Based on the experimental study on the processes of frosting and defrosting of the air conditioner when it works as heat pump

this paper reports a new technique of fuzzy self-tuning defrosting control

which can not only adapt to all weathers but also discern and correct the regulative parameter on line. This technique judges the point at which defrosting begins according to the difference between the evaporating temperature and the outdoor temperature and the ratio of variety of these two temperatures

and evaluates the quality of defrosting in terms of the defrosting time and the temperature of pipes as defrosting ends. Also it adjusts control parameter timely to achieve optimal heating effect. The results of experimental research show that this control method is reliable in a wide climate zone

and can grasp the point at which defrosting starts or ends

and defrosting is clean.