Hardware-in-the-loop-simulation of a vehicle climate controller with a combined HVAC and passenger compartment model

A good example for a complex mechatronic system is a modern vehicle. It covers a lot of subsystems which solve different tasks but are often coupled. The automatic air conditioning system is one of those subsystems. It consists, especially in vehicles of higher categories, of a high number of distributed mechatronic actuators and sensors and a central controller. The aim of such a system is to achieve a desired climatic condition in the vehicle interior which leads to a higher comfort for the passengers and therefore it also increases indirect the safety in road traffic. The climatic condition is defined by the interior temperature, its layering, the humidity and the velocity of the airflow blowing through the passenger compartment. For the adjustment of the desired interior climate with the available air conditioning components complex control algorithms are necessary. This control task is performed by the climate controller, which includes all control strategies in form of software programs. Beneath the construction of all system parts, a further challenge is the design of the control which includes the design of the controller hardware as well as the control strategies. By applying modern structured development methods for mechatronic systems like the modified V-model [VDI 2206, 2004] the development time and the costs can be reduced whereas the quality can be improved by using a model based approach. Fundamental part of this strategy are the X-in-the-loop-simulation (XIL-simulation) methods, where all system parts, which can be pure virtual in form of models or real elements, are considered in interaction. This is done for verification and validation of the system parts and the software. By using this technique in the concrete case of the climate controller, its hardware as well as the applied control strategies can be tested and optimized in conjunction with a real time computer that is connected to the controller via appropriate interfaces. Models running on the real time computer simulate the air conditioning system. Thus it is possible to close the control loops in a partially virtual system. In contrast to this approach, conventional development strategies, where most control loops can be considered for the first time at the assembled system, are very time consuming and cost intensive because real test drives have to be carried out for the verification and validation processes. This is especially essential for tests under different climatic conditions like summer and winter tests. In case of the software- and hardware-in-the-loop-simulation (SIL- and HIL-simulation) for an air conditioning controller, models of the heating, ventilation and air conditioning elements (HVAC) and the passenger compartment are necessary. A main demand for the HIL-Simulation is the real time capability. Therefore it is a challenge to create simple but accurate models, that enable a fast calculation of the wanted values. In this paper both models, the HVAC and the single zone passenger compartment model and their interfaces would be presented. Further results of both models interacting in a HIL-simulation on a commercial hardware platform connected via interfaces to the climate controller would be shown