Winding Drum Position Detection Using Dual Encoder Segmentation
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Solution Overview
Problem
Motorized screen winding systems face inaccuracies in positioning due to uncertainties from flexible damping elements, component aging, and differential thermal expansions, leading to positioning errors, especially in solar protection screens requiring precise alignment.
Innovation Solution
A motorized apparatus with a first encoder integrated with the rotor and a second encoder secured to the drum, along with processing means and a comparator, to generate signals indicative of the screen's position and detect indexed positions, allowing for precise rotation measurement and correction of offset values, thereby improving positioning accuracy without additional costly instrumentation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a flexible damping element is interposed between the motor and drum to reduce vibrations and noise, then vibration decoupling and noise reduction are improved, but positioning accuracy deteriorates due to creep and torque variations
Solution Approach 1:
The system segments the measurement function into two independent parts: a rotor-mounted encoder for high-speed rotation measurement and a drum-mounted indexed position sensor for reference positioning. This segmentation allows each sensor to operate optimally without being affected by the flexible element's creep, as they measure different aspects of the system independently.
Solution Approach 2:
The control system acts as an intermediary that combines information from both encoders and calculates the offset between rotor and drum positions. This intermediary processing reconciles the measurements from both sides of the flexible element, compensating for the positioning errors introduced by the damping element's deformation.
2Measurement precision
If a high-precision sensor is positioned between the drum and fixed support to achieve +/- 3 to 5° positioning accuracy, then positioning precision is improved, but device complexity and cost increase
Solution Approach 1:
Instead of directly measuring drum position with a high-precision sensor, the system uses a simplified indexed position sensor on the drum that generates reference signals. The control system then copies and processes these reference signals along with rotor encoder data to calculate the actual drum position, effectively creating a virtual high-precision measurement through software processing rather than hardware complexity.
Solution Approach 2:
The patent replaces the need for a complex mechanical high-precision position sensor with an electronic solution combining two simpler encoders and computational processing. The offset calculation algorithm substitutes for the complex mechanical measurement system, achieving the same positioning accuracy through electronic computation rather than mechanical precision.
3Device complexity
If component aging and thermal expansion are allowed to occur naturally, then system simplicity is maintained, but positioning reliability deteriorates over time
Solution Approach 1:
The system implements continuous feedback by constantly monitoring the offset between rotor and drum positions through the two encoders. This feedback mechanism detects positioning drift caused by aging and thermal expansion in real-time, allowing the control system to compensate for these changes and maintain reliable positioning throughout the system's operational life without increasing mechanical complexity.
Solution Approach 2:
The indexed position sensor on the drum provides preliminary reference information about drum position that is used in advance to calculate offsets. This preliminary measurement from the drum side, combined with the rotor encoder data, enables the system to proactively identify and correct positioning drift before it accumulates to problematic levels.
Data Source
AI summary
An apparatus (10) for winding a screen (12) comprises a winding drum (14) for winding the screen (12) which can rotate about an axis of rotation (16) with respect to a fixed frame of reference over more than one revolution between at least one first end-of-travel position and a second end-of-travel position, a motor assembly (30) comprising a motor (32) equipped with a stator (32.1) intended to be fixed to a fixed support (23, 26) and a rotor (32.2) kinematically connected to the winding drum (14). A first measurement assembly (51) comprises a first encoder (46) secured to the rotor (32.2), a first sensor for reading the first encoder (46) and generating a first counting signal when the first encoder (46) turns. First processing means (50) generate, as a function of the first counting signal, a first signal indicative of the position of the screen, which signal is monotonous when the drum moves from the first end-of-travel position to the second end-of-travel position. A second measurement assembly (64) makes it possible to detect at least one indexed position of the drum (14) per revolution of the drum in the fixed frame of reference. A calibration memory (56) stores at least one first calibration value for the first signal indicative of the position of the screen in the indexed position of the drum and at least one first quantitative algebraic comparison between a current value of the first signal indicative of the position of the screen as measured on passing through the indexed position during an observation phase and the first calibration value is delivered.