Abstract: A system for measuring a length of tape available for a record operation has both a tape supply reel which rotates as a tape leaves the supply reel during a tape transfer process, and a tape take-up reel which receives tape from the supply reel, and the tape take-up reel also rotates as it receives the tape during the tape transfer process. There are provided an encoder responsive to movement of the tape, a first angular position transducer to measure an angular position of the tape supply reel, a second angular position transducer to measure an angular position of the tape take-up reel, and a third transducer responsive to the encoder. A Kalman filter, responsive to an angular position measurement by the first angular position transducer, the second angular position transducer, and also the third angular position transducer, calculates the length of tape available for a record operation.

Abstract: A tape system that uses a Kalman filter to produce both an estimate of the tape pack radius and an estimate of the associated estimation error variance. The Kalman filter produces the estimates based on current and prior angular estimation position measurements of the reel, capstan, and tension arm, and the prior estimates of both the tape pack radius and the estimation error variance. The filter gain is based on prior estimation error variance and a calculated measurement error variance, which is a function of the current and prior measurements. Preferably, the system uses two Kalman filters, one to produce the estimates for the supply reel and one to produce the estimates for the take-up reel.