In this paper, practical robust position control of a cassette type tape drive is presented. This is a reel-to-reel tape drive where most of the tape path is inside an enclosure. Due to cost considerations and lack of space, such drives are operated without any tension transducer. Position control in this type of drive is inherently difficult because of lack of tension transducer to cut down the tension oscillations during starts and stops and other difficult position maneuvers. These types of drives are prone to failures while in position control mode especially while reading and writing short records in the vicinity where tape is being pulled onto a reel of large radius while that reel is controlling the position of the reel. Two solutions to this problem are presented in this paper. One solution utilizes the decoupled transfer function design of the reel-to-reel tape servo and the other solution utilizes the presence of two tachometers one on each reel and the symmetry of the drive. Finally, test results are presented to illustrate the effectiveness of the design techniques.
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