Web speed control system

For use in a reel driven web transport system including a supply reel, a takeup reel, a pair of drive motors each coupled to a respective reel, a control circuit for maintaining substantially constant linear web speed of a web moving between said reels, said control circuit comprising:

• first tachometer means coupled to said supply reel and operative to provide a first signal representative of the rotational speed thereof;
• second tachometer means coupled to said takeup reel and operative to provide the second signal representative of the rotational speed thereof;
• a first circuit operative in response to said first signal to provide a third signal representative of the period of rotation of said supply reel;
• a second circuit operative in response to said second signal to provide a fourth signal representative of the period of rotation of said takeup reel;
• means for providing a reference signal;
• means for comparing the sum of said third and fourth signals and said reference signal to provide an error signal indicative of the difference between said reference signal and said summed signal;
• and
• output circuit means operative in response to said error signal to provide a controlled driving signal to said takeup reel drive motor to provide substantially constant linear web speed.

For use in a reel driven web transport system including a supply reel, a takeup reel, a drive motor coupled to said takeup reel and a web movablefrom said supply reel to said takeup reel, a method for providing substantially constant linear web speed comprising the steps of:

• providing first and second signal indications of a rotational characteristic of said respective reels;
• non-linearly processing the respective signal indications of said rotational characteristics to provide respective modified signal indications thereof;
• providing a signal indication of the sum of said modified signal indications;
• deriving an error signal from said signal indication of said sum;
• providing a control signal in response to said error signal;
• and
• applying said control signal to said drive motor to cause movement of said web at a substantially constant linear speed.

For use in a reel driven web transport system including a supply reel, a takeup reel, a drive motor coupled to said takeup reel and a web movable from said supply reel to said takeup reel, a method for providing substantially constant linear web speed comprising the steps of:

• providing first and second signal indications of the period of rotation of said respective reels;
• providing a signal indication of the sum of said first and second signal indications;
• deriving an error signal from said signal indication of said sum;
• and
• providing in response to said error signal a control signal for application to said drive motor to cause movement of said web at a substantiallyconstant linear speed.