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 calculates the solar elevation angle to dynamically adjust the cloudy-day threshold, enabling or disabling the sunlight penetration limiting mode based on these conditions 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, leading to glare issues
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 day detection without causing false glare prevention actions during transitional periods.
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. By storing multiple threshold values corresponding to different time periods and selecting appropriate thresholds based on current time information, the system achieves adaptive detection accuracy 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 the system may incorrectly control treatments on cloudy days around sunrise and sunset, reducing daylight utilization
Solution Approach 1:
The system uses dynamic threshold adjustment based on time of day to reliably distinguish between sunny and cloudy conditions. By adapting the detection threshold to natural light level variations during sunrise and sunset, the system avoids false positives that would trigger incorrect glare prevention actions, thereby improving the reliability of sunny versus cloudy day differentiation.
Solution Approach 2:
The system incorporates feedback by continuously monitoring light sensor readings and comparing them against time-adjusted thresholds. This feedback mechanism enables the system to accurately determine whether to activate glare prevention control, ensuring that window treatments are only controlled when actual glare conditions exist rather than during normal transitional lighting periods.
3Measurement precision
If the cloudy-day threshold is adjusted dynamically based on solar elevation angle, then detection accuracy improves, but computational complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing threshold values corresponding to different solar elevation angles or times of day. Instead of performing complex real-time calculations, the system retrieves pre-stored threshold values based on current time information, achieving high detection accuracy while minimizing computational complexity during operation.
Solution Approach 2:
The system implements dynamic threshold adjustment by selecting from pre-stored threshold values based on the current solar elevation angle or time of day. This approach provides the benefits of dynamic adaptation without requiring complex real-time calculations, as the computational burden is shifted to the initial setup phase rather than ongoing operation.
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 sun glare by accurately differentiating between sunny and cloudy days, ensuring optimal sunlight control and occupant comfort by adjusting the motorized window treatments accordingly.
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.