fiber optic sensor

A web edge sensor is disclosed. The web edge sensor has a light source directing light incident to an edge of a web. The edge of the web scatters the light and a sensor array that detects a first portion of the light scattered from the edge of the web and rejects a second portion to determine a position of the web edge.

This paper discusses the development of a linear quadratic optimal control algorithm for web guides, and implementation of the control algorithm using web lateral position feedback from a new, experimental fiber optic sensor. The lateral dynamic model of the web and the measurement characteristics of the fiber optic sensor are conducive for a linear quadratic regulator design. The performance of the optimal control algorithm with web lateral position feedback from the fiber optic edge sensor is evaluated by conducting experiments on a web platform. Experiments were also conducted using the same controller but with an existing industrial infrared sensor for web lateral position measurement. Results from a series of comparative experiments indicate that the optimal control algorithm with feedback from the fiber optic sensor provides accurate lateral position regulation in the presence of disturbances, at various web transport speeds, and with web materials with different mechanical, physical and geometric properties. Based on the analysis of the web lateral dynamic model, recommendations for proper guide operation and selection of appropriate web transport conditions for good guiding performance are also discussed.

The design and development of a new fiber-optic sensor for measuring the velocity of a continuous material (also called a web) in material processing systems is described. The development of the proposed sensor is based on the dual beam laser Doppler velocimetry technique and the unique properties of different types of optical fibers. The developed sensor is capable of measuring the true web transport velocity as opposed to the existing methods which infer web transport velocity based on the roller angular speed. Since the sensor design utilizes fibers, signal processing can be performed away from the measurement area, and as a result the sensor can be used in harsh environments within the web processing line. The proposed sensor has been constructed and experiments have been conducted on an experimental web platform. The performance of the sensor is evaluated for a range of web velocities and different web materials. Sensor design, its construction, and a representative sample of the results are presented and discussed.

A new sensor for web flutter measurement is proposed in this paper. The sensor is based on the principle of scattering of light and directional properties of optical fibers. A collimated beam of light is incident on the web edge and scattered light from the web edge is collected using a linear array of optical fibers. As the web flutters the point of scattering moves. Due to the directional property of the optical fibers, each fiber collects scattered light that is incident on it at certain angles. The motion of the scattering point as the web flutters is directly related to which fibers are being illuminated within the fiber array. The other end of the fiber array is terminated onto a linear array of photodiodes (pixels). Based on which fibers in the array are receiving scattered light and the amount of light received, the transverse displacement (web flutter) of the web can be determined. This paper describes the construction and working of the new sensor for web flutter measurement. Experiments conducted on a web platform show that the sensor is capable of accurately measuring web flutter. The frequency response of the sensor is limited only by the scanning rate of the pixel array and not by the flutter measurement method. A dedicated signal processing circuit can be used to obtain a desired scanning rate, thus, a desired frequency response.

A laser based fiber-optic sensor was proposed in our previous work. The sensor developed was based on the principle of scattering of light and the sensitivity directional property of optical fibers. A beam of light is incident on a surface or an edge, the scattered light is received by a linear array of optical fibers. The lateral position of the web edge is determined based on the intensity of light received by each fiber in the fiber array. Static experiments were conducted to show the feasibility of the sensing strategy. In this work, the performance of the sensor is evaluated on an actual web handling platform. The analysis of static and dynamic (with non-zero web transport velocity) experimental data of the sensor under various realistic operating conditions and disturbances is conducted. A direct comparison of the fiber optic sensor and two existing industrial sensors is presented. The experimental data from the sensors are compared using different web materials and under different operating conditions. The new fiber optic sensor is more accurate and the measurements are less noisy. Further, the new sensor overcomes some of the key limitations of existing sensors. The problem of determining the actual position of the web when it is completely outside the sensing window or when it completely covers the sensing windows is resolved; the solution consists of a new configuration. The new configuration also improves the precision of the sensor.

Existing edge sensors use the concept of blocking/unblocking for measuring web lateral position. The most commonly used sensors employ either ultrasonic or infrared signals to detect the web edge position by measuring the amount of signal attenuation due to blocking/unblocking of the signal. The main drawback of this sensing method is nonuniform signal attenuation due to web material variations and opacity. The research in this paper develops a new sensor which utilizes the phenomena of light scattering from the web edge and the directional sensitivity of optical fibers. A collimated laser beam is incident on the web edge and scattered light is collected by a linear array of fibers spatially positioned above the web edge. The theory of operation and the development of the sensor is described. Experiments are conducted with different web materials to validate the proposed sensing method. A representative sample of the results are presented and discussed.

A novel sensor to measure web flutter is proposed in this letter. The sensing principle is based on scattering of light and directionally sensitive coupling properties of optical fibers. A linear array of optical fibers, oriented appropriately, is used to collect light scattered from a web. The flutter amplitude is determined by observing the amount of light transmitted by the fibers in the fiber array. Experiments were conducted to demonstrate the ability of the proposed sensing strategy in measuring web flutter with different kinds of web material.

Existing edge sensors use the concept of blocking/unblocking to determine web lateral position. The most commonly used sensors employ either ultrasonic or optical signals to detect the web edge position by measuring the amount of signal attenuation due to blocking/unblocking of the signal. The main drawback of this sensing method is nonuniform signal attenuation for web material variations and opacity. The research in this paper develops a new sensor which utilizes the phenomena of light scattering from the web edge and the directional sensitivity of optical fibers to determine the web lateral position.