Detuned PID Filter for Web Cutter Torque Reduction
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Solution Overview
Problem
Existing paper handling systems, particularly web cutters, face limitations in throughput due to destructive forces experienced by the web during cutting, leading to breakages, especially at the point of entry and due to high nominal forces and force disturbances.
Innovation Solution
Implementing a detuned digital filter in the motor control subsystem of the web handling mechanism to reduce peak forces by adjusting the coefficients of the PID controller, allowing for larger position errors to be compensated by a high capacity vacuum box, thereby minimizing web breakages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a conventional dancer roller is used to control the web, then the web can be kept taut during cutting operations, but the mass of the dancer roller creates high peak instantaneous torques that cause web breakages
Solution Approach 1:
The patent replaces the mechanical dancer roller system with a motor-driven web handling mechanism. This substitution eliminates the mass-related inertial forces of the dancer roller while maintaining web tautness through active motor control. The motor system can precisely regulate web tension without the mechanical constraints of a physical roller mass.
Solution Approach 2:
The patent introduces a vacuum box that uses vacuum pressure to hold the web taut during cutting operations. This pneumatic/hydraulic approach replaces the mechanical tensioning force of the dancer roller with a pressure-based holding mechanism, eliminating the source of high peak torques while maintaining web stability.
2Manufacturing precision
If the web is stopped between cuts to ensure reliable paper control, then cutting precision is improved, but throughput is reduced due to the additional stop time
Solution Approach 1:
The patent positions the web at the desired location before the cutting operation begins, using the motor-driven mechanism to advance the web precisely to the cut position. The vacuum box is activated in advance to hold the web taut, ensuring the web is ready for cutting without requiring stopping time after the cut is initiated.
Solution Approach 2:
The patent enables continuous web movement through the cutting operation by maintaining web tension with the vacuum box during the cut. The motor-driven mechanism continues to move the web at a controlled speed without complete stops, eliminating idle time between cuts while maintaining cutting precision through active tension control.
3Measurement precision
If the digital filter is tuned for precise position control, then position accuracy is improved, but peak forces increase causing web breakages
Solution Approach 1:
The patent detunes the digital filter by modifying its parameters (coefficients) to reduce the aggressive correction actions that cause peak forces. This parameter change trades some position accuracy for significantly reduced peak forces, preventing web breakages. The vacuum box compensates for the reduced position control aggressiveness by providing stable web holding.
Data Source
AI summary
A method of controlling a web in, for example, a web cutter that minimizes the destructive forces that are experienced by the web. The method includes providing a motor system for driving a web handling mechanism structured to move the web, wherein the motor system includes a motor and a motor control subsystem having a digital filter (such as a PID controller or some other suitable closed loop controller), detuning the digital filter, and using the motor system having the detuned digital filter to drive the web handling mechanism.