1 Department of Electronic Systems, The Faculty of Engineering and Science (ENG), Aalborg University, VBN2 Automation & Control, The Faculty of Engineering and Science (ENG), Aalborg University, VBN3 The Faculty of Engineering and Science (TECH), Aalborg University, VBN4 Strategic Research Centre on Zero Energy Buildings, The Faculty of Engineering and Science (ENG), Aalborg University, VBN5 Aalborg University Space Center, The Faculty of Engineering and Science (ENG), Aalborg University, VBN6 Aalborg U Robotics, The Faculty of Humanities, Aalborg University, VBN
An important aspect of efficient and safe operation of refrigeration and air conditioning systems is superheat control for evaporators. This is conventionally controlled with a pressure sensor, a temperature sensor, an expansion valve and Proportional-Integral (PI) controllers or more advanced model based control. In this paper we show that superheat can be controlled without a pressure sensor and without a model of the system. This is achieved by continuous excitation of the system and by applying Fourier analysis, which gives an error signal that can be used together with standard PI control. The proposed method works for systems with ”S” shaped input/output maps that satisfy sigmoid function properties and such behavior has been identified in both an air conditioning and a refrigeration system. Tests on these systems show that the superheat can be controlled to a low level over a large operating range with only one sensor. It is believed that the method in general is applicable to a wide variety of nonlinear systems for which the desired operating points are close to points of zero mean curvature of system nonlinearities.
Proceedings of the Ieee Conference on Control Applications, 2012, p. 757-763
Main Research Area:
I E E E International Conference on Control Applications. Proceedings
2012 IEEE Multi-conference on Systems and Control, 2012