Skew Correction Using Phase-Differing Pulse Trains
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Solution Overview
Problem
Existing systems for correcting skew in web materials being fed through machines, such as printers, are limited by resolution due to the need for high-frequency stepper motor drivers, which are costly and not adaptable for all motor modes, restricting effective skew correction.
Innovation Solution
The method involves establishing corrective pulse train sections for stepper motors with differing phases and time intervals to achieve relative displacement between pinch assemblies, allowing for high-resolution skew correction without requiring high-frequency drivers or half-step/quarter-step motor capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-frequency stepper motor drivers are used to increase resolution, then skew correction resolution is improved, but system cost increases
Solution Approach 1:
The system dynamically adjusts the frequency of pulse trains based on the magnitude of skew correction required. For small skew values, high-frequency pulse trains provide fine resolution. For larger skew values, the frequency is reduced while maintaining adequate correction precision, eliminating the need for expensive high-frequency drivers across all operating conditions.
Solution Approach 2:
The invention changes the frequency parameter of the pulse trains driving the stepper motors. By varying the frequency according to the skew magnitude, the system achieves high resolution when needed without permanently requiring high-frequency hardware, thus reducing overall system cost while maintaining measurement precision.
2Measurement precision
If transmission ratio in the transmission system is increased to improve resolution, then skew correction resolution is improved, but skew correction time increases
Solution Approach 1:
The system dynamically adjusts pulse train frequency based on the required correction magnitude. For small skew corrections, high-frequency pulse trains are used to achieve fine resolution without requiring increased transmission ratios. For larger corrections, lower frequencies are used, maintaining fast correction speeds. This dynamic adaptation eliminates the trade-off between resolution and correction time.
Solution Approach 2:
The control system determines the appropriate pulse train frequency in advance based on the measured skew value. This preliminary selection of operating parameters allows the system to optimize both resolution and correction time before the actual correction begins, avoiding the need for mechanical transmission ratio changes.
3Ease of manufacture
If standard stepper motors are used instead of high-frequency capable motors, then system cost is reduced, but skew correction resolution deteriorates
Solution Approach 1:
The invention changes the operating frequency parameter of standard stepper motors to match the correction requirements. By generating pulse trains at appropriate frequencies for each correction scenario, the system achieves high resolution with standard motors that do not require expensive high-frequency capable hardware.
Solution Approach 2:
The system dynamically adapts the pulse train frequency to the specific correction needs, allowing standard stepper motors to operate at optimal frequencies for each situation. This dynamic parameter adjustment enables standard motors to achieve resolution comparable to what would require expensive specialized high-frequency motors.
Data Source
AI summary
A system for correcting skew of a web of material being fed through a machine includes first and second pinch assemblies placed at a distance transversely to a direction of feeding. First and second stepper motors drive the first and second pinch assemblies, respectively. A control provides first and second pulse trains to drive the first and second stepper motors, respectively. A device determines a value for the skew of the web of material. A method for controlling the system includes establishing first and second corrective pulse train sections for the first and second stepper motors, respectively, in accordance with a determined skew value, and providing first and second pulse trains for driving the first and second stepper motors, respectively.