Motorized Window Treatment Bus Voltage Control
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Solution Overview
Problem
Motorized window treatments, such as roller shades, face issues with motor overload and low-line conditions that cause the microprocessor to reset, leading to inaccurate position information and failure to move the shade fabric effectively.
Innovation Solution
A method and apparatus that monitor the bus voltage and adjust the current supplied to the motor by comparing it to voltage thresholds, using pulse-width modulation to maintain the voltage within desired ranges, thereby preventing resets and ensuring continuous operation during overload or low-line conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the motor is driven at full power during overload condition, then the motor can overcome obstacles and complete movement, but the bus voltage drops below the threshold causing microprocessor reset
Solution Approach 1:
The system dynamically adjusts motor current based on real-time bus voltage monitoring. When voltage drops below the threshold, the system automatically reduces motor current to prevent microprocessor reset, and restores full current when voltage recovers, creating a dynamic response to maintaining both power delivery and operational stability
Solution Approach 2:
The system implements a feedback mechanism where the microprocessor continuously monitors bus voltage and adjusts motor current accordingly. The voltage threshold triggers a feedback loop that modulates power delivery to the motor, ensuring the microprocessor remains operational while still enabling motor function during overload conditions
2Reliability
If the motor current is reduced to maintain bus voltage, then the microprocessor remains operational, but the motor cannot overcome obstacles and complete movement
Solution Approach 1:
The system employs periodic action by cycling motor current between reduced and full power levels based on bus voltage conditions. When voltage drops, current is reduced to maintain stability; when voltage recovers above the threshold, full current is restored to enable complete movement, creating a periodic pattern that balances reliability and power delivery
Solution Approach 2:
The system takes preliminary action by proactively reducing motor current before the microprocessor resets occurs. By monitoring bus voltage and preemptively adjusting current when the threshold is approached, the system prevents the harmful reset event while maintaining enough power to eventually complete the movement task
3Reliability
If the microprocessor resets during shade movement, then the system can recover from error states, but position information becomes inaccurate preventing further movement
Solution Approach 1:
The system applies preliminary anti-action by preventing the harmful reset event from occurring in the first place. Through continuous bus voltage monitoring and proactive current adjustment, the system counteracts the conditions that would lead to microprocessor reset, thereby preserving position information and avoiding the need for error recovery that would result in information loss
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
The solution effectively prevents microprocessor resets during motor overload or low-line conditions, maintaining accurate position control and uninterrupted movement of the shade fabric, ensuring reliable operation of motorized window treatments.
Implementation Method 1
A motor drive circuit is coupled to the motor for driving the motor from a bus voltage
Implementation Method 2
using pulse-width modulation to maintain the voltage within desired ranges
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A method of controlling a motorized window treatment provides for continued operation of the motorized window treatment during an overload or low-line condition. The motorized window treatment is driven by an electronic drive unit having a motor, a motor drive circuit, and a controller. The controller controls the motor drive circuit to drive the motor with a pulse-width modulated signal generated from a bus voltage. The controller is operable to monitor the magnitude of the bus voltage. If the bus voltage drops below a first voltage threshold, the controller stops the motor or reduces the duty cycle of the pulse-width modulated signal to allow the bus voltage to increase to an acceptable magnitude. When the bus voltage rises above a second voltage threshold, the controller begins driving the motor normally once again. During an overload or low-line condition, the controller is prevented from resetting, while driving the motor with minimal interruption to the movement of the motorized window treatment.