A control system for a converting line, wherein the converting line has an upstream roller and a downstream roller downstream from the upstream roller, the upstream roller and downstream roller being adapted to direct web material through the converting line along a span defined by the upstream roller and the downstream roller, at least one of the upstream roller and downstream roller comprising a driven roller, the control system comprising:
- a drive for driven roller, the drive being adapted and configured for controlling the driven roller;
- a torque sensor for the drive of the driven roller, the torque sensor of the driven roller being adapted and configured to generate a torque signal representative of a torque associated with the driven roller;
- a tension sensor for sensing tension of the web in the span;
- a velocity sensor for the upstream roller, the velocity sensor of the upstream roller being adapted and configured to generate a velocity signal representative of a velocity of the web material at the upstream roller;
- a velocity sensor for the downstream roller, the velocity sensor of the downstream roller being adapted and configured to generate a velocity signal representative of a velocity of the web material at the downstream roller;
- and
- a controller of the control system, the controller of the control system comprising a processor and a memory coupled with the processor, wherein the memory is configured to store instructions that, when executed by the processor, cause the processor to:
- (a) within a mechanical characterization module of the controller associated with the driven roller:
- (i) receive the velocity signal from the driven roller and receive the torque signal from the torque sensor associated with the drive of the driven roller, and
- (ii) based upon parameters representative of mechanical properties associated with the driven roller, generate a signal representative of an estimate of an applied web force at the driven roller;
- (b) within a web stiffness estimator module of the controller associated with the driven roller:
- (i) receive the signal representative of the estimate of the applied web force from the mechanical characterization module;
- (ii) receive the span tension signal from the span tension sensor;
- (iii) receive the velocity signal from the upstream roller sensor;
- (iv) receive the velocity signal from the downstream roller sensor;
- and
- (v) based upon the span length, the velocity signal from the upstream roller sensor, the velocity signal from the downstream roller sensor, the span tension signal from the span tension sensor, and the signal representative of the estimate of the applied web force from the mechanical characterization module, generate a signal representative of an estimate of a span stiffness, a signal representative of a tension estimate in a previous span of the web prior to the upstream roller, and a signal representative of a span time constant;
- and
- (c) within a tension control module of the controller associated with the driven roller:
- (i) receive the signal representative of the estimate of the span stiffness from the web stiffness estimator;
- (ii) receive the signal representative of the previous span tension estimate from the web stiffness estimator;
- (iii) receive the web span time constant from the web stiffness estimator;
- (iv) receive the span tension signal from the span tension sensor;
- and
- (v) based at least in part upon the signal representative of the estimate of the span stiffness, the signal representative of the previous span tension estimate, the web span time constant, the span tension signal, and a span tension setpoint, generate a velocity trim command signal for the drive of the driven roller.