Method of controlling a motorized window treatment
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Solution Overview
Problem
Existing load control systems for motorized window treatments struggle to accurately distinguish between sunny and cloudy days, leading to potential glare issues around sunrise and sunset on sunny days due to incorrect threshold settings.
Innovation Solution
The system measures total light intensity and adjusts the cloudy-day threshold based on the solar elevation angle, enabling or disabling the sunlight penetration limiting mode accordingly to prevent glare, with the threshold varying near sunrise and sunset to accurately differentiate between day types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a constant cloudy-day threshold is used to control motorized window treatments, then the system operates simply and reliably during midday sunny conditions, but it fails to accurately distinguish between sunny and cloudy conditions around sunrise and sunset, leading to glare issues
Solution Approach 1:
The patent applies the dynamics principle by making the cloudy-day threshold variable rather than constant. The threshold is dynamically adjusted based on the solar elevation angle, transitioning from a constant value during midday to a time-varying function near sunrise and sunset. This allows the system to adapt to changing lighting conditions throughout the day, accurately distinguishing between sunny and cloudy conditions at different times while maintaining operational simplicity.
Solution Approach 2:
The patent implements parameter changes by modifying the threshold parameter based on the solar elevation angle. When the solar elevation angle falls below a predetermined threshold (indicating sunrise or sunset periods), the cloudy-day threshold is adjusted as a function of time. This parameter change enables accurate glare prevention during low-sun periods while maintaining the simplicity of constant threshold operation during midday hours.
2Reliability
If the sunlight penetration limiting mode is always enabled to prevent glare, then occupant comfort is improved, but unnecessary window treatment movements occur during cloudy days, reducing energy efficiency and increasing wear
Solution Approach 1:
The system dynamically enables or disables the sunlight penetration limiting mode based on real-time detection of actual lighting conditions. By using a variable threshold that accounts for solar elevation angle, the system can reliably determine whether to activate glare prevention. This dynamic operation ensures the mode is enabled only when genuinely needed (sunny conditions with low solar angle), preventing both glare and unnecessary energy consumption.
Solution Approach 2:
The patent implements feedback by continuously monitoring total light intensity and comparing it against the dynamically adjusted cloudy-day threshold. This feedback mechanism allows the system to accurately determine whether sunny or cloudy conditions exist at any given time, enabling precise control decisions. The feedback loop ensures the sunlight penetration limiting mode is activated only when actual glare conditions are present, avoiding unnecessary operations during cloudy days.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively prevents direct sun glare by accurately determining sunny versus cloudy conditions, ensuring optimal sunlight control and occupant comfort by adjusting the motorized window treatments based on real-time light intensity and solar position.
Implementation Method 1
The load control system may comprise a photosensor (i.e., a daylight sensor or a radiometer) mounted to a window or to the outside of the building for detecting a cloudy condition. The load control system may detect the cloudy condition, for example, if a total light level measured by the photosensor is below a constant threshold
Data Source
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AI summary
A method comprises measuring a light intensity at a window; determining if the light intensity exceeds a cloudy-day threshold; operating in a sunlight penetration limiting mode to control the motorized window treatment to control the sunlight penetration distance in the space; enabling the sunlight penetration limiting mode if the light intensity is greater than the cloudy- day threshold; and disabling the sunlight penetration limiting mode if the total lighting intensity is less than the cloudy-day threshold. The cloudy-day threshold is maintained at a constant threshold if a calculated solar elevation angle is greater than a predetermined solar elevation angle, and the cloudy-day threshold varies with time if the calculated solar elevation angle is less than the predetermined solar elevation angle. The cloudy-day threshold is a function of the calculated solar elevation angle if the calculated solar elevation angle is less than the predetermined solar elevation angle.