Motorized Window Treatment Control Using Dynamic Cloudy-Day Threshold
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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 sunlight penetration control.
Innovation Solution
Implement a method that measures total light intensity and calculates solar elevation angle to adjust a cloudy-day threshold dynamically, enabling or disabling sunlight penetration limiting modes based on these factors to prevent glare.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a constant threshold is used to detect cloudy conditions, then the system can operate simply, but it cannot accurately distinguish between sunny and cloudy days around sunrise and sunset
Solution Approach 1:
The patent applies dynamics by transitioning from a static constant threshold to a dynamic time-varying threshold that changes based on the time of day. The threshold is adjusted according to pre-stored time information to account for natural light level variations during sunrise and sunset, enabling accurate cloudy condition detection throughout all times of day without requiring complex additional hardware.
Solution Approach 2:
The patent changes the parameter of the detection threshold from a fixed constant value to a variable value that depends on time of day. By storing multiple threshold values corresponding to different time periods and selecting the appropriate threshold based on current time, the system achieves high detection accuracy across varying lighting conditions while maintaining operational simplicity.
2Object-affected harmful factors
If the system controls window treatments to limit sunlight penetration on sunny days, then glare is prevented, but incorrect control around sunrise and sunset on sunny days causes unnecessary movements
Solution Approach 1:
The patent implements feedback by continuously monitoring light sensor readings and comparing them against time-adjusted threshold values. This feedback mechanism enables the system to accurately determine whether to activate sunlight penetration limiting mode, ensuring that window treatments are only adjusted when actually needed to prevent glare, thereby avoiding unnecessary movements that would distract occupants.
3Object-affected harmful factors
If the system activates sunlight penetration limiting mode based on light intensity alone, then glare prevention is simple, but it fails to account for time-of-day variations in natural lighting
Solution Approach 1:
The patent applies preliminary action by pre-storing time information and corresponding threshold values in memory before the system operates. This preparation allows the control logic to simply query the appropriate threshold based on current time and compare it with real-time light sensor readings, achieving effective glare control that accounts for time-of-day variations without requiring complex real-time calculations or adjustments.
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
Accurately controls sunlight penetration to prevent glare by distinguishing between sunny and cloudy days, enhancing occupant comfort and reducing distractions.
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 THCONST.
Data Source
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.