Sampled data servo positioning system and sector disk file employing same

Claim 1

A sampled data servo positioning system for moving a member between a current and a target position comprising. an actuator (50) responsive to applied drive signals to move such a member; a position transducer (5) movable with or patl of the member for producing signals in response to motion thereof; position signal generating means (32, 35) respenal to tne position transducer signals to produce at least one incremental position signal representative of the position of the member at sampling times; a model (60, 61, 64) responsi to an input signal to produce at least one continually available model incremental position signal; profile signal generating means (30, 31) for generating a profile which corresponding to a predetermined velocity profile as input signal for tne model; pnase comparing means (70) for comparing and indicating the phase difference between the sampled and model position sijnals at the sampling times; actuator feedforward signal generating means (80, 82) for generating a feedforward control signal for the actuator corresponding to the predetermined velocity profile; and stage indicating means (130, 132, 133) for indicating various stages of the motion in accordance with predetermined conditions; the system being characterized by switching means (52, 53, 62, 63) responsive to the stage indicating means to switch the system between first and second operational configurations, by a source of saturation control signals (54, 55) of opposite polarity for application to the actuator to cause maximum acceleration or deceleration thereof, and by means (57, 58) for deriving a continuous performance signal representative of actuator motion; and wherein, in the first operational configuration the switching means connects the saturation control signal scurce to the actuator and connect a combination ot the actuator cerformance signal as feedforward input and the position phase difference signal as a feedback input to the model so that the model tracks the actuator system, and wherein, in the second operational configuration, the switching means connects the model input profile signal to the model, and connects a combination of the actuator feedforward control signal as a feedforward input and the position phase difference signal as a feedback input to the actuator so that the actuator tracks the model.

Claim 10

A system as claimed in any preceding claim in which the model comprises both a velocity model (64, 65) and a position model (60, 61) which produces the model incremental position signal, the actuator performance signal being representative of actuator currtht and being applied to the velocity model which integrates it to produce a model velocity signal application to the position model in the first operational configuration and in which the profile signal ia a velocity profile signal which is applied directly to the position model in the second operational configuration.

Claim 13

A system as claimed in any preceding claim in which the actuator feedforward signal generating means includes a store (80) from which the actuator feedforward control signal is read out as a function of the position of the member, the feedforward control signal being zero at greater than a predetermined distance from the target position, and being of substantially trapezoidal form between the predetermined distance and the target position so as to include an initial portion of gradually diminishing amplitude and a terminal portion of steeply falling amplitude which falls to zero at the target position.