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Browse Prior Art Database

Continuous Web Servo System

IP.com Disclosure Number: IPCOM000034648D
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 3 page(s) / 30K

Publishing Venue

IBM

Related People

Janssen, DM: AUTHOR [+2]

Abstract

The lateral position of a continuous web traveling over a number of rolls is controlled via a closed-loop, electromechanical servo system. This closed-loop system permits the mechanical tolerances on the web and host system to be increased and also results in extended web life because mechanical edge guiding is eliminated. Web wandering approaches zero due to the fine resolution of the stepper motor actuator. Referring to the figure, web 3 is suspended between two rollers and travels in the longitudinal direction depicted by the arrow labeled "V". Roller 1 is fixed in space and is driven by an external means (not shown) to impart longitudinal motion to the web. Roller 2 is the control means that results in controlling and maintaining the lateral position of the web.

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Continuous Web Servo System

The lateral position of a continuous web traveling over a number of rolls is controlled via a closed-loop, electromechanical servo system. This closed-loop system permits the mechanical tolerances on the web and host system to be increased and also results in extended web life because mechanical edge guiding is eliminated. Web wandering approaches zero due to the fine resolution of the stepper motor actuator. Referring to the figure, web 3 is suspended between two rollers and travels in the longitudinal direction depicted by the arrow labeled "V". Roller 1 is fixed in space and is driven by an external means (not shown) to impart longitudinal motion to the web. Roller 2 is the control means that results in controlling and maintaining the lateral position of the web. End 2A of roller 2 is fixed in space, and end 2B is configured such that it can move normal to a plane defined by the roller axes. Linear stepper motor 8 is attached to roller end 2B. Motion of the stepper motor causes skew between the rollers and results in lateral motion of the web. The control electronics 11 provides the intelligence for the control system. At power on, the initial position of stepper motor 8 must be set to mid stroke. Since no sensor is provided to detect stepper motor position, an alternate means is provided with the aid of hard stop 9. Hard stop 9 limits the travel of roller end 2B and thus stepper motor 8 in both directions of their travel. The hard stop is located such that roller end 2B nominally has equal plus and minus motion about zero skew between rollers 1 and 2. The number of stepper motor steps, NO, required to travel between the extremes of the hard stop is a known quantity. Initialization is accomplished by the control electronics issuing slightly more than NO step commands via power driver 10 to drive the stepper in a predetermined direction. This action guarantees that the stepper is at the end of its travel and roller end 2B is against the hard stop. The control electronics then issue NO/2 steps commands in the opposite direction, and the stepper motor and roller end 2B are at mid stroke which completes the system initialization. Sensor as...