Position feedback device with prediction

An electronic line shaft, comprising:

• a signal source operable to generate a reference velocity signal;
• a virtual encoder coupled to the signal source and operable to generate a reference position signal based on the reference velocity signal;
• and
• a master drive unit operable to receive the feedback position signal, the reference velocity signal, and the reference position signal, comprising:
• a motor;
• a first encoder associated with the motor to generate at least one feedback position signal indicative of rotation of the motor;
• a motor controller operable to provide a torque input signal to the motor;
• a feedback unit, comprising:
• a comparator operable to generate a first position signal including a plurality of edges based on the position feedback signal;
• a counter operable to count the edges to periodically generate position values at a predetermined update interval;
• and
• a prediction unit operable to receive a position data request at a first time and predict a position of the drive at the first time as a function of at least a subset of the position values generated prior to the first time and a misalignment between the first time and the predetermined update interval to generate an aligned position signal.

A method for determining position of a rotating load, comprising:

• receiving at least one feedback position signal indicative of movement of the rotating load;
• generating a first position signal including a plurality of edges based on the feedback position signal;
• counting the edges to periodically generate position values at a predetermined update interval;
• receiving a position data request at a first time;
• and
• predicting a position of the rotating load at the first time as a function of at least a subset of the position values generated prior to the first time and a misalignment between the first time and the predetermined update interval to generate an aligned position signal.

A printing system including a plurality of printing stations for processing a web, comprising:

• a signal source operable to generate a reference velocity signal;
• a virtual encoder operable to generate a reference position signal based on the reference velocity signal;
• and
• a plurality of drive units for moving the web through the printing stations in accordance with the reference position signal and the reference velocity signal, each of the drive units comprising:
• a motor;
• a first encoder operable to generate at least one feedback position signal indicative of rotation of the motor;
• a motor controller operable to provide a torque input signal to the motor;
• a feedback unit, comprising:
• a comparator operable to generate a first position signal including a plurality of edges based on the position feedback signal;
• a counter operable to count the edges to periodically generate position values at a predetermined update interval;
• and
• a prediction unit operable to receive a position data request at a first time and predict a position of the drive at the first time as a function of at least a subset of the position values generated prior to the first time and a misalignment between the first time and the predetermined update interval to generate an aligned position signal.