Cycle rate control algorithm

• US 20070168084A1
• Filed: 01/18/2006
• Published: 07/19/2007
• Est. Priority Date: 01/18/2006
• Status: Active Grant

• Current Assignee: Computime Electronics Company Limited
• Original Assignee: Computime Electronics Company Limited
• Inventors: Cheng, Chung
• Granted Patent: US 7,400,942 B2
• Time in Patent Office: Days
• US Class Current: 700/276
• 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 11/46 Improving electric energy efficiency or saving
• CPC Class Codes: F24F 11/61 using timers
• 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 11/65 for selecting an operating mode
• CPC Class Codes: F24F 2110/10 Temperature
• CPC Class Codes: G05D 23/1917 using digital means

Abstract

The present invention controls a room temperature by controlling an environmental control unit. A total span about a setpoint temperature is adjusted in accordance with a previous total span and a multiplicative factor. The multiplicative factor is periodically updated from a desired cycle time and a previous cycle time. The room temperature may also be controlled by adjusting a duty cycle for controlling an environmental control unit. The duty cycle is adjusted based on an error associated with a previous control cycle and an attenuation factor. A new control cycle may be started by cutting the previous control cycle or a current control cycle may be extended if a predetermined condition is detected. The control mode is selected based on environmental characteristics and room characteristics. The control mode may include a span control mode and a duty cycle control mode that is selected from the cycle rate.

Claims

1. A method for controlling a room temperature with an environmental control unit, the method comprising:

(a) determining a proportional error;

(b) determining a rate error; and

(c) adjusting a current duty cycle from a previous duty cycle, the rate error and the proportional error.

2. The method of claim 1, wherein (a) comprises:

(a)(i) determining a first constant;

(a)(ii) determining the proportional error from the first constant, an average temperature, and a setpoint temperature.

3. The claim of claim 1, wherein (b) comprises:

(b)(i) determining a second constant;

(b)(ii) determining the rate error from the second constant, an average temperature, and a cycle time.

4. The method of claim 1, further comprising:

(d) limiting the current duty cycle.

5. The method of claim 1, further comprising:

(d) determining a temperature band; and

(e) modifying the current duty cycle so that the room temperature returns within the temperature band when the room temperature is outside the temperature band.

6. The method of claim 5, wherein (e) comprises:

(e)(i) if a cycle cut condition occurs, adjusting the current duty cycle.

7. The method of claim 5, wherein (e) comprises:

(e)(i) if a cycle extension condition occurs, adjusting the current duty cycle.

8. The method of claim 1, wherein the environmental control unit comprises a heating unit.

9. The method of claim 1, wherein the environmental control unit comprises a cooling unit.

10. A method for controlling a temperature of a room with an environmental control unit, the method comprising:

(a) determining an error of a previous control cycle;

(b) attenuating the error by an attenuation factor to obtain a correction variable; and

(c) modifying a duty cycle of a current control cycle with the correction variable.

11. An apparatus that controls a temperature of a room, the apparatus comprising:

a temperature sensor that measures the temperature; and

a processing unit that controls an environmental control unit and that is configured to perform;

(a) determining a control mode;

(b) if the control mode equals a span control mode, adjusting a current total span of a current control cycle based on a desired cycle time and a previous cycle time; and

(c) if the control mode equals a duty cycle control mode, adjusting a duty cycle of the current control cycle based on an error of a previous control cycle.

12. The apparatus of claim 11, wherein the processing unit is further configured to perform:

(b)(i) obtaining a previous total span of the previous control cycle; and

(b)(ii) multiplying the previous total span by a multiplicative factor.

13. The apparatus of claim 11, wherein the multiplicative factor is determined from a ratio equal to the desired cycle time divided by the previous cycle time.

14. The apparatus of claim 11, wherein the processing unit is further configured to perform:

(c)(i) determining the error from a setpoint temperature and a predicted temperature.

15. The apparatus of claim 14, wherein the predicted temperature is based on an average temperature and a temperature change of the previous control cycle.

16. The apparatus of claim 14, wherein the processing unit is further configured to perform:

(c)(ii) multiplying the error by an attenuation factor.

17. The apparatus of claim 16, wherein the processing unit is further configured to perform:

(c)(iii) adjusting the attenuation factor to match a characteristic of the room.

18. The apparatus of claim 11, wherein the environmental control unit comprises a heating unit.

19. The apparatus of claim 11, wherein the environmental control unit comprises a cooling unit.

20. The apparatus of claim 11, wherein the processing unit is further configured to perform:

(a)(i) if a cycle rate exceeds a predetermined limit, setting the control mode to the duty cycle control mode; and

(a)(ii) if the cycle rate is less than or equal to the predetermined limit, setting the control mode to the span control mode.