| High performance tape transport is important for high density high data rate linear tape drives. High-speed operations provide high data transfer rate, and accurate tension regulation provides proper head-tape spacing, which is crucial for achieving accurate data reading.; This dissertation concerns the MIMO control of a direct-drive tape transport testbed, which was developed as standard instrument for conducting transport dynamics research, head/media testing and tribology studies. The control specifications are to move 12.5 mm tape at speeds of 0.5–20 m/sec and 0.25–2 N (1–8 oz) tension. The direct-driven tape transport system has dynamics that make achieving these specifications difficult, and thus it is a good system for testing various control strategies. These dynamics include slowly time-varying dynamics due to changing tape pack radii, stiction causing stick-slip phenomenon during start-up, air entrainment dynamics that rapidly and nonlinearly change spring constants in the system, and the periodic disturbances with time-varying frequencies. Both traditional and robust modelling are made to describe these dynamics as the first step in the design process.; To compensate for the air entrainment dynamics and reel-radii dynamics, both the conventional loop-shaping methods with gain scheduling and advanced robust controller design are examined. In gain scheduling a specific controller is designed for every operating point, which is effective provided there is good tuning of the machines over a wide operating range. Alternatively, in robust control techniques one robust controller is designed for all of the operating points, which vastly reduces the complexity of implementation.; While the normal MIMO controller design provides good attenuation of broadband disturbances, stiction and periodic disturbances from reel eccentricities merit special attention. A disturbance observer is studied and implemented to compensate for the stick-slip compensation, with a novel loop-shaping based filter design. Adaptive feedforward cancellation is used for the attenuation of periodic disturbances. To maintain the system stability during tape transportation, the poles of the compensator are placed off-jω axis. Both compensation methods achieve sufficient attenuation on stiction and periodic disturbances. |
