Design of an Automatic Control Algorithm for Energy-Efficient ...

13 Conclusion 129
13.2 Possible improvements
At large, more or better information allows better control. Better system models can
increase the control accuracy. Inclusion of the interior thermal masses temperature as a
separate state could improve the disturbance estimation, but would require an additional
sensor. Air leakage could be integrated - if known - into the model, too. In general, a
validation of the models will be required to some extent to assure good control in the real
car. Not only the system, but also the objective models can be improved, most impor-
tantly the thermal comfort model. For example, the effect of air jets with temperatures
different from the cabin air temperature could be included.
On the hardware side a better temperature and comfort estimation could be ob-
tained with a solar sensor, especially when it is coupled with an adapted comfort model.
For better carbon dioxide concentration values a sensor could be added. With more ac-
curate values, more use of recirculation could be made, resulting in savings of heating
energy. In particular this applies if water in the cabin (from shoes or clothes) causes the
CO2 simulation to give too high values.
For the HVAC-system, better control over the air flow is required. Influences like
the car speed, flaps or recirculation can be taken into account by different means. One
way is to measure the effects and to implement a model to compensate for them. Another
way are additional sensors capturing the pressure drop and allowing closed-loop control.
Finally, the hardware can be adapted to reduce some effects. This is possible for the
recirculation with the help of a so-called ram door (cf. Section 3.2.1).
The HVAC-unit in the MUTE project is taken from a “normal” car which will
probably cause minor problems in the way it is used. The openings and the flap are
not designed for partial recirculation. This can lead to direct air inflow through the
recirculation path at higher car speeds. An adapted design would also reduce the pressure
drop, the acoustics, the size, and it could improve the controllability.
13.3 Outlook
The designed and implemented controller includes a means of using recirculated air to
reduce energy consumption. Simultaneous it takes into account comfort and windscreen