For a long time, due to the regional air conditioning unit can flexibly control the start and stop of the indoor temperature, and can save space and cost, fan coil plus fresh air system (FCU) has been in the guest rooms and business to rent industry, hotels and office buildings and other buildings preferred semi central air conditioning system type. The room temperature controller is the key to control the cooling and heat of the fan coil unit (FCU), and realize the temperature control and energy saving.

The fan coil temperature controller is an independent closed loop temperature control system, which is composed of a temperature sensor, a dual position controller, a temperature setting mechanism, a manual three speed switch and a hot and cold switching device. The control principle is the controller based on the double position control signal comparison results of temperature sensor measured at room temperature and the set value, the control of electric water valve and cold water circulation pipeline (two valve or a three-way valve switch is cut off) and open the way to the circulation of the coil, regulating air temperature (cooling capacity). The indoor temperature control in the settings on a range (precision air conditioning) within (Fig. 1).

The first generation of the thermostat is mainly electrical products, the temperature sensor adopts a double metal sheet or a pneumatic temperature package, through a given temperature adjustment for preload disc "to set the temperature conversion, three speed fan switch and switch on for season type mechanical switch gear. This kind of products generally exist the problem of "the temperature setting value is too thick", "the time constant is too big", "the mechanical switch is easy to damage" and so on.

The second generation of temperature controller for electronic products, the temperature sensor uses thermistor or thermal resistance, temperature and wind speed part of the switch through the touch keys and LCD screen to realize man-machine interface, and automatically switch, operational amplifier circuit and switching circuit to realize the double position control. This kind of product has improved the man-machine interaction interface, solved the problem of "the setting value of temperature is too thick" and so on, but there are still some problems, such as "the control precision is not high", "the time constant is big", "the operation is more complex" and so on.

At present, the domestic and foreign manufacturers are researching and developing the third generation intelligent room temperature controller. At present, domestic manufacturers have produced intelligent room temperature controller, and has been applied to practical engineering.

1 the principle and characteristics of the new intelligent temperature controller

Fan coil temperature controller in air conditioning system in the application of "large amount", and the essential meaning, product quality and energy saving effect of major products, it must consider the cost and modification cost. Beijing pan analysis of Fuzzy Technology Research Institute developed FHK-1 intelligent temperature controller is developed by using a new control method - fuzzy switching control, without changing the original control wiring, without increasing the cost under the premise to realize from the simple "double control" to "intelligent fuzzy control" leap.

Design of fuzzy switching control technique is: using the fuzzy reasoning method of real-time adjustment of double position control in the process of upper and lower threshold, which is controlled in response to rising in order to reduce the overshoot, advance T1 seconds off the hot air, so in order to prevent the controlled response decreased overshoot, T2 seconds ahead of the hot air (Fig. 2). T1 and T2 are obtained by the fuzzy reasoning method in the real-time control process. The fuzzy inference engine uses the FC-3 fuzzy inference machine which is developed by the independent property right. The inference engine has the characteristics of fast reasoning speed, high resolution, strong anti-interference ability and low price. (see Figure 2)

In addition, a group of experts on the intelligent temperature controller, automatic arrangement, generation of three air according to the indoor and the number of doors and windows, to track the fastest speed, reasonable adjustment, avoid misoperation, saving water consumption.

This kind of intelligent fuzzy control method still belongs to the closed loop control system, and its control principle is shown in figure 3. According to the measured temperature and the set temperature value are compared with the results for reasoning and issued a switch control signal fuzzy reasoning machine, switch control electric water valve or a fan, if the temperature is high, cold water and open the fan (for air); if the temperature of material "low" is broken and the water stop the fan (stop the cold wind). According to the room temperature change rate (derivative), the expert intelligent system judges the indoor number and the load characteristics of doors and windows. (see Figure 3)

It can be seen that the whole control process only needs to set a temperature value, which can realize the automatic intelligent operation, and avoid the problem of "room temperature control failure" due to the unreasonable setting of the fan speed.

2 air conditioning accuracy, human comfort and energy saving

We know that the higher the air conditioning accuracy, the better the comfort of the human body, the less the energy loss of the overshoot. However, the higher the control precision of the traditional control method, the higher the cost of the automatic control system. For the economic consideration, the general comfort air conditioning system is not strict to the air conditioning accuracy. This caused the general comfort air conditioning system lacks effective temperature control means, can only rely on the experience of the personnel management or operation of manual adjustment, strong subjectivity, adjusting the cold / heat loss, serious waste of energy situation.

The most important significance of the application of the fuzzy switch control intelligent temperature controller in the fan coil air conditioning system is that it can improve the control precision of the comfort air conditioning system without increasing the cost". Figure 4 and figure 5 compares common switch transition process experimental record, thermostat and intelligent temperature control air conditioning room temperature can be seen in the "survey" and "difference" and "recovery time" and other quality indicators.