Abstract:
Sensing, actuation of apparatus, and a control algorithm for use in automatically controlling an air-conditioning system by sensing multiple conditions and responding by actuating the mechanical components of the air-conditioning system to optimize the temperature of the coolant fluid, provide improved zone temperature control, provide status of system components, and provide an alert if there is overheating of a supply side system mechanical component.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is related to patent application identified by Attorney docket number 210-1051 PCT both of which are subject to assignment to Carrier Corporation, and each of which is being filed on even date herewith. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of temperature control systems, and in particular, to a control algorithm for use in automatically controlling an air-conditioning system by sensing multiple conditions and responding by actuating the mechanical components of the air-conditioning system. 
       BACKGROUND OF THE INVENTION 
       [0003]    Many air conditioning zone control systems include a single sensor that monitors the temperature of the ambient air or the temperature of the air returning from the zone whose temperature is being controlled. This sensor provides feedback to an air-conditioning system controller in order for the controller to adjust various air-conditioning components such as supply air fans, coil coolant fluid proportional valves (cooling or heating mode), and electric heaters, if any, to attempt to maintain a temperature setpoint in the zone. 
         [0004]    A controller using a control algorithm that only references a zone&#39;s ambient or return air temperature against a user entered setpoint can yield large temperature fluctuations in the zone because, for example, the supply air is of a much lower temperature than the zone&#39;s temperature. When this supply air is delivered to the zone, it causes a large temperature drop below the setpoint and the controller must affect an immediate adjustment in the opposite direction to provide warmer air to the zone. 
         [0005]    This cycling is undesirable because it causes the controller to frequently adjust the system components in an effort to achieve the setpoint in the zone, and as a result, it merely increases equipment wear and causes periodic temperature fluctuations above and below the setpoint in the zone. 
         [0006]    Certain algorithms exist to minimize the aforementioned cycling using only the ambient temperature in the zone or the return air sensor, but without additional sensors, they are not capable of providing for optimization of the temperature fluctuations in the coolant fluid, detecting air-conditioning system mechanical component failures, providing supply end equipment overheating alerts to a system user or building management system, or providing smart temperature controls for an air conditioned zone. 
       SUMMARY OF THE INVENTION 
       [0007]    A control algorithm for implementation in a zone air-conditioning controller is provided wherein multiple sensors connected to the controller provide representative signals that the controller selectively employs through the control algorithm to provide, based on numerous user programmable parameter inputs, command signals to to actuators of mechanical components of the system. 
         [0008]    In one embodiment, the control algorithm can use the supply coolant fluid and return coolant fluid temperature signals to control actuators in the system to optimize the delta temperature between the inlet and outlet of the coolant fluid in the temperature adjusting coil while maintaining the desired zone temperature when the system is in operation. 
         [0009]    In another embodiment, the control algorithm can use the supply air temperature signal to selectively provide information that a system component in the system has failed. 
         [0010]    In still another embodiment, the control algorithm can use the supply air temperature signal to selectively provide for a safety warning of hazardous equipment failure. 
         [0011]    In yet another embodiment, the control algorithm can use the supply air temperature input and the return air temperature input to enable a smart temperature control system to create desirable effects in the zone controlled by the controller. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    For a further understanding of these and other objects of the invention, reference will be made to the following detailed description of the invention which is to be read in connection with the accompanying drawing, where: 
           [0013]      FIG. 1  diagrammatically depicts a zone air-conditioning system and its component parts; 
           [0014]      FIG. 2  displays numerous inputs and outputs connected to the air-conditioning system zone controller to be used by the new algorithm; 
           [0015]      FIG. 3  schematically depicts the prior art control of a proportional coolant fluid flow valve of an air-conditioning system using only a return air sensor and a zone setpoint; 
           [0016]      FIG. 4  schematically depicts a coolant fluid delta temperature controlling embodiment of the new control algorithm; 
           [0017]      FIG. 5  shows, in the form of curves, the values of the setpoint and the delta temperature of the coolant fluid with and without the new algorithm active in the controller. 
           [0018]      FIG. 6  schematically depicts a supply side equipment overheating and warning system embodiment of the new control algorithm. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Referring initially to  FIG. 1 , there is illustrated a diagrammatical depiction of a zone air-conditioning system generally referenced at  10 , that illustrates a direction of air flow coming into the system  12 , from the air-conditioned zone  14  and a direction of conditioned air flow exiting the system  13 . Entrance of the air flow from the zone  14 , passes over a return air temperature sensor  16 , then through a supply side filter  18 , then through at least one supply side air fan  20 , a supply side air temperature adjusting coil  32 , and finally over a supply air temperature sensor  24 . The conditioned air is then supplied to the zone  14 . A supply side proportional coolant fluid flow valve  34 , is disposed in the piping that the supplies the supply coolant fluid  35 , to the supply side of the air temperature adjusting coil  32 . The temperature of the supply coolant fluid  35 , is sensed by a supply coolant fluid temperature sensor  36 , if present, or broadcast by a building monitoring system. The temperature of the return coolant fluid  38  from the air temperature adjusting coil  32 , is monitored by a return coolant fluid temperature sensor  37 . 
         [0020]    Turning now to  FIG. 2 , some inputs and outputs to air-conditioning system controller  51 , are shown that are used by the control algorithm  50 , running therein. The controller  51 , contains a microprocessor having a clock speed of at least 16 MHz, internal RAM memory of at least 3.84 Kbytes, internal FLASH memory of at least 128 Kbytes, internal E 2  memory of at least 1 Kbyte, a built in A/D converter of at least 10 bits with a 1 LSB error, and a watchdog that is on the chip hardware. 
         [0021]    In one embodiment, the control algorithm  50 , primarily controls the temperature of the zone  14 , and secondarily strives to optimize the delta temperature of the coolant fluids  35 ,  38 , of the air-conditioning system  10 , to a temperature of about 5-6 degrees Fahrenheit. Delta temperature is defined as the difference between the supply coolant fluid  35 , temperature as sensed by the supply coolant fluid temperature sensor  35 , if present, or as a value broadcast to the controller  51 , by a building management system  54 , and the return coolant fluid  38 , temperature as sensed by a return coolant fluid temperature sensor  37 . 
         [0022]    Referring now to  FIG. 3 , a schematic depiction of the prior art relating to proportional coolant fluid flow valve  34 , is shown wherein the proportional position reference  134 , is determined solely by the zone  14 , ambient air temperature or the return air temperature sensor  16 . As mentioned above, this system has many undesirable effects relating to zone temperature fluctuations and equipment wear. It should be noted that this prior art is included as a portion of the present invention&#39;s proportional coolant fluid flow valve&#39;s  34 , control algorithm  50 . 
         [0023]    Referring now to  FIG. 4 , an embodiment of the proportional coolant fluid flow valve  34 , system control algorithm  50 , is shown. The upper half of the schematic depicts a standard control loop wherein the user entered zone setpoint  9 , input by a thermostatic device or programmed by a system user, and the return air temperature sensor  16 , input values are combined in symbolic sigma block  102 , to provide zone setpoint error point signal  104 , which is conditioned through an adjustable fan gain block  106 , and an adjustable fan PI block  108 , to yield a fan speed reference signal  19 , to at least one variable speed fan  20 . A symbolic sigma block is defined as a graphical depiction of a mathematical summation of the values entering into it with the resulting value exiting it. Zone setpoint error point signal  104 , is also conditioned through an adjustable proportional coolant fluid flow valve gain block  110 , and an adjustable proportional coolant fluid flow valve PI Block  112 , to yield a proportional coolant fluid flow valve positioning reference signal  111 , that is input to symbolic sigma block  114 , whose output is the position reference signal  134 , to proportional coolant fluid flow valve  34 . It should be noted that  FIG. 4  depicts the coolant fluid to be water, however, those skilled in the art will appreciate that other refrigerants well known in the art could be used. 
         [0024]    Without the new algorithm, the bottom portion of the schematic, a zero value would come into symbolic sigma block  114 , and yield the prior art calculation for positioning the proportional coolant fluid flow valve  34 , and would suffer from the frequent adjustment of its position and the temperature of the supply coolant fluid  35 , used to supply the air temperature adjusting coil  32 . As noted above, this type of control scheme using only the zone air temperature setpoint  9 , and the return air temperature sensor  16 , input is undesirable because it only results in temperature fluctuations above and below the user entered zone air temperature setpoint  9 , and increased supply side equipment wear. 
         [0025]    To minimize this fluctuation, the new algorithm (the bottom portion of the schematic in  FIG. 4 ) provides a dampening (transient response minimizing) proportional feedback loop that is implemented using the actual difference of the supply coolant fluid  35 , and return coolant fluid  38 , temperatures compared against a user selectable coolant fluid delta temperature setpoint parameter  120 , which is optimally about 5-6 degrees Fahrenheit. The new proportional loop supplies the control algorithm  50 , with the temperature of the supply coolant fluid  35 , via the supply coolant fluid temperature sensor  36 , or a value broadcast from a building management system, and the temperature of the return coolant fluid  38 , via the return coolant fluid temperature sensor  37 . The supply coolant  35 , temperature is combined with the return coolant temperature  37 , in symbolic sigma block  116 , and yields a coolant fluid delta temperature signal  118 , as the system  10 , is operation. 
         [0026]    This proportional coolant feedback delta temperature signal  118 , is combined with the user entered coolant fluid delta temperature setpoint  120 , in symbolic sigma block  122 , which yields a coolant fluid delta temperature error  124 . A unit delay block  126 , and an adjustable gain block  128 , condition the coolant fluid delta temperature error  124 , which is combined in multiplication block  132 , with a delta coolant temperature controller output  130 , to create a coolant proportional control loop output signal  100 . This coolant proportional control loop output signal  100 , is negated and then combined with the return air controlled proportional valve position reference  111 , in symbolic sigma block  114 , to yield the proportional position reference  134 , to the proportional coolant fluid flow valve  34 . 
         [0027]    The effect of utilizing this control algorithm  50 , with the coolant fluids  35 ,  38 , temperature feedback is to dampen the amplitude of the coolant fluids  35 ,  38 , temperature fluctuations to a point that they are not as greatly affected by variations of the return air  12 , to the air-conditioning system  10 , and can strive to achieve the optimum temperature of about 5-6 degrees Fahrenheit. 
         [0028]    Referring now to  FIG. 5 , the aforementioned dampening of the coolant fluid temperature response to fluctuating readings from the return air sensor  16 , and the effect of using the new control algorithm  50 , are demonstrated in the form of response curves from a system running the exact same simulation. One simulation had the control algorithm  50 , activated and the other did not. 
         [0029]    The more active temperature signal trace depicts the erratic behavior of the coolant delta temperature signal  118 , with the new control algorithm deactivated and the coolant temperature being controlled only by the return air temperature sensor  16 , input compared to the user entered zone setpoint  9 . 
         [0030]    The more stable temperature signal trace depicts a more controlled behavior of the delta temperature signal  118 , with the new control algorithm  50 , activated using the return air temperature sensor  16 , input, the supply air temperature sensor  24 , input, the coolant fluid supply sensor  36 , input, the coolant fluid return sensor  37 , input, and the proportional coolant fluid flow valve  34 , positioning reference output signal  111 , in operation. As can be seen, the delta temperature response of the coolant fluids  35 ,  38 , in relationship to the user entered coolant fluid delta temperature setpoint  120 , in this case, 6 degrees Fahrenheit, is much closer because of the dampened response of the position reference signal  134 , to proportional coolant fluid flow valve  34 . 
         [0031]    Turning now to  FIG. 6 , in another embodiment, the air-conditioning system controller  51 , can selectively provide information that a system component in the system has failed. Using inputs from the supply air temperature sensor  24 , and the return air temperature sensor  16 , and combining these values through symbolic sigma block  200 , yields an air delta temperature signal  202 , value that is combined with a user programmed system component failed parameter  19 , to yield a system component status signal  208 , that the control algorithm  50 , can use to determine that the system is functioning abnormally and that there has been a component failure or significant decrease in a component&#39;s functionality. Upon this detection, the control algorithm  50 , can send a component failure signal  40 , to alert a system user  52 , via a visual device or a building management system  54 , to inform a proper individual of the probable malfunction. 
         [0032]    In another embodiment, the control algorithm  50 , selectively provides for a safety warning of a hazardous equipment failure. For example, if the supply air temperature sensor  24 , detects a temperature input exceeding a programmable high supply air temperature limit parameter  301 , the control algorithm  50 , can send a hazardous condition signal  302 , to alert a system user  52  by a visual device, or a building management system  54 , to inform a proper individual of the probable malfunction, and automatically shut down the air-conditioning system  10 . 
         [0033]    In still another embodiment, the control algorithm  50 , selectively enables smart temperature control of the air-conditioned zone  14 . For example, using the supply air temperature sensor  24 , input and the control algorithm  50 , the “cold shower effect” in the heating mode can be avoided if a “no cold air inrush in heating mode” parameter  500 , is programmed by the system user  52 , to do so. The “cold shower effect” is realized when at least one of the supply air fans  20 , is turned on at a high speed and pushes air that has been cooled  17 , by remaining in the ductwork  21 , between the air-conditioned zone  14 , and the supply equipment. When this cooled air  17 , is forced into the zone  14 , at a high speed before any air-conditioned air is mixed with it, the result is air delivery that is cool at first and then warms up after the ductwork is purged of the cooled air  17 . 
         [0034]    The control algorithm  50 , is adapted to reduce the variable speed fan reference signal  19 , of at least one of the supply air fans  20 , raise the temperature of the supply air flow through the use of the supply side air temperature adjusting coil  32 , to slowly mix the cooler air already in the ductwork  21 , with the higher temperature air flow exiting the system  13 , and then deliver air to the zone  14 , that is initially much closer to user entered air temperature setpoint  9 . 
         [0035]    Yet another example of smart temperature control using the supply air temperature sensor  24 , input and the control algorithm  50 , is to avoid potential condensation risks of supply side components in the cooling mode. If an “optimize supply side temperature in cooling mode”  7 , parameter is programmed by the user to do so, the control algorithm  50 , will use the detected supply air temperature sensor  24 , input and raise the temperature of the supply side coolant fluid  35 , to heat the supply side equipment as much as possible to avoid condensation risks without affecting the overall air-conditioning purpose of the system  10 . 
         [0036]    While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by the claims.