| 摘要 |
A system is described for controlling the speed and direction of rotation of first and second spools in a web transport system in which a web is advanced between the spools by first and second drive motors. The system incorporates a servo control which continuously reacts to variations in the speed of the spools so as to drive the spools at respective speeds whose sum is constant and proportional to a selectable control voltage. To achieve this result, the first and second spools, driven, respectively by the first and second drive motors, are coupled to means, such as a corresponding pair of servo generators, for generating electrical outputs representative of the direction and speed of rotation of the spools. A control voltage, proportional to the sum of the desired speeds of the two spools, is continuously and algebraically summed with the outputs of the two servo generators, the summed signal constituting a motor drive signal. A motor drive control receives the motor drive signal and selectively applies it to the drive motor associated with the spool upon which the web is to be wound. The pull thus exerted on the web by the actively driven spool rotates the other spool, both spools thereby rotating their corresponding servo generators. The motor drive signal, derived from the control voltage and the outputs of the servo generators, continuously reflects the changing outputs of the servo generators so as to cause the spools to rotate at respective speeds whose sum is constant and proportional to the control voltage.
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