Estimering av laster i PTO-kraftutag
To extend the possible use of a truck it can be equipped with auxillary equipment
for handling cargo and different working tools. These are powered using a Power
Take-Off (PTO) connected to the vehicle´s drivetrain. In the current situation
the control system lacks information about these loads, which can have a negative
impact on the control. In this thesis a method for estimating the unknown
PTO torque is presented. The method is based on Newtons second law of motion
describing the motion of the flywheel. The driving torque from the drivetrain is
described by a dynamic model. By calculating how much torque that should suffice
in the present driving situation and comparing this to the torque delivered by the
engine, the parasitic losses and unknown external loads can be estimated.
A sensitivity analysis of the ambient influence on the model and the PTO
estimation shows that the estimation cannot be performed in a robust and reliable
way. The errors that arise from faulty input to the model such as deficient road
slope and vehicle mass information result in errors with greater magnitude than the
load torque to be estimated. It is also concluded that in the Engine Management
System (EMS), the calculation of the torque delivered by the engine can show a
static error of up to approximately 70Nm.
Magnus Seldén
2011
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