Abstract:
A system for sensing movement comprising an elongate object having a restrained end and an unrestrained end which is free to move in at least two degrees of freedom in response to an applied force, the unrestrained end of the elongated object being configured to move in response to the applied force. An electrically conductive element is disposed on the elongate object and is configured to cooperate with the elongate object in producing a signal usable to determine the magnitude and direction of the movement of the unanchored end due to the applied force. Sensing circuitry is electrically coupled to the electrically conductive element and is configured for processing the signal from the electrically conductive element so as to determine a magnitude and a direction of deformation and produce a signal indicative of the magnitude and direction.

Description:
This application is a DIV of U.S. patent application Ser. No. 10/386,375, filed Mar. 10, 2003 ABN, which is a divisional of U.S. patent application Ser. No. 08/744,381, filed Nov. 7, 1996, now issued as U.S. Pat. No. 6,531,861; which is a DIV of U.S. patent application Ser. No. 08/480,018 filed Jun. 7, 1995, now issued as U.S. Pat. No. 5,594,330; which is a DIV of U.S. patent application Ser. No. 07/898,216 filed Jun. 12, 1992, now issued as U.S. Pat. No. 5,481,184; which is a CIP of U.S. patent application Ser. No. 07/816,628 filed Dec. 31, 1991, now issued as U.S. Pat. No. 5,269,882; which is a CIP of U.S. patent application Ser. No. 07/647,659 filed Jan. 28, 1991, now issued as U.S. Pat. No. 5,106,455. 

   BACKGROUND OF THE INVENTION 
   This invention relates to systems for effecting movement of an object and, in desired applications, sensing the movement of objects, especially of micro-structures. 
   With recent developments in non-planar lithography, the fabrication of micro-structures, including both three-dimensional mechanical parts and three-dimensional electrical components, has become more readily achievable. See, for example, U.S. Pat. No. 5,106,455 and co-pending application, Ser. No. 816,628, filed Dec. 12, 1991. Such micro-structures are finding use in a variety of areas including medical devices, robotics, navigation equipment, motors and similar equipment. It is oftentimes desired in such applications to cause the controlled movement of very small mechanical parts, such as fibers or filaments, and also to detect the movement of mechanical parts, both the degree or extent of such movement and the direction. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide systems for effecting movement in micro-structural elements. 
   It is also an object of the invention to provide systems for detecting or sensing movement of micro-structural elements, including the degree and direction of such movement. 
   It is a further object of the invention to provide such systems which are especially adapted for effecting movement of micro fibers or micro filaments, and for sensing movement therein. 
   The above and other objects of the invention are realized in a specific illustrative embodiment of a movement actuator which includes an elongate fiber, and one or more strips of actuable material disposed on the surface of the side of the fiber. The actuable material is responsive to an actuation signal for changing its shape to thereby cause the fiber to move to accommodate the change in shape of the material. An actuation signal generator is also provided for selectively applying actuation signals to the strip or strips of actuable material to cause them to change shape and thereby cause the fiber to move as desired. 
   The strips of actuable material may be placed lengthwise on the fiber and caused to shorten to thereby cause the fiber to bend. Alternatively, the strips may be placed helically about the fiber and again caused to shorten to thereby cause the fiber to twist. Other patterns for the strips of actuable material may also be provided to cause various kinds of movements of the fiber. 
   The strips of actuable material may be so-called shape memory alloys which change from one shape to another when external heat or an electrical current which causes heat to be generated internally, is applied thereto. When the heat or electrical current is removed and the internally generated heat dissipates, the strips then return to their original shape. Alternatively, the strips of actuable material may be comprised of bimetals, i.e., two layers of different metals with different coefficients of thermal expansion, so that when heated, the strips are caused to change shape and thereby cause movement of the fiber. 
   In accordance with one aspect of the invention, the fibers may be made of a piezoelectric material and the strips of actuable material may consist of conductive elements positioned on the side of the fiber so that as voltage signals are applied to the conductive elements, the fiber is caused to bend. Various patterns of conductive elements could be provided to cause bending of the fiber, shortening or lengthening of the fiber, etc. 
   Alternatively, flexible fibers may be coated with piezoelectric strips so that when voltages are applied to the strip the strips bend and cause the fiber to bend. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the invention will become apparent from a consideration of the following detailed description presented in connection with the accompanying drawings in which: 
       FIGS. 1A and 1B  show schematic, perspective views of two embodiments of an actuator for causing movement of a rod or filament, utilizing shape memory alloys, made in accordance with the principles of the present invention; 
       FIGS. 2A and 2B  show schematic, perspective views of two embodiments of actuators for causing movement of a rod or filament, utilizing piezoelectric materials; 
       FIG. 3  is a schematic, perspective view of a sensor system for sensing movement, both the degree and direction, of a rod or filament, in accordance with the present invention; 
       FIG. 4  is a schematic, perspective view of an actuator for causing rotational movement of an object; 
       FIG. 5  is a schematic, perspective view of an actuator for causing the bending of a rod or filament at several locations along the length thereof; 
       FIG. 6  is a schematic, perspective view of a feedback control system for causing controlled bending of a rod or filament; 
       FIG. 7  is a schematic, perspective view of an electrical generator for generating electricity from a piezoelectric rod or filament; 
       FIG. 8  is a schematic, perspective view of a slit tube valve made in accordance with the principles of the present invention; 
       FIG. 9  is a side, cross-sectional view of a valve, utilizing two tubes, made in accordance with the present invention; 
       FIG. 10  is a side, cross-sectional view of another embodiment of a valve, utilizing a bendable rod or filament, in accordance with the present invention; 
       FIG. 11  is a side, cross-sectional view of an accelerometer, made in accordance with the principles of the present invention; and 
       FIG. 12  is a side, cross-sectional view of another embodiment of an accelerometer, also made in accordance with the principles of the present invention. 
   

   DETAILED DESCRIPTION 
   Referring to  FIG. 1A , there is shown a schematic, perspective view of one embodiment of a movement actuator made in accordance with the present invention. The actuator is comprised of a rod  4  (the terms “rod”, “bar”, “fiber” and “filament” are used interchangeably herein to indicate an elongate element). The bar  4  is attached or anchored at one end to a fixed support  8 , with the other end being free to move in accordance with the present invention. The other end is shown to be pointed and is positioned adjacent a scale  12  to indicate where on the scale the free end of the bar is pointing. Disposed on one side of the bar  4  is a strip  16  of shape memory alloy which has the capability of changing its shape upon the application of external heat or electric current (which generates internal heat) to some other shape and then assuming the original shape when cooled or electric current is removed and the heat dissipates. Example of such shape memory alloy is nitonol comprised of about 50 percent nickel and 50 percent titanium. The bar  4  is made of a laterally flexible material such as ceramic, metal or plastic, so that when the shape memory alloy strip  16  is caused to change shape, such as contract along its length, the bar will be caused to bend as indicated by the double headed arrow  20 . 
   An electrical current source  24  is coupled to the strip of shape memory alloy  16  to selectively supply electrical current thereto to cause the strip to change its shape. The amount of current supplied to the strip  16  determines the degree to which the strip changes shape and thus the degree to which the rod  4  is bent or deflected. 
   An alternative to use of the strip of shape memory alloy  16  is the use of a bimetal laid down in the same location as the strip  16  on the bar  4 . A bimetal is comprised of two layers of different metals having different thermal coefficients of expansion. Thus, when heat or an electrical current is supplied to the bimetal strip it is caused to bend to, in turn, cause the bar  4  to bend. Bimetals are well known. Still another alternative is the use of piezoelectric strips on the bar  4  to cause bending of the bar in response to applied voltages. 
   Although the diameter of the bar  4  is shown to be relatively large compared to the length, these proportions are used for purposes of illustration only and it should be understood that generally the diameter would be much smaller compared to the length, and would more often resemble a thin fiber or filament, such as the fibers used in fiber optic applications. The strip of shape memory alloy  16  could be deposited upon the bar  4  using techniques disclosed in co-pending patent application, Ser. No. 07/816,628, filed Dec. 31, 1991. 
     FIG. 1B  shows a schematic, perspective view of another actuator having a rod  28  anchored at one end in a base  32  and having a strip of shape memory alloy  36  disposed in a helical pattern around the rod. When a current source  40  selectively supplies electrical current to the strip  36 , the strip is caused to contract (or elongate) to thereby cause the free end of the bar  28  to twist or rotate as indicated by the double headed arrow  44 . A pointer  48  is mounted on the free end of the bar  28  to indicate by a scale  52  the amount of rotation occurring at the free end. 
   It will be evident that a variety of shape memory alloy patterns could be provided on the side exterior of rods or filaments to cause the rods or filaments to bend, elongate, twist, contract, etc. For example, if a strip of shape memory alloy is disposed on a bar to extend from near the anchor end longitudinally and partially circumferentially about the bar, the bar may be caused to both bend and twist. 
     FIGS. 2A and 2B  show two embodiments of movement actuators utilizing piezoelectric material.  FIG. 2A  is a schematic, perspective view of such a movement actuator having an elongate bar  56  anchored at one end to a base  60 , and being made of a piezoelectric material such as PZT. Disposed on one side of the bar  56  in a longitudinal array are a plurality of electrically conductive elements or electrodes  64 . A voltage source  68  selectively supplies a voltage of one polarity to alternate ones of the elements  64  and a voltage of opposite polarity to the remaining elements to thereby produce a localized electric field which will cause the bar  56  to bend as generally indicated by the double headed arrow  72 . Piezoelectric materials, of course, are well known to change shape physically in response to application of electrical voltages and to produce electrical voltages when distorted, squeezed, bent, etc. 
     FIG. 2B  shows an alternative embodiment of a movement actuator again utilizing an elongate bar  76  made of a piezoelectric material. In this embodiment, conductive strips  80  (only two of which are shown in  FIG. 2B  with two others not shown being formed on the other side of the bar) are disposed to extend longitudinally on the bar  76 . A voltage source  84  selectively supplies voltage signals to the strips  80  to establish electric fields in the bar  76  to cause the bar to contract or extend longitudinally as indicated by the double headed arrow  88 . 
   It should be noted that both configurations in  FIGS. 2A and 2B  could be adapted to be movement sensors  82  by simply replacing the voltage sources  68  and  84  with sensing circuitry  70  as shown in FIG.  2 C. Then, when the piezoelectric bars  56  and  76  were bent or longitudinally compressed respectively, voltages would be developed in the bars and these voltages would be detected by the sensing circuitry  70  to thereby sense movement of the respective bars. 
     FIG. 3  is a schematic, perspective view of a sensor system for sensing movement, including determination of the degree of movement and the direction of movement, of a flexible rod  92 . The rod  92  is anchored at one end in a base  102  so that the free end of the rod is subject to forces in various directions indicated by the arrows  106 . Disposed circumferentially about the bar  92  are four strain gauges  110 , such as those disclosed in U.S. Pat. No. 4,964,306. The strain gauges  110  produce signals whose magnitudes are an indication of the degree of strain occurring at the location of the strain gauges. Thus, as a force is applied to the free end of the rod  92 , to cause it to bend, the bar strains differently at different circumferential locations about the rod and these strains, at least at the location of the strain gauges  110 , are detected and signals indicating the amount of strain are supplied to a microprocessor  114 . The microprocessor  114 , in turn, calculates the direction of bending of the rod  92  and the degree of the bend, from the magnitude of the signals received from the four strain gauges  110 . The use of three or more strain gauges spaced circumferentially about the rod  92  are sufficient to determine the direction and degree of bend of the rod. This is because when the rod  92  is bent, there will always be at least one strain gauge which is subject to compression (being more on the side of the rod in the direction of the bend), and one strain gauge will be subject to expansion (being on the side of the rod more away from the direction of the bend). The strain gages are preferably disposed in substantially perpendicular directions so as to detect strain about orthogonal axes of the elongate member. 
     FIG. 4  is a schematic, perspective view of an actuator for causing rotational movement of an object, in this case a disk  120 . The actuator includes four flexible bars  124  having fixed ends attached to a base  128  at circumferentially spaced-apart locations. The bars  124  extend outwardly from the base  128 , generally in parallel with one another, to join the disk  120 . Strips of shape memory alloy  132  are disposed on the rods  124  on sides in line with the circumferential spacing of the rods, as shown, and the strips are each coupled to a current source  136 . When current is applied to the strips  132 , the strips cause the rods  124  to bend in a direction in line with the circumferential spacing to thereby cause the disk  120  to rotate in the direction indicated by the arrow  140 . 
     FIG. 5  shows a flexible elongate rod  144  with shape memory alloy patches  148  disposed at longitudinally spaced-apart locations along the bar. A current source  152  is coupled by way of a buss  156  to each of the patches  148  to selectively supply current thereto. Thus, the bar  144  can be caused to bend at various locations along the length thereof as determined by the current source  152 . 
     FIG. 6  shows a feedback control system for effecting controlled bending of a flexible rod  160  anchored at one end to a base  164 . Disposed on one side of the rod  160  is a strip of shape memory alloy  168  coupled to a current source  172  which operates to supply current to the strip  168  under control of a logic unit  176 . Disposed on the other side of the bar  160  is a strain gauge  180  coupled to a sensor circuit  184 . The sensor circuit  184  produces a signal whose magnitude is indicative of the strain to which the bar  160  is subjected and this signal is supplied to a summing circuit  188 . A signal source  192  also supplies a signal to the summing circuit  188  in which the signal&#39;s value represents a degree of bending desired for the rod  160 . The summing circuit  188  effectively compares the two input signals and if there is a difference, it signals the logic circuit  176  as to the amount of this difference and the logic circuit, in turn, signals the current source to cause further bending (or unbending) of the rod  160  so that the output signal of the sensor  184  will move closer in value to the signal supplied by the signal source  192 . This is a conventional feedback control circuit for ensuring that a result represented by an input signal is more accurately achieved, the result in this case being the bending of the rod  160 . 
     FIG. 7  is a schematic, perspective view of an electricity generator composed of an elongate, flexible piezoelectric filament  200  disposed and held in place by bearings  204  and  208  located at the ends of the filament so that the filament follows an arc-shaped locus of points. A power source  212  is coupled to the filament  200  to cause the filament to rotate about an axis coincident with the arc-shaped locus of points. As a result, the filament  200  is continually stressed and compacted (that portion of the rod on the concave side of the arc being compacted and that portion of the rod on the convex side of the arc being stressed) to thereby develop voltages which are supplied to wiper elements or electrodes  216  disposed on opposite sides of the filament. In this manner, electrical voltage, and thus electrical current, may be developed or generated from a mechanical rotation of the piezoelectric filament  200 . Conversely, by supplying an appropriately commutated voltage to the elements  216 , the filament  200  can be caused to rotate and thus operate as a motor. 
     FIGS. 8-10  show three different embodiments of a valve using the technology of the present invention. In  FIG. 8 , a flexible tube  220  is shown attached at a closed end to a base  224 , and having an open end  228  for receiving a fluid. A strip of shape memory alloy  232  is helically disposed about the exterior of the tube  220  and is coupled to a current source  236  which, by supplying current to the strip  232 , selectively causes a change in shape of the strip to thereby cause a twisting of the tube  220  in the direction indicated by the arrow  240 . When the tube  220  is twisted as indicated, a slit  244  formed in the side of the tube is caused to open to allow the outflow of fluid. When the tube  220  is untwisted, the slit  244  is closed to prevent the outflow of fluid. In this manner, the flow of fluid through and out the tube  220  can be controlled by controlling the twisting of the tube. The tube  220  could be made of a resilient ceramic or hard rubber. 
     FIG. 9  shows another embodiment of a valve utilizing the present invention. In this embodiment, two flexible tubes  250  and  254  are anchored respectively on bases  258  and  262 . The free ends of the tubes are positioned to mate together in a colinear fashion to seal the inside of the tubes from the outside when the tubes are undeflected. An access port  266  is formed in the tube  250  to allow introduction of fluid to the inside of the tubes. Of course, such access could be provided through the other tube  254  or through the bases  258  or  262 . Strips of shape memory alloy are disposed on the upper sides of the tubes  250  and  254  and are selectively heated by a current source to cause the tubes to deflect or bend upwardly, as indicated by dotted lines in FIG.  9 . When such deflection occurs, the ends of the tubes  250  and  254  are exposed to allow escape of fluid which has been introduced into the insides of the tubes. The flow of fluid through the valve of  FIG. 9  is indicated by the arrows. When current to the strips of shape memory alloy is terminated so that the strips cool, the strips return to their original shape causing the tubes to deflect back to their original colinear position to again seal the inside of the tubes from the outside and prevent further outflow of fluid. 
     FIG. 10  shows a cross-sectional, elevational view of a third embodiment of a valve which, in this case, utilizes a selectively bendable rod  270  disposed to extend from a closed end of a housing  274  towards an open end  278 . A conical cap  282  is disposed on the end of the bar  270  and is positioned in the open end  278  of the housing  274 . The diameter of the conical cap  282  is greater than the opening in the open end  278  of the housing  274  so that if the cap is moved towards the closed end of the housing, it seats in the open end to seal off the inside of the housing from the outside. Fluid is introduced into the inside of the housing  274  through an inlet port  286 . The bar  270  is made of a piezoelectric material and conductive strips are disposed on the sides of the bar (not shown) so that when a voltage is supplied thereto, the bar is caused to selectively lengthen or shorten depending upon the polarity of the voltages. When the bar  270  is caused to shorten, the conical cap  282  is caused to seat on and close off the opening at the open end  278  of the housing  274  to prevent the outflow of fluid. When the bar  270  is caused to lengthen, the conical cap  278  is moved outwardly from the opening to allow the outflow of fluid from inside the housing  274 , as indicated by the arrows. 
     FIGS. 11 and 12  show side, cross-sectional views of two embodiments of an accelerometer made in accordance with the present invention. In  FIG. 11 , the accelerometer is shown to include a housing  290  in which is disposed a flexible rod  294 , one end of which is fixed at one end of the housing  290  to extend toward the other end of the housing as shown. Disposed on the free end of the rod  294  is a field emitter  298  for developing an electric field which emanates radially outwardly. Disposed on the interior of the housing  290  circumferentially about the field emitter  298 , but spaced therefrom, are a plurality of field detectors  302 . The field detectors  302  are coupled to a signal processor  306  for determining which of the field detectors  302  is producing the strongest signal, indicating that the field emitter  298  is closest to that field detector. When the housing  290  is accelerated, the rod  294  is caused to deflect in the direction opposite the acceleration to move the field emitter  298  closest to one of the plurality of field detectors  302 , and the signal processor  306  determines which field detector that is and therefore in which direction the acceleration is occurring. Also, the degree of deflection by the rod can be determined by the strength of the electric field detected and this provides an indication of the magnitude of the acceleration. The use of field emitters and field detectors for sensing movement is well known. See U.S. Pat. No. 4,767,973. 
     FIG. 12  shows a side, cross-sectional view of another embodiment of an accelerometer which also includes a housing  310  in which is disposed a piezoelectric rod  314  extending from one end of the housing toward the other end. Disposed about the sides of the rod  314  are a plurality of electrically conductive elements  318  for conducting to a signal processor  322  voltages developed in the rod  314  when it is deflected. Such voltages would be developed when the housing  310  were accelerated in a direction lateral of the housing  310  and the amount of voltage developed would provide an indication of the degree of deflection of the rod  313  and thus of the magnitude of the acceleration. Also, the polarity of the voltages developed at each of the electrically conductive elements  318  would provide an indication of the direction of the acceleration. 
   It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present invention. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present invention and the appended claims are intended to cover such modifications and arrangements.