Room pressure control apparatus having feedforward and feedback control and method

• US 6,033,302 A
• Filed: 11/07/1997
• Issued: 03/07/2000
• Est. Priority Date: 11/07/1997
• Status: Expired due to Term

• Current Assignee: Siemens Industry Incorporated (Siemens AG)
• Original Assignee: Siemens Building Technologies Incorporated (Siemens AG)
• Inventors: Ahmed, Osman, Klein, Sanford A., Mitchell, John W.
• Primary Examiner(s): Joyce, Harold
• Application Number:
  US08/965,982
• Time in Patent Office: 851 Days
• Field of Search: 454/56, 454/61, 454/238, 454/255, 454/340
• US Class Current: 454/238
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
• CPC Class Codes: F24F 11/63 Electronic processing
• CPC Class Codes: F24F 2011/0004 to create overpressure in a room
• CPC Class Codes: G05B 11/42 for obtaining a characteristic which is both proportional and time-dependent, e.g. P. I., P. I. D.
• CPC Class Codes: G05B 13/041 in which a variable is automatically adjusted to optimise the performance
• CPC Class Codes: G05B 13/042 in which a parameter or coefficient is automatically adjusted to optimise the performance
• CPC Class Codes: G05B 13/048 using a predictor
• CPC Class Codes: G05B 17/02 electric

Abstract

A controller for heating, ventilating and air-conditioning distribution systems, which includes a feedforward and feedback control strategies. The controller has a feedforward control strategy that generates a control signal based on control set points and identified characteristics of the system, and which adaptively adjusts such set points based on changes that are measured with respect to the identified characteristics. The controller is particularly adapted for controlling the differential air pressure in a controlled space relative to adjacent spaces.

Claims

1. A controller for controlling the air pressure within a room in a building having at least one space adjacent to the room, the building having a heating, ventilating and air conditioning (HVAC) system with a supply duct adapted to supply air to the room and an exhaust duct adapted to exhaust air from the room, the system having a component for controlling the supply air flow into the room, the room having at least one additional exhaust independent of the HVAC system, said apparatus comprising:

a feedforward means for generating a feedforward control signal based on desired flow set points in the supply duct and general exhaust duct and based on identifying characteristics of the component, said component comprises a supply damper/actuator and an exhaust damper/actuator, the characteristics comprising the flow rate of air entering the room, the set point of the flow rate of air entering the room, the flow rate of exhaust air leaving the room, the set point of the flow rate of the exhaust air leaving the room, the authority of the supply damper/actuator, the authority of the general exhaust damper/actuator and calculated system variables;

a feedback means for generating a feedback control signal based on measured system variables; and

means for combining the feedforward control signal and the feedback control signal to achieve control of the local component.

2. A controller as defined in claim 1 wherein said identifying characteristics of said damper are determined by a General Regression Neural Network (GRNN).

3. A controller as defined in claim 2 wherein said identifying characteristics are determined by the equation:

##EQU12##

4. A controller for controlling a component comprising a supply damper/actuator and a general exhaust damper/actuator of a building heating, ventilation and air-conditioning (HVAC) fluid distribution system that affects at least the air pressure in a particular room, the room having an air supply duct and at least one general air exhaust duct, the controller being adapted to control the air flow into and out of the room to maintain a predetermined differential pressure relative to an adjacent space in the building, the controller comprising:

an identification means for periodically producing identified characteristics of the component to be controlled, said identified characteristics comprising the authority of said damper/actuators;

a feedforward means coupled to the identification means, for generating a feedforward control signal based on control set points and the identified characteristics of the component, said control set points being determined to be those which maintain the mass of the air entering the room substantially equal to the mass of the air being exhausted from the room;

a feedback means for generating a feedback control signal based on measured system variables; and

means for combining the feedforward control signal and the feedback signal to achieve control of the local component.

5. A controller as defined in claim 4 wherein said control set points comprise the supply air flow rate set point and the general exhaust air flow rate set point.

6. A controller as defined in claim 5 wherein said control set points are adaptively changed as a function of changes in said identified characteristics.

7. A controller as defined in claim 6 wherein said supply air flow rate set point (ν

_s|sp) is determined from the equations;

##EQU13## and where;

P_s|sp is the supply air pressure set point;

T_s|sp is the supply air temperature set point;

ν

_s|sp is the supply air flow rate set point;

P_ad|sp is the infiltration air pressure set point;

T_ad|sp is the infiltration air temperature set point;

ν

_s|sp is the infiltration flow rate set point;

P.sub.|sp is the room pressure set point;

ν

_e|sp is the exhaust flow rate set point;

T.sub.|sp is the room temperature set point.

8. A controller as defined in claim 4 wherein said identifying characteristics of said damper are determined by a General Regression Neural Network (GRNN).

9. A controller as defined in claim 8 wherein said identifying characteristics are determined by the equation:

##EQU14##