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This invention pertains to processing continuous webs such as paper, film, composites, and the like, in dynamic continuous processing operations. More particularly, it relates to accumulating limited lengths of such continuous webs and to controlling tension in such continuous webs during the proces

This invention pertains to processing continuous webs such as paper, film, composites, and the like, in dynamic continuous processing operations. More particularly, it relates to accumulating limited lengths of such continuous webs and to controlling tension in such continuous webs during the processing operation. Both tension control and limited accumulations are achieved in festoon systems by connecting corresponding movably mounted festoon rolls to an actuator, sensing parameters such as position, tension, velocity, and acceleration related to the web and the festoon, and providing active force commands, in response to the sensed variables, to cause translational movement, generally including a target acceleration, in the movably mounted festoon rolls to control tension in the web while providing limited accumulation of a length of the web. The festoon control system can be used to attenuate tension disturbances, in the alternative to create controlled tension disturbances.

대표청구항 ▼

1. Processing apparatus defining a processing line, for advancing a continuous web of material through a processing step along a given section of the processing line, the processing apparatus comprising:(a) first and second rolls defining a first nip; (b) third and fourth rolls defining a second nip

1. Processing apparatus defining a processing line, for advancing a continuous web of material through a processing step along a given section of the processing line, the processing apparatus comprising:(a) first and second rolls defining a first nip; (b) third and fourth rolls defining a second nip, the first and second nips collectively defining the given section of the web; (c) a festoon, including at least one fixedly mounted festoon roll and at least two movably mounted festoon rolls, operating on the web in the given section of the processing line, thereby to control tension in the web and to accumulate a limited length of the web sufficient to sustain operation of the process on the length of web during routine temporary stoppages of web feed to the given section of the processing line or taking the web away from the given section of the processing line; (d) an actuator applying net translational force to the movably mounted festoon rolls; and (e) a controller driving the festoon, and computing and controlling net translational acceleration of the movably mounted festoon rolls such that the festoon is effective to control tension, at a desired level of constancy, and to accumulate a limited length of the web, in the respective section of the processing line. 2. Processing apparatus as in claim 1, the actuator applying a first static force component to the movably mounted festoon rolls, having a first value and direction, balancing said movably mounted festoon rolls against static forces and the average dynamic tension in the respective section of the web, said controller outputting a second variable force component, through said actuator, effective to control the net actuating force imparted to said movably mounted festoon rolls by said actuator, and effective to periodically adjust the value and direction of the second variable force component, each such value and direction of the second variable force component replacing the previous such value and direction of the second variable force component, and acting in combination with the first static force component to impart the target net translational acceleration to said movably mounted festoon rolls, the second variable force component having a second value and direction, modifying the first static force component, such that the net translational acceleration of said movably mounted festoon rolls is controlled by the net actuating force enabling said festoon to control the web tension, and further comprising apparatus for computing acceleration (Ap) of said movably mounted festoon rolls, said controller comprising a computer controller providing control commands to said actuator based on the computed acceleration of said movably mounted festoon rolls.3. Processing apparatus as in claim 1, including a sensor for sensing tension in the web after said festoon, said controller being adapted to use the sensed tension in computing the value and direction of the second variable force component, and for imparting the computed value and direction through said actuator to said movably mounted festoon rolls.4. Processing apparatus as in claim 3, said sensor being effective to sense tension at least 1 time per second, and effective to recompute the value and direction of the second variable force component, thereby to adjust the value and direction of the computed second variable force component at least 1 time per second.5. Processing apparatus as in claim 3, said sensor being effective to sense tension at least 500 times per second, said controller being effective to recompute the value and direction of the second variable force component, thereby to adjust the value and direction of the computed second variable force component at least 500 times per second, said actuator being effective to apply the recomputed second variable force component to said movably mounted festoon rolls at least 500 times per second according to the values and directions computed by said controller, thus to control the net translational acceleration.6. Processing apparatus as in claim 3, said sensor being effective to sense tension at least 1000 times per second, said controller comprising a computer controller effective to recompute the value and direction of the second variable force component and thereby to adjust the value and direction of the computed second variable force component at least 1000 times per second, said actuator being effective to apply the recomputed second variable force component to said movably mounted festoon rolls at least 1000 times per second according to the values and directions computed by said computer controller, thus to control the net translational acceleration.7. Processing apparatus as in claim 2, said controller controlling the actuating force imparted to said movably mounted festoon rolls, and thus acceleration of said movably mounted festoon rolls, including compensating for any inertia imbalance of said festoon not compensated for by the first static force component.8. Processing apparatus as in claim 1, including an observer for computing translational acceleration (Ap) of said movably mounted festoon rolls, said observer comprising one of (i) a subroutine in said computer program or (ii) an electrical circuit, which computes an estimated translational acceleration and an estimated translational velocity of said movably mounted festoon rolls.9. Processing apparatus as in claim 2, and further including:(f) first apparatus for measuring a first velocity of the web after said festoon; (g) second apparatus for measuring a second velocity of the web at said festoon; (h) third apparatus for measuring translational velocity of said movably mounted festoon rolls; and (i) fourth apparatus for sensing the position of said movably mounted festoon rolls. 10. Processing apparatus as in claim 9, and further including:(j) fifth apparatus for measuring web tension before said festoon; and (k) sixth apparatus for measuring web tension after said festoon. 11. Processing apparatus as in claim 10, said controller comprising a computer controller computing a force command using the equation:F*servo=F*d static+F*frictionSign(Vp)+ba(V*p?Vp)+ka(F*c?Fc)+Ma(A*p?Ap) wherein the translational velocity set-point V*p of said movably mounted festoon rolls reflects the equation:V*p=[EAo/(EAo?Fc)][V2(1?Fb/EAo)?V3(1?Fc/EAo)], to control said actuator based on the force so calculated, wherein:F*d static=static force component on said movably mounted festoon rolls and is equal to Mg+2F*c, Fc=tension in the web after the last movable festoon roller, F*c=tension in the web, target set point, per process design parameters, Fb=tension in the web ahead of the last movably mounted festoon roller, F*friction=Friction in either direction resisting movement of the movably mounted festoon rolls, F*servo=Force to be applied by said actuator, ba=control gain constant regarding festoon translational velocity, in Newton seconds/meter, ka=control gain constant regarding web tension, Mg=mass of said movably mounted festoon rolls times gravity, MA=active mass, Me=active mass and physical mass, Vp=instantaneous translational velocity of said movably mounted festoon rolls immediately prior to application of the second variable force component, Sign(Vp)=positive or negative value depending on the direction of movement of the movably mounted festoon rolls, V2=velocity of the web at the last movably mounted festoon roll, V3=velocity of the web after the festoon, V*p=reference translational velocity of said movably mounted festoon rolls, set point, r=radius of a respective pulley on said actuator, E=Modulus of elasticity of the web, Ao=cross-sectional area of the unstrained web, A*p=target translational acceleration of said movably mounted festoon rolls, set point, and Ap=translational acceleration of said movably mounted festoon rolls. 12. Processing apparatus as in claim 11, the target acceleration A*p being computed using the equation:A*p=[V*p?Vp]/ΔT where ΔT=scan time for said computer controller.13. Processing apparatus as in claim 12, said computer controller providing control commands to said actuator based on the sensed position of said movably mounted festoon rolls, and the measured web tensions, acceleration and velocities, and thereby controlling the actuating force imparted to said movably mounted festoon rolls by said actuator thus either to maintain a substantially constant web tension or to provide a predetermined pattern of variations in the web tension.14. Processing apparatus as in claim 2, and further including:(f) first apparatus for measuring translational velocity of said movably mounted festoon rolls; (g) second apparatus for measuring web tension force after said festoon; and (h) third apparatus for sensing the current of said actuator. 15. Processing apparatus as in claim 14, said controller comprising a computer controller computing a derivative of web tension force from the web tension force over the past sensing intervals, and including an observer computing said translational velocity of said movably mounted festoon rolls, and said computer controller computing a derivative of the web tension force.16. Processing apparatus as in claim 14, said controller comprising a computer controller, and including a fuzzy logic subroutine stored in said computer controller for computing a derivative of web tension force from the web tension force and the translational velocity of said movably mounted festoon rolls, said fuzzy logic subroutine inputting web tension force error, the derivative of web tension force error, and acceleration error, the fuzzy logic subroutine proceeding through the step of fuzzy inferencing of the above errors, and de-fuzzifying of inferences to generate a command output signal, said fuzzy logic subroutine being executed during each scan of said sensing apparatus.17. Processing apparatus as in claim 2, and further including:(f) first apparatus for measuring translational velocity of said movably mounted festoon rolls; and (g) second apparatus for sensing the current of said actuator. 18. Processing apparatus as in claim 17, said controller computing the estimated translational acceleration of said movably mounted festoon rolls from the equation:Ape=[k1(Vp?Vpe)+kteI?F*d static?FfrictionSign(Vp)]/M2e whereApe=estimated translational acceleration of said movably mounted festoon rolls, F*d static=static force component on said movably mounted festoon rolls and is equal to Mg+2F*c, F*friction=Friction in either direction resisting movement of the movably mounted festoon rolls, Sign(Vp)=positive or negative value depending on the direction of movement of the movably mounted festoon rolls, k1=Observer gain, Vp=instantaneous translational velocity of said movably mounted festoon rolls, Vpe=estimated translational velocity, kte=Servo motor (actuator) torque constant estimate, I=actuator current, and M2e=Estimated physical mass of the movably mounted festoon rolls. 19. Processing apparatus as in claim 18, said processing apparatus including a zero order hold for storing force values for application to said movably mounted festoon rolls.20. Processing apparatus as in claim 18, said processing apparatus actively compensating for coulomb and viscous friction, and acceleration, to actively cancel the effects of mass.21. Processing apparatus as in claim 2, and further including:(f) first apparatus for measuring translational position of said movably mounted festoon rolls; (g) second apparatus for measuring web tension force after said festoon; and (h) third apparatus for sensing the motor current of said actuator. 22. Processing apparatus as in claim 21, including an observer for computing estimated translational velocity and estimated translational acceleration of said movably mounted festoon rolls from the change in position of said movably mounted festoon rolls.23. Processing apparatus as in claim 2, and further including:(f) first apparatus for measuring translational position of said movably mounted festoon rolls; and (g) second apparatus for sensing the motor current of said actuator; and (h) an observer for computing translational acceleration of said movably mounted festoon rolls. 24. Processing apparatus as in claim 2, and further including:(f) first apparatus for measuring web tension Fc after said festoon; and (g) second apparatus for sensing the motor current of said actuator. 25. Processing apparatus as in claim 24, including an observer utilizing the motor current and force on the web, in combination with an estimate of system mass M2e, to compute an estimate of translational acceleration Ape of said movably mounted festoon rolls.26. Processing apparatus as in claim 25, said observer integrating the translational acceleration to compute an estimate of translational velocity Vpe and integrating the estimated translational velocity to compute an estimated web tension force Fce, and changing values until the estimated web tension force equals the actual web tension force.27. Processing apparatus as in claim 2, said controller providing the control commands to said actuator thereby controlling the actuating force imparted to said movably mounted festoon rolls by said actuator, and thus controlling acceleration of said movably mounted festoon rolls, such that said actuator maintains inertial compensation for the festoon system.28. Processing apparatus as in claim 1, the first nip comprising a wind-up roll downstream from the festoon and the second nip comprising driving rolls upstream from the festoon, the controller sending control signals to the wind-up roll and the driving rolls.29. Processing apparatus as in claim 1, including first velocity apparatus for measuring a first velocity of the web after the festoon, and second velocity apparatus for measuring a second velocity of the web at the festoon, the controller comprising a computer controller computing a velocity command V*p using the first and second sensed velocities and web tension before and after the festoon.30. Processing apparatus as in claim 2, the controller comprising a computer controller intentionally periodically varying the variable force component to unbalance the system, and thus the tension on the web by periodically inputting command forces through the actuator causing sudden temporary alternating-direction movements of the movably mounted festoon rolls such that the movably mounted festoon rolls intermittently impose alternating higher and lower levels of tension on the web.31. Processing apparatus as in claim 30, the periodic input of force causing the alternating-direction movements of the movably mounted festoon rolls to be repeated more than 200 times per minute.32. Processing apparatus as in claim 1 wherein said at least two movably mounted festoon rolls are positioned lower than said at least one fixedly mounted festoon roll.33. Processing apparatus as in claim 1 wherein said at least two movably mounted festoon rolls are positioned laterally beside said at least one fixedly mounted festoon roll such that a such continuous web of material is oriented generally horizontally, and travels in a generally horizontal path, between said at least two movably mounted festoon rolls and said at least one fixedly mounted festoon roll.34. Processing apparatus as in claim 1 wherein said at least two movably mounted festoon rolls are positioned laterally beside said at least one fixedly mounted festoon roll, and wherein said at least two movably mounted festoon rolls move translationally in generally horizontal directions.35. In a processing operation wherein a continuous web of material is advanced through a processing step defined by first and second spaced nips, each nip being defined by a pair of nip rolls, a method of controlling web tension, and of accumulating a limited length of the web, in the respective section of web, the method comprising:(a) providing a festoon, having at least one fixedly mounted festoon roll and at least two movably mounted festoon rolls, operative on the respective section of web; (b) applying a first generally static force component to the movably mounted festoon rolls, the first generally static force component having a first value and direction; (c) applying a second variable force component to the movably mounted festoon rolls, the second variable force component having a second value and direction, modifying the first generally static force component, and thereby modifying (i) the effect of the first generally static force component on the movably mounted festoon rolls and (ii) corresponding translational acceleration of the movably mounted festoon rolls; and (d) adjusting the value and direction of the second variable force component repeatedly, each such adjusted value and direction of the second variable force component (i) replacing the previous such value and direction of the second variable force component and (ii) acting in combination with the first static force component to provide a target net translational acceleration to the movably mounted festoon rolls. 36. A method as in claim 35, including adjusting the value and direction of the second variable force component at least 500 times per second.37. A method as in claim 35, including sensing tension in the web after the festoon, and using the sensed tension to compute the value and direction of the second variable force component.38. A method as in claim 35, including sensing tension in the respective section of the web at least 1 time per second, recomputing the value and direction of the second variable force component and thereby adjusting the value and direction of the computed second variable force component at least 1 time per second, and applying the recomputed value and direction to the festoon at least 1 time per second.39. A method as in claim 35, including adjusting the force components and target net translational acceleration so as to maintain an average dynamic tension in the web throughout the processing operation while controlling translational acceleration such that system effective mass equals the polar inertia of the movably mounted festoon rolls collectively, divided by outer radius of the rolls, squared.40. A method as in claim 35, including periodically and intentionally varying the variable force component to unbalance the system, and thus the tension on the web by periodically inputting command forces through the actuator causing sudden temporary alternating-direction movements of the movably mounted festoon rolls such that the movably mounted festoon rolls intermittently impose alternating higher and lower levels of tension on the web.41. A method as in claim 40, the periodic input of force causing the alternating-direction movement of the movably mounted festoon rolls to be repeated more than 200 times per minute.42. A method as in claim 35 wherein the first and second force components are applied simultaneously to the movably mounted festoon rolls as a single force, by an actuator, and wherein the step of applying a force to the movably mounted festoon rolls includes:(e) measuring a first velocity of the web after the festoon; (f) measuring a second velocity of the web at the festoon; (g) measuring translational velocity of the movably mounted festoon rolls; (h) sensing the position of the movably mounted festoon rolls; (i) measuring web tension before the festoon; and (j) measuring web tension after the festoon, and (k) applying the force to the movably mounted festoon rolls computed according to the equation: F*servoF*d static+F*frictionSign(Vp)+ba(Vp?Vp)+ka(F*c?Fc)+Ma(A*p?Ap) wherein:F*d static=static force component on said movably mounted festoon rolls and is equal to Mg+2F*c, F*friction=Friction in either direction resisting movement of the movably mounted festoon rolls, Fc=tension in the web after the movably mounted festoon rolls, F*c=tension in the web, target set point, per process design parameters, F*servo=Force generated by the actuator, ba=control gain constant regarding translational velocity of the movably mounted festoon rolls, in Newton seconds/meter, ka=control gain constant regarding web tension, Mg=mass of said movably mounted festoon rolls times gravity, MA=active mass, Me=active mass and physical mass, Vp=instantaneous translational velocity of the movably mounted festoon rolls immediately prior to application of the second variable force component, Sign(Vp)=positive or negative value depending on the direction of movement of the movably mounted festoon rolls, A*p=reference translational acceleration of the movably mounted festoon rolls, set point, Ap=translational acceleration of the movably mounted festoon rolls, and wherein the translational velocity set-point V*p of the movably mounted festoon rolls reflects the equation:V*p=[EAo/(EAo?Fc)][V2(1?Fb/EAo)?V3(1?Fc/EAo)], to control the actuator based on the force so computed, wherein:Fb=tension in the web ahead of the last movable festoon roll, V2=velocity of the web at the last movable festoon roll, V3=velocity of the web after the festoon, V*p=reference translational velocity of the movably mounted festoon rolls, set point, r=radius of a respective pulley on said actuator, E=Modulus of elasticity of the web, and Ao=cross-sectional area of the unstrained web. 43. A method as in claim 42, the target acceleration A*p being computed using the equation:A*p=[Vp?Vp]/ΔT where ΔT=scan time, the computations being repeated and the force adjusted at least 1 time per second.44. A method as in claim 35 wherein the first and second force components are applied simultaneously to the movably mounted festoon rolls as a single force, and wherein applying a force to the movably mounted festoon rolls includes:(e) measuring translational velocity of the movably mounted festoon rolls; (f) measuring web tension force after the festoon; and (g) sensing the current of said actuator, such measuring and sensing occurring during periodic sensing intervals, (h) computing a derivative of web tension force from the web tension force based on present and past sensing intervals; (i) computing the translational velocity of the movably mounted festoon rolls; and (j) computing a derivative of the web tension force. 45. A method as in claim 44, wherein applying a force to the movably mounted festoon rolls includes executing a fuzzy logic subroutine by inputting web tension force error, the derivative of web tension force error, and acceleration error,the fuzzy logic subroutine proceeding through the step of fuzzy inferencing of the above errors, and de-fuzzifying inferences to generate a command output signal, the fuzzy logic subroutine being executed during each of the measuring and sensing intervals. 46. A method as in claim 35 wherein the first and second force components are applied simultaneously to the movably mounted festoon rolls as a single force, and wherein applying a force to the movably mounted festoon rolls includes:(e) measuring the translational velocity of the movably mounted festoon rolls; (f) sensing the current of an actuator; and (g) computing the estimated translational acceleration of the movably mounted festoon rolls from the equation Ape[F*d static+F*frictionSign(Vp)+k1(Vp?Vpe)+kteI]/M2e where:Ape=estimated translational acceleration of the movably mounted festoon rolls, F*d static=static force component on the movably mounted festoon rolls and is equal to Mg+2F*c, F*friction=Friction in either direction resisting movement of the movably mounted festoon rolls, Sign(Vp)=positive or negative value depending on the direction of movement of the movably mounted festoon rolls, k1=Observer gain, Vp=instantaneous translational velocity of the movably mounted festoon rolls, Vpe=estimated translational velocity, kte=Servo motor (actuator) torque constant estimate, I=actuator current, and M2e=Estimated physical mass of the movably mounted festoon rolls. 47. A method as in claim 35 wherein the first and second force components are applied simultaneously to the movably mounted festoon rolls as a single force, and wherein applying a force to the movably mounted festoon rolls includes:(e) measuring the translational position of the movably mounted festoon rolls; (f) measuring web tension force after the festoon; and (g) sensing the motor current of an actuator applying the force to the movably mounted festoon rolls, the above measuring and sensing occurring at each sensing interval, the method further including computing a derivative of web tension from the present measured web tension and the web tension measured in the previous sensing interval.48. A method as in claim 47, including computing estimated translational velocity and estimated translational acceleration of movably mounted festoon rolls from the change in position of the movably mounted festoon rolls.49. A method as in claim 35 wherein the first and second force components are applied simultaneously to the movably mounted festoon rolls as a single force, and wherein applying a force to the movably mounted festoon rolls includes:(e) measuring the translational position of the movably mounted festoon rolls; (f) sensing the motor current of an actuator applying the force to the movably mounted festoon rolls; (g) computing an estimated translational velocity of the festoon upper rolls by subtracting the previous sensed value for translational position from the present sensed value of translational position and then dividing by the time interval between sensing of the values; and (h) computing a new force command for application to the actuator in response to the earlier computed values. 50. A method as in claim 35 wherein the first and second force components are applied simultaneously to the movably mounted festoon rolls as a single force, and wherein applying a force to the movably mounted festoon rolls includes:(e) measuring web tension Fc after the festoon; (f) sensing motor current of an actuator; and (g) utilizing the motor current and force on the web, in combination with an estimate of system mass M2e, to compute an estimate of translational acceleration Ape. 51. A method as in claim 50, including integrating the translational acceleration to compute an estimate of translational velocity Vpe and integrating the estimated translational velocity to compute an estimated web tension force Fce.52. In a processing operation wherein a continuous web of material is advanced through a processing step, a method of controlling the tension in the respective section of the web, comprising:(a) providing a festoon, having at least one fixedly mounted festoon roll, and at least two movably mounted festoon rolls, operative for controlling tension on the respective section of web; (b) providing an actuator to apply an actuating force to the movably mounted festoon rolls; (c) measuring a first velocity of the web after the festoon; (d) measuring a second velocity of the web at the festoon; (e) measuring motor current of the actuator; (f) measuring web tension before the festoon; (g) measuring web tension after the festoon; (h) measuring translational velocity of the movably mounted festoon rolls; (i) sensing the position of the movably mounted festoon rolls; (j) measuring acceleration of the movably mounted festoon rolls; and (k) providing force control commands to the actuator based on the above measured values, including computed acceleration A*p of the movably mounted festoon rolls, to thereby control the actuating force imparted to the movably mounted festoon rolls by the actuator to control the web tension. 53. A method as in claim 52, including providing force control commands to the actuator based on the equationF*servo=F*d static+F*frictionSign(Vp)+ba(V*p?Vp)+ka(F*c?Fc)+Ma(A*p?Ap), wherein the translational velocity set-point V*p of the movably mounted festoon rolls reflects the equationV*p=[EAo/(EAo?Fc)][V2(1?Fb/EAo)?V3(1?Fc/EAo)], to control the actuator based on the force so calculated wherein:F*d static=static force component on the movably mounted festoon rolls and is equal to Mg+2F*c, F*friction=Friction in either direction resisting movement of the movably mounted festoon rolls, F*servo=Target force to be applied by the actuator, Fc=tension in the web after the festoon, F*c=target tension in the web, set point, Fb=tension in the web ahead of the last movable festoon roller, ba=control gain constant re translational velocity of the movably mounted festoon rolls, in Newton seconds/meter, ka=control gain constant re web tension, Mg=mass of the movably mounted festoon rolls times gravity, MA=active mass, Me=active mass and physical mass, Vp=instantaneous translational velocity of the movably mounted festoon rolls, Sign(Vp)=positive or negative value depending on the direction of movement of the movably mounted festoon rolls, V2=velocity of the web at the last movably mounted festoon roller, V3=velocity of the web after the festoon, V*p=target translational velocity of the movably mounted festoon rolls, set point, r=radius of a respective pulley on the actuator, E=Modulus of elasticity of the web, Ao=cross-sectional area of the unstrained web, A*p=target translational acceleration of the movably mounted festoon rolls, set point, and Ap=translational acceleration of the movably mounted festoon rolls. 54. A method as in claim 53, including computing the target acceleration A*p using the equation:A*p=[V*p?Vp]/ΔT where ΔT=scan time or interval between sensing of translational velocity.55. A method as in claim 52, including applying the actuator and thereby controlling acceleration of the movably mounted festoon rolls, such that the actuator maintains inertial compensation for the movably mounted festoon rolls.