Autonomous, low-cost, automatic window covering system for daylighting applications

• US 5,663,621 A
• Filed: 01/24/1996
• Issued: 09/02/1997
• Est. Priority Date: 01/24/1996
• Status: Expired due to Fees

• Current Assignee: Pradeep P. Popat
• Original Assignee: Pradeep P. Popat
• Inventors: Popat, Pradeep P.
• Primary Examiner(s): Masih, Karen
• Application Number:
  US08/590,766
• Time in Patent Office: 587 Days
• Field of Search: 318/254, 318/138, 318/439, 318/480, 318/648, 388/933, 160/5, 160/166.1, 160/900, 160/1, 49/25, 250/203.4
• US Class Current: 318/480
• CPC Class Codes: E06B 9/32 Operating, guiding, or securing devices therefor operation of tilting bars E06B9/307
• CPC Class Codes: H04L 12/2816 Controlling appliance services of a home automation network by calling their functionalities arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station; in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom H04Q9/00
• CPC Class Codes: Y02A 30/24 Structural elements or technologies for improving thermal insulation
• CPC Class Codes: Y02B 80/00 Architectural or constructional elements improving the thermal performance of buildings

Abstract

A system for the automatic regulation of daylight admitted into a room, specifically intended for daylighting applications. A preferred embodiment, system 10, consisting of a conventional control unit 11, a conventional exterior brightness sensor 12, and a conventional electronically controlled window covering 13, operates to block direct solar radiation while admitting substantial diffuse illumination. Control unit 11, brightness sensor 12, and window covering 13 are interconnected in a known manner to enable control unit 11 to register the brightness of the external illumination, and to actuate window covering 13. Control unit 11 consists of a conventional microcontroller 14, a conventional real-time clock/calendar 15, and a conventional Non-Volatile Memory (NVM) 16. Microcontroller 14, clock/calendar 15, and NVM 16 are interconnected in a known manner to enable microcontroller 14 to register the output of clock/calendar 15, and to exchange data with NVM 16. NVM 16 holds pre-stored data which defines a desired setting of window covering 13 as a function of the time of the day and the day of the year, for the prevailing latitude, longitude, and window azimuth orientation. In the preferred embodiment, this desired setting is one which will block the admission of incident direct solar radiation, while still admitting substantial diffuse illumination. Microcontroller 14 periodically registers the exterior brightness as measured by sensor 12, registers the data stored in NVM 16, estimates a desired setting of window covering 14 on the basis of these data, and actuates window covering 13 to the desired setting.

Claims

1. A method of control of a window covering to regulate illumination admitted through a window, said window covering having an adjustable setting, said window having a certain geographic location, a certain orientation, and an outside surface receiving an incident illumination, said incident illumination produced by a sun, said sun having a relative angular position with respect to said window, said relative angular position varying with time of day and day of year, said relative angular position further dependent on said certain geographic location and said certain orientation of said window, said relative angular position uniquely defined by a pair of angular variables, said method including the steps of:

a) providing storage means for storing and recalling digital information;

b) providing time-registering means for registering a current time of day and a current day of year;

c) predicting a first expected value of at least one angular variable of said pair of angular variables, said first expected value associated with a first arbitrary time of day on a first arbitrary day of year, said predicting step performed prior to said first arbitrary time of day on said first arbitrary day of year;

d) defining a first digital value as a first predetermined function of a first plurality of quantities, said first plurality of quantities including said first expected value of said one angular variable, said defining step performed prior to said first arbitrary time of day on said first arbitrary day of year;

e) storing said first digital value in said storage means, said storing step performed prior to said first arbitrary time of day on said first arbitrary day of year;

f) recalling said first digital value from said storage means;

g) establishing a desired setting of said window covering as a second predetermined function of a second plurality of quantities, said second plurality of quantities including;

i) said first digital value,

ii) said current time of day and said current day of year, and

iii) said first arbitrary time of day and said first arbitrary day of year; and

h) adjusting said window covering to said desired setting.

2. The method of claim 1, wherein said establishing step includes the step of equating said desired value to said first digital value, said equating step performed under a predetermined set of conditions, said set of conditions including:

a) a first condition under which a first absolute value of a first difference between said current brightness value and said first arbitrary value of said brightness is less than a first predetermined threshold;

b) a second condition under which a second absolute value of a second difference between said current time of day and said first arbitrary time of day is less than a second predetermined threshold; and

c) a third condition under which a third absolute value of a third difference between said current day of year and said first arbitrary day of year is less than a third predetermined threshold.

3. The method of claim 1, wherein said method further includes the steps of:

a) predicting a second expected value of said second angular variable, said second expected value associated with a second arbitrary time of day on said first arbitrary day of year;

b) obtaining a second digital value by evaluating said first predetermined function for said second expected value of said one angular variable; and

c) storing and recalling said second digital value from said storage means;

and wherein said establishing step includes the step of interpolating between said first digital value and said second digital value to obtain said desired setting, said desired setting corresponding to said current time of day on said current day of year.

4. A method of operating a venetian blind to regulate illumination admitted through a window, wherein:

a) said venetian blind has a plurality of louvers, each of said plurality of louvers rotatable in a plane perpendicular to said window, said plurality of louvers having a common tilt angle, said tilt angle corresponding to rotational displacement of said louvers in said plane with respect to a reference orientation, said tilt angle variable over an operating range, said operating range bounded by a minimum limit value and a maximum limit value;

b) said window has a geographic location, an orientation, and an outside surface receiving an incident illumination, said incident illumination including a direct component;

c) said direct component is produced by a sun, said sun having a relative angular position with respect to said window, said relative angular position uniquely defined by a first angular variable and a second angular variable, said first angular variable defining said angular position of said sun in said plane, said first angular variable and said second angular variable varying with time of day and day of year, said first angular variable and said second angular variable further varying with said geographic location and said orientation of said window; and

d) said direct component passes through said venetian blind for a critical range of values of said tilt angle, said direct component being blocked for values of said tilt angle outside said critical range, said critical range contained within said operating range, said critical range bounded by a minimum critical angle and a maximum critical angle, said minimum critical angle and said maximum critical angle varying with said first angular variable;

said method including the steps of;

e) providing storage means for storing and recalling information;

f) providing time-registering means for registering a current time of day and a current day of year;

g) selecting a first reference value of said tilt angle from a first blocking range of values of said tilt angle, said first blocking range bounded by said minimum limit value and a first critical value of said minimum critical angle, said first critical value associated with a first expected value of said first angular variable, said first expected value of said first angular variable corresponding to said relative angular position of said sun at a first arbitrary time of day on a first arbitrary day of year, said selecting step performed prior to said first arbitrary time of day on said first arbitrary day of year;

h) storing said first reference value in said storage means, said storing step performed prior to said first arbitrary time of day on said first arbitrary day of year;

i) recalling said first reference value from said storage means;

j) defining a desired value of said tilt angle as a first predetermined function of a first plurality of quantities, said first plurality of quantities including;

i) said first reference value of said tilt angle,

ii) said first arbitrary time of day and said first arbitrary day of year, and

iii) said current time of day and said current day of year; and

k) adjusting said tilt angle of said plurality of louvers to said desired value.

5. The method of claim 4, wherein said defining step includes the step of equating said desired value of said tilt angle to said first reference value, said equating step performed under a predetermined set of conditions, said predetermined set of conditions including:

a) a first condition under which a first absolute value of a first difference between said current time of day and said first arbitrary time of day is less than a first predetermined threshold; and

b) a second condition under which a second absolute value of a second difference between said current day of year and said first arbitrary day of year is less than a second predetermined threshold.

6. The method of claim 4, wherein said method further includes the steps of:

a) selecting a second reference value of said tilt angle from a second blocking range of values of said tilt angle, said second blocking range bounded by said minimum limit value and a second critical value of said minimum critical angle, said second critical value associated with a second expected value of said first angular variable, said second expected value of said first angular variable corresponding to said relative angular position of said sun at a second arbitrary time of day on said first arbitrary day of year; and

b) storing and recalling said second digital value from said storage means;

and wherein said defining step includes the step of interpolating between said first reference value and said second reference value to obtain said desired value, said desired value associated with said current time of day on said current day of year.

7. A method of operating a venetian blind to regulate illumination admitted through a window, wherein:

a) said venetian blind has a plurality of louvers, each of said plurality of louvers rotatable in a plane perpendicular to said window, said plurality of louvers having a common tilt angle, said tilt angle corresponding to rotational displacement of said louvers in said plane with respect to a reference orientation, said tilt angle variable over an operating range, said operating range bounded by a minimum limit value and a maximum limit value;

b) said window has a geographic location, an orientation, and an outside surface receiving an incident illumination, said incident illumination including a direct component;

e) said direct component is produced by a sun, said sun having a relative angular position with respect to said window, said relative angular position uniquely defined by a first angular variable and a second angular variable, said first angular variable defining said angular position of said sun in said plane, said first angular variable and said second angular variable varying with time of day and day of year, said first angular variable and said second angular variable further varying with said geographic location and said orientation of said window; and

d) said direct component passes through said venetian blind for a critical range of values of said tilt angle, said direct component being blocked for values of said tilt angle outside said critical range, said critical range contained within said operating range, said critical range bounded by a minimum critical angle and a maximum critical angle, said minimum critical angle and said maximum critical angle varying with said first angular variable;

said method including the steps of;

e) providing storage means for storing and recalling information;

f) providing time-registering means for registering a current time of day and a current day of year;

g) estimating a first reference value of said minimum critical angle, said first reference value associated with a first expected value of said first angular variable, said first expected value of said first angular variable corresponding to said relative angular position of said sun at a first arbitrary time of day on a first arbitrary day of year, said estimating step performed prior to said first arbitrary time of day on said first arbitrary day of year;

h) storing said first reference value in said storage means, said storing step performed prior to said first arbitrary time of day on said first arbitrary day of year;

i) recalling said first reference value from said storage means;

j) establishing a current critical value of said minimum critical angle as a first predetermined function of a first plurality of quantities, said first plurality of quantities including;

i) said first reference value,

ii) said first arbitrary time of day and said first arbitrary day of year, and

iii) said current time of day and said current day of year; and

k) selecting a desired value of said tilt angle from a blocking range of values, said blocking range bounded by said minimum limit value and said current critical value; and

l) adjusting said tilt angle of said plurality of louvers to said desired value.

8. The method of claim 7, wherein:

a) said incident illumination has a brightness;

b) said method includes the step of providing measuring means to measure said brightness, said measuring means producing a current brightness value; and

c) said selecting step includes the step of evaluating a second predetermined function of said current brightness value, said desired value of said tilt angle thereby varying with said current brightness value but constrained within said blocking range.

9. The method of claim 7, wherein said establishing step includes the step of equating said current critical value of said minimum critical angle to said first reference value, said equating step performed under a predetermined set of conditions, said predetermined set of conditions including:

a) a first condition under which a first absolute value of a first difference between said current time of day and said first arbitrary time of day is less than a first predetermined threshold; and

b) a second condition under which a second absolute value of a second difference between said current day of year and said first arbitrary day of year is less than a second predetermined threshold.

10. The method of claim 7, wherein said method further includes the steps of:

a) estimating a second reference value of said minimum critical angle, said second reference value associated with a second expected value of said first angular variable, said second expected value of said first angular variable corresponding to said relative angular position of said sun at a second arbitrary time of day on said first arbitrary day of year; and

b) storing and recalling said second reference value from said storage means;

and wherein said establishing step includes the step of interpolating between said first reference value and said second reference value to obtain said current critical value, said current critical value associated with said current time of day on said current day of year.

11. A method of operating a venetian blind to regulate illumination admitted through a window, wherein:

a) said venetian blind has a plurality of louvers, each of said plurality of louvers rotatable in a plane perpendicular to said window, said plurality of louvers having a common tilt angle, said tilt angle corresponding to rotational displacement of said louvers in said plane with respect to a reference orientation, said tilt angle variable over an operating range, said operating range bounded by a minimum limit value and a maximum limit value;

b) said window has a geographic location, an orientation, and an outside surface receiving an incident illumination, said incident illumination including a direct component;

c) said direct component is produced by a sun, said sun having a relative angular position with respect to said window, said relative angular position uniquely defined by a first angular variable and a second angular variable, said first angular variable defining said angular position of said sun in said plane, said first angular variable and said second angular variable varying with time of day and day of year, said first angular variable and said second angular variable further varying with said geographic location and said orientation of said window; and

d) said direct component passes through said venetian blind for a critical range of values of said tilt angle, said direct component being blocked for values of said tilt angle outside said critical range, said critical range contained within said operating range, said critical range bounded by a minimum critical angle and a maximum critical angle, said minimum critical angle and said maximum critical angle varying with said first angular variable;

said method including the steps of;

e) providing storage means for storing and recalling information;

f) providing time-registering means for registering a current time of day and a current day of year;

g) predicting a first reference value of said first angular variable, said first reference value of said first angular variable corresponding to said relative angular position of said sun at a first arbitrary time of day on a first arbitrary day of year, said predicting step performed prior to said first arbitrary time of day on said first arbitrary day of year;

h) storing said first reference value in said storage means, said storing step performed prior to said first arbitrary time of day on said first arbitrary day of year;

i) recalling said first reference value from said storage means;

j) establishing a current value of said first angular variable as a first predetermined function of a first plurality of quantities, said first plurality of quantities including;

i) said first reference value of said first angular variable,

ii) said first arbitrary time of day and said first arbitrary day of year, and

iii) said current time of day and said current day of year; and

k) selecting a desired value of said tilt angle from a blocking range of values of said tilt angle, said blocking range bounded by said minimum limit value and a critical value of said minimum critical angle, said critical value associated With said current value of said first angular variable; and

l) adjusting said tilt angle of said plurality of louvers to said desired value.

12. The method of claim 11, wherein:

a) said incident illumination has a brightness;

b) said method includes the step of providing measuring means to measure said brightness, said measuring means producing a current brightness value; and

c) said selecting step includes the step of evaluating a second predetermined function of said current brightness value, said desired value of said tilt angle thereby varying with said current brightness value but constrained within said blocking range.

13. The method of claim 11, wherein said establishing step includes the step of equating said current value of said first angular variable to said first reference value, said equating step performed under a predetermined set of conditions, said predetermined set of conditions including:

a) a first condition under which a first absolute value of a first difference between said current time of day and said first arbitrary time of day is less than a first predetermined threshold; and

b) a second condition under which a second absolute value of a second difference between said current day of year and said first arbitrary day of year is less than a second predetermined threshold.

14. The method of claim 11, wherein said method further includes the steps of:

a) predicting a second reference value of said first angular variable, said second reference value of said first angular variable corresponding to said relative angular position of said sun at a second arbitrary time of day on said first arbitrary day of year; and

b) storing and recalling said second reference value from said storage means;

and wherein said establishing step includes the step of interpolating between said first reference value and said second reference value to obtain said current value of said first angular variable, said current value associated with said current time of day on said current day of year.

15. A method of regulating illumination admitted through a window, said window having a certain geographic location, a certain orientation, and an outside surface receiving an incident illumination, said incident illumination having a brightness, said incident illumination produced by a sun, said sun having a relative angular position with respect to said window, said relative angular position varying with time of day and day of year, said relative angular position further dependent on said certain geographic location and said certain orientation of said window, said relative angular position uniquely defined by a first angular variable and a second angular variable, said method including the steps of:

a) providing a window covering having an adjustable setting;

b) measuring said brightness of said incident illumination, said measuring step producing a current brightness value;

c) inferring an absence of a direct component of said incident illumination, said inferring step including the steps of;

i) inferring an expected value of said first angular variable, said expected value corresponding to said relative angular position of said sun at a certain time of day on a certain day of year;

ii) comparing said expected value to a predetermined threshold, said comparing step producing a result; and

iii) declaring said absence if said result has a predetermined value;

d) estimating a desired setting of said window covering, said desired setting dependent on said current brightness value and said inferred absence of said direct component; and

e) adjusting said window covering to said desired setting.