Feedforward control to attenuate tension error in time-varying tape systems

This paper presents two feedforward control algorithms to attenuate the tension error in digital tape systems. Tape systems are time-varying because the reel radii change as a result of both tape winding and reel eccentricities. The first algorithm addresses the time-varying nature of the reel radii due to tape winding by introducing a time-varying feedforward filter for the reference input. The second algorithm is designed to attenuate the tension error caused by periodic reel eccentricities. We investigate the error in previous periods and calculate the compensation input that should have canceled it. This input is then fed forward to the system for future periods. Simulation results show that the time-varying reference input achieved from the first feedforward filter leads to zero tension error if the variations in the radius are known. The second feedforward compensation input reduces the tension error caused by reel eccentricities by about three orders of magnitude.