Abstract:
A net rotation speed control system for an oscillatory shaker head assembly driven by a force-balance drive carried on a crop harvester has a harvester forward velocity signal input. Also provided is an operator input for selecting appropriate speed relationship between the harvester velocity and the net shaker head rotation velocity. The system is useful as an open loop system, but is improved to correct for otherwise uncontrolled operating conditions by incorporating a speed sensor for net shaker head rotation velocity and closing the loop by connecting an output from the net rotation speed sensor to the control system.

Description:
SUMMARY OF THE INVENTION  
         [0001]    The invention disclosed herein relates to an apparatus for controlling net rotation speed of an oscillating shaker head produced by an oscillatory driver operating to drive the shaker head about an oscillation axis for contacting foliage of vines, bushes and trees to dislodge crops therefrom. The oscillating shaker head is mounted on a mobile vehicle for moving at a controlled speed past and proximate to the foliage. The apparatus includes means for sensing the controlled speed of the mobile vehicle, wherein the means for sensing provides a vehicle speed proportional signal. Also included is means for receiving the vehicle speed proportional signal and for providing a shaker head control signal related to vehicle speed. Further, means is provided for receiving the shaker head control signal and for providing a predetermined control torque about the oscillation axis of the shaker head so that net rotation speed of the oscillating shaker head is controlled relative to the speed of the mobile vehicle.  
           [0002]    The invention disclosed herein also relates to an apparatus for controlling net rotation speed of an oscillating shaker head produced by an oscillatory driver operating to drive the shaker head about an oscillation axis for contacting foliage of vines, bushes and trees to dislodge crops therefrom. The oscillating shaker head is mounted on a mobile vehicle for moving at a controlled speed past and proximate to the foliage. The apparatus includes means for sensing the controlled speed of the mobile vehicle, wherein the means for sensing provides a vehicle speed proportional signal. Also included is means for receiving the vehicle speed proportional signal and for providing a braking signal related to vehicle speed. Further, means is provided for receiving the braking signal and for providing braking resistance about the oscillation axis of the shaker head so that net rotation speed of the oscillating shaker head is controlled relative to the speed of the mobile vehicle.  
           [0003]    In another aspect of the invention a harvesting vehicle moves over an underlying surface at a controlled speed and carries a force balance crop shaker head having a drive mechanism connected to drive a shaker drum assembly in an oscillatory manner about a rotation axis. The drive mechanism operates to drive the shaker drum assembly to produce a net shaker drum rotation speed. The shaker drum assembly operates to engage foliage on a crop for dislodging the crop therefrom. A speed sensor on the harvesting vehicle is provided for sensing the controlled speed and for providing a vehicle speed indicative signal. Means is also provided for generating an operator control signal and control means is present for receiving the vehicle speed indicative signal and the operator control signal and for providing a braking signal output corresponding to the received signals. Means receives the braking signal for providing an operator controlled braking action for the shaker drum assembly rotation about the rotation axis. In this manner, net shaker drum rotation speed is operator controlled relative to the harvesting vehicle controlled speed.  
           [0004]    The invention further includes a method for controlling net rotation speed of an oscillating shaker head in a crop harvester for dislodging crops from crop foliage, wherein the net rotation speed is produced about an oscillation axis by an oscillatory driving mechanism for the shaker head. The harvester is moved at a controlled speed past and proximate to the crop foliage. The method includes the steps of sensing the speed of the crop harvester and providing a vehicle speed indicative signal corresponding thereto. A further step relates to conversion of the vehicle speed indicative signal into a corresponding shaker head control signal. Subsequently, torque is applied about the oscillation axis corresponding to the shaker head control signal, so that net rotation speed of the oscillating shaker head is controlled relative to the harvester controlled speed.  
           [0005]    The invention further includes a method for controlling net rotation speed of an oscillating shaker head in a crop harvester for dislodging crops from crop foliage, wherein the net rotation speed is produced about an oscillation axis by an oscillatory driving mechanism for the shaker head. The harvester is moved at a controlled speed past and proximate to the crop foliage. The method includes the steps of sensing the speed of the crop harvester and providing a vehicle speed indicative signal corresponding thereto. A further step relates to conversion of the vehicle speed indicative signal into a corresponding braking signal. Subsequently, braking action is applied about the oscillation axis corresponding to the braking signal, so that net rotation speed of the oscillating shaker head is controlled relative to the harvester controlled speed.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 is a schematic depiction of one embodiment of the system of the present invention.  
         [0007]    [0007]FIG. 2 is a block diagram of another embodiment of the present invention.  
         [0008]    [0008]FIG. 2A shows a variation from the embodiment of FIG. 2.  
         [0009]    [0009]FIG. 3 is a block diagram of an additional embodiment of the present invention.  
         [0010]    [0010]FIG. 3A is a detail from the embodiment of FIG. 3.  
         [0011]    [0011]FIG. 3B shows a variation from the embodiment of FIG. 3A.  
         [0012]    [0012]FIG. 4A is a flow diagram showing the method of the present invention.  
         [0013]    [0013]FIG. 4B is a flow diagram showing a variation of the method of the present invention.  
         [0014]    [0014]FIG. 5 is a partial view illustrating one set of operating conditions in which the invention functions.  
         [0015]    [0015]FIG. 6 is a partial view illustrating another set of operating conditions in which the invention functions.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    Force balance type shakers having tines for extending into and engaging the foliage of vines, bushes and trees to dislodge a crop therefrom are typified by the harvesting shaker shown and described in U.S. Pat. No. 4,341,062, issued Jul. 27, 1982. Foliage shakers such as depicted in the &#39;062 patent are used on olive and tomato harvesters, and have a drive motor for driving an eccentric weight assembly. Apart from driving the foliage shaker in an oscillatory fashion about an oscillation axis, the drive motor creates a torque in the tine or brush assembly that causes the oscillating brush assembly or shaker head to accelerate in one rotational direction about the oscillation axis and ultimately to rotate out of control. The one rotational direction is in the same direction of rotation as that in which the eccentric weight assembly is driven. To counteract the tendency for the shaker head to rotate in one direction at motor drive speed a brake is used to brake the unidirectional rotation of the brush assembly in the shaker head. The braking action is applied on the shaker head oscillation axis. Coulomb friction is applied through the use of a band, drum or disc brake. Another approach is to use a viscous friction brake such as a hydraulic pump or motor connected to the shaker&#39;s center axle. A manually operated flow control valve located downstream from the drive motor is sometimes used to limit oil flow therethrough and to thus reduce rotation of the shaker head about the rotation axis. The drive motor may be a hydraulic pump or a hydraulic motor.  
         [0017]    To this point there has been no “smart brake” capable of preventing the aforementioned uncontrolled rotation about the shaker head axis without reducing the necessary oscillation to obtain the function of the shaker head. When mechanical brakes are used, the braking friction generates heat and the brakes tend to fade upon heating and also to wear. When a viscous friction type brake utilizing a hydraulic pump or motor is used, braking characteristics tend to change as the hydraulic oil heats and changes viscosity. For a given friction brake setting, braking action is not as effective as shaker head oscillation speed or frequency increases. No means has been available to compensate for these undesirable characteristics. Further, if shaker net rotation at the tips of the shaker tines that penetrate the foliage of the crop is not synchronized within certain limits with the forward speed of the harvester, tree or foliage damage occurs. If the net rotation speed of the shaker is appreciably beyond those limits, faster or slower than the harvester forward ground speed, branches are broken, leaves are stripped, future crop yields are reduced and the harvester must separate extra trash from the harvested crop. Harvesters available previous to the instant invention have not effectively addressed these problems accompanying the use of an oscillatory force balance shaker head.  
         [0018]    With reference now to FIG. 1 of the drawings, one embodiment of the invention disclosed herein will be described. The harvester  10  is shown in general outline in FIG. 1 supported by a pair of wheels  11  and  12  so that the harvester may be advanced along an underlying surface  13 . A shaker head  14  is shown mounted in bearings  16  and  17  so that the shaker head is journaled for rotation within the framework of the crop harvester  10 . A series of tines  14   a  is seen extending laterally from the shaker head  14  in FIG. 1, wherein the tines operate to penetrate the foliage of vines, bushes or trees carrying a crop to be harvested therefrom. Mounted also on the framework of the crop harvester  10  is a known force balance mechanism  18  having contra-rotating weights driven by a motor and found collectively in the item  18 . As mentioned hereinbefore, the driver for the force balance assembly  18  that drives the shaker head  14  in an oscillatory manner about a shaker head axis  19  in FIG. 1 is disclosed in the &#39;062 patent issued to Scudder in July, 1982. A ground speed sensor  21  is shown mounted adjacent an axle on which supporting wheel  11  is mounted to provide a signal indicative of vehicle forward velocity. The signal from sensor  21  is delivered through a line  22  to a controller  23 . The controller  23  produces an output signal, which may be termed a shaker head control signal, that is connected to a metering device  24  as seen in FIG. 1. The shaker head control signal is termed a braking signal in one aspect of the invention and a torque-enhancing signal in another aspect of the invention. In general it is called an imposed torque signal in this description. A control torque element  26  is shown in FIG. 1 mounted on the axis of oscillation  19  of the shaker head  14 . Connection is made between the control torque element  26  and the metering element  24  so that the metering element is situated in a path between the control torque element  26  and a power source  27 . In FIG. 1 the metering element is situated upstream of the control torque element  26  for a purpose to be described herein. The power source  27  is utilized to drive the force balance mechanism  18  as well as, in the FIG. 1 embodiment, the control torque element  26 . Power to the force balance mechanism  18  is not affected by the metering element because they are in parallel paths, as may be seen in FIG. 1. As a result, the torque imposed by element  26  on the oscillatory motion of the shaker head  14  about the oscillation axis  19  is controlled by the metering element  24  receiving the shaker head control signal from controller  23  so that the imposed torque is selectively controlled relative to the forward speed of the harvester  10  over the underlying surface  13 .  
         [0019]    In addition to the harvester ground speed input, an operator input is provided at a control point  28  in FIG. 1 for control  23 . In this instance, the shaker head control signal output from control  23  is a combination of the harvester velocity signal from sensor  21  and the manual input at  28  provided by an operator of the harvester  10 . The net rotation speed of the harvester shaker head  14  is then a function of harvester velocity and harvester operator input.  
         [0020]    Continuing reference to FIG. 1 of the drawings shows a second speed sensor  29  mounted adjacent to a portion of a shaft  31  on the oscillation axis  19  of the shaker head  14 . The speed sensor  29  functions to sense the speed of the shaft  31  about the axis  19 . In a preferred embodiment, the speed or velocity sensors  29  and  21  provide a frequency output proportional to the sensed speed. In this fashion the speed sensor  29  is able to detect net rotation speed of the oscillatory shaker head  14  and the direction of the net speed about the oscillation axis  19 . The speed of interest is the speed near the free ends of the tines  14   a,  the tangential tine tip speed. For example, a speed sensed providing ten pulses per second forward and eight pulses per second backward provides an indication of net angular rotation speed for the shaker head assembly  14  in the forward direction of two pulses per second. This of course is converted to tangential tine tip velocity to indicate the net velocity near the tine tips on the shaker head assembly. Consequently, when the controller  23  is set to provide a forward/backward signal difference of three pulses per second, the controller will adjust the signal to the metering element  24  to eliminate the one pulse per second error and provide a three pulses per second difference between the forward and the backward oscillatory rotational speeds sensed by the speed sensor  29 .  
         [0021]    It may be seen that the simplest embodiment, wherein only a ground speed signal from sensor  21  is connected to the control  23 , allows the system to function open loop. The presumption here is that for a given metered amount of power from the power source  27  by the metering element  24  the shaker head assembly  14  will rotate at a known and repeatable speed. However, changing conditions, lumped herein within the term “uncontrolled operating conditions”, tend to change the rotational frequency and amplitude of the oscillatory shaker head assembly  14 . The specific uncontrolled operating conditions will be discussed in conjunction with specific embodiments of the invention discussed hereinafter.  
         [0022]    With regard to one specific embodiment of the present invention, attention is drawn to FIG. 2. Item numbers in FIG. 2 corresponding to items numbers described in conjunction with FIG. 1 will be assigned a suffix “a”. The ground speed signal for the harvester  10  is picked up adjacent a wheel  21   a  in FIG. 2 seen traversing the underlying surface or ground  13 . Ground speed detector  21   a  transmits the ground speed signal through line  22   a  to controller  23   a.  The resultant shaker head control signal, called a braking signal in this embodiment, is connected to metering control  24   a  that is seen in FIG. 2 placed downstream in series with control torque element termed braking element  26   a , which in this embodiment is a hydraulic motor or pump. Such a device may be driven by hydraulics as a motor or may be driven by mechanical input at its shaft and function as a hydraulic pump. Even though the device may work as both a motor and a pump, it will be designed to operate optimally as one or the other. A hydraulic motor primary design is preferred in this instance, because a motor allows more “slip” due to comparatively less efficient construction and greater internal leakage in the motor. The motor/pump braking element  26   a  in FIG. 2 is seen coupled to the oscillation axis  19  for shaker head assembly  14 . The metering element  24   a  in FIG. 2 is a hydraulic flow control valve that allows a measured amount of oil to flow through it in accordance with the shaker head control output signal from controller  23   a  resulting from input of the ground speed control signal from sensor  21   a . Motor/pump  26   a , acting as a pump in this embodiment, has its pump output connected to the flow control valve  24   a . Shaker rotation is thus controlled to correspond to harvester  10  ground speed by limiting flow through the hydraulic flow control  24   a , and therefore pump net oscillatory speed, in accordance with the vehicle ground speed. The hydraulic open loop system is powered by the motor  26   a  acting as a hydraulic pump. When motor  26   a  acts as a pump, it is the power producing element in the isolated hydraulic system containing a hydraulic oil reservoir  30  in FIG. 2. As just described, the system functions adequately in theory without consideration of uncontrolled operating conditions, such as change in internal clearances in motor  26   a  due to temperature change or changes in the temperature of the hydraulic oil and the attendant viscosity in accordance with any particular temperature. Lower hydraulic oil viscosity from higher oil temperatures allows more internal motor slip in the hydraulic motor  26   a , thereby affording increased rotational speed for the shaker head  14  as hydraulic oil temperature increases for a given setting in the hydraulic flow control valve  24   a.    
         [0023]    [0023]FIG. 2 also shows an operator input at  28   a  to the controller  23   a  that is combined with the ground speed signal from ground speed detector  21   a  to provide a shaker head control or braking signal output from the controller  23   a  connected to the hydraulic flow control valve  24   a  In this fashion, the operator has some control over the aforementioned change of speed of rotation about the shaker head assembly axis  19  due to temperature caused change in the hydraulic oil allowed to pass through the hydraulic motor  26   a  by the hydraulic flow control valve  24   a  or change in internal clearances in motor  26   a  An operator through the input  28   a  may therefore implement manual compensation.  
         [0024]    Closure of the control loop is implemented in the embodiment of FIG. 2 by providing the speed sensor  29   a  described herein to detect the net speed of oscillatory motion about the oscillation axis  19  for the shaker head assembly  14 . The signal generated by the speed sensor  29   a  is also connected to the controller  23   a  so that a difference between the ground speed signal from sensor  21   a  and the net shaker head oscillation speed signal obtained from the sensor  29   a  is held to a particular value by the controller  23   a  as it is selected at the operator input  28   a . As explained hereinbefore, if the difference is three cycles per second (both sensor signals being in form of frequency outputs proportional to speed), a variation from the three cycle setting will be corrected by speeding up or slowing down the braking element represented by the hydraulic motor  26   a  in FIG. 2. There may be instances where it is desirable to control the tine  14   a  tip speed to be greater than or less than the forward speed of the harvester  10  over the underlying surface  13 . Desirable characteristics such as net tine tip speed rotation being equal to, greater than or less than the harvester forward ground speed are dependent upon the type of crop being harvested and the characteristics of the foliage carrying that crop.  
         [0025]    Accumulators  33  and  34  are seen in FIG. 2 that tend to facilitate oscillation in the shaker head  14  without relying on slip within the motor  26   a . This feature is installed to reduce heat generated by motor slip as well as to reduce hydraulic motor wear and to afford increase in oscillation amplitudes where desirable, in the shaker head assembly  14 .  
         [0026]    Another uncontrolled operating condition exists within the flow control valve  24   a  A flow control valve  24   a  that operates well in a preferred embodiment is an electronically adjustable proportional pressure compensated valve, that is a two port, five gallon per minute valve provided by J. B. Rand Hydraulics of Omaha, Nebraska. The valve is shown m FIG. 2A functioning in series with the hydraulic motor  26   a . As in FIG. 2, the valve  24   a  receives a shaker head control signal  25   a , termed the “braking signal” in the embodiment of FIG. 2, but better called the imposed torque signal in the embodiment of FIG. 2A as discussed previously. The imposed torque signal is produced by the controller  23   a  upon reception and combination of the harvester velocity signal from sensor  21   a  and either or both of the operator control signal from point  28   a  and the shaker head assembly  14  net rotational speed signal from sensor  29   a . A distinction between the systems of FIGS. 2 and 2A is noted wherein the flow control valve  24   a  is now upstream of the motor pump  26   a  and a hydraulic power source  27   a  has a pressure side connected to an input on the flow control valve. The flow control valve output is now connected to the input side of the motor  26   a  in FIG. 2A and is able to drive the motor to produce tine tip speeds higher than harvester ground speed if required. The hydraulic path containing the flow control valve is parallel to the path containing the force balance mechanism  18 . The system of FIG. 2A compensates for all errors contributed by system components including those from oil viscosity changes that increase slip in the braking motor  26   a  as well as inaccuracies in the flow control valve  24   a . As a result, rotation of the shaker head assembly  14  is adjustable to be proportional to the ground speed of the harvester  10 . Moreover, net rotation speed of the oscillating shaker head assembly  14  is adjustable to assume a speed at the portions of the shaker tines within the crop foliage anywhere within the range of 90 percent to 110 percent of harvester ground speed according to the requirements of the crop being harvested. When the net tine tip speed or net rotational speed of the shaker head is referenced relative to the forward ground speed of the harvester  10 , the referenced speed is the net speed of the shaker head assembly tines within the crop being harvested.  
         [0027]    [0027]FIG. 3 shows a system wherein the advantages of the invention disclosed herein are obtained using electrically powered components and a suitable electrical speed control. A “b” will be used in FIG. 3 to designate similar functional elements described in conjunction with FIG. 1 that appear in the electrical system of FIG. 3. A metering element  24   b  in FIG. 3 is shown in FIG. 3A as a rheostat  24   b  connected between an electrical power supply  27   b  and an electric motor/generator  26   b . The motor/generator is connected to the oscillatory axis  19  as shown for providing an imposed torque, which will be termed a braking action to the oscillation of the shaker head assembly  14  in the embodiment of FIG. 3A. A vehicle speed pickup  21   b  as described hereinbefore is delivered through a line  22   b  to a controller  23   b . The controller  23   b  provides a braking output signal  25   b  connected to the metering element  23   b , in this instance the aforementioned rheostat, as seen in FIG. 3A. As a result an open loop system is provided for a harvester  10  that controls the rotational speed of the shaker head assembly  14  to correspond to the forward velocity of the harvester  10  over the underlying surface  13 . This open loop system suffers from similar deficiencies caused by uncontrolled operating conditions, as does the open loop system discussed in conjunction with the description of FIG. 2.  
         [0028]    [0028]FIG. 3 also shows an operator input  28   b  connected to the controller  23   b . The operator control input is combined with the harvester velocity input from speed sensor  21   b  to provide a braking signal output  25   b  from the controller  23   b  to adjust the electrical metering element  24   b  to provide the desired power to the motor/generator  26   b . In this fashion, the electrical system described thus far has the ability to provide a net speed on the portions of the tines  14   a  within the crop foliage that is proportional to the forward velocity of the harvester  10  plus or minus an adjustable amount inputted by an operator at the point  28   b . The system thus far described is still open loop and subject to uncontrolled operating conditions as described hereinbefore.  
         [0029]    [0029]FIGS. 3 and 3A also show a speed sensor  29   b  providing the shaker head speed signal discussed hereinbefore as an additional input to the controller  23   b . The signals from sensors  21   b  and  29   b  together with the operator input signal from  28   b  are combined within the controller  23   b  to provide the braking output signal  25   b  connected to electrical metering device  24   b . In this instance, the rheostat  24   b  seen in FIG. 3A represents electrical metering device  24   b . Electrical metering device  24   b  therefore provides power to motor generator  26   b  sufficient to control net rotation speed of the tines within the crop foliage that is dependent on the forward velocity of the harvester  10  and is corrected by the net rotation speed sensed at the shaker head assembly  14 . Net tine tip velocity is therefore controlled in accordance with the greater or lesser comparative velocities selected by the operator through the point  28   b . The system of FIG. 3 therefore is able to adjust the net rotation of the shaker head assembly tines  14   a  so that the net rotation speed is set at a selected proportion of the ground speed of the harvester  10 . Further, the closed loop embodiment of the system of FIG. 3 containing the speed sensor  29   b  has the capability of maintaining a ratio between harvester ground speed and net tine rotation speed within a predetermined range as determined by an operator of the harvester.  
         [0030]    [0030]FIG. 3B depicts the electrical embodiment of the present invention that corresponds somewhat to the hydraulic embodiment of FIG. 2A. The arrangement of FIG. 3B is similar to that of FIG. 3A, but illustrates conditions wherein a higher potential is available from rheostat  24   b  for application to the terminals of motor/generator  26   b  than was available in the embodiment of FIG. 3A. The function of the embodiment of FIG. 3B is to afford adjustment of the shaker head control signal to obtain tine  14   a  tip net velocities of from 90% to as high as 110% of harvester ground velocity. As in the embodiment of FIG. 2A, the signal  25   b  of FIG. 3B is called an imposed torque signal.  
         [0031]    Turning now to FIG. 4A of the drawings, the method of the present invention will be described. The method relates to controlling net rotation speed of an oscillating shaker head in a crop harvester that is used for dislodging crops from crop foliage. The net rotation of the shaker head and the speed thereof is produced about an oscillation axis by an oscillatory driving mechanism for the shaker head as previously described. The harvester is moved at a controlled speed past the crop foliage and proximate thereto. At the start of the process, a speed for the harvester is sensed by the aforementioned magnetic pickup type speed sensor  21  positioned adjacent one of the harvester wheels (item  11  in FIG. 4A). The sensed harvester speed is continually scanned and sent to a control  23  where it is converted into a head control signal  25 . The head control signal is applied to a torque control, item  24 , termed a metering element in FIG. 1, that is used to urge a predetermined torque application about the oscillation axis  19  through the control torque element  26 , described hereinbefore. In this fashion net rotation speed of the oscillating shaker head is controlled relative to a controlled harvester speed.  
         [0032]    The method described in conjunction with FIG. 4A also includes an operator-controlled input at  28 , corresponding to the input  28  in FIG. 1. The operator input is combined in the controller  23  with the speed sensed signal from sensor  21  and provided as an output from the controller  23 , seen in FIG. 4A as the head control signal  25 . In this fashion, while the system is yet operating open loop, the operator is able to exercise some control over the relationship between the net rotation speed of the tines on the shaker head assembly  14  and the forward speed of the harvester  10 . Uncontrolled operating conditions may cause the operator to find it necessary to occasionally readjust operator input  28  to maintain the desirable relationship between harvester forward speed and shaker head net rotational speed.  
         [0033]    Further, in accordance with the diagram of FIG. 4A it is seen that the speed sensor  29  described in conjunction with FIG. 1 is present. The method includes the step of sensing the net rotation speed of the oscillating shaker head and providing a corresponding net rotation speed indicative signal to the control  23 . The harvester forward velocity signal, the operator input signal and the sensed net rotation speed of the oscillating shaker head signal are combined in control  23  to provide the head control signal  25 . The head control signal  25  is applied to metering or torque control  24  to provide torque control to the control torque element  26  to close the loop and maintain the harvester forward speed and the net rotational speed of the shaker head assembly in a desired predetermined relationship. As mentioned hereinbefore, the control torque element  26  may either be driven externally at a shaft or internally as a motor to fit the circumstances for maintaining control of the shaker head net rotational velocity. FIGS. 2, 2A,  4 A and  4 B provide examples of the manner in which these methods are practiced.  
         [0034]    As seen in FIG. 4B, a more specific embodiment of the method of the present invention is described. Item numbers in FIG. 4B are assigned numbers corresponding to those appearing in FIG. 2. As with the method described in conjunction with FIG. 4A, at the start of the process a speed of the harvester  10  is sensed by an aforementioned magnetic pickup type speed sensor  21   a  positioned adjacent one of the harvester wheels  11   a . The sensed harvester speed is continually scanned and sent to a control position  23   a  where it is converted into a braking signal  25   a . The braking signal is applied to a brake control, item  24   a , termed a metering element in FIG. 1, that is used to urge a braking action about the oscillation axis  19  through a braking element  26   a , described hereinbefore. In this fashion net rotation speed of the oscillating shaker head is controlled relative to a controlled harvester speed.  
         [0035]    The method described in conjunction with FIG. 4B also includes an operator-controlled input  28   a  in FIG. 4B, corresponding to the input point  28  in FIG. 1. The operator input is combined in the controller  23   a  with the speed sensed signal from sensor  21   a  and provided as an output from the controller  23   a , seen in FIG. 4B as the braking signal  25   a . In this fashion, while the system is yet operating open loop, the operator is able to exercise some control over the relationship between the net rotation speed of the tines on the shaker head assembly  14  and the forward speed of the harvester  10 . Uncontrolled operating conditions may cause the operator to find it necessary to occasionally readjust operator input to maintain the desirable relationship between harvester forward speed and shaker head rotational speed.  
         [0036]    Further, in accordance with the diagram of FIG. 4B it is seen that a speed sensor  29   a  similar to that described in conjunction with FIG. 1 is present. The method includes the step of sensing the net rotation speed of the oscillating shaker head and providing a corresponding net rotation speed indicative signal to the control  23   a . The harvester forward velocity signal, the operator input signal and the sensed net rotation speed of the oscillating shaker head signal are combined in control  23   a  to provide the braking signal  25   a . The braking signal  25   a  is applied to metering control or brake control  24   a  to provide braking to the brake element  26   a  to close the loop and maintain the harvester forward speed and the net rotational speed of the shaker head assembly in the predetermined relationship.  
         [0037]    [0037]FIG. 5 illustrates one set of operating conditions for the present invention. The Figure shows crop foliage  36  wherein an oscillating shaker head  14  has a tip on tine  14   a  engaging the foliage. An arrow  37  indicates the direction of travel of the harvester  10  that has the oscillatory shaker head  14  mounted therein as previously described. In FIG. 5 one unbalance weight  38  of a pair of such weights in the known force balance mechanism  18  is shown rotating in a counter clockwise sense. This produces a counter clockwise torque about shaker axis  19  resulting in net oscillating shaker angular velocity indicated by arrow  39 . A drag torque induced by foliage  36  for the indicated velocity  37  of the harvester has the same sense as angular velocity  39 . In the embodiment of FIG. 2, for example, when circumstances are as described for FIG. 5 and control torque is imposed only by pump  26   a , the shaker head may not be able to drive the pump to produce sufficient power to obtain tine  14   a  tip velocity of 110% of harvester speed even when the flow control valve  24   a  is fully open. Additionally, in the example, where it is desirable to obtain a tine  14   a  tip velocity of 90% of harvester velocity in the direction of arrow  37 , the cumulative torque from crop drag and from rotation of weight  38  may be too great to maintain net rotation velocity control even when the flow control valve  24   a  is fully closed. This occurs because of internal “slip” due to leakage in pump/motor  26   a.    
         [0038]    [0038]FIG. 6 shows a solution for the foregoing control maintenance problem. Foliage  36  appears in FIG. 6 and an oscillatory shaker head  14  is shown driven by force balance mechanism  18  having weights, one shown at  38  in FIG. 6, rotating in a clockwise direction. This produces a clockwise torque about shaker axis  19  resulting in net oscillating shaker angular velocity indicated by arrow  41 . This clockwise torque is opposed by crop drag torque due to harvester  10  velocity  37  as indicated in FIG. 6. In the embodiment of FIG. 2A, torque is imposed by element  26   a  acting as a motor driven by outside hydraulic power source  27   a  metered by flow control valve  24   a . In this instance, if it is desirable to set net tine  14   a  rotation velocity so the tine tip travels at 110% of harvester velocity, hydraulic power metered through valve  24   a  to motor  26   a  is more likely to be capable of maintaining net shaker velocity control. When net shaker velocity is set to produce tine  14   a  tip velocity of 90% of harvester velocity, flow control valve  24   a  can meter enough power to motor  26   a  to maintain control of net shaker velocity unless crop drag torque becomes greater than the clockwise imposed rotation torque. When this happens, the motor  26   a  reverts to being a pump. Properly sized elements in the embodiments of FIGS. 2 and 2A will avoid these difficulties, but the embodiment of FIG. 2A possesses the disclosed advantages.  
         [0039]    Although the best mode contemplated for carrying out the present invention has been shown and described herein, it will be understood that modification and variation may be made without departing from what is regarded to be the subject matter of the invention.