Blind Screen Direction Detection via Motor Duty Cycle
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Solution Overview
Problem
Existing methods for determining the direction of movement of an occultation screen, particularly with synchronous motors, are unreliable due to interference from mechanical brakes and minimal voltage variations between upward and downward directions, limiting their applicability.
Innovation Solution
A method involving measuring the duty cycle of the supply voltage of a synchronous electric motor during movements in both directions, with the actuator switched between nominal and learning configurations to enhance measurement differentiation, allowing reliable direction determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If motor torque is measured by motor current to determine direction of movement, then the method works for DC motors, but it is disturbed by mechanical brake drag torque in synchronous motors
Solution Approach 1:
The patent replaces mechanical torque measurement with electrical parameter measurement. Instead of measuring motor current which is affected by mechanical brake drag torque, the invention measures the duty cycle of the supply voltage to the synchronous motor, which provides direction information without being disturbed by mechanical brake interference.
Solution Approach 2:
The patent changes the measurement parameter from motor current to duty cycle of supply voltage. By measuring the duty cycle instead of current, the system can determine movement direction without the measurements being corrupted by the mechanical brake's drag torque on synchronous motors.
2Adaptability or versatility
If voltage of phase shift capacitor is measured to determine motor torque for asynchronous motors, then the method can be applied to asynchronous motors, but the voltage varies very little for low weight roller shutters or oversized motors making direction determination unreliable
Solution Approach 1:
The patent creates a universal direction detection method that works for both synchronous and asynchronous motors. By using duty cycle measurement of the supply voltage, the system achieves consistent reliability across different motor types and roller shutter configurations, eliminating the precision problems encountered with phase shift capacitor voltage measurement.
3Measurement precision
If the actuator is switched to learning configuration with higher speed and power, then the differentiation of duty cycle values between directions is enhanced, but the energy consumption increases
Solution Approach 1:
The patent uses preliminary action by switching to learning configuration only during the initial direction detection phase before normal operation begins. The enhanced duty cycle differentiation is obtained during this brief setup period, after which the system returns to nominal configuration for energy-efficient operation.
Solution Approach 2:
The learning configuration with higher energy consumption is used periodically only when direction detection is needed (during installation or after power loss), rather than continuously. This allows the system to obtain precise measurements when necessary while minimizing overall energy consumption during normal operation.
Data Source
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AI summary
This method for detecting the direction of movement of a blackout screen (2) controlled by an electromechanical actuator (4) comprises the steps of a) moving the blackout screen using the actuator in a first direction of movement (D1) and measuring a first value of a predefined displacement parameter, b) moving the blackout screen using the actuator in a second direction of movement (D2), opposite to the first direction of movement, and measuring a second value of the predefined displacement parameter, c) comparing the values of the predefined parameter measured in steps a) and b), and d) determining the direction of the first and second directions of movement based on the result of step c). The electromechanical actuator includes a synchronous electric motor, and the predefined displacement parameter is a duty cycle of the supply voltage of the synchronous electric motor.