Modelling and Control of the AC-system in Heavy Duty Vehicles
Abstract
The aim of this thesis is to investigate the Air Conditioning system in a heavy duty
truck and to develop a control strategy for the case when low cooling capacity is
needed from the AC-system.
A model of the AC-system was developed in order for an efficient controller to be
designed. The model was designed to comprise of all the basic behaviours that the AC-
system has, rather than to be an exact model of the system. As the AC-system showed
to be very complex, a number of limitations in the model had to be made.
The AC-system has two temperature sensors and is actuated by turning the AC-
compressor on or off. Two different control strategies were tested for the control of the
AC-compressor. The first was to use a controller to directly control the compressor
clutch and the second one utilised a pulswidth modulated control structure were the
controller stated the pulswidth to be used.
Both control structures were implemented in the computer model, the AC-rig and in a
truck in a climate chamber. Both control strategies showed to fulfil the demands on the
system in the somewhat idealistic circumstances during which they were tested.
Magnus Eriksson
2001
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