CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Provisional Application Ser. No. 60/042,839 filed Mar. 31, 1997 for “Micro Actuator” by Frederick M. Stefansky, Longmont, Colo.; Kenneth J. Altshuler, Boulder, Colo.; Wallis A. Dague, Louisville, Colo. and Provisional Application Ser. No. 60/047,373 filed Jun. 2, 1997 for “Micro-Machine” by Frederick M. Stefansky and Wallis A. Dague. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a flexure microactuator, and more particularly to a high resolution head positioning mechanism having a piezoelectric element for moving a flexure carrying a slider to selectively move the head on the slider radially with respect to a rotatable disc. 
     The density, or radial spacing, between concentric data tracks on magnetic discs continues to increase, requiring greater precision in head positioning. Conventionally, head positioning is accomplished by operating an actuator arm with a large-scale actuator motor, such as a voice coil motor, to position a head on a flexure at the end of the actuator arm. The large-scale motor lacks sufficient resolution to effectively accommodate high track-density discs. Thus, a high resolution head positioning mechanism is necessary to accomplish the more densely spaced tracks. 
     One promising design for high resolution head positioning involves employing a high resolution microactuator in addition to the conventional low resolution actuator motor, thereby effecting head positioning through dual-stage actuation. Various microactuator designs have been considered to accomplish high resolution head positioning. However, these designs all have shortcomings that limit the effectiveness of the microactuator. For example, where the microactuator was implemented directly on the slider, the complexity of slider design was increased and noise generated by the microactuator and by signal paths to it was induced into the head. New fabrication techniques had to be developed to integrate the slider and microactuator into a single structure. Where the microactuator was to be formed by thin-film wafer techniques onto the flexure, the entire flexure assembly had to be redesigned because the microactuator required a silicon substrate support and conventional gimbaling flexures were not constructed of silicon. Where the microactuator was implemented at the head mounting block (where the actuator arm connects to the head suspension load beam), high forces were required from the microactuator to move the mass associated with the head suspension at a speed (frequency) large enough to accommodate rapid track access. If the force was not great enough, the microactuator operated with lower natural frequency than was desirable, and track settling time was sacrificed. Therefore, the prior designs did not present ideal microactuator solutions. 
     There is a need in the art for a simple microactuator design to provide efficient high resolution head positioning in a dual-stage actuation system, that can be implemented by readily available manufacturing processes. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is a mechanism for positioning a transducing head with respect to a selected radial track of a rotatable recording disc in a disc drive. The disc drive includes an actuator arm and a suspension load beam connected to the actuator arm. A plate is hingedly attached to the suspension load beam. A flexure is attached to the plate, and a slider supporting the transducing head is attached to the flexure. A microactuator is attached to the plate, and is operable in response to electrical control signals to move the plate relative to the load beam in the general plane of the load beam to selectively radially position the transducing head proximate to the selected track on the rotatable recording disc. In one form of the invention, the hinged attachment between the load beam and the plate is formed by a hinged portion of the load beam, distortable in response to operation of the microactuator to move the plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top view of a disc drive actuation system for positioning a slider over tracks of a disc. 
     FIG. 2 is a perspective view of a portion of a disc drive system implementing a microactuator assembly at the interface between the load beam and the flexure according to a first embodiment of the present invention. 
     FIG. 3 is a top view of the microactuator assembly shown in FIG.  2 . 
     FIG. 4 is a side view of the microactuator assembly shown in FIG.  2 . 
     FIG. 5 is a section view of the microactuator assembly taken at line  5 — 5  in FIG.  3 . 
     FIG. 6 is a perspective view of a portion of a disc drive system implementing a microactuator assembly at the interface between the load beam and the flexure according to a second embodiment of the present invention. 
     FIG. 7 is a top view of the microactuator assembly shown in FIG.  6 . 
     FIG. 8 is a perspective view of a portion of a disc drive system implementing a microactuator assembly at the interface between the load beam and the flexure according to a third embodiment of the present invention. 
     FIG. 9 is a top view of the microactuator assembly shown in FIG.  8 . 
     FIG. 10 is a perspective view of a portion of a disc drive system implementing a microactuator assembly at the interface between the load beam and the flexure according to a fourth embodiment of the present invention. 
     FIG. 11 is a top view of the microactuator assembly shown in FIG.  10 . 
     FIG. 12 is a perspective view of a portion of a disc drive system implementing a microactuator assembly at the interface between the load beam and the flexure according to a fifth embodiment of the present invention. 
     FIG. 13 is a top view of the microactuator assembly shown in FIG.  12 . 
     FIG. 14 is a diagram of a unimorph bending motor for use with the microactuator assembly of the present invention. 
     FIG. 15 is a diagram of the unimorph bending motor of FIG. 14 in its actuated position. 
     FIG. 16 is a diagram of two complementary unimorph bending motors for use with the microactuator assembly of the present invention. 
     FIG. 17 is a diagram of the two complementary unimorph bending motors of FIG. 16 in their actuated positions. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a top view of a disc drive actuation system  10  for positioning slider  24  over a track  34  of disc  30 . Actuation system  10  includes voice coil motor (VCM)  12  arranged to rotate actuator arm  16  around axis  14 . Head suspension  18  is connected to actuator arm  16  at head mounting block  20 . Flexure  22  is connected to an end of head suspension  18 , and carries slider  24 . Slider  24  carries a transducing head (not shown in FIG. 1) for reading and/or writing data on concentric tracks  34  of disc  30 . Disc  30  rotates around axis  32 , so that windage is encountered by slider  24  to keep it aloft a small distance above the surface of disc  30 . 
     VCM  12  is selectively operated to move actuator arm  16  around axis  14 , thereby moving slider  24  between tracks  34  of disc  30 . However, for disc drive systems with high track density, VCM  12  lacks sufficient resolution and frequency response to position a transducing head on slider  24  over a selected track  34  of disc  30 . Therefore, a higher resolution actuation device is necessary. 
     FIGS. 2-5 illustrate a portion of disc drive system  10  implementing a microactuator assembly at the interface between load beam  18  and flexure  22  according to a first embodiment of the present invention. Lever plate  42  is operatively attached between load beam  18  and flexure  22  to effect high resolution positioning of head  40  on slider  24 . Lever plate  42  includes tab  46  extending through aperture  45  and over the top surface of load beam  18 . Tab  48  on load beam  18  provides a landing at the same general plane as the landing formed by tab  46 . Piezoelectric element  44  is mounted to and connected between tab  46  and tab  48 . 
     A plurality of apertures  50  are formed, such as by etching or punching, in load beam  18  to form hinges  52  in the structure of load beam  18 . Lever plate  42  is attached to load beam  18  proximate to hinges  52  by welded joints  53 . Aperture  56  extends through load beam  18 , lever plate  42  and flexure  22 , and permits registration of the actuator assembly. Flexure  22  is rigidly attached to lever plate  42  along the length of the plate  42 . 
     Tab  58  is optionally provided on lever plate  42 , protruding through aperture  54  in load beam  18 , and includes a dampening material beneath it to reduce the effects of vibrations on the microactuator assembly, both vertically and in the plane of slider actuation. Tongue  27  of flexure  22  is attached to slider  24 , supporting the slider and permitting flexibility of elevation of the slider. Load beam  18  applies a load to slider  24  through lever plate  42  and tongue  27  of flexure  22  at load point  60 , ensuring that head  40  is maintained in close proximity with the surface of disc  30 . 
     In operation, after coarse positioning has been accomplished by VCM  12  (FIG.  1 ), a voltage is applied to piezoelectric element  44  by two leads (not shown) to selectively cause expansion or contraction of the element. Tab  48  of load beam  18  is effectively a fixed or restrained point, while tab  46  of lever plate  42  is effectively a movable or unrestrained point, so that expansion and contraction of piezoelectric element  44  results in movement of tab  46  in the direction indicated by arrows  62 . This linear movement of tab  46  of lever plate  42  is translated into arcuate rotational motion by the arrangement of hinges  52  of load beam  18 . A linear force on tab  46  in the direction of arrows  62  forces hinges  52  to distort and bend, because of the connection between lever plate  42  and load beam  18  at aperture  56 . The distortion of hinges  52  causes lever plate  42  and flexure  22  to rotate on the axis of aperture  56 , resulting in arcuate displacement of transducing head  40  at the trailing edge of slider  24  in the direction indicated by arrows  64 , in the general plane of load beam  18 . The motion of head  40  is extremely small and precisely controllable by the expansion and contraction of piezoelectric element  44 , thereby allowing head  40  to be finely positioned over a selected radial track of a rotating disc. 
     FIG. 6 is a perspective view, and FIG. 7 is a top view of a portion of disc drive system  10  implementing a microactuator assembly at the interface between load beam  18  and flexure  22  according to a second embodiment of the present invention. Lever plate  70  is attached to load beam  18  and flexure  22  to effect high resolution positioning of head  40  on slider  24 . Lever plate  70  includes bent flaps  72   a  and  72   b  extending perpendicular to the general plane of load beam  18 . Piezoelectric element  74   a  is mounted to flap  72   a,  forming a unimorph bending motor, the operation of which is discussed below with respect to FIGS. 14 and 15. In an optional embodiment, piezoelectric element  74   b  is mounted to flap  72   a  opposite piezoelectric element  74   a  to form a second complementary unimorph bending motor, the operation of which is discussed below with respect to FIGS. 16 and 17. In another optional embodiment, piezoelectric elements  74   c  and  74   d  are mounted to opposite sides of flap  72   b,  thereby forming two pairs of complementary unimorph bending motors on both flaps  72   a  and  72   b.  Piezoelectric elements  74   a,    74   b,    74   c  and  74   d  are preferably formed and terminated prior to attachment to flaps  72   a  and  72   b,  and are preferably insulated from flaps  72   a  and  72   b  by an insulating adhesive, for example. 
     Aperture  81  is formed in load beam  18  to leave an extension tab portion  79  connected to a distal end of load beam  18  by narrow hinge  80 . Aperture  78  is formed through extension tab portion  79  of load beam  18 , lever plate  70  and flexure  22  to permit registration of the actuator assembly. Tab  76  on load beam  18  provides a landing on a plane parallel to the plane of load beam  18 . Cross beam  77  of lever plate  70  is rigidly attached to tab  76  at welded joints  82 , and lever plate  70  is also rigidly attached to extension tab portion  79  of load beam  18  at welded joints  84 . Flexure  22  is rigidly attached to lever plate  70  along the length of the plate  70 . Flexure  22  may include a tongue, like tongue  27  in the embodiment shown in FIGS. 2-5, attached to slider  24  to support the slider and permit flexibility of elevation of the slider. Load beam  18  applies a load to slider  24  through lever plate  70  and flexure  22  at load point  60 , ensuring that head  40  is maintained in close proximity with the surface of disc  30 . 
     In operation, after coarse positioning has been accomplished by VCM  12  (FIG.  1 ), a voltage is applied across piezoelectric element  74   a  to selectively cause expansion or contraction of the element. Tab  76  of load beam  18  is effectively a fixed or restrained point while extended tab portion  79  of load beam  18  is effectively a movable or unrestrained point due to the hinging effect of hinge  80 , so that expansion and contraction of piezoelectric element  74   a  to apply force to flap  72   a  results in bending of hinge  80 . The distortion of hinge  80  causes lever plate  70  and flexure  22  to rotate on an axis at hinge  80 , resulting in arcuate displacement of transducing head  40  at the trailing edge of slider  24  in the direction indicated by arrows  86 , in the general plane of load beam  18 . The motion of head  40  is extremely small and precisely controllable by the expansion and contraction of piezoelectric element  74   a  and the resulting bending of hinge  80 , thereby allowing head  40  to be finely positioned over a selected radial track of a rotating disc. The detailed operation of piezoelectric element  74   a  (for a single unimorph configuration) and of piezoelectric elements  74   a  and  74   b,  and  74   c  and  74   d  (for a complementary dual unimorph configuration) is discussed below with respect to FIGS. 14 and 15 and FIGS. 16 and 17, respectively. 
     FIG. 8 is a perspective view, and FIG. 9 is a top view of a portion of disc drive system  10  implementing a microactuator assembly at the interface between load beam  18  and flexure  22  according to a third embodiment of the present invention. Lever plate  70  is attached to load beam  18  and flexure  22  to effect high resolution positioning of head  40  on slider  24 . Lever plate  70  includes bent flaps  72   a  and  72   b  extending perpendicular to the general plane of load beam  18 . Piezoelectric element  74   a  is mounted to flap  72   a,  forming a unimorph bending motor, the operation of which is discussed below with respect to FIGS. 14 and 15. In an optional embodiment, piezoelectric element  74   b  is mounted to flap  72   a  opposite piezoelectric element  74   a  to form a second complementary unimorph bending motor, the operation of which is discussed below with respect to FIGS. 16 and 17. In another optional embodiment, piezoelectric elements  74   c  and  74   d  are mounted to opposite sides of flap  72   b,  thereby forming two pairs of complementary unimorph bending motors on both flaps  72   a  and  72   b.  Piezoelectric elements  74   a,    74   b,    74   c  and  74   d  are preferably formed and terminated prior to attachment to flaps  72   a  and  72   b,  and are preferably insulated from flaps  72   a  and  72   b  by an insulating adhesive, for example. 
     Load beam  18  includes an aperture  81  and an extension tab portion  79  connected to a distal end of load beam  18  by narrow hinge  80  and extending distally away from load beam  18 . Apertures  78  are formed through load beam  18  at the distal end and through extension tab portion  79  of load beam  18 , through lever plate  70  and through flexure  22  to permit registration of the actuator assembly. Tab  76  on load beam  18  provides a landing on a plane parallel to the plane of load beam  18 . Cross beam  77  of lever plate  70  is rigidly attached to tab  76  at welded joints  82 , and lever plate  70  is also rigidly attached to extension tab portion  79  of load beam  18  at welded joints  84 . Flexure  22  is rigidly attached to lever plate  70  along the length of the plate  70 . Flexure  22  may include a tongue, like tongue  27  in the embodiment shown in FIGS. 2-5, attached to slider  24  to support the slider and permit flexibility of elevation of the slider. Load beam  18  applies a load to slider  24  through lever plate  70  at load point  60 , ensuring that head  40  is maintained in close proximity with the surface of disc  30 . 
     In operation, after coarse positioning has been accomplished by VCM  12  (FIG.  1 ), a voltage is applied across piezoelectric element  74   a  to selectively cause expansion or contraction of the element. Tab  76  of load beam  18  is effectively a fixed or restrained point, while extended tab portion  79  of load beam  18  is effectively a movable or unrestrained point due to the hinging effect of hinge  80 , so that expansion and contraction of piezoelectric element  74   a  to apply force to flap  72   a  results in bending of hinge  80 . The distortion of hinge  80  causes lever plate  70  and flexure  22  to rotate on an axis at hinge  80 , resulting in arcuate displacement of transducing head  40  at the trailing edge of slider  24  in the direction indicated by arrows  86 , in the general plane of load beam  18 . The motion of head  40  is extremely small and precisely controllable by the expansion and contraction of piezoelectric element  74   a  and the resulting bending of hinge  80 , thereby allowing head  40  to be finely positioned over a selected radial track of the rotating disc. The detailed operation of piezoelectric element ensuring that head  40  is maintained in close proximity with the surface of disc  30 . 
     In operation, after coarse positioning has been accomplished by VCM  12  (FIG.  1 ). A voltage is applied across piezoelectric element  74   a  to selectively cause expansion or contraction of the element. Tab  77  attached to load beam  18  is effectively a fixed or restrained point, while extended tab portion  79  of load beam  18  is effectively a movable or unrestrained point due to the hinging effect of hinge  80 , so that expansion and contraction of piezoelectric element  74   a  to apply force to flap  72  results in bending of hinge  80 . The distortion  80  causes lever plate  70  and flexure  22  to rotate on an axis at hinge  80 , resulting in arcuate displacement of transducing head  40  at the trailing edge of slider  24  in the direction indicated by arrows  86 , in the general plane of load beam  18 . The motion of head  40  is extremely small and precisely controllable by the expansion and contraction of piezoelectric element  74   a  and the resulting bending of hinge  80 , thereby allowing head  40  to be finely positioned over a selected radial track of the rotating disc. The detailed operation of piezoelectric element  74   a  (for a single unimorph configuration) and of piezoelectric elements  74   a  and  74   b  (for a complementary dual unimorph configuration) is discussed below with respect to FIGS. 14 and 15 and FIGS. 16 and 17, respectively. 
     FIG. 12 is a perspective view, and FIG. 13 is a top view of a portion of disc drive system  10  implementing a microactuator assembly at the interface between load beam  18  and flexure  22  according to a fifth embodiment of the present invention. Lever plate  70  is attached to load beam  18  and flexure  22  to effect high resolution positioning of head  40  on slider  24 . Lever plate  70  includes bent flaps  72   a  and  72   b  extending perpendicular to the general plane of load beam  18 . Piezoelectric element  74   a  is mounted to flap  72   a,  forming a unimorph bending motor, the operation of which is discussed below with respect to FIGS. 14 and 15. In an optional embodiment, piezoelectric element  74   b  is mounted to flap  72   b,  thereby forming two pairs of unimorph bending motors on both flaps  72   a  and  72   b.  In another optional embodiment, which is not shown pictorially in FIGS. 12 and 13 for clarity, additional piezoelectric elements may  74   a  (for a single unimorph configuration) and of piezoelectric elements  74   a  and  74   b,  and  74   c  and  74   d  (for a complementary dual unimorph configuration) is discussed below with respect to FIGS. 14 and 15 and FIGS. 16 and 17, respectively. 
     FIG. 10 is a perspective view, and FIG. 11 is a top view of a portion of disc drive system  10  implementing a microactuator assembly at the interface between load beam  18  and flexure  22  according to a fourth embodiment of the present invention. Lever plate  70  is attached to load beam  18  and flexure  22  to effect high resolution positioning of head  40  on slider  24 . Lever plate  70  includes bent flap  72  extending perpendicular to the general plane of load beam  18 . Piezoelectric element  74   a  is mounted to flap  72 , forming a unimorph bending motor, the operation of which is discussed below with respect to FIGS. 14 and 15. In an optional embodiment, piezoelectric element  74   b  is mounted to flap  72  opposite piezoelectric element  74   a  to form a second complementary unimorph bending motor, the operation of which is discussed below with respect to FIGS. 16 and 17. Piezoelectric elements  74   a  and  74   b  are preferably formed and terminated prior to attachment to flap  72 , and are preferably insulated from flap  72  by an insulating adhesive, for example. 
     Load beam  18  includes an aperture  81  and an extension tab portion  79  connected to a distal end of load beam  18  by narrow hinge  80  and extending distally away from load beam  18 . Apertures  78  are formed through load beam  18  at the distal end and through extension tab portion  79  of load beam  18 , through lever plate  70  and through flexure  22  to permit registration of the actuator assembly. Tab  77  of lever plate  70  is rigidly attached to load beam  18  at welded joint  82 , and lever plate  70  is also rigidly attached to extension tab portion  79  of load beam  18  at welded joints  84 . Flexure  22  is rigidly attached to lever plate  70  along the length of the plate  70 . Flexure  22  may include a tongue, like tongue  27  in the embodiment shown in FIGS. 2-5, attached to slider  24  to support the slider and permit flexibility of elevation of the slider. Load beam  18  applies a load to slider  24  through lever plate  70  at load point  60 , be mounted to flaps  72   a  and  72   b  opposite piezoelectric elements  74   a  and  74   b  to form complementary unimorph bending motors, the operation of which is discussed below with respect to FIGS. 16 and 17. Piezoelectric elements  74   a  and  74   b  are preferably formed and terminated prior to attachment to flaps  72   a  and  72   b,  and are preferably insulated from flaps  72   a  and  72   b  by an insulating adhesive, for example. 
     Load beam  18  includes an extension tab portion  79  connected to a distal end of load beam  18  by narrow hinge  80  and extending distally away from load beam  18 . Apertures  78  are formed through load beam  18  at the distal end and through extension tab portion  79  of load beam  18 , through lever plate  70  and through flexure  22  to permit registration of the actuator assembly. Cross beam  77  of lever plate  70  is rigidly attached to load beam  18  at welded joint  82 , and lever plate  70  is also rigidly attached to extension tab portion  79  of load beam  18  at welded joints  84 . Flexure  22  is rigidly attached to lever plate  70  along the length of the plate  70 . Flexure  22  may include a tongue, like tongue  27  in the embodiment shown in FIGS. 2-5, attached to slider  24  to support the slider and permit flexibility of elevation of the slider. Load beam  18  applies a load to slider  24  through lever plate  70  at load point  60 , ensuring that head  40  is maintained in close proximity with the surface of disc  30 . The configuration of lever plate  70  shown in FIGS. 12 and 13, with bent flaps  72   a  and  72   b  extending along the outside of load beam  18 , allows a standard load beam  18  to be used, including its associated registration apertures, simplifying the process required to implement the microactuator. 
     In operation, after coarse positioning has been accomplished by VCM  12  (FIG.  1 ), a voltage is applied across piezoelectric element  74   a  to selectively cause expansion or contraction of the element. Cross beam  77  attached to load beam  18  is effectively a fixed or restrained point, while extended tab portion  79  of load beam  18  is effectively a movable or unrestrained point due to the hinging effect of hinge  80 , so that expansion and contraction of piezoelectric element  74   a  to apply force to flap  72   a  results in bending of hinge  80 . The distortion of hinge  80  causes lever plate  70  and flexure  22  to rotate on to opposite sides of plate  112  by respective insulating adhesives  113   a  and  113   b,  for example, between respective conductive plates  115   a  and  115   b  and plate  112 . Plate  112  is restrained at a proximal end by restraining clamp  118 . Piezoelectric elements  114   a  and  114   b  are poled in opposite directions, as indicated by arrows  116   a  and  116   b.  Terminal  120  connects the surface of piezoelectric element  114   a  opposite plate  112 , and also conductive plate  115   b  (contacting the surface of piezoelectric element  114   b  nearest plate  112 ) to a high potential. Terminal  122  connects the surface of piezoelectric element  114   b  opposite plate  112 , and also conductive plate  115   a  (contacting the surface of piezoelectric element  114   a  nearest plate  112 ) to a lower potential. 
     In operation, when the potential difference between terminals  120  and  122  is applied across piezoelectric elements  114   a  and  114   b,  element  114   a  contracts along its length and element  114   b  expands along its length, forcing bending of the entire apparatus as indicated in FIG.  17 . In this way, deflection at the distal tip of plate  112  may be achieved. Conversely, application of an opposite potential difference between terminals  120  and  122  across piezoelectric elements  114   a  and  114   b  results in opposite bending and opposite deflection at the distal tip of plate  92 . 
     The implementation of lever plates  42  and  70  to radially move along with flexure  22  has several advantages. The movement of plates  42  and  70  and flexure  22  with respect to load beam  18  causes wear on the interface between load beam  18  and the moving part around load point  60 . Employing plates  42  and  70  between load beam  18  and flexure  22  spreads the load forces and absorbs the wear that would otherwise occur on flexure  22  and potentially generate contamination and result in undesirable operating characteristics. Additionally, by designing plates  42  and  70  as separate parts to act as a lever for translating motion of piezoelectric elements  44  and  74   a  into rotational motion of head  40 , a conventional flexure may be used, which is desirable because of the relatively high precision required and already in place in flexure design. 
     Many proposed microactuator designs use cantilevered components with micro-springs and air gaps, which are typically very sensitive an axis at hinge  80 , resulting in arcuate displacement of transducing head  40  at the trailing edge of slider  24  in the direction indicated by arrows  86 , in the general plane of load beam  18 . The motion of head  40  is extremely small and precisely controllable by the expansion and contraction of piezoelectric element  74   a  and the resulting bending of hinge  80 , thereby allowing head  40  to be finely positioned over a selected radial track of the rotating disc. The detailed operation of piezoelectric element  74   a  (for a single unimorph configuration) and of piezoelectric element  74   b  (for a second single unimorph configuration), is discussed below with respect to FIGS. 14 and 15. 
     FIG. 14 is a diagram of a unimorph bending motor  90  in its neutral position, and FIG. 15 is a diagram of unimorph bending motor  90  in its actuated position. Piezoelectric element  94  has a conductive plate  95  forming a contact to its bottom surface, and is attached to plate  92  by an insulating adhesive  93 , for example, between conductive plate  95  and plate  92 . Plate  92  is restrained at a proximal end by restraining clamp  98 . Piezoelectric element  94  is poled in the direction indicated by arrow  96 . Terminal  100  connects the surface of piezoelectric element  94  most distant from plate  92  to a high potential, while terminal  102  connects conductive plate  95  (contacting the surface of piezoelectric element  94  nearest plate  92 ) to a lower potential. 
     In operation, when the potential difference between terminals  100  and  102  is applied across piezoelectric element  94 , the element contracts along its length, forcing bending of piezoelectric element  94  and plate  92  as indicated in FIG.  15 . In this way, a deflection at the distal tip of plate  92  may be achieved. Conversely, application of an opposite potential difference between terminals  100  and  102  across piezoelectric element  94  results in opposite bending and opposite deflection at the distal tip of plate  92 . 
     FIG. 16 is a diagram of complementary dual unimorph bending motors  110  in their neutral position, and FIG. 17 is a diagram of the complementary dual unimorph bending motors  110  in their actuated position. Piezoelectric elements  114   a  and  114   b  have respective conductive plates  115   a  and  115   b  forming contacts to their surfaces nearest plate  112 , and are attached to shock, vibrations, and even complications in the primary actuation process. The flexural pivot of the microactuator of the present invention is realized in the structure of load beam  18 , between the piezoelectric element and slider  24 . This configuration insulates the microactuator from shock and vibrations, by locating the pivot near the center of mass of the microactuating structure, and also allows the pivot to be designed with more stiffness than other microactuator designs, further reducing susceptibility to shock and vibration and improving the frequency (speed) of response of the microactuator. 
     The microactuator assembly is preferably located to minimize the effects of noise and interference from other resonant structures in the disc drive. Implementing the piezoelectric element of the microactuator at the interface between load beam  18  and flexure  22  is effective due to its relatively close proximity to transducing head  40  itself, which is designed in the disc drive to be kept free of interfering noise effects. Realizing the pivot at a point distant from slider  24  allows the motion of the piezoelectric element to be amplified into a greater motion by head  40 ; for example, a motion of piezoelectric element  44  of about 0.1% of its active length is able to alter the position of head  40  by approximately four data tracks (that is, plus or minus two tracks) for a track density of 15,000 tracks per inch. Similarly, where piezoelectric element  74   a  is 0.14 inch in length, the position of head  40  may be altered by approximately four data tracks (that is, plus or minus two tracks) for a track density of 15,000 tracks per inch. 
     The microactuator of the present invention may be constructed using conventional stainless steel sheet metal materials and the conventional processes of stamping, etching, bending and welding miniature components into a form suitable for disc drive components. These processes are well known in the art, and present minimal additional manufacturing difficulty and expense to one skilled in the art. The piezoelectric elements are also simple to manufacture. The present invention therefore provides effective head micropositioning capability with minimal additional complexity and expense compared to conventional designs, as low as 35 cents additional cost per unit. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.
A mechanism is provided to position a transducing bead with respect to a selected radial track of a rotatable recording disc in a disc drive including an actuator arm and a suspension load beam connected to the actuator arm. A plate is hingedly attached to the load beam, and a flexure is attached to the plate. A slider supporting the transducing head is attached to the flexure. A microactuator is attached to the plate and is operable in response to electrical control signals to move the plate relative to the load beam in the general plane of the load beam to selectively position the transducing head proximate to the selected radial track on the rotatable recording disc.