alternatives
2013 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The optimal control of wheel loader operation is used in order to investigate the potentials for fuel cost and cycle time minimization during the short loading cycle. The wheel loader is modeled as a nonlinear system with three control inputs and four state variables where a diesel engine generates the power utilized for lifting and traction. The lifting system is modeled considering the limitations in the hydraulics and also the structural constraints. A torque converter is included in the driveline model which introduces nonlinearities into the system and operates in different modes affecting the fuel consumption. The gear shifts during the loading cycle impose a discrete variable into the system and this is taken care of by representing the loading cycle as a multi-phase optimal control problem with constant gearbox gear ratio in each phase. Minimum fuel and minimum time system transients are calculated and analyzed for two alternative cases one where the torque converter is used to stop the vehicle before reaching the reversing point and another where the service brakes are utilized. The optimal control problem is iteratively solved in order to obtain the trade-off between fuel consumption and cycle time for both braking alternatives. It is shown that although the engine operates at lower speeds when the torque converter is used for braking, the fuel consumption increases as higher torques are demanded from the engine during braking. The increase in fuel consumption is higher in faster cycle operations as the vehicle travels at higher speeds and larger torques are required to stop the vehicle. Wheel loader operators tend to use torque converter braking alternative as it is more convenient; however, it accompanies higher fuel consumption which highlights the importance of developing intelligent and easy to use braking systems.

Place, publisher, year, edition, pages
IEEE, 2013
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-105772 (URN)10.1109/VPPC.2013.6671736 (DOI)000332155200084 ()978-147990720-5 (ISBN)
Conference
9th IEEE Vehicle Power and Propulsion Conference, IEEE VPPC 2013; Beijing; China
Available from: 2014-04-04 Created: 2014-04-04 Last updated: 2016-05-30
3. Optimal lifting and path profiles for a wheel loader considering engine and turbo limitations
Open this publication in new window or tab >>Optimal lifting and path profiles for a wheel loader considering engine and turbo limitations
2014 (English)In: Optimization and optimal control in automotive systems / [ed] Harald Waschl, Ilya Kolmanovsky, Maarten Steinbuch and Luigi del Re, Cham: Springer, 2014, 301-324 p.Chapter in book (Refereed)
Abstract [en]

Time and fuel optimal control of an articulated wheel loader is studied during the lift and transport sections of the short loading cycle. A wheel loader model is developed including engine (with turbo dynamics), torque converter, transmission and vehicle kinematics, lifting hydraulics and articulated steering. The modeling is performed with the aim to use the models for formulating and solving optimal control problems. The considered problem is the lift and transport section of the wheel loader that operates in the short loading cycle, with several different load receiver positions, while the considered criteria are minimum time and minimum fuel. The problem is separated into four phases to avoid solving a mixed integer problem imposed by the gearshifting discontinuities. Furthermore, two different load lifting patterns are studied one with the lifting free and one with the lifting performed only in the last 30 % of the transport. The results show that the optimal paths to the load receiver are identical for both minimum time and minimum fuel cycles and do not change when the loading lifting pattern is altered. A power break-down during the wheel loader operation is presented for the selected cycles of normal and delayed lifting where it is shown that the cycle time remains almost unchanged when lifting is delayed while the fuel consumption slightly decreases in minimum time transients.

Place, publisher, year, edition, pages
Cham: Springer, 2014
Series
Lecture Notes in Control and Information Sciences, ISSN 0170-8643 ; 455
Keyword
Control, Calculus of Variations and Optimal Control Optimization, Automotive Engineering
National Category
Vehicle Engineering Other Mechanical Engineering
Identifiers
urn:nbn:se:liu:diva-128707 (URN)10.1007/978-3-319-05371-4_18 (DOI)9783319053707 (ISBN)9783319053714 (ISBN)
Available from: 2016-05-30 Created: 2016-05-30 Last updated: 2016-08-17Bibliographically approved
4. Wheel loader optimal transients in the short loading cycle
Open this publication in new window or tab >>Wheel loader optimal transients in the short loading cycle
2014 (English)In: Proceedings of the 19th IFAC World Congress, 2014 / [ed] Edward Boje and Xiaohua Xia, Elsevier, 2014, Vol. 47, no 3, 7917-7922 p.Conference paper, Published paper (Refereed)
Abstract [en]

Abstract A nonlinear wheel loader model with nine states and four control inputs is utilized to study the fuel and time efficient optimal control of wheel loader operation in the short loading cycle. The wheel loader model consists of lifting, steering and powertrain subsystems where the nonlinearity originates from the torque converter in the drivetrain. The short loading cycle, from loading point to a load receiver and back to the loading point, for a fork lifting application is described in terms of boundary conditions of the optimization problem while the operation is divided into several phases with constant gearbox gear ratios in order to avoid discontinuities due to discrete gear ratios. The effect of load receiver standing orientation on the wheel loader trajectory, fuel consumption and cycle time is studied showing that a small deviation from the optimal orientation (≈ 20 [deg]) results in up to 18 % higher fuel consumption in the minimum time cycles. Also, an alternative lifting strategy where for operation safety load is lifted only when wheel loaders moves forward is studied showing that this increases the fuel consumption of a typical 25 [sec] cycle only less than 2 %. The wheel loader path between loading point and load receiver is also calculated by optimization and analyzed for different cases. It is shown that when the load receiver orientation is not optimized and is set manually, the time or fuel optimal paths will differ from the shortest distance path, however when the load receiver orientation is calculated by optimization the fuel, time and shortest distance paths become identical.

Place, publisher, year, edition, pages
Elsevier, 2014
Series
World Congress, ISSN 1474-6670 ; Volume, 19, Part 1
Keyword
Optimal control, switching control variable, nonlinear system, wheel loader, loading cycle
National Category
Vehicle Engineering Other Mechanical Engineering
Identifiers
urn:nbn:se:liu:diva-128708 (URN)10.3182/20140824-6-ZA-1003.02419 (DOI)978-3-902823-62-5 (ISBN)
Conference
Proceedings of the 19th IFAC World Congress, 2014, Augustg 24-28, Cape Town, South Africa
Note

19th IFAC World Congress

Available from: 2016-05-30 Created: 2016-05-30 Last updated: 2016-05-30Bibliographically approved
5. Turbocharger Dynamics Influence on Optimal Control of Diesel Engine Powered Systems
Open this publication in new window or tab >>Turbocharger Dynamics Influence on Optimal Control of Diesel Engine Powered Systems
2014 (English)In: SAE International Journal of Engines, ISSN 1946-3936, Vol. 7, no 1, 6-13 p.Article in journal (Refereed) Published
Abstract [en]

The importance of including turbocharger dynamics in diesel engine models are studied, especially when optimization techniques are to be used to derive the optimal controls. This is done for two applications of diesel engines where in the first application, a diesel engine in wheel loader powertrain interacts with other subsystems to perform a loading operation and engine speed is dictated by the wheel speed, while in the second application, the engine operates in a diesel-electric powertrain as a separate system and the engine speed remains a free variable. In both applications, mean value engine models of different complexities are used while the rest of system components are modeled with the aim of control study. Optimal control problems are formulated, solved, and results are analyzed for various engine loading scenarios in the two applications with and without turbocharger dynamics. It is shown that depending on the engine loading transients, fuel consumption and operation time can widely vary when the turbocharger dynamics are considered in the diesel engine model. Including these, have minor effects on fuel consumption and operation time at minimum fuel operations of the first application (~0.1 %) while the changes are considerable in the second application (up to 60%). In case of minimum time operations however, fuel consumption and operation time are highly affected in both applications implying that not considering turbocharger dynamics in the diesel engine models may lead to overestimation of the engine performance especially when the results are going to be used for control purposes.

Place, publisher, year, edition, pages
SAE International, 2014
National Category
Control Engineering
Identifiers
urn:nbn:se:liu:diva-117316 (URN)10.4271/2014-01-0290 (DOI)
Available from: 2015-04-23 Created: 2015-04-23 Last updated: 2016-05-30
6. A framework for modeling and optimal control of automatic transmission systems
Open this publication in new window or tab >>A framework for modeling and optimal control of automatic transmission systems
2015 (English)In: 4th IFAC Workshop on Engine and Powertrain Control, Simulation and Modeling (E-COSM 2015): Proceedings of a meeting held 23-26 August 2015, Columbus, Ohio, USA / [ed] Simona Onori, Elsevier, 2015, Vol. 48 Issue 15, no 15, 285-291 p.Conference paper, Published paper (Refereed)
Abstract [en]

Abstract Development of efficient control algorithms for the control of automatic transmission systems is crucial to maintain passenger comfort and operational life of the transmission components. An optimization framework is developed by state space modeling of a powertrain including a nine speed automatic transmission, diesel engine, torque converter and a model for longitudinal vehicle dynamics considering drive shaft as the only flexibility of the driveline. Emphasis is set on the kinematics of the automatic transmission with the aim of modeling for gearshift optimal control during the inertia phase. Considering the interacting forces between planetary gearsets, clutches and brakes in the transmission, kinematic equations of motion are derived for rotating transmission components enabling to calculate both transmission dynamics and internal forces. The model is then used in optimal control problem formulations for the analysis of optimal control transients in two up-shift cases.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
Automatic transmission, optimal control, modeling and simulation framework
National Category
Vehicle Engineering Other Mechanical Engineering
Identifiers
urn:nbn:se:liu:diva-128710 (URN)10.1016/j.ifacol.2015.10.041 (DOI)9781510818248 (ISBN)
Conference
4th IFAC Workshop on Engine and Powertrain Control, Simulation and Modeling E-COSM 2015, Columbus, Ohio, USA, 23-26 August 2015
Available from: 2016-05-30 Created: 2016-05-30 Last updated: 2016-05-30Bibliographically approved
7. Wheel loader operation-Optimal control compared to real drive experience
Open this publication in new window or tab >>Wheel loader operation-Optimal control compared to real drive experience
2016 (English)In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 48, 1-9 p.Article in journal (Refereed) Published
Abstract [en]

Wheel loader trajectories between loading and unloading positions in a repetitive loading cycle are studied. A wheel loader model available in the literature is improved for better fuel estimation and optimal control problems are formulated and solved using it. The optimization results are analyzed in a side to side comparison with measurement data from a real world application. It is shown that the trajectory properties affect the operation productivity. However, efficient trajectories are not the only requirement for high productivity operation and all major power consuming sources such as vehicle dynamics, lifting and steering have to be included in the optimization for productivity analysis. The effect of operator steering capability is also analyzed showing that development of autonomous vehicles can be envisaged especially for repetitive cycles. (C) 2015 Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
Optimal control; Modeling for control; Powertrain modeling and simulation; Trajectory optimization
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-126245 (URN)10.1016/j.conengprac.2015.12.015 (DOI)000370906700001 ()
Available from: 2016-03-21 Created: 2016-03-21 Last updated: 2017-11-30
8. Optimal control of a diesel-electric powertrain during an up-shift
Open this publication in new window or tab >>Optimal control of a diesel-electric powertrain during an up-shift
2016 (English)Conference paper, Published paper (Refereed)
Abstract [en]

To investigate the optimal controls of a diesel-electric powertrain during a torque controlled gearshift, a powertrain model is developed. A validated diesel-electric model is used as the power source and the transmission dynamics are described by different sets of differential equations during torque phase, synchronization phase and inertia phase of the gearshift. Using the developed model, multi-phase optimal control problems are formulated and solved. The trade-off between gearshift duration and driveline oscillations are calculated and efficient gearshift transients for a diesel-electric and pure diesel powertrain are then compared and analyzed.

Place, publisher, year, edition, pages
SAE International, 2016
Series
SAE Technical Paper, ISSN 0148-7191
Keyword
Transmissions, Hybrid engines, Heavy trucks, Hybrid electric vehicles (HEV)
National Category
Vehicle Engineering Other Mechanical Engineering
Identifiers
urn:nbn:se:liu:diva-128711 (URN)10.4271/2016-01-1237 (DOI)
Conference
SAE 2016 World Congress and Exhibition, Detroit, MI, USA,April 12-14 2016
Available from: 2016-05-30 Created: 2016-05-30 Last updated: 2017-10-09Bibliographically approved
9. Optimal control of engine controlled gearshift for a diesel-electric powertrain with backlash
Open this publication in new window or tab >>Optimal control of engine controlled gearshift for a diesel-electric powertrain with backlash
2016 (English)In: IFAC PAPERSONLINE, IFAC , 2016, Vol. 49, 762-768 p.Conference paper, Published paper (Refereed)
Abstract [en]

Gearshift optimal control of a hybrid powertrain with a lumped/decoupled transmission model and backlash dynamics in the driveline is studied. A model is used for a heavy duty powertrain including a validated mean value diesel engine model with electric generator, transmission dynamics representing the dynamics of the automated manual transmission system and driveshaft flexibilities. Backlash dynamics are also included in the driveline model by introducing a switching function. By applying numerical optimal control methods and dividing the gearshift process into separate phases, optimization problems are solved to investigate the minimum time and low Jerk gearshift transients. The controls are also calculated with fuel penalties added to the minimum Jerk optimization and the transients are analyzed.

Place, publisher, year, edition, pages
IFAC, 2016
Series
IFAC PAPERSONLINE, ISSN 2405-8963
Keyword
Plant Modelling and System Identification, XEV (HEV, EV, FCEV, etc.)/Solar-Powered Vehicles
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-128778 (URN)10.1016/j.ifacol.2016.08.111 (DOI)000383464400111 ()
Conference
8th IFAC International Symposium on Advances in Automotive Control, June 19-23, 2016, Kolmården Wildlife Resort, Norrköping, Sweden
Available from: 2016-05-30 Created: 2016-05-30 Last updated: 2016-10-24Bibliographically approved
10. Analysis of optimal diesel-electric powertrain transients during a tip-in maneuver
Open this publication in new window or tab >>Analysis of optimal diesel-electric powertrain transients during a tip-in maneuver
2016 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Optimal transients of a hybrid powertrain are calculated with the aim to give a smooth and time efficient acceleration. It is shown that there is a trade-off between time and driveline oscillations where high oscillations can be avoided by slightly longer acceleration time and proper control of the electrical and diesel power sources. During a low oscillation acceleration, there is still the possibility to reduce the amount of total consumed electrical and fuel energy. This is investigated by calculation of optimal controls during acceleration for a fixed time while penalizing the usage of energy in a low oscillation acceleration. The balance between electrical and diesel energy usage during the acceleration is also investigated. The results show that to avoid extreme transients by optimal control, a multidimensional formulation of the objective function including different properties should be considered.

Place, publisher, year, edition, pages
IEEE, 2016
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-128779 (URN)
Conference
The 9th Eurosim Congress on Modelling and Simulation, 12 - 16 September 2016, Oulu Finland
Available from: 2016-05-30 Created: 2016-05-30 Last updated: 2016-05-30Bibliographically approved

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