Abstract:
The invention provides a system for creating a prescribed vibration profile on a mechanical device comprising a sensor ( 30 ) for measuring an operating condition of the mechanical device, a circular force generator CFG ( 20 ) for creating a controllable rotating force vector comprising a controllable force magnitude, a controllable force phase and a controllable force frequency, a controller ( 22 ) in electronic communication with said sensor and said circular force generator, the controller operably controlling the controllable rotating force vector, wherein the difference between the measured operating condition and a desired operating condition is minimized.

Description:
[0001]    Some mechanical devices perform specific functions through use of induced vibratory motion. Such devices include monitoring damage detection and structural assessment of civil structures and mechanical devices, damping in civil structures, searching for oil and gas with seismic impulse exciters, medical device and equipment, controlling fluid flow in a pipe, deliquifying screens, material separators, vibratory feeders and conveyors, attrition mills, mold shakeout machines, and vibratory compactors. Typically these devices utilize one or more force generators to create a predefined force profile for inducing vibration within the device. These force generators may include linear drives or imbalanced rotors driven by synchronous motors or induction motors whose speed is an integer fraction of the electrical source frequency. To vary the frequency of vibration, variable frequency drives (VFDs) are used in conjunction with these motors. To tailor the shape of the vibration profile or create a resonance for the purpose of amplifying the vibration response, springs, stabilizers, and/or mechanical pivots are used. When multiple synchronous or asynchronous motors are used on the same device and are coupled through common base vibration, they tend to synchronize with each other to produce a consistent and predesigned force profile. 
         [0002]    The aforementioned devices are incapable of maintaining a desired vibration profile when operating conditions change, such as a change in material loading, changes in temperature, changes in material properties, or other variables that can alter the response of the mechanical device. In some cases, the aforementioned devices cannot create certain desirable vibration profiles. In other cases, the aforementioned devices cannot create a variety of selectable vibration profiles within limits imposed by the authority of their respective force generators. 
       SUMMARY OF THE INVENTION 
       [0003]    In accordance with the present invention a system for creating a prescribed operating function within a mechanical device. The system comprises a mechanical device, at least one circular force generator (CFG), at least one sensor and a controller. The CFG is affixed to the mechanical device. The CFG is capable of producing a rotating force vector, wherein the rotating force vector includes a magnitude, a phase, and a frequency, wherein the CFG creates at least one vibration profile in the mechanical device. The at least one sensor is positioned on the mechanical device, wherein the sensor measures an operating function associated with and enabled by the vibration profile. The controller is in electronic communication with the sensor and with the CFG, the controller operably controlling the force vector based upon the measurement of the operating function, wherein the magnitude, phase and frequency are independently controllable by the controller, wherein the controller changes the force vector. Wherein a difference between the measured operating function and a prescribed operating function is reduced. 
         [0004]    In accordance with the present invention a system for creating a prescribed vibration profile within a mechanical device. The system comprises a mechanical device, at least one circular force generator (CFG), at least one sensor and a controller. The CFG is affixed to the mechanical device. The CFG is capable of producing a rotating force vector, wherein the rotating force vector includes a magnitude, a phase, and a frequency, wherein the CFG creates at least one vibration profile in the mechanical device. The at least one sensor is positioned on the mechanical device, wherein the sensor measures a vibration profile associated with and enabled by the vibration profile. The controller is in electronic communication with the sensor and with the CFG, the controller operably controlling the force vector based upon the measurement of the vibration profile, wherein the magnitude, phase and frequency are independently controllable by the controller, wherein the controller changes the force vector. Wherein a difference between the measured vibration profile and a prescribed vibration profile is reduced. 
         [0005]    In another aspect, the invention provides for a method for creating a prescribed operating function on a mechanical device having at least one CFG capable of producing a rotating force vector with a controllable magnitude, phase and frequency, a sensor and a controller, and the CFG is capable of creating at least one vibration profile in the mechanical device, the method comprising the steps of:
       (a) defining a prescribed operating function;   (b) measuring an operating function with the sensor;   (c) communicating the measured operating function from the sensor to the controller;   (d) calculating an error by comparing the measured operating function to the desired operating function;   (e) processing the error in the controller using an algorithm, wherein the processing produces a command for the CFG, the command including changes to the magnitude, the phase, and/or the frequency of the rotating force vector;   (f) communicating the changes to the force vector to the CFG such that the difference between the measured operating function and the prescribed operating function is reduced.       
 
         [0012]    Numerous objects and advantages of the invention will become apparent as the following detailed description of the preferred embodiments is read in conjunction with the drawings, which illustrate such embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  illustrates a perspective view of a deliquifying screen with circular force generators positioned thereon. 
           [0014]      FIG. 2  illustrates a typical vibration prescribed vibration profile enabled by the present invention. 
           [0015]      FIG. 3  illustrates a perspective view of a vibratory conveyor with circular force generators positioned thereon. 
           [0016]      FIG. 4  illustrates a perspective view of a vibratory material separator with circular force generators positioned thereon. 
           [0017]      FIG. 5A  illustrates one embodiment of a Circular Force Generator (CFG). 
           [0018]      FIG. 5B  illustrates a partial cut-away view of the CFG of  FIG. 5A . 
           [0019]      FIG. 6  illustrates another embodiment of a CFG. In this case the CFG comprises two separate identical components, one of which is shown. 
           [0020]      FIG. 7  illustrates yet another embodiment of a CFG. In this case the CFG comprises two separate identical components, one of which is shown. 
           [0021]      FIGS. 8A-C  illustrate force generation using two co-rotating imbalanced rotors to create a circular force with controllable magnitude and phase, thereby providing a CFG. 
           [0022]      FIG. 9  illustrates two CFGs coaxial mounted on both sides of a mounting plate. 
           [0023]      FIG. 10  illustrates two CFGs mounted side-by-side on a mounting plate. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    The invention described herein is applicable to a wide range of devices where a mechanically induced vibration is desired, the non-limiting examples of vibratory deliquifying machines, conveyors, and separators are used for illustration purposes. 
         [0025]    Referring to the drawings,  FIG. 1  shows the invention as applied to the non-limiting example of a vibratory deliquifying machine illustrated and generally designated by the numeral  10 . The non-limiting example vibratory deliquifying machine  10 , as illustrated, includes inlet  12 , screen  14 , exit  16 , springs  18 , and force generators  20 . Force generators  20  are preferably CFG  20 . 
         [0026]    In vibratory deliquifying machine  10 , slurries (not shown) enter inlet  12  where a vibratory motion causes the slurry to convey across screen  14  suspended on springs  18 . As the slurry is conveyed across screen  14 , liquid passes through screen  14  while dry material (not shown) is extracted at exit  16 . 
         [0027]    Existing vibratory deliquifying machines  10  have a specific elliptical vibratory motion at one specific frequency providing for optimal performance. CFG  20 , including controller  22 , enables the use of a prescribed elliptical vibratory motion for optimal performance. In the case of the non-limiting example of vibratory deliquifying machine  10 , the prescribed elliptical vibratory motion from CFGs  20  increases the separation of liquid and solid matter. This also enables the maintenance of the optimal vibratory motion even when the mass of the slurry or the center-of-gravity of the slurry on screen  14  changes with time or operating condition. 
         [0028]    In  FIG. 1  two, CFGs  20  are mounted to screen structure  24  of vibratory deliquifying machine  10 . Referring to  FIGS. 8A-8C  for CFG  20 , each CFG  20  is capable of creating rotating force vector  26  having a controllable magnitude F 0 , a controllable phase φ, and a controllable frequency ω. Two CFGs  20  operating at the same frequency ω and proximal to each other, as shown in FIGS.  1  and  8 A- 8 C, where one is producing a clockwise rotating force vector and one is producing a counter clockwise rotating force vector, produce a resultant that is a controllable two degree-of-freedom planar force. These applied forces act on screen structure  24  and produce an induced vibratory motion. 
         [0029]    In the non-limiting example illustrated in  FIG. 1 , CFGs  20  are mounted on centerline  28  of vibratory deliquifying machine  10 . This placement avoids creating a side-to-side rocking motion from applied forces. Screen structure  24  is assumed to be a rigid body, whereby the two proximal CFGs  20  create two degrees-of-freedom of controllable planar motion. The addition of more CFGs  20  will increase the degrees-of-freedom of controllable motion. For example, the application of a third CFG  20  will allow for three degrees-of-freedom of controllable planar motion. The maximum of six CFGs  20  will allow for a full six degrees-of-freedom rigid body control of motion. Depending upon the need, two-to-six CFGs  20  are utilized on a rigid body to create controllable motion from two to six two degrees-of-freedom, respectively. 
         [0030]    In the non-limiting example of vibratory deliquifying machine  10  illustrated in  FIG. 1 , sensors  30  are used to provide input to controller  22 . Sensors  30  are applied to the screen structure  24 . The location of sensors  30  is determined by the particular data element being sensed. Sensors  30  monitor an aspect of vibratory deliquifying machine  10  performance related to the induced vibratory motion. 
         [0031]    The signals from sensors  30  are received by controller  22 . Controller  22  commands the force magnitude, phase, and frequency of each CFG  20 . Within controller  22  resides at least one algorithm comparing performance, as measured by sensors  30 , with a desired performance to produce an error. The algorithm then produces CFG commands that that will reduce or minimize this error. Many methods are known to those skilled in the art for reducing an error based on sensor  30  feedback, including various feedback control algorithms, open-loop adaptive algorithms, and non-adaptive open-loop methods. In one exemplary embodiment, controller  22  uses a filtered-x least mean square (Fx-LMS) gradient descent algorithm to reduce the error. In another exemplary embodiment, the controller uses a time-average gradient (TAG) algorithm to reduce the error. 
         [0032]    Sensors include all types of vibration sensors, including digital, analog, and optical. Sensors also include accelerometers, thermocouples, infrared sensors, mass flow rate sensors, particle matter sensors, load sensors and optical sensors. The sensors may be selected from the group consisting of vibration sensors, accelerometers, thermocouples, infrared sensors, mass flow rate sensors, particle matter sensors, load sensors, optical sensors and combinations thereof. A plurality of sensors of the same type or a plurality of different types sensors are employed to maximize the measurement of the operating condition. 
         [0033]    The mechanical devices contemplated herein perform specific operating functions through use of induced vibratory profiles. Operating functions material flow or movement, material separation, material compaction, drying, pumping, as well as others. All of the operating functions are enabled by the induced vibratory profile and react to vibratory input from CFGs  20 . 
         [0034]    In an exemplary embodiment, sensors  30  are accelerometers directly measuring the operating function of screen structure  24 . In this non-limiting embodiment, the operating condition measured is the vibration profile of screen structure  24 . Within controller  22  the measured operating function is compared with a desired or prescribed vibration profile to produce an error. Controller  22  then implements an algorithm that produces CFG commands such that the measured operating function moves toward the prescribed vibration profile reducing the error. By way of illustration,  FIG. 2  shows both a prescribed vibration profile (labeled as “Command”) and a measured vibration profile as measured by a biaxial accelerometer located near the center-of-gravity of the screen assembly. In  FIG. 2  the prescribed vibration profile is illustrated as a solid line and labeled as “Command,” and the measured vibration profile is illustrated as a dotted line and labeled as “Measured.” It can be seen that the difference, or error, between these profiles is small. 
         [0035]    In another illustrative non-limiting example,  FIG. 3  shows the present invention applied to vibratory feeder  100 . Material is fed onto feeder bed  102  of vibratory feeder  100  from hopper  104 . Vibratory motion conveys the material along feeder bed  102  where it is then metered into another machine, or a package, or any one of a number of secondary systems. 
         [0036]    Application of the present invention enables a prescribed elliptical vibratory motion for optimal performance of vibratory feeder  100 . Optimal performance includes precision metering of material flow or high material conveyance rate without damaging or dispersing the material. The present invention also enables the maintenance of the optimal vibratory motion even when the mass of the material on feeder bed  102  or the center-of-gravity of the material on feeder bed  102  changes with time or operating condition. In other embodiments or other uses the prescribed vibration is selected from the group consisting of linear, elliptical and orbital, as determined by the desired outcome. 
         [0037]    Vibratory feeder  100  illustrated in  FIG. 3  is used similarly to the application to vibratory deliquifying machine  10  described hereinabove and illustrated in  FIGS. 1 and 2 . Feedback sensors  106  shown are accelerometers, but may be sensors  106  that directly or indirectly measure material flow rate. By way of non-limiting example, sensors  106  shown in  FIG. 3  are embedded within CFG  20  thereby eliminating extra connectors and wiring harnesses associated therewith. 
         [0038]    Referring to  FIG. 4  vibratory material separator  200  is illustrated as another non-limiting example. Vibratory material separator  200 , as illustrated, uses screens (not shown) and induced vibratory motion to separate granular materials or aggregates based on grain size and/or density. Using prescribed vibratory motion generated by CFGs  20 , the performance of material separators is optimized. Optimal performance includes improving separation, or improving throughput, or a combination thereof. Optimal performance also includes enhancement of the screen life and anti-fouling of the screen. The optimal vibratory motion is maintained even when the mass of the material or the center-of-gravity of the material within vibratory material separator  200  changes with time or operating condition. The application of the present invention to vibratory material separator  200  illustrated in  FIG. 4  is very similar to the application to previous examples described hereinbefore. 
         [0039]      FIGS. 5A-8C  provide non-limiting examples of CFG  20  in different variations. Referring to  FIGS. 5A-6 , CFG  20  consists of two imbalanced masses  32   a ,  32   b  each attached to a shaft  34  and each suspended between two rolling element bearings  36   a ,  36   b . Each imbalance mass  32   a ,  32   b  is driven by motor  38   a ,  38   b . In exemplary embodiments, the two motors  38   a ,  38   b  within CFG  20  are brushless permanent magnet motors, sometimes called servo motors. Each motor  38   a ,  38   b  includes a sensor  40  for sensing the rotary position of imbalanced masses  32   a ,  32   b . Within the aforementioned controller  22 , an algorithm employing Equation (1) that receives the rotary position sensor feedback, and uses common servo motor control techniques controls the rotary position  8  of each motor. The equation employed is illustrated by Equation (1): 
         [0000]      θ( t )=φ t+ω   (Equation (1)
 
         [0000]    where ω is the rotational speed and φ is the rotational phase. Rotational phase φ corresponds to the phase of the motor (and thus the imbalanced mass) with respect to an internal reference tachometer signal. Both imbalanced masses  32   a ,  32   b  co-rotate at nominally the same speed ω, and each imbalanced mass  32   a ,  32   b  creates a centrifugal force whose magnitude is mathematically determined by using Equation (2): 
         [0000]      | F|=mr ω   2   Equation (2)
 
         [0000]    where mr is the magnitude of imbalanced mass  32   a ,  32   b  which is typically expressed in units of Kg-m. The phase of the first imbalanced mass  32   a  with respect to the second imbalanced mass  32   b  (i.e., the relative phase) within CFG  20  will determine the magnitude of resultant rotating force vector  26 . 
         [0040]    Referring to  FIGS. 8A-C , a zero-force case and a full-force case of imbalance masses  32   a  and  32   b  of CFG  20  are both illustrated. In the zero-force case the relative phase φ 2 -φ 1  is 180 degrees and resulting force rotating vector  26  has a magnitude of zero. In the full-force case, the relative phase φ 2 -φ 1  is 0 degrees and resulting rotating force vector  26  has a maximum magnitude of 2|F|. For relative phases φ 2 -φ 1  between 0 and 180 degrees, the magnitude of resulting rotating force vector  26  will be between zero and maximum. Furthermore, the collective phase γ of rotating force vector  26  can be varied to provide phasing between CFGs  20 . Through control of phase φ of each imbalance mass  32   a ,  32   b  the magnitude and absolute phase of the rotating force vector  26  produced by CFG  20  can be controlled. 
         [0041]    Referring to  FIGS. 1-8C , the particular structure carrying CFGs  20  includes n vibration sensors  30  and m CFGs  20 , wherein n≧m and (with m whole number equal to or greater than one). Controller  22  detects at least one vibration signal from at least one vibration sensor  30 , the vibration signal providing a magnitude, a phase, and a frequency of the detected vibration. Controller  22  generates a vibration reference signal from the detected vibration data and correlates it to the relative vibration of the particular structure carrying CFGs  20  relative to the CFGs  20 . 
         [0042]    Preferably, the first CFG  20  includes the first imbalance mass  32   a  controllably driven about a first mass axis  42  with a first controllable imbalance phase φ 1  and a second imbalance mass  32   b  controllably driven about a second mass axis  44  with a second controllable imbalance phase φ 2 , the first controllable imbalance phase φ 1  and the imbalance phase φ 2  controlled in reference to the vibration reference signal. The m th  CFG  20  includes a first imbalance mass (mass m     —     1 )  32   a  controllably driven about a first mass axis  42  with a first controllable imbalance phase and a second imbalance mass  32   b  controllably driven about a second mass axis  44  with a second controllable imbalance phase, the imbalance phase and the imbalance phase controlled in reference to the vibration reference signal. The vibration reference signal is typically an artificially generated signal within the controller and is typically a sine wave at the desired operational frequency. 
         [0043]    Referring to  FIGS. 5A-8 , CFG  20  includes a first imbalance mass  32   a  with a first controllable imbalance phase φ 1  and a second imbalance mass  32   b  with a second controllable imbalance phase φ 2 . The first imbalance mass  32   a  is driven with first motor  38   a  and second imbalance mass  32   b  is driven with second motor  38   b.    
         [0044]    Referring to  FIGS. 6 and 7 , an embodiment implementing CFG  20  as two identical, but separate, units  46  is illustrated. Each unit  46  contains a single imbalanced mass  32  driven by a single motor  38 . By positioning the two units  46  in close proximity, the functionality of CFG  20  is achieved.  FIGS. 6 and 7  show additional embodiments of CFG  20 . In these figures, only one of two units  46  comprising CFG  20  is shown. The same basic elements previously described are identified in the embodiments shown in  FIGS. 6 and 7 . Two units  46  may be applied to a mechanical device in proximity to one another to enable CFG  20 . For example, two units  46  may be applied coaxially on either side of mounting plate to enable CFG  20  as illustrated in  FIG. 9 . In another example illustrated in  FIG. 10 , two units  46  are mounted non-coaxially side-by-side to enable CFG  20 . 
         [0045]    Other embodiments of the current invention will be apparent to those skilled in the art from a consideration of this specification or practice of the invention disclosed herein. Thus, the foregoing specification is considered merely exemplary of the current invention with the true scope thereof being defined by the following claims.