Pulse modulation adaptive control method for activating an electrical device

• US 6,647,318 B2
• Filed: 11/07/2001
• Issued: 11/11/2003
• Est. Priority Date: 11/08/2000
• Status: Expired due to Term

• Current Assignee: Johnson Controls Technology Company (Johnson Controls International plc)
• Original Assignee: Johnson Controls Technology Company (Johnson Controls International plc)
• Inventors: Salsbury, Timothy I.
• Primary Examiner(s): Picard, Leo
• Assistant Examiner(s): JARRETT, RYAN A
• Application Number:
  US10/040,069
• Publication Number:
  US 20020116075A1
• Time in Patent Office: 734 Days
• Field of Search: 700/276, 700/278, 700/299, 700/300, 700/41, 700/34, 700/54, 236/1.C, 236/91.D, 236/78.D, 236/1.E, 165/267-269
• US Class Current: 700/276
• CPC Class Codes: G05B 11/28 using pulse-height modulation; using pulse-width modulation
• CPC Class Codes: G05B 13/024 in which a parameter or coefficient is automatically adjusted to optimise the performance

Abstract

A facility management system includes a device which produces a change of an environmental characteristic in a building. A method for operating the device involves sensing the environmental characteristic to provide a measured value, and defining a desired maximum amplitude of variation within which the measured value may vary. A control signal is produced in response to the difference between the measured value and a desired value for the environmental characteristic. The control signal is then used to produce an output signal that turns the device on and off, wherein the output signal has a cycle period during which a pulse of a given duration occurs. The cycle period and the given duration are varied in response to the control signal without permitting the measured value to deviate more than desired.

Claims

1. A method for controlling a device of a facility management system, wherein the device controls an operational parameter of a building, said method comprising:

receiving a control signal (u) representative of a deviation in magnitude between a measured value of the operational parameter and a desired value of the operational parameter;

defining a desired maximum amplitude of variation (D) for the measured value; and

producing a pulsed output signal (h) that turns the device on and off, wherein the pulsed output signal is a pulse-width, pulse-frequency modulated signal having a cycle period during which a pulse of a given duration (TON) occurs, the cycle period and the given duration being dynamically calculated in response to changes in the control signal to maximize the cycle period while maintaining the amplitude of variation of the measured value equal to or below the maximum amplitude of variation (D) when the system is in a steady state pulsing condition.

2. The method of claim 1, further including sensing the operational parameter to provide the measured value.

3. The method of claim 1, wherein the maximum amplitude of variation (D) is defined as a constant value.

4. The method of claim 1, wherein the control signal (u) is an analog signal.

5. The method of claim 1, wherein the device has a plurality of stages and the producing step comprises responding to the control signal by:

determining, in response to the control signal (u), a number of stages (R) that are to operate at full capacity; and

determining, in response to the control signal (u), a fractional amount (v) of full capacity that another stage is to operate at, wherein the fractional amount is employed to determine the cycle period and the given duration.

6. A method for controlling a device of a facility management system, the device producing a change of an environmental characteristic in a building, said method comprising:

specifying a desired value for the environmental characteristic;

defining a desired maximum amplitude of variation (D) in the measured value;

receiving a control signal (u) representative of a deviation of a measured value from the desired value for the environmental characteristic; and

producing a pulse train (h) that controls turning on and off the device, the pulse train being a pulse-width, pulse-frequency modulated signal having a cycle period during which occurs a pulse of a given duration (T_ON), wherein the cycle period and the given duration are dynamically varied in response to the control signal so that the cycle period is maximized while an amplitude of variation of the measured value is maintained no greater than the maximum amplitude of variation (D) when the system is in a steady state pulsing condition.

7. The method of claim 6, wherein the device is turned on in response to an occurrence of a pulse in pulse train.

8. The method of claim 6, wherein the cycle period C is varied according to the expression:

$C=-\mathrm{\tau <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\ln <br><br>\text{\hspace{1em}<br><br>}\left[\frac{\left(D/G\right)-1+{\mathrm{<br><br>}}^{\frac{-\mathrm{Ton}}{\mathrm{\tau <br><br>}}}}{\left(D/G\right)+1-{\mathrm{<br><br>}}^{\frac{\mathrm{Ton}}{\mathrm{\tau <br><br>}}}}\right]$

where τ

is a time constant of the device and G is the process gain.

9. The method of claim 6, wherein the given duration TON is varied according to the expression:

$T_{\mathrm{ON}}=C<br><br>\left\{u<br><br>\text{\hspace{1em}<br><br>}\left[1-\frac{1}{C_{\mathrm{MAX}}}<br><br>\left(T_{\mathrm{MIN},\mathrm{ON}}+T_{\mathrm{MIN},\mathrm{OFF}}\right)\right]+\frac{T_{\mathrm{MIN},\mathrm{ON}}}{C_{\mathrm{MAX}}}\right\}$

where C is the cycle period, T_MIN,ON is a minimum amount of time that the device should be turned on, and T_MIN,OFF is a minimum amount of time that the device should be turned off.

10. The method of claim 6, wherein the maximum amplitude of variation (D) is defined as a constant value.

11. The method of claim 6, wherein the control signal (u) is an analog signal.

12. The method of claim 6, wherein defining the maximum amplitude of variation (D) utilizes the expression:

${\hat{G}}_{j+1}=\frac{{\left(\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>y\right)}_i<br><br>{\hat{G}}_j}{{\stackrel{\_}{D}}_j}$

where Δ

y is a change in the measured value and G is a gain of the process for changing the environmental characteristic in the building.

13. The method of claim 6, wherein the device has a plurality of stages, the method further comprising:

determining, in response to the control signal (u), a number of stages (R) that are to operate at full capacity; and

determining, in response to the control signal (u), a fractional amount (v) of full capacity that another stage is to operate at, wherein the fractional amount is employed to determine the cycle period and the given duration.

14. A method for controlling a device of a facility management system, wherein the device has a plurality of stages and produces a change of an environmental characteristic in a building, the method comprising:

specifying a desired value for the environmental characteristic;

defining a desired maximum amplitude of variation (D) within which the measured value is permitted to vary;

receiving a control signal (u) representative of a difference in magnitude between a measured value for the environmental characteristic and the desired value for the environmental characteristic;

determining, in response to the control signal (u), a number of first stages (R) that are to operate at full capacity;

determining, in response to the control signal (u), a fractional amount (v) of full capacity that a second stage is to operate at; and

producing a pulsed output signal (h) that controls turning on and off of the second state, wherein the output signal is a pulse-width, pulse-frequency modulated signal having a cycle period during which a pulse of a given duration occurs, the cycle period and the given duration of the pulse being varied in response to the fractional amount (v) so that the cycle period is maximized while variation of the measured value is maintained no greater than the maximum amplitude of variation D when the system is in a steady state pulsing condition.

15. The method of claim 14, wherein the maximum amplitude of variation (D) is defined as a constant value.

16. The method of claim 14, wherein defining the maximum amplitude of variation (D) varies the value of the maximum amplitude of variation amount in response to changes in performance of the device in controlling the operational parameter.

17. An apparatus for controlling a device of a facility management system, wherein the device controls an operational parameter of a building, comprising:

means for receiving a control signal (u) representative of a deviation in magnitude between a measured value of the operational parameter and a desired value of the operational parameter;

means for defining a desired maximum amplitude of variation (D) for the measured value; and

means for producing a pulsed output signal (h) that turns the device on and off, wherein the output signal is a pulse-width, pulse-frequency modulated signal having a cycle period during which a pulse of a given duration (T_ON) occurs, the cycle period and the given duration of the pulse being dynamically calculated in response to changes in the control signal to maximize the cycle period while maintaining the amplitude of variation of the measured value equal to or below the maximum amplitude of variation (D) when the system is in a steady state pulsing condition.

18. The apparatus of claim 17, further including means for sensing the measured value.

19. The apparatus of claim 17, wherein the cycle period C is varied according to the expression:

$C=-\mathrm{\tau <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\ln <br><br>\left[\frac{\left(D/G\right)-1+{\mathrm{<br><br>}}^{\frac{-\mathrm{Ton}}{\mathrm{\tau <br><br>}}}}{\left(D/G\right)+1-{\mathrm{<br><br>}}^{\frac{\mathrm{Ton}}{\mathrm{\tau <br><br>}}}}\right]$

where τ

is a time constant of the device and G is the process gain.

20. The apparatus of claim 17, wherein the given duration T_ON is varied according to the expression:

$T_{\mathrm{ON}}=C<br><br>\left\{u<br><br>\left[1-\frac{1}{C_{\mathrm{MAX}}}<br><br>\left(T_{\mathrm{MIN},\mathrm{ON}}+T_{\mathrm{MIN},\mathrm{OFF}}\right)\right]+\frac{T_{\mathrm{MIN},\mathrm{ON}}}{C_{\mathrm{MAX}}}\right\}$

where C is the cycle period, T_MIN,ON is a minimum amount of time that the device should be turned on, and T_MIN,OFF is a minimum amount of time that the device should be turned off.