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Wheel loader optimal transients in the short loading cycle
Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
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 (Refereed)Text
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. Vol. 47, no 3, 7917-7922 p.
Series
, World Congress, ISSN 1474-6670 ; Volume, 19, Part 1
Keyword [en]
Optimal control, switching control variable, nonlinear system, wheel loader, loading cycle
National Category
Vehicle Engineering Other Mechanical Engineering
Identifiers
URN: urn:nbn:se:liu:diva-128708DOI: 10.3182/20140824-6-ZA-1003.02419ISBN: 978-3-902823-62-5OAI: oai:DiVA.org:liu-128708DiVA: diva2:931729
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
In thesis
1. Modeling and Optimal Control of Heavy-Duty Powertrains
Open this publication in new window or tab >>Modeling and Optimal Control of Heavy-Duty Powertrains
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
Powertrain, transmission system, optimal control, modeling for control
National Category
Control Engineering
Identifiers
urn:nbn:se:liu:diva-128002 (URN)10.3384/diss.diva-128002 (DOI)978-91-7685-748-9 (Print) (ISBN)
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

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Nezhadali, VaheedEriksson, Lars
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