Abstract:
A motion conversion system is described. The motion conversion system comprises a first torsional member operative for rotating in a first direction. A second torsional member is offset a distance from the first torsional member, wherein the second torsional member is operative for rotating in a direction opposite from the first direction. And, a lateral member has a lower surface connected to the first and second torsional members. Wherein, translational movement of the lateral member results from rotational movement of the first and second torsional members.

Description:
CROSS REFERENCE TO A RELATED APPLICATION 
     This application claims priority under 35 §USC 119(e)(1) to a provisional application entitled, “Motion Conversion System,” with application No. 60/871,588 that was filed Dec. 22, 2006. 
    
    
     DESCRIPTION OF RELATED ART 
     With the evolution of electronic devices, there is a continual demand for enhanced speed, capacity and efficiency in various areas including electronics, communications, and machinery. Many modern devices include moving components. Efficient operation of these devices may depend upon effectively measuring movement of their components. Techniques for measuring movement may differ depending upon the type of system used. Some systems may have rotational movement that needs to be measured. A micro-electromechanical system (MEMS) is usually a system that has electrically controllable micro-machines (e.g., a motor, gear, optical modulating element) formed monolithically on a semiconductor substrate using integrated circuit techniques. Measuring movement within a MEMS system may differ substantially from a non MEMS system. In addition, there are few motion conversion systems that are applicable to various kinds of electrical, mechanical, or electromechanical devices. Moreover, any motion conversion system that is applicable to various environments must also be reliable, robust, and cost effective. Consequently, there remain unmet needs relating to motion conversion systems. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be better understood with reference to the following figures. The components within the figures are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts or blocks throughout the different views. 
         FIG. 1  is an environmental drawing illustrating a variety of devices that may incorporate a motion conversion system. 
         FIGS. 2A-2D  are block diagrams illustrating various implementations of a motion conversion system. 
         FIGS. 3A-3C  are perspective views of the cooperative movement of a pair of the motion conversion devices. 
         FIG. 4  is a detailed view of the pair of motion conversion devices. 
         FIG. 5  is a cross-sectional view of a two-layer implementation of a pair of motion conversion devices. 
         FIG. 6  is a cross-sectional view of a one-layer implementation of a pair of motion conversion devices. 
         FIG. 7  is a flow chart for a motion conversion technique. 
     
    
    
     While the motion conversion system is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and subsequently are described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the motion conversion system to the particular forms disclosed. In contrast, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the motion conversion as defined by this document. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
     As used in the specification and the appended claim(s), the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Similarly, “optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not. 
     Torsion generally refers to motion resulting from twisting one end of an object in one direction about a longitudinal axis, while the other end is held motionless or twisted in the opposite direction. Torsional stiffness is an inertial force that may hinder an object from torsional movement. When this stiffness is overcome, torsion may be used to measure movement (e.g., road movement) even when the movement is irregular, or non-uniform. 
     The present motion conversion system may measure movement by converting rotational motion to translational motion. In general, this system provides a reliable, efficient conversion of rotational motion into translational motion enabling a wide range of applications, such as sensor applications. To accomplish this, the motion conversion system utilizes a hinge architecture that is space-efficient and compact with a high degree of design control and optimization. Furthermore, this motion conversion system may be easily implemented in a wide variety of cost-effective commercial semiconductor fabrication processes. In one implementation, the motion conversion system includes two motion conversion devices, or torsion hinge elements, offset by a finite, fixed distance. The torsional rigidity across a motion conversion device, or torsion hinge element, is independent of deposition stresses and variances. Thus it is uniform. Since the motion conversion system, or dual torsion hinge, is in an offset relationship, this renders the separation distance of the offset torsion hinges an optimizable (or tunable) design parameter. The rigidity of each torsion hinge element within a design may be individually adjusted to provide a desired effect. As a result, the physical relationship of these hinge elements convert rotational movement of an assembly into a linear translational motion, without reliance on complicated, multi-component assemblies. 
     This motion conversion system may be integrated into a host of devices. Turning now to  FIG. 1 , this is an illustrative environmental drawing of a variety of devices that may incorporate a motion conversion system  100 , such as MEMS device  110 . This device may have freely moving elements that may move translationally, rotationally, or a combination of these. Often, the translational movement of an individual sensing element within this type of MEMS device  110  is dependent upon the effective conversion on the rotational motion of these freely moving elements. Since the MEMs device  110  includes the motion conversion system  100 , this device may more easily extrapolate and process movement data. Examples of these kinds of MEMS devices may include pressure sensors, accelerometers, inertial sensors, and the like. 
     More specifically, the fabrication of MEMS device  110  may begin with the fabrication of a complete complementary metal-oxide semiconductor (CMOS) circuit. Since the motion conversion system  100  uses torsional motion, the same fabrication processes may be used for the remaining portions of this MEMS device. In other words, these portions, or the MEMS superstructure, may use the same CMOS fabrication process, which enables harmonization between the underlying circuitry and the superstructure. This harmonization reduces effects associated with transitioning from one material to another. More components can be within a same area. As a result, the implementation of a single chip module becomes more likely. 
     Returning to  FIG. 1 , the motion conversion system  100  may also be integrated into other devices. These devices may include a microphone  120 , speaker  130 , electromechanical device  140 , and the like. In fact, the motion conversion system  100  may be implemented in any kind of system where translational motion is desired, such as variable capacitor  150 . 
     The motion conversion system  100  may be implemented in various configurations as more clearly shown in  FIGS. 2A-2D . Each of the illustrated motion conversion systems includes one pair of complementary motion conversion devices, such as motion conversion devices  205 ,  207 .  FIG. 2A  illustrates a motion conversion system  210  that only includes the motion conversion devices  205 ,  207 . Additional details regarding these complementary motion conversion devices are described in additional detail with regard to  FIG. 3 . Each of these motion conversion devices may be a torsional hinge element. The complementary motion conversion devices  205 ,  207  may be collectively referred to as a dual-offset torsion hinge. In addition, either one, or both, of the motion conversion devices that form the dual-offset torsion hinge may be stationary. For the sake of illustration, neither of the motion conversion devices  205 ,  207  are shown as stationary. In contrast, the motion conversion system  220  of  FIG. 2B  includes one stationary, or fixed, motion conversion device and one non-stationary motion conversion device.  FIG. 2C  illustrates a motion conversion system  230  that includes two stationary, or fixed, motion conversion devices and one non-stationary motion conversion device. This implementation illustrates that a motion conversion system may include either an even or an odd number of motion conversion devices. 
       FIG. 2D  depicts a motion conversion system  240  that has four dual-offset torsion hinges. While this system includes four of these hinges, the number of hinges included in a motion conversion system  240  may be 6, 3, 10, or some other suitable number. In fact, the number of hinges may be selected to achieve some overall design objective. In the motion conversion system  240 , each dual torsion hinge includes one stationary motion conversion device  243  and one non-stationary motion conversion device  245 . As described in greater detail with reference to  FIG. 3 , rotational movement of the motion conversion devices  243  may cause a corresponding translation movement of the motion conversion devices  245 . Since these devices are not stationary, they may freely move vertically or horizontally. When a lateral member  247  (e.g., a layer, lamina, or the like) is attached to the motion conversion devices  245 , these devices may collectively displace the lateral member  247  vertically or horizontally when they are working in concert. For example, the motion conversion devices  245  may vertically displace the lateral member  247 . The amount of this displacement may be customized by altering the number of dual-offset torsion hinges, the relative positions of the dual-offset torsion hinges, the types of motion conversion devices (e.g., fixed motion conversion device) within these hinges, the relative positions of these motion conversion devices within each dual offset hinge, and the like. 
     Turning now to  FIG. 3A , this figure illustrates the cooperative movement between motion conversion devices within a motion conversion system, such as an offset torsion hinge  300 . As mentioned with regard to  FIGS. 2A-2D , a motion conversion system (e.g., motion conversion system  230 ) may include at least two motion conversion devices that operate cooperatively. Similarly, the offset torsion hinge  300  may include multiple motion conversion devices, such as 3, 6, 11, or some other suitable number of motion conversion devices. As an example, the offset torsion hinge  300  includes two motion conversion devices labeled  310 ,  320 . 
     The offset torsion hinge  300  includes a stationary motion conversion device and a nonstationary motion conversion device. The stationary motion conversion device has a stationary support  310 ; the nonstationary motion conversion device is a movable support  320 . A lever  330  is pivotably connected to the stationary support  310  and fixably attached to the movable support  320 . A lateral member  340  extends from the lever  330 . When this lever pivots about the stationary support  310 , the lever  330  vertically displaces the movable support  320 , which correspondingly displaces the lateral member  340 . This movement is more clearly seen in  FIGS. 3B-3C .  FIG. 3B  illustrates how this lever&#39;s pivoting in the direction shown by the arrow causes downward displacement of the movable support  320 . This downward displacement produces a corresponding downward displacement of the lateral member  340 . Similarly, pivoting the lever  330  causes an upward displacement of the movable support  320  and the lateral member  340  as shown in  FIG. 3C . 
     As illustrated in  FIGS. 3A-3C , the offset torsion hinge effectively converts rotational motion to translational motion. More specifically, the pivoting motion of the lever  330  produces a translational displacement of the movable support  320 . This correspondingly produces a translational displacement of the lateral member  340 . These displacements may depend on several factors, which enable this displacement to be customized. For example, the displacement may depend on the distance between the stationary support  310  and the movable support  320 . Additional information regarding customizing the displacement is described with reference to  FIG. 4 . 
       FIG. 4  is a detailed view of a motion conversion system  400  when implemented in a MEMS device, such as MEMS device  110  (see  FIG. 1 ). Though some aspects of this motion conversion device are described with reference to the MEMS device  110 , the motion conversion device  300  may be integrated into many other types of devices as described with reference to  FIG. 1 . 
     In  FIG. 4 , a motion conversion system  400  is implemented in a dual-offset torsion hinge architecture. This motion conversion system includes a first segment  401  that has a first MEMS component  402  coupled to a second MEMS component  404  by a hinge element  406 . Though not shown, the motion conversion system  400  may include numerous other motion conversion devices, as described with reference to  FIGS. 2A-2C . For purposes of explanation and illustration, the MEMS component  402  may be a freely moving MEMS structure (e.g., an inertial sensor component) and the MEMS component  404  may be considered a fixed support structure. 
     The relation among the first MEMs component  402 , the second MEMS component  404 , and the hinge component  406  is described in greater detail. A first end  408  of the hinge element  406  is coupled to the component  404  at a first attachment portion  410  and a second attachment portion  412 . The attachment portions  410 ,  412  are in opposing relation to one another on opposite sides of the end  408 . They are also offset by a distance  414 . A second end  416  of the hinge element  406  is coupled to the component  402  at a first attachment portion  418  and a second attachment portion  420 . Like the attachment portions  410 ,  412 , the attachment portions  418 ,  420  are also in opposing relation to one another on opposite sides of the end  416 . They are offset by a distance  422 . 
     Within the motion conversion device  400 , the range of motion may be customized for optimal performance. There is a clearance distance  424  between the component  402  and the component  404 . Together this clearance distance and the length of the element  406  may be selected produce a desired range of motion. More specifically, the distance  426  between the ends  410  and the end  418  may vary the desired range of motion. The desired range of motion corresponds to the displacement described with reference to  FIGS. 3A-3C . In other words, the clearance distance  424 , the length of the component  404 , or the distance  426 , may be selected such that a desired displacement, or range of motion, is achieved. 
       FIG. 4  merely illustrates one design of the illustrated components, though numerous alternatives may result from varying this illustration. For example, the form factor and geometry of the hinge element  406  may be varied greatly for performance reasons. In the embodiment depicted, the hinge element  406  includes a central offset portion  428  that extends symmetrically and orthogonally from the central section of the hinge element  406 . This current implementation can impact this element&#39;s flexion properties, such as properties that limit a rotational range of motion. Altering these properties for the hinge element  406  may affect its movement. To change the flexion properties, many aspects of the hinge element  406  can be altered. For example, the central offset portion  428  may be smaller, have a different geometry, or the like. Even still, the central offset portion  428  can be completely eliminated, such that the hinge element  406  only includes a central beam section. In the embodiment depicted, the geometries of the constituent parts of the hinge element  406  (e.g., end  408 , end  416 , and central offset portion  428 ) utilize right-angled junctions; these parts of the hinge element  406  are also symmetric in nature. In alternative embodiments, however, these parts may utilize acute angles, obtuse angles, combinations of acute and obtuse angles, or various curvatures at element junctions. Alternatively, these parts or portions of these parts may have completely asymmetric geometries, partially asymmetric geometries, or the like. Any of these variations can impact the flexion properties and correspondingly impact the movement. 
     Returning to  FIG. 4 , the MEMS component  402 , the MEMS component  404 , and the hinge element  406  are coplanar structures with identical thicknesses. In an alternative embodiment, they may not be coplanar structures. Moreover, the thickness of one or more of them may be different. For example, the hinge element  406  may have a smaller thickness than the MEMS component  402 ; this MEMS component may have a smaller thickness than the MEMS component  404 . In another alternative embodiment, the MEMS component  402 , the MEMS component  404 , and the hinge element  406  may be formed from different materials or from the same material. For example, they may be formed from semi-conducting materials. In another alternative embodiment, these MEMS components may be formed from a semi-conducting material and the hinge element  406  may be formed from a different material. 
     The hinge element  406  converts rotational movement to translational movement. More specifically, the hinge element  406  is designed and formed such that it converts rotational movement about an axis (B-B)  431  (analogous to rotational movement about the axis of stationary support  310  in  FIGS. 3A-3C ) into translational movement in a direction orthogonal to axis  431  and also orthogonal to a shared axis (A-A)  430  along which the MEMS components  402 ,  404 ,  406  are aligned. For example, a device (not shown) may have the MEMS component  404  fixed for rotation about an axis (B-B) within it. Movement of this device may elicit a rotational movement in the direction of the arrow  432  about the axis  431  at the end  408 . Since the MEMS component  404  is fixed, the dimensions and geometry of the hinge element  406  causes a corresponding, complementary rotational movement  434  about an axis (C-C)  433  at the end  416 . A net effect is translational movement depicted by the arrow  436  in a direction orthogonal to the rotational axes (B-B)  431  and (C-C)  433 , and also orthogonal to the shared alignment axis  430 . While only briefly described with reference to  FIG. 4 , a detailed description of this type of motion was described with reference to  FIGS. 3A-3C . The complementary rotational movement  434  of the first MEMS component will then similarly elicit a corresponding, complementary rotational movement in the next MEMS component, and so on, until a rotational movement  438  depicted by arrow  438  about an axis (D-D)  435  is elicited in a last motion conversion device aligned along axis (A-A)  430 . (The rotational direction  438  indicated in  FIG. 4  which is the same as direction  434  assumes an even number of MEMS components in the depicted system  400 .) 
     The design of the hinge element  406  facilitates customization of the motion conversion device  400 . In effect, stretching, or flexing, portions of the hinge element  406  increases the torsional stress of that element. As this element rigidity increases, there is a greater resistance to additional movement. This resistance is self-limiting. The self-limiting properties of this hinge element are particularly evident as the ends  408 ,  416  are flexed. Therefore, one can select the material, design, and geometry of the hinge element  406 , such that a desired goal (e.g., a designated amount of translational movement) is accomplished using the self-limiting properties of this hinge element. 
     While the self-limiting properties of the hinge element  406  is described with reference to a motion conversion system  400  within a MEMS device, these concepts are equally applicable to the motion conversion systems described with reference to  FIGS. 1-3C . In fact, the motion conversion system  400  is applicable to variations and adaptations depending upon specific MEMS design or operational objectives. This motion conversion system may be easily integrated in most high-volume commercial semiconductor fabrication processes. To optimize it for a particular system, any one of above-mentioned factors can be adjusted including the self-limiting properties. 
       FIG. 5  is a cross-sectional view of a two-layer implementation of a motion conversion system  500 . In this embodiment, the MEMS device  402  and the MEMS device  404  are formed in a first device layer, such as metal layer M 4 . In contrast, the hinge element  406  with ends  408 ,  416  is formed in a parallel and adjoining device layer, such as metal layer M 5 . Metal layer M 5  is positioned above the metal layer M 4 . As mentioned above, the same material may be selected for both metal layer M 4  and metal layer M 5 . Alternatively, different materials may be selected for these layers. The selection of the material for each layer as well as other factors, such as the thickness of the layer, may be done to achieve design goals. 
     Turning now to  FIG. 6 , this figure is a cross-sectional view of a one-layer implementation of a motion conversion system  600 . In other words, this embodiment depicts a hinge element  406  that is coplanar with the MEMS device  402  and the MEMS device  404 . This hinge element is in parallel, but adjoining, planar relation with these MEMS devices. 
     Turning now to  FIG. 7 , this figure is a flow chart  700  for a motion conversion technique that can be accomplished with any of the previously discussed motion conversion devices. This technique effectively converts rotational motion to translational motion. Any process descriptions or blocks in flow charts can be understood as representing modules, or segments, which may include one or more executable instructions for implementing specific logical functions or blocks in the process. Alternative implementations are included within the scope of the invention in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as can be understood by those reasonably skilled in the art. 
     The motion conversion technique of flow chart  700  begins at block  710  by positioning a first support. This first support may be either a stationary support, movable support, or the like. In fact, this support may be a support within any of the motion conversion devices described with reference to  FIGS. 1-6 . Selecting the position for this support may be based upon certain system related assessments, such as the area available and amount of movement desired. For example, the position for this support member may differ when it is within the microphone  120  than when it is within a MEMS device  110 . 
     Block  710  is followed by block  720 . In this block a first lever is pivotably coupled to the first support. In other words, this lever is coupled to the first support in a manner that enables the lever to pivot about the first support. The physical properties of this lever as well as the manner in which it is coupled to the first support may be selected to comply with design objectives, system constraints, or performance objectives. An example of this lever may be lever  330  described with reference to  FIG. 3  or the hinge element  406  described with reference to  FIGS. 4-6 . 
     Block  730  follows block  720 . In an alternative embodiment (not shown), block  720  and block  730  may be completed contemporaneously. In block  730 , a second support is positioned at an offset distance from the first support. Like the first support, the second support may be a stationary support, movable support, or the like. In addition, the offset distance between the first support and the second support may be selected to generate design constraints. For example, the offset distance between these supports may be selected to produce a certain amount of translational motion from rotational motion. 
     Block  740  follows block  730 . In an alternative embodiment, block  730  and block  740  may be completed contemporaneously. Block  750  follows block  740 . These blocks work together to help facilitate the conversion of rotational motion to translational motion. As the lever pivots, it correspondingly moves an extender coupled to the lever. Moving the extender displaces a translational member coupled to the extender. The extender and translational member can be jointly referred to as the lateral member  340  described with reference to  FIG. 3 . Selecting the physical properties of the extender and the translational member may also be based on design constraints. For example, the dimensions of these members may be customized in light of a desired amount of translational motion. 
     While various embodiments of the motion conversion system have been described, it may be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of this system. Although certain aspects of the motion conversion system may be described in relation to specific techniques or structures, the teachings and principles of the present system are not limited solely to such examples. All such modifications are intended to be included within the scope of this disclosure and the present motion conversion system and protected by the following claim(s).