Abstract:
A method of controlling vibration of a dynamic surface includes providing at least one piezoelectric actuator in communication with the dynamic surface, and providing a mass over the at least one piezoelectric actuator so that the at least one piezoelectric actuator lies between the mass and the dynamic surface. The method includes sensing vibration of the dynamic surface, and activating the at least one piezoelectric actuator after sensing vibration of the dynamic surface for applying a counter force between the dynamic surface and the mass for reducing or controlling vibration of the dynamic surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present application is a divisional of U.S. patent application Ser. No. 09/500,111, filed Feb. 8, 2000, which, in turn, is a continuation of U.S. patent application Ser. No. 09/425,594 filed Oct. 22, 1999, entitled “System and Method for Controlling Deflection of a Dynamic Surface.” The disclosures set forth in the &#39;111 and &#39;594 applications are hereby incorporated by reference herein.  
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to controlling vibration in surfaces and in particular relates to a system for controlling and/or damping vibration of dynamic surfaces.  
           [0003]    In many industries, such as paper making, food processing, and textiles, or any other industry that processes a web of material, rolls are used for various processing functions, and in many instances, the stability of the roll is very important. For example, in a paper making assembly, roll vibration may cause variations in the thickness of the product being produced. Thus, it is desirable for the rolls to be as stable as possible and devoid of any imperfections, deflections or variations so that the paper being formed will be smooth and uniform. In addition to resulting in the production of inferior products, roll vibration may also result in damage to the roll itself or the machinery containing the roll. Thus, various attempts have been made to control vibration of rolls so as to avoid these problems.  
           [0004]    One response to this problem has been to lower the rotational speed of the rolls in order to avoid or correct vibration-induced defects.  
           [0005]    U.S. Pat. No. 5,961,899 to Rossetti et al. discloses a vibration control apparatus for processing a calendered medium that controls vibration between two or more rolls by controlling vibration induced thickness variations in a medium exiting from a nip. The apparatus includes a frame, first and second rolls relative to the frame and a force generator, such as an electromechanical active actuator, a servo-hydraulic actuator, a controllable semi-damper, and Active Vibration Absorber (AVA), or an Adaptive Tune Vibration Absorber (ATVA), providing canceling forces to control vibration between the first and second rolls, thereby controlling vibration induced thickness variations in the calendered medium. In certain preferred embodiments, the apparatus includes at least one sensor for providing a signal indicating a vibration condition of at least one of the first and second rolls, and a digital controller for controlling the signal representative of the vibration condition according to a feed-forward-control and providing a control signal to a force generator. Vertical and/or lateral vibration of the rolls may thus be controlled simultaneously. In addition, fundamental vibrational frequencies and their harmonics may be controlled individually, or in combination.  
           [0006]    U.S. Pat. No. 5,447,001 to Nishimura et al. discloses a vibration control device for buildings. In one preferred embodiment, a building has mounted on its roof a hollow concrete-steel first mast carried on damping rubber supports. Within the hollow of the first mast, a second mast is mounted on anti-friction rollers, which roll on a low coefficient of friction interior floor of the first mast. The first and second masses are interconnected with a single element to vibrate these masses with a period of vibration that can be synchronized with the vibration period of the building to attenuate building vibration.  
           [0007]    U.S. Pat. No. 5,403,447 to Jarvinen et al discloses a system in a press section of a paper machine for monitoring and controlling the running of a press felt. The press felts are guided by rolls having axial directions that are altered by means of an actuator so as to control the running of the press felts. The system includes detector devices for detecting one or more alignment stripes on the felts and oscillation detectors for detecting oscillation of the press rolls. The system also includes a microprocessor base controller for monitoring signals fed to the controller from the detectors. The controller analyzes the detector data in order to detect any felt-induced oscillations. The control system then generates signals for regulating the actuators of the guide roll that guide the running of the felts so that when the oscillation levels of the press rolls rise above certain limits, the direction of the guide roll on the felt that causes the oscillation is turned until an acceptable level of oscillation and/or a level of oscillation is reached.  
           [0008]    U.S. Pat. No. 4,902,384 to Anstotz et al. discloses a wet press having vibration control. In one preferred embodiment, a wet press of a papermaking machine includes a pair of rolls defining a roll gap through which the paper being treated passes. The felt is guided in a closed loop path by additional rolls, which include a tightening roll. The tightening roll can be tilted to reduce roll vibrations by tightening the felt to set vibratory marks formed in the felt at an angle relative to the transverse width of the felt and the roll gap. A controllable positioning device is provided which includes a motor operated by a controller to automatically vary the tilt angle in response to sensed vibrations.  
           [0009]    Vibration is also a problem when using a wet press of a papermaking machine. In such wet presses, as the felt and paper web to be drained are simultaneously conducted through a roll gap, water is pressed out of the paper web and transferred onto the felt web. The absorbed water is removed from the felt at another point along its closed loop path by, for example, a suction roll. The pairs of rolls forming the roll gap, along with their guides which engaged roll journals and the elastically resilient felt, form a vibrating system with a large number of resonance vibrations that can be excited during operation of the web press.  
           [0010]    US. Pat. No. 5,785,636 to Bonander discloses a roll having an outer surface made of a fabricated fiber matrix for strengthening and reinforcing the roll to maximize roll stability.  
           [0011]    U.S. Pat. No. 4,301,582 to Riihinen discloses a system that removes deflections from a roll using magnetic forces. The roll has a non-rotating axle with ends having a load imposed thereat and a cylindrical shell rotatably supported by bearings on the axle. A magnetic core is formed in the axle and a plurality of pole shoes are spaced from the shell by an air gap. A plurality of electromagnetic windings, each wound on the core at one of the pole shoes, produce a magnetic compensating force field between the shell and the core for responding to deflections in the roll.  
           [0012]    U.S. Pat. No. 4,357,743 to Hefter, et al., discloses a controlled deflection roll having a roll shell which is radially movable in at least one plane in relation to a roll support. Position feelers or sensors are arranged at the ends of the roll shell for detecting one or more deflections in the roll shell as a function of deviations from a predetermined reference or set point. The position feelers control regulators operatively associated with pressure or support elements positioned between the roll support and the roll shell so that the roll shell is maintained in the reference or set position.  
           [0013]    U.S. Pat. No. 4,062,097 to Riinhinen discloses a roll having magnetic deflection compensation that may be used in the calender or press section of a paper machine. The roll has an inner non-rotating axle and an outer shell surrounding and rotatable with respect to the axle, the axle and the shell having a common axis. The axle includes an inner magnetic structure while the shell includes an outer magnetic structure that rotates together with the shell. These inner and outer magnetic structures cooperate to provide attraction between the shell and axle on one side of the above axis and repulsion between the shell and axle on the opposite side of the axis, thereby achieving deflection control and/or compensation.  
           [0014]    Other techniques used to reduce the detrimental effects of roll vibration include running process machinery at slower speeds in order to avoid resonance problems, and using back-up roll systems to reduce vibration.  
           [0015]    Therefore, there is a need to have a vibration control system for a dynamic surface that damps or eliminates vibrations in the dynamic surface. There is also a need for a vibration control system that enables vibrations to be induced into a dynamic surface for any purpose necessary.  
         SUMMARY OF THE INVENTION  
         [0016]    The present invention addresses the above-identified problems by providing a system and method for controlling vibration of a dynamic surface. In its broadest sense, the present invention may be used to eliminate undesirable vibrations from a dynamic surface or to actively induce vibrations into the dynamic surface. In preferred embodiments, the present invention may be used to control vibration of a dynamic surface on any object that rotates including, but not limited to, a roll that engages a web, a gear, wheels and/or tires. The present invention may also be used to reduce or control vibrations in aerodynamic surfaces or one or more surfaces of a loom. In highly preferred embodiments, the inventive system includes at least one piezoelectric actuator in communication with the dynamic surface of a roll and a mass overlying the piezoelectric actuator so that the piezoelectric actuator is between the mass and the dynamic surface for controlling vibration of the roll and/or actively inducing vibration into the roll.  
           [0017]    As is well known to those skilled in the art, piezoelectric elements may be used to covert electrical energy into mechanical energy and vice versa. For nanopositioning, the precise motion that results when an electric field is applied to a piezoelectric material is of great value. Actuators using this effect have changed the world of precision positioning. As used herein, the term “piezoelectric actuator” means a piezoelectric device or element, or any electronic device that operates in a similar fashion to a piezoelectric element such as an electromagnet or a magnetostatic device.  
           [0018]    As set forth herein, the term “dynamic surface” means any surface that may change with respect to time, regardless of whether the change occurs over 5-10 seconds or over a time period as small as one microsecond. However, as micro-technology improves and microprocessors operate at faster speeds, it is contemplated that the present invention could be used for dynamic surfaces that change over a period of time as small as 1 nanosecond. The present invention may be used for a broad range of applications whereby the system components move at various speeds. For example, the vibration control system of the present invention can be used when making a paper web moving at approximately 5000 feet/minute, when making textile materials moving at approximately 100-300 feet/minute or when making paper maker&#39;s clothing (PMC) moving at approximately 1-30 feet/minute.  
           [0019]    In accordance with one aspect of the present invention, there is provided a system for controlling vibration of a dynamic surface, such as the exterior surface of a roll. The system preferably includes at least one sensor in communication with the dynamic surface for measuring vibration of the dynamic surface and generating a feedback signal upon measuring vibration. The feedback signal may be proportional to the velocity, displacement and/or acceleration of the measured vibration. The feedback signal may consist of one or more of these variables. As used herein, the term “vibration” includes any dynamic surface response to any force to which the dynamic surface may be subjected including pressure forces, compressive forces, tensile forces, resonance, thermal action or other process forces. Moreover, the above-listed vibration forces may be applied in any direction with respect to the dynamic surface including directions that are substantially perpendicular to the dynamic surface and directions that are substantially parallel to the dynamic surface. The system also includes at least one piezoelectric actuator in communication with the dynamic surface and at least one mass overlying the at least one piezoelectric actuator so that the at least piezoelectric actuator lies between the mass and the dynamic surface.  
           [0020]    The system also preferably includes a controller in communication with the at least one sensor for receiving the feedback signal and sending the output signal to the at least one piezoelectric actuator. If the feedback signal indicates that the dynamic surface is undergoing vibration, the piezoelectric actuator, upon receiving the output signal, applies a counter force between the dynamic surface and the mass upon receiving the output signal for reducing or controlling vibration of the dynamic surface. The at least one piezoelectric actuator may also be activated when no vibration is sensed in order to actively induce vibrations into the dynamic surface.  
           [0021]    The application of piezoelectric elements to dynamic surfaces, such as the exterior surface of a roll, resolves vibration problems in a much more efficient manner than is available with the vibration control methods described above. Piezoelectric actuators can apply forces independently in various magnitudes, and in various combinations. This is not possible with most if not all of the existing roll control methodologies. Piezoelectric actuators are extremely precise, allowing repeatable nanometer and sub-nanometer movements. In addition, piezoelectric actuators can produce significant amounts of force over relatively small areas and are capable of moving heavy loads of up to several tons. Moreover, because piezoelectric elements derive their motion through solid state crystal effects and have no moving parts the response time of piezoelectric elements is in the kilohertz range so that they may be activated at very high frequencies. Finally, piezoelectric elements require very little power and require no maintenance.  
           [0022]    The at least one piezoelectric actuator preferably includes a plurality of piezoelectric actuators that are provided in contact with the dynamic surface. The piezoelectric actuators are preferably piezoelectric foils having a length of approximately 1 to 5 centimeters, a width of approximately 1 to 5 centimeters and a height of less than 1 centimeter. As such, one piezoelectric actuator preferably covers an area of approximately 1-25 cm 2 . In other preferred embodiments, piezoelectric actuators of any size and/or dimension may be used. Thus, the present invention is not limited to using actuators of the size/type listed above.  
           [0023]    The present invention preferably applies a plurality of piezoelectric actuators in contact with the dynamic surface of a roll so that relatively large controlling forces may be applied to the dynamic surface. Because each piezoelectric actuator can be controlled separately by the controller, it is possible to impart virtually any type of vibration or shape in the dynamic surface that is desired, thereby providing for unlimited performance possibilities not available in prior art technologies.  
           [0024]    In one preferred embodiment, the dynamic surface is preferably provided on a roll shell secured over a roll support. The roll shell may be a non-coated or a coated roll. The roll shell is preferably flexible and substantially cylindrical, has an interior surface defining an inner diameter of the roll shell and an exterior surface defining an outer diameter of the roll shell. The exterior surface of the roll shell preferably includes the dynamic surface. The sensors and piezoelectric actuators are preferably connected to the interior surface of the roll shell; and one or more masses overlie the piezoelectric actuators so that the piezoelectric actuators lie between the masses and the interior surface of the roll shell. In certain embodiments, the ratio of masses to piezoelectric actuators could be 1:1, however, in other embodiments the number of piezoelectric actuators may greatly exceed the number of masses or the number of masses may greatly exceed the number of piezoelectric actuators. In other embodiments, the sensors and piezoelectric actuators may be connected to either the inner or exterior surface of the roll shell or any combination thereof, so long as the masses overlie the piezoelectric actuators so that the piezoelectric actuators lie between the masses and the dynamic surface. In other embodiments, the sensors are in communication with, but not in contact with, the roll shells.  
           [0025]    The roll shell preferably has a longitudinal axis and preferably rotates about a central axis substantially parallel to the longitudinal axis. The roll shell is desirably mounted on a roll shell support that supports rotation of the roll shell about the central axis thereof. The roll shell support may include an axle mounted to an external support structure. The axle may rotate.  
           [0026]    In certain embodiments, the counter vibrating force applied by the piezoelectric actuators generates either a compressive force or a tensile force between the mass and the dynamic surface of the roll shell. The compressive and tensile forces are applied through the piezoelectric actuators and directly to the dynamic surface and the corresponding mass surfaces. The compressive and tensile forces are generally opposed to one another. In other words, the compressive forces compress the mass and the dynamic surface toward one another while the tensile forces urge the mass and the dynamic surface away from one another. The piezoelectric actuators may be aligned to exert compressive and tensile forces in directions substantially parallel to or substantially perpendicular to the longitudinal axis of the shell. The piezoelectric actuators may also be aligned to apply compressive and tensile forces to the dynamic surface in a plurality of various directions that are neither perpendicular to nor parallel to the longitudinal axis of the shell.  
           [0027]    The vibration control system of the present invention preferably includes a plurality of sensors in communication with the shell. The sensors are designed for detecting and/or measuring the magnitude of the vibration of the dynamic surface of the shell. The sensors are preferably spaced apart from one another and interspersed between the piezoelectric actuators. In certain preferred embodiments, the piezoelectric actuators are aligned in rows over the interior surface of the shell and the sensors are interspersed between the piezoelectric actuators. The rows of aligned piezoelectric actuators may extend in directions substantially parallel to or perpendicular to the longitudinal axis of the shell, or may extend in any number of directions between those that are substantially perpendicular and those that are substantially parallel to the longitudinal axis of the shell. The ratio of piezoelectric actuators to sensors is preferably about 100:1. The sensor may be one of a wide variety of sensors including but not limited to a piezoelectric element, a strain gauge, a laser used in conjunction with a reflective element, an optical device, a capacitive device and/or a magnetic device. In other preferred embodiments, the ratio of piezoelectric actuators to sensors will vary. The ratio may be 1:1, or the number of sensors may outnumber the number of piezoelectric actuators.  
           [0028]    The vibration control system of the present invention also preferably includes a controller having a microprocessor and a memory device. The memory may have stored therein look-up tables, a control strategy algorithm and/or an adaptive feedback control strategy algorithm. The controller is preferably designed for receiving feedback signals from the sensors. The controller then processes the feedback signals to determine the presence or absence of a vibration. If an undesirable vibration state is detected at one or more regions of the dynamic surface, the controller transmits output signals to the piezoelectric actuators at those vibrating regions for removing the vibrations. The control system of the present invention may also be used to actively induce vibrations into the dynamic surface.  
           [0029]    In certain preferred embodiments, the system for controlling vibration of a dynamic surface may be utilized for a web support structure located between two rolls so as to support the web as it passes by the web support structure. In these particular embodiments, the web support structure includes a supporting element having a web support layer. The web support layer has a top surface including the dynamic surface and a bottom surface remote therefrom. The dynamic surface is designed to engage the web passing thereover, such as a web of partially formed paper moving over the dynamic surface during a paper forming process. The control system of the present invention may also be used for processing textile materials and/or paper maker&#39;s clothing felts or any other process involving web handling. In these particular embodiments, the sensors and the piezoelectric actuators are provided in contact with the second surface of the web support layer and one or more masses overlie the piezoelectric actuators so that the piezoelectric actuators lie between the second surface of the web and the masses. However, in other embodiments, the sensors and piezoelectric actuators may be in contact with either the first surface or the second surface or any combination thereof, and the masses overlie the piezoelectric actuators. The dynamic surface of the web support layer may be substantially flat or have an arcuate section. In certain embodiments, the one or more sensors preferably determine the position of the dynamic surface in relation to the supporting element for detecting the presence of a deflecting force upon the dynamic surface.  
           [0030]    In these embodiments, at least one of the piezoelectric actuators is sandwiched between the at least one mass and the interior surface of the shell. In certain applications, there is a need to operate rolls at a speed that coincides with the resonance of the roll. When operated at or near resonance, a roll&#39;s dynamic response may cause detrimental effects on the roll itself, the machinery containing the roll and the process that the roll is completing. Using piezoelectric devices mounted between the roll (or other machine members) and a mass, and having the piezoelectric actuator connected to and controlled by a properly designed control device, vibrations in the dynamic surface of the roll can be reduced and/or controlled, thereby eliminating or reducing detrimental effects. Similarly, vibrations can be induced into rolls or other machine members for any purposes necessary.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]    [0031]FIG. 1A is a schematic side view of a prior art roll and mating roll engaging a web at a nip.  
         [0032]    [0032]FIG. 1B is a schematic side view of another prior art roll engaging a web.  
         [0033]    [0033]FIG. 2A is a sectional view of the prior art roll of FIG. 1A taken along lines IIA-IIA.  
         [0034]    [0034]FIG. 2B is a sectional view of the prior art roll of FIG. 1B taken along lines IIB-IIB.  
         [0035]    [0035]FIG. 3A shows a simplified view of the prior art roll of FIG. 1A during rotation of the roll.  
         [0036]    [0036]FIG. 3B shows a simplified view of the prior art roll of FIG. 1B during operation of the roll.  
         [0037]    [0037]FIG. 4A is a schematic cross-sectional view of a roll including a system for controlling vibration of the roll, in accordance with certain preferred embodiments of the present invention.  
         [0038]    [0038]FIG. 4B is a fragmentary schematic cross-sectional view of a roll, in accordance with further preferred embodiments of the present invention.  
         [0039]    [0039]FIG. 4C is a fragmentary schematic cross-sectional view of a roll, in accordance with still further preferred embodiments of the present invention.  
         [0040]    [0040]FIG. 4D is a fragmentary schematic cross-sectional view of a roll, in accordance with yet further preferred embodiments of the present invention.  
         [0041]    [0041]FIG. 5 is a fragmentary view of a the roll of FIG. 4A taken along lines V-V including a plurality of sensors in contact with the dynamic surface of the roll and a plurality of masses overlying piezoelectric actuators, in accordance with certain preferred embodiments of the present invention.  
         [0042]    [0042]FIG. 6 shows a fragmentary view, on an enlarged scale, of the dynamic surface of the roll shown in FIG. 5.  
         [0043]    [0043]FIG. 7 shows the roll shown in FIG. 4A during operation of the roll.  
         [0044]    [0044]FIG. 8A is a schematic cross-sectional view of a non-coated roll including a system for controlling vibration of the roll, in accordance with further preferred embodiments of the present invention.  
         [0045]    [0045]FIG. 8B is a schematic side view of a coated roll including a system for controlling vibration of the roll, in accordance with still further preferred embodiments of the present invention.  
         [0046]    [0046]FIG. 9 shows a schematic side view of a system for controlling vibration of a dynamic surface, in accordance with further preferred embodiments of the present invention.  
         [0047]    [0047]FIG. 10A is a sectional view taken along lines X-X of FIG. 9, showing the dynamic surface of a web support layer.  
         [0048]    [0048]FIG. 10B shows a sectional view of a system for controlling deflection of a dynamic surface including a mating roll for creating nip pressure, in accordance with further preferred embodiments of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0049]    FIGS.  1 A- 3 B show prior art rolls. Referring to FIG. 1A, the roll  20  is a non-coated roll including an axle  22  loaded at its ends. A non-coated roll generally includes rolls having metal tubes, such as a steel roll or tube. In contrast, a coated roll is understood to be a roll that is coated with a layer of flexible material such as rubber, fabric or cloth. The loading forces F are shown in FIG. 1. The forces F, together with the weight of the roll, provide the required nip pressure at the nip N formed by the interface of roll  20  and a mating roll  24 . The forces shown in FIG. 1 and described above are dependent upon the position of the roll  20  relative to the mating roll  24 . For example, these forces would change if the roll  20  were under the mating roll  24  (i.e., under the nip). The roll  20  includes a roll shell  26  that is secured about axle  22  via bearings  28 . The roll shell has an interior surface  30  and an exterior surface  32 . The longitudinal axis or centerline of the axle  22  is indicated by A-A.  
         [0050]    [0050]FIG. 1B shows another prior art non-coated roll  20 ′ that does not have an axle extending therethrough as shown in FIG. 1A. The roll  20 ′ includes a roll shell  26 ′ having an interior surface  30 ′ and an exterior surface  32 ′. The roll  20 ′ includes supports  22 A′ and  22 B′ that support the interior surface  30 ′ of the roll shell  26 ′ as the roll shell rotates about a longitudinal axis A′-A′. The supports  22 A′ and  22 B′ includes extensions  27 ′ supported by bearings  28 ′.  
         [0051]    [0051]FIG. 2A shows a cross sectional view of the roll  20  and the mating roll  24  of FIG. 1A taken along line IIA-IIA of FIG. 1A. The roll  20  and mating roll  24  are designed for allowing a web  34  to pass therebetween at the nip N. Mating rolls facilitate the development of nip pressures between two rolls, thereby minimizing deflection of one or more rolls. Mating rolls, such as mating roll  24 , may also be used as backup or support rolls. The roll  20  and the mating roll  24  may typically be incorporated into any assembly that processes a web of material such as a paper making assembly, a textile making assembly, a paper maker&#39;s clothing making assembly, a printing assembly, a metal rolling assembly, an embossing assembly or a calendaring assembly.  
         [0052]    [0052]FIG. 2B shows a cross-sectional view of the roll  20 ′ of FIG. 1B taken along line IIB-IIB of FIG. 1B. The roll  20 ′ of FIG. 2B is a singular roll that is not in contact with a mating roll for creating nip pressure.  
         [0053]    [0053]FIG. 3A shows a simplified view of the roll  20  of FIGS. 1A and 2A when the roll is vibrating. The mating roll  24  may also vibrate as indicated by the dashed lines. The vibration of the roll  20  may be the result of vibrating forces applied to the exterior surface  32  of the roll by a web (not shown), or by the resonance frequencies of the rolls or other exciting energies such as vibrational energy transmitted from any other part of a machine that causes a roll to go into resonance or drives a roll into a vibrating state. FIG. 3B shows a simplified view of the roll  20  of FIGS. 1B and 2B when the roll is vibrating. The roll vibration shown in FIGS. 3A and 3B can have detrimental effects on the rolls, the machinery containing the rolls or the products being produced using the rolls. The present invention is directed towards a control system that both detects roll vibration anywhere on a roll and actively corrects the condition for rapidly and efficiently returning the roll to a non-vibrating state. In certain embodiments, it may be preferable to detect and/or correct roll vibration only at the portion of the roll at the nip. To a broader extent, the present invention is directed toward providing a control system for a dynamic surface for detecting the occurrence of a vibration in a dynamic surface, measuring the velocity, acceleration or displacement of the vibration, and then operating actuators to return the dynamic surface to a non-vibrating condition.  
         [0054]    [0054]FIG. 4A shows a deflection control system  100  for a roll  102  in accordance with certain preferred embodiments of the present invention. The roll  102  includes an axle  104  having bearings  106  for supporting a roll shell  108 . The roll shown in FIG. 4A is commonly referred to as a non-coated roll. A non-coated roll is typically made by providing a roll shell, such as a solid steel shell, that supplies the main support for the roll. The roll shell  108  has a longitudinal axis that is substantially parallel to the longitudinal axis B-B of axle  104 . The roll shell  108  is generally cylindrical or tubular and includes an inner surface  110  defining an inner diameter and an exterior surface  112  defining an outer diameter. The outer diameter (O.D.) of the roll  102  is defined by the exterior surface  112  of roll shell  108 .  
         [0055]    The vibration control system also includes a plurality of sensors  114  and a plurality of piezoelectric actuators  116  connected to the interior surface  110  of the roll shell  108 . The sensors  114  and piezoelectric actuators  116  are in signal sending and receiving communication with a controller  118  via conductive traces  120  extending between the sensors  114  and piezoelectric actuators  116 , and the controller  118 . For clarity of illustration, FIG. 4A shows only one sensor  114  and one piezoelectric actuator  116  connected to controller  118 , however, it should be understood that all of the sensors and actuators are preferably in signal sending and receiving communication with the controller. The control system also includes a mass  125  overlying each piezoelectric actuator  116 . As a result, each piezoelectric actuator is positioned between the inner surface  110  of the roll shell  108  and one of the masses  125  overlying the piezoelectric actuators.  
         [0056]    In the particular embodiment shown in FIG. 4A, the controller  118  is located within the roll  102  for rotating simultaneously with the roll, the sensors  114 , the piezoelectric actuators  116  and the masses  125 . Power for the controller may be provided from a stationary power source  122  through a power line  123  that extends through axle  104 . The energy is transmitted from the stationary power source to the rotating controller via a connection mechanism, such as a slip ring, that will not twist the power line  123  as the roll rotates. The controller  118  preferably includes a microprocessor  124  and a memory device  126  for storing a deflection control strategy or data related to preferred operating conditions for the roll  102  and roll shell  108 . The controller  118  preferably uses one or more software applications stored therein, the software applications being capable of receiving feedback signals from the sensors  114 , comparing the feedback signals with data stored in the memory device  126  and generating a series of output signals for transmission to the piezoelectric actuators  116 . Upon receiving the output signals, the piezoelectric actuators are actuated for drawing the masses and the dynamic surface toward one another or forcing the masses and the dynamic surface away from one another so as to remove vibrations from the roll shell  108 , as will be described in more detail below.  
         [0057]    In operation, a moving web (not shown) passes through a nip N created by roll  102  and mating roll  130 . The roll  102  and mating roll  130  are shown in a generally horizontal orientation, however, the vibration control system of the present invention is also intended for use when the rolls  102 ,  130  have a substantially vertical orientation or any other geometric orientation with respect to the ground or one another. For clarity of illustration, FIG. 4A shows two rolls: roll  102  and mating roll  130 . However, the present invention may also be used for controlling vibrations in systems having three or more rolls in contact with one another including a calendar stack of rolls whereby at least one of the rolls in the stack has two or more nip surfaces.  
         [0058]    [0058]FIG. 4B shows a fragmentary view of a roll having a vibration control system in accordance with further preferred embodiments of the present invention. The FIG. 4B embodiment is substantially similar to the embodiment shown in FIG. 4A, however, the FIG. 4B embodiment includes a coated roll  102 ′ having a roll shell  108 ′. The roll shell  108 ′ includes a flexible coating  108 A′ overlying a structural support member  108 B′. The flexible coating preferably includes a flexible material such as an elastomer (e.g. rubber) or cloth. When the flexible material is an elastomer, the structural support member  108 B′ is preferably a solid tube, such as a steel tube. The outer diameter of the coated roll  102 ′ is defined by the exterior surface  112 ′ of the flexible coating  108 A′. The system includes a plurality of piezoelectric actuators  116 ′ and sensors  114 ′ overlying the inner surface  110 ′ of the roll shell  108 B′ and masses  125 ′ overlying the piezoelectric actuators.  
         [0059]    [0059]FIG. 4C shows another embodiment of the present invention having the sensors  114 ″ and piezoelectric actuators  116 ″ on the outer diameter  112 ″ of the roll  102 ″. The roll  102 ″ is a coated roll including a roll shell  108 ″ including a flexible coating  108 A″ overlying a structural support member  108 B″. The sensors  114 ″ and piezoelectric actuators  116 ″ are on the exterior surface  112 ″ of the flexible coating  108 A″. Masses  125 ″ are provided over the piezoelectric actuators  116 ″ so that the piezoelectric actuators  116 ″ are sandwiched between the exterior surface  112 ″ of the flexible coating  108 A″ and the masses  125 ″. In further embodiments, the roll may be a non-coated roll and the sensors, actuators and masses are provided on the exterior surface of the roll shell (i.e., the exterior surface of the structural support member).  
         [0060]    [0060]FIG. 4D shows a fragmentary view of a roll having a vibration control system in accordance with further preferred embodiments of the present invention. In FIG. 4D the ratio of masses  125 ′″ to piezoelectric actuators  116 ′″ may be 1:1, or the number of masses  125 ′″. may exceed or be less than the number of piezoelectric actuators  116 ′″. The left side of the roll has two masses  125 A′″ and  125 B′″ overlying one piezoelectric actuator. In the center of the roll, one mass  125 C′″ overlies three piezoelectric actuators. On the right side of the roll, the ratio of masses to actuators is 1:1 as three masses  125 D′″,  125 E′″ and  125 F′″ overlie three separate piezoelectric actuators.  
         [0061]    Although the present specification provides a detailed description of the vibration control system of the present invention when describing the roll  102  embodiment shown in FIG. 4A, the present invention is equally applicable to the coated roll  102 ′ embodiment shown in FIG. 4B, the roll  102 ″ embodiment shown in FIG. 4C, or any other type of dynamic surface.  
         [0062]    [0062]FIG. 5 shows a fragmentary view of FIG. 4A, taken along lines V-V, showing sensors  114  and masses  125 /piezoelectric actuators  116  connected to the inner surface  110  of the roll shell  108 . The masses  125  overlie the piezoelectric actuators which are not shown. The piezoelectric actuators and the masses overlying the piezoelectric actuators are preferably aligned in rows C, D, E, F, G, H and I that extend substantially parallel to the longitudinal axis B-B of the roll shell  108 . Each mass is preferably in registration with one of the piezoelectric actuators. Each mass  125  preferably has a length of approximately 1 to 5 centimeters, a width of approximately 1 to 5 centimeters, and a height of less than one centimeter. Thus, each mass  125  generally covers an area of approximately 1-25 cm 2 . The piezoelectric actuators generally cover the same area as the masses. The sensors  114  are interspersed between the masses  125  and are preferably spaced so that the controller is able to monitor the entire dynamic surface of the roll. As mentioned above, the sensors are designed for detecting the presence of vibration of the dynamic surface of the roll shell  108 .  
         [0063]    The number of piezoelectric actuators  116  and masses  125  generally outnumber the number of sensors  114  by a significant amount. In one preferred embodiment, the ratio of masses and piezoelectric actuators to sensors is approximately 100:1. Preferred sensors include piezoelectric elements, strain gauges, a laser and reflective element sub-assembly, an optical device, a capacitive device, and/or a magnetic device. In the preferred embodiment shown in FIGS. 4A and 5, the sensors are piezoelectric elements capable of detecting a vibration of the dynamic surface of the roll. Such vibration will strain the piezoelectric sensor to stretch or compress. The piezoelectric sensor will then transform the physical movement into an electric feedback signal, whereby the magnitude of the electric feedback signal may be proportional to the magnitude of the physical movement of the sensor. The electric feedback signal is sent to the controller. The electric signal may be either an electric voltage signal or a current signal.  
         [0064]    [0064]FIG. 6 shows an enlarged fragmentary view of rows D, E and F of FIG. 5. Each row includes masses  125  overlying piezoelectric actuators (not shown) with sensors  114  interspersed between the masses and piezoelectric actuators. The sensors  114  preferably monitor a specific region of the roll shell  108  to detect whether that region is subjected to vibration. Each sensor  114  operates independently of the other sensors. For example, sensor  114  F in row F may detect a vibration while sensor  114 E of row E detects no vibration. The piezoelectric actuators may also operate independently of one another. For example, piezoelectric actuator  116 F may apply a counter vibrating force to the roll shell while piezoelectric actuator  116 E is not actuated and applies no counter vibrating force to the roll shell. Moreover, piezoelectric actuators adjacent one another may apply counter vibrating forces having different magnitudes; e.g. the piezoelectric actuator underlying mass  125 E applies a counter vibrating force having a greater magnitude that the force applied by the piezoelectric actuator underlying mass  125 E′. The actual magnitude of the counter vibrating force applied by any one piezoelectric actuator is typically proportional to the magnitude of the electric signal received from the controller  118  (FIG. 4). Although the masses  125  and the actuators  116  underlying the masses are depicted in rows, the present invention includes embodiments where the masses and actuators are arranged randomly or in a pattern. The sensors  114  may also be arranged in a pattern or randomly.  
         [0065]    Referring to FIGS. 4A and 6, during operation or rotation of the roll  102 , the region of the roll shell  108  overlying row D may be in contact with a moving web while regions of the roll shell overlying rows E and F are not in contact with the web. As a result, the moving web vibrates the roll shell overlying row D while rows E and F are not vibrating. Thus, the sensors  114 D in row D will detect vibration while the sensors  114 E and  114 F of respective rows E and F will not detect vibration. In response, output signals sent from the controller to piezoelectric actuators of row D will physically move those piezoelectric actuators for damping vibration of the dynamic surface of the roll shell  108  overlying actuators  116 D. However, no output signals will be sent to the piezoelectric actuators  116 E and  116 F in rows E and F. As such, piezoelectric actuators will only be activated by output signals when necessary to control and/or damp vibration of the roll shell or when it is desirable to actively vibrate the dynamic surface of the roll shell. The force applied by each actuator in any one row may vary. For example, the actuators in the center of a row may apply more force than the actuators adjacent a journal. In addition, in any one row, the actuators adjacent one journal may provide more force than the actuators adjacent an opposed journal.  
         [0066]    [0066]FIGS. 7 and 8 show the roll  102  of FIG. 4A before activation of the vibration control system of the present invention. During operation of the roll, a web  128  (not shown in FIG. 7) passes between the roll  102  and mating roll  130 . The rotational speed of the roll  102  is dependent upon a number of factors including the speed of the web passing between roll  102  and mating roll  130  and the outer diameter of the roll. Referring to FIG. 8, in response to a number of vibrating forces, including the high rate of rotation of the roll (e.g., 5000 revolutions/minute) web tension, nip pressure and gravity, the roll  102  and the roll shell  108  vibrate. As set forth above, vibration of the roll is undesirable because it will have an adverse effect on the material  128  (e.g., a web) passing between the roll  102  and the mating roll  130 .  
         [0067]    Referring to FIG. 7, during operation the sensors  114  are activated for detecting vibration of the dynamic surface of the roll  102  and to send feedback signals back to the controller (FIG. 4) upon sensing vibration. Upon receiving feedback signals from the sensors, the controller will determine the magnitude of the vibration. The controller will then calculate output signals to be sent to each of the piezoelectric actuators  116  connected to the roll shell. The magnitude of the output signals sent to the individual piezoelectric actuators may vary because the amount of damping force or attenuating force required at each particular region of the roll may vary. Upon receiving the output signals from the controller, the piezoelectric actuators  116  will exert tensile and/or compressions forces on the dynamic surface of the roll for damping and/or controlling vibration of the dynamic surface. In certain embodiments, one or more piezoelectric actuators may saturate or “max out”; i.e. a condition where the piezoelectric actuator is exerting a maximum force and this maximum force is not enough to completely damp or control a localized vibration in the dynamic surface. In these instances, piezoelectric actuators located outside the area of the vibration may be actuated to assist the “maxed out” piezoelectric actuators.  
         [0068]    [0068]FIG. 8A shows a vibration control system  200  for a non-coated roll  202  in accordance with further preferred embodiments of the present invention. The roll  202  includes a roll shell  208  having first and second ends  215 A and  215 B. The system includes first and second supports  217 A and  217 B for supporting the first and second ends  215 A and  215 B of the roll shell  208 . The supports  217 A and  217 B are connected with the interior surface  210  of the roll shell  208  for supporting rotation of the roll  202 . The supports  217 A and  217 B extend beyond the ends  215 A and  215 B of the roll shell  208  to bearings  206  so that the roll  202  may rotate about longitudinal axis C-C. The roll  202  includes a controller  218  for controlling vibration of the roll shell  208 . The controller  218  is in communication with sensors  214  and piezoelectric actuators  216  via traces  220 . FIG. 8A shows only one sensor  214  and one piezoelectric actuator  216  connected to controller  218 , however, it should be understood that all of the sensors and actuators are preferably in signal sending and receiving communication with the controller. Masses  225  overlie the piezoelectric actuators  216  so that the piezoelectric actuators  216  lie between the inner surface  210  of the roll shell  208  and the masses  225 . The controller  218  is preferably located within roll shell  208  for rotating simultaneously with the roll shell, the sensors  214  and the piezoelectric actuators  216 . Power for the controller  218  may be provided from a power source  222  through a power line  223  that extends through one of the structural members  217 . The controller  118  operates in a manner that is substantially similar to that described above in regards to FIG. 4A.  
         [0069]    [0069]FIG. 8B shows another embodiment of the present invention that is substantially similar to the FIG. 8A embodiment, however, the FIG. 8B embodiment includes a coated roll  202 ′. The coated roll  202 ′ includes a roll shell  208 ′, having a flexible coating  208 A′ surrounding structural support member  208 B′. The outer diameter of the coated roll  202 ′ is defined by the exterior surface  212 ′ of the flexible coating  208 A′. Both the non-coated roll  202  of FIG. 8A and the coated roll  202 ′ of FIG. 8B are dynamically flexible and include dynamic surfaces as that term is defined herein. As a result, the non-coated and coated rolls disclosed herein may deflect and/or vibrate during operation.  
         [0070]    [0070]FIGS. 9 and 10A show a deflection control system in accordance with further preferred embodiments of the present invention. Referring to FIG. 9, a web support element  300  is provided between two rolls  302  and  304 . The web support element  300  supports a web  306  moving between first roll  302  and second roll  304 . Referring to FIG. 10A, the web support element  300  includes a web support layer  308  having a first surface  310  for engaging the web  306  and a second surface  312  remote therefrom. The second surface  312  of the web support layer  308  includes sensors  314  and piezoelectric actuators  316  connected thereto. Masses  325  overlie the piezoelectric actuators for damping vibrational forces on the web support layer  308 .  
         [0071]    [0071]FIG. 10B shows another embodiment, similar to the embodiment of FIG. 10A, including a mating roll  330 ′, whereby a web  306 ′ passes between the mating roll and the web support layer  308 ′.  
         [0072]    Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. For example, the present invention may be incorporated into the wing of an airplane or onto a surface of a machine for controlling vibration of these surfaces. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.