Control and operation of reel-to-reel tape drives without tension transducer

Abstract

This paper presents the control and operation of reel-to-reel tape drives without any tension transducer. First, the tape drive model is validated while operating in the read/write or the velocity mode. Utilizing the coupled nature of the velocity-tension loop and the fact that the system is completely observable, the tension errors are estimated based on the validated model using state estimation techniques. The tension error estimates do not correlate well with the actual tension errors primarily due to the periodic disturbances caused by reel eccentricities during steady running and are not used for feedback purposes. In this paper, the controller design for such transports for the velocity and the position loops are presented. Due to lack of forced air in the tape path in such drives, there is considerable stiction/friction during start-up when the position loop is used. Feed forward currents which are functions of desired tension at the head and tape velocity are used for proper friction compensation. For systems using two tachometers, one for each reel, a linear velocity difference technique is presented which shuts down the drive in case of excessive or low tape tension and thus preserves tape integrity. Finally, test results are presented to illustrate the effectiveness of the design techniques.