Modeling and Optimal Control of a Wheel Loader in the Lift-Transport Section of the Short Loading Cycle
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.
Vaheed Nezhadali and Lars Eriksson
2013
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Last updated: 2021-11-10
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