Shaft rotation interlock system for film editing tables and the like

Apparatus for bi-directionally interlocking two or more shaft rotating systems to interlock the rotation of one or more slave shafts with one remote master shaft, said apparatus comprising:

• (a) an individual differential amplifier means having its output connected for controlling the speed and direction of rotation of each one of said slave shafts respectively;
• (b) means for generating a first output of digital pulses having a characteristic representative of the actual instantaneous speed of rotation of said one slave shaft and having simultaneous directional information encoded therein;
• (c) means for generating a second output of digital pulses having a characteristic representative of the actual instantaneous speed of rotation of said remote master shaft and having simultaneous directional information encoded therein;
• (d) quadrature decoder means for decoding said directional information to feed first and second pairs of up-down pulse lines;
• (e) means taking its input from the first of said up-down pulse line pairs for deriving a first analog voltage having a magnitude proportional to said characteristic of said first output of digital pulses and a polarity determined by said directional information encoded in said first output, said first analog voltage being connected as at least a part of a first input to said differential amplifier means;
• (f) means taking its input from the second of said up-down pulse line pairs for deriving a second analog voltage having a magnitude proportional to said characteristic of said second output of digital pulses and a polarity determined by said directional information encoded in said second output, said second analog voltage being connected as at least a part of a second input to said differential amplifier means;
• (g) means including digital mixer means taking its input from said quadrature decoder means and up-down counter means for deriving a third analog voltage having a magnitude proportional to the sum or difference between said directionally encoded characteristic of said first output of pulses and said directionally encoded characteristic of said second output of pulses;
• and
• (h) means for mixing said third analog voltage with one of said first or second analog voltages to form therewith a composite input to said differential amplifier, said mixing means connecting said third analog voltage to said differential amplifier in a second order error correcting feedback loop parallel to the two branch first order feedback loop comprising said means for deriving and connecting said first and second analog voltages respectively to said differential amplifier, said two branch first order loop maintaining a basic bi-directional interlock between the speed and direction of rotation of said slave shaft and said remote master shaft and said second order loop maintaining a digitally controlled precise bi-directional interlock therebetween.

A bi-directional servo system for interlocking the rotation of a slave motor to that of a master motor, comprising:

• (a) first and second means for deriving first and second digital signal pulse outputs, each having a characteristic respectively representative of the speed of rotation of said motor and said slave motor, and each having encoded directional information;
• (b) quadrature decoder means for decoding said directional information to feed first and second pairs of up-down pulse lines;
• (c) first order feedback loop means for controlling the speed and direction of rotation of said slave motor comprising first and second tracking electronic tachometer means taking its inputs from said quadrature decoder means for converting each of said first and second digital signal pulse outputs respectively, to first and second analog voltage signals;
• (d) second order overshoot correcting feed-back loop means connected for controlling the speed and direction of rotation of said slave motor connected in parallel to said first order feedback loop and comprising means including digital mixer means taking its input from said decoder means and up down counter means for continuously digitally determining the sum or difference between said characteristic of said first and second digital pulse trains and for continuously producing a third digital signal representative of said sum or difference and means for converting said third digital signal to a third bi-polar analog signal of magnitude proportional thereto, and of polarity determined by said digital mixer;
• and
• (e) means for mixing said first, second and third bi-polar analog signals to produce a combined error signal for controlling the speed and direction of rotation of said slave motor.

A bi-directional servo system for interlocking the rotation of a slave motor to that of a master motor, comprising:

• (a) first and second means for deriving first and second digital signal pulse outputs, each having a characteristic respectively representative of the speed of rotation of said motor and said slave motor, and each having encoded directional information;
• (b) quadrature decoder means for decoding said directional information to feed first and second pairs of up-down pulse lines;
• (c) first order feedback loop means for controlling the speed and direction of rotation of said slave motor comprising first and second tracking electronic tachometer means taking its inputs from said quadrature decoder means for converting each of said first and second digital signal pulse outputs, respectively, to first and second analog voltage signals, and differential amplifier means for combining said analog signals as inputs to produce an error signal output proportional to the sum or difference between said analog signals in the absence of any other signal for controlling the speed and direction of rotation of said slave motor;
• and
• (d) second order overshoot correcting feedback loop means connected for controlling the speed and direction of rotation of said slave motor connected in parallel to said first order feedback loop and comprising means including a digital mixer taking its input from said quadrature decoder means and up down counter means for continuously digitally determining the sum or difference between said characteristic of said first and second digital pulse outputs and for continuously producing a third digital signal representative of said sum or difference, means for converting said third digital signal to a third bipolar analog signal of magnitude proportional thereto and of polarity determined by said digital mixer, and means for mixing said third analog signal with one of said first or second analog signals to produce a combined input to said differential amplifier means.