Dual mode control system for controlling tape position in a reel to reel

Abstract

A control system for controlling the position of tape in a reel to reel tape transport system which includes a loop position responsive generator for generating loop reference signals representing a desired tape position in associated buffers; transducing means for measuring the position of tape loops in the buffers; a plurality of current generators for producing an output signal in response to one of the reference signals and the desired position signal; selector means for selecting an output control signal from one of the current generators selected control signal, and amplifying means for applying current to the reel drive motor. A constant current control mode is used when the tape position error is large, and a linear position control is used when the tape position error is small. Control is switched between the two modes as required for achieving the desired control while using minimal power. The system handles the worst case capstan reversal with a minimum turnaround time. Tape position is sampled at a rate that is a multiple of the mechanical resonance of the tape in the buffers thereby minimizing the effect of the resonance on the measurement. The system further uses a feedforward signal generator during the initial stage of motor control to compensate for the lag in the position transducer means.