Patent Publication Number: US-2023139980-A1

Title: Inflatable bladder system and method

Description:
CROSS REFERENCE TO THE RELATED APPLICATIONS 
     This application is a non-provisional of and claims priority to U.S. Patent Application 63/274,884, filed Nov. 2, 2021, entitled “INFLATABLE BLADDER SYSTEM AND METHOD,” with attorney docket number 0105935-011PR0. This application is hereby incorporated herein by reference in its entirety and for all purposes. 
     This application also related to U.S. patent application Ser. No. 16/423,899, filed May 28, 2019, entitled “TUBULAR FLUIDIC ACTUATOR SYSTEM AND METHOD” with attorney docket number 0105935-006US0. This application is hereby incorporated herein by reference in its entirety and for all purposes. 
     This application is also related to U.S. application Ser. Nos. 14/064,070 and 14/064,072, both filed Oct. 25, 2013, which claim the benefit of U.S. Provisional Application Nos. 61/719,313 and 61/719,314, both filed Oct. 26, 2012. All of these applications are hereby incorporated herein by reference in their entirety and for all purposes. 
    
    
     BACKGROUND 
     Conventional solar panel arrays are static and unmoving or configured to track the sun throughout the day to provide optimal capture of solar energy. Static solar panel arrays are often undesirable because they are unable to move and accommodate the changing angle of the sun during the day and throughout the year. 
     On the other hand, conventional moving solar panel arrays are also often undesirable because of their high cost of installation, the complexity of the mechanisms that move the solar panels, and the relatively high energy cost associated with actuating the solar panels. For example, some systems include motors that move individual solar panels or groups of solar panels. Such motors and other complex moving parts are expensive to install and maintain. 
     In view of the foregoing, a need exists for an improved solar panel actuation system and method in an effort to overcome the aforementioned obstacles and deficiencies of conventional solar panel actuation systems. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS.  1   a  and  1   b    illustrate a respective top perspective and bottom perspective view of a solar tracker in accordance with various embodiments. 
         FIG.  2    illustrates a side view of a solar tracker during movement. 
         FIG.  3    illustrates a side view of an actuator in accordance with one embodiment, which comprises an inverted V-shaped bottom plate, a planar top-plate, and a set of bladders that are disposed between the top and bottom plates. 
         FIG.  4    illustrates an example of a solar tracking system that includes a row controller that controls a plurality of rows of solar trackers. 
         FIGS.  5   a ,  5   b  and  5   c    illustrate side cross-sectional views of a bladder unit in accordance with different embodiments. 
         FIGS.  6   a ,  6   b  and  6   c    illustrate a perspective, side and top view of a bladder assembly in accordance with an embodiment. 
         FIGS.  7   a  and  7   b    illustrate a perspective and a side view of a bladder assembly and fluidic lines in accordance with an embodiment. 
         FIG.  8    illustrates a close-up cross-sectional view of a coupling between fluidic lines and a bladder assembly in accordance with an embodiment. 
         FIGS.  9   a  and  9   b    illustrate a perspective view and a side view of a top plate in accordance with an embodiment. 
         FIGS.  10   a  and  10   b    illustrate a perspective view and a side view of a bottom plate in accordance with an embodiment and in a first configuration. 
         FIGS.  11   a  and  11   b    illustrate a perspective view and a side view of the bottom plate of  FIGS.  10   a  and  10   b    in accordance with an embodiment and in a second configuration. 
         FIGS.  12   a  and  12   b    illustrate a perspective view and a side view of the actuator assembly having the bottom plate of  FIGS.  11   a  and  11   b    in the second configuration. 
         FIG.  13   a    illustrates an example of a bladder in an actuator comprising a plurality of layers, including an external layer, a central layer and an internal layer. 
         FIG.  13   b    illustrates an example of a wall of a bladder comprising a plurality of layers, including an external layer, a central layer and an internal layer. 
         FIG.  14    illustrates an example embodiment of a bladder having a cylindrical elongated body with first and second ends that have been closed. 
         FIG.  15    illustrates an example embodiment of a bladder having an elongated body with a teardrop shape with first and second ends that have been closed. 
         FIGS.  16  and  17    illustrate example embodiments where bladders are held by a retention system that can comprise one or more sheets that encircle and retain the bladders. 
         FIG.  18    illustrates an example of a bladder defined by an inner-portion and an enclosure where the inner portion is configured to be disposed within a cavity defined by the enclosure by inserting the inner portion into a first end of the enclosure. 
         FIG.  19    illustrates an example of a bladder that includes cords laminated into the body of the bladder in longitudinal and transverse directions. 
         FIG.  20    illustrates a cross-sectional view of an example embodiment of a bladder with a tab coupled to an edge of the bladder. 
         FIG.  21    illustrates another example embodiment of a bladder comprising a tab. 
         FIG.  22    illustrates an example embodiments where a first and second bladder are coupled together via respective tabs to generate bladder unit. 
         FIG.  23    is a close-up view of a coupling between adjacent portions of the sheet material of a bladder. 
         FIG.  24    illustrates an example embodiment of a portion of a bladder comprising a plurality of layers. 
         FIG.  25    illustrates various views of a bladder in accordance with one embodiment. 
         FIG.  26   a    illustrates various views of a bladder in accordance with another embodiment. 
         FIG.  26   b    illustrates various views of a bladder in accordance with a further embodiment. 
         FIG.  27   a    illustrates various views of a bladder in accordance with yet another embodiment. 
         FIG.  27   b    illustrates various views of a bladder in accordance with an embodiment. 
         FIG.  28   a    illustrates a side view of an actuator assembly in accordance with another embodiment. 
         FIG.  28   b    illustrates a perspective view of the actuator assembly of  FIG.  28     a.    
         FIG.  29   a    illustrates a side view of an actuator assembly in accordance with a further embodiment. 
         FIG.  29   b    illustrates a perspective view of the actuator assembly of  FIG.  29     a.    
     
    
    
     It should be noted that the figures are not drawn to scale and that elements of similar structures or functions are generally represented by like reference numerals for illustrative purposes throughout the figures. It also should be noted that the figures are only intended to facilitate the description of the preferred embodiments. The figures do not illustrate every aspect of the described embodiments and do not limit the scope of the present disclosure. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Since currently available solar panel actuation systems are deficient, a fluidic actuation system as described herein can prove desirable and provide a basis for a wide range of applications, such as efficiently and cost-effectively moving solar panels about one or more axes. This result can be achieved, according to various embodiments disclosed herein, by a compliant pressurized fluid-filled actuator, hereafter referred to as a bladder, bellows, or the like, that can be part of an actuator assembly. For example, the present disclosure, in some aspects, relates to inflatable bladders that can be used in fluidic actuators of solar trackers. 
     In some embodiments, the walls of an air-filled portion of a bladder can be made of a composite of materials. One example can include co-extruding softer materials on an outer layer of the wall and stiffer materials on the inner layer of the wall, which can cause the air bladder to experience less displacement driven load (and stress) when compressed while maintaining a desired stiffness to hold pressurized air when extended. The different materials in some embodiments can be different durometers of the same material family (e.g., TPV blends) or multiple materials which share the same base polymer (e.g., Santoprene, polypropylene, or the like). The air bladders can be sealed on the north/south ends in a variety of suitable ways, including welding, pinching, or via a gasketed connection to a manifold. In some embodiments, coextrusion can be used to create section properties which can improve range of motion (ROM) while maintaining burst pressure rating. 
       FIGS.  1   a  and  1   b    illustrate respective top perspective and bottom perspective views of a solar tracker  100  in accordance with various embodiments.  FIG.  2    illustrates a side view of the solar tracker  100 . As shown in  FIGS.  1   a ,  1   b    and  2 , the solar tracker  100  can comprise a plurality of photovoltaic cells  103  disposed along a length having axis X 1  and a plurality of pneumatic actuators  101  configured to collectively move the array of photovoltaic cells  103 . As shown in  FIG.  1   b   , the photovoltaic cells  103  are coupled to rails  102  that extend along parallel axes X 2 , which are parallel to axis X 1 . Each of the plurality of actuators  101  extend between and are coupled to the rails  102 , with the actuators  101  being coupled to respective posts  104 . As shown in  FIG.  2   , the posts  104  can extend along an axis Z, which can be perpendicular to axes X 1  and X 2  in various embodiments. In various embodiments, solar cells or photovoltaic cells  103  can be embodied in various way, including as a solar panels or photovoltaic panels. 
     As shown in  FIG.  2   , and discussed in more detail herein, the actuators  101  can be configured to collectively tilt the array of photovoltaic cells  103  based on an angle or position of the sun, which can be desirable for maximizing light exposure to the photovoltaic cells  103  and thereby maximizing electrical output of the photovoltaic cells  103 . In various embodiments, the actuators  101  can be configured to move the photovoltaic cells  103  between a plurality of configurations as shown in  FIG.  2   , including a neutral configuration N where the photovoltaic cells  103  are disposed along axis Y that is perpendicular to axis Z. From the neutral configuration N, the actuators  101  can be configured to move the photovoltaic cells  103  to a first maximum tilt position A, to a second maximum tilt position B, or any position therebetween. In various embodiments, the angle between the neutral configuration N and the maximum tilt positions A, B can be any suitable angle, and in some embodiments, can be the same angle. Such movement can be used to position the photovoltaic cells  103  toward the sun, relative to an angle of the sun, to reflect light toward a desired position, or the like. 
     In one preferred embodiment as shown in  FIGS.  1   a  and  1   b   , a solar tracker  100  can comprise a plurality of photovoltaic cells  103  that are collectively actuated by four actuators  101  disposed along a common axis. However, in further embodiments, a solar tracker  100  can comprise any suitable number of actuators  101 , including one, two, three, four, five, six, seven, eight, nine, ten, fifteen, twenty, fifty, one hundred, or the like. Similarly, any suitable number of photovoltaic cells  103  can be associated with a solar tracker  100  in further embodiments. Additionally, while photovoltaic cells  103  are shown in example embodiments herein, in further embodiments, actuators  101  can be used to move various other objects or structures, including mirrors, reflectors, imaging devices, communications devices, and the like. 
     In various applications, the ability to lock out actuator rotation can be desirable. In some embodiments, the lock out can be generated at predetermined angles. Locking out in a flat or 0 degree, 45 degree or max range of motion lock can be desired in various applications. Other applications can include instantaneous lockout, or the ability to freeze motion and increase stiffness at any angle. 
     In applications that may require specific angle lockouts, a variety of mechanisms can be employed. For extreme angle lockouts, hard stops can be employed. A hard stop can be a solid state feature that prevents rotation past a set angle. In some examples, a bladder  300  (See  FIG.  3   ) can be over pressurized to press up against a hard stop, increasing its stiffness at the extreme angle. 
     Hard stop features can take a variety of forms. For example, in some embodiments, the actuator assembly  101  can comprise one or more tensile rope or webbing coupled to and extending between top plate  330  and bottom plate  310  of the actuator assembly  101  (see  FIG.  3   ). In another example, positive bosses can be provided as part of the actuator assembly  101  or proximate to the actuator assembly such that contact with the bosses constrains the range of motion of the actuator assembly. In various embodiments, such hard stops can be beneficial for preventing damage to the actuator assembly in high winds or exposure to other forces that might over-extend the actuator assembly. Pressurizing against a hard stop can also prevent excitation of destructive resonant frequencies induced by oscillatory loads (such as wind). In some embodiments, it can be beneficial to stow the actuator assembly against a hard stop when exposure to undesirable forces is anticipated (e.g., during a storm, or the like). These hard stops can also have a locking feature in order to stop all movement of the tracker when hit. This can serve as a stow mechanism that can further prevent damage to the tracker in a high-wind event. 
     In some embodiments, positional lockout at 0 degrees, or plumb to gravity, can be desirable. Mechanisms that can achieve this behavior include but are not limited to: 4 bar linkages, pneumatic rams, solenoids, lockable dampers, spring returns, inflated bladders, pressure sensitive toggles, and the like. 
     Stow, lockouts or hard stops can be provided in various suitable ways in accordance with further embodiments. For example, in one embodiment, there can be a separate actuator lockout for purposes of stow. For example, a separate small bladder can be used to actuate a locking mechanism that rigidly, or near rigidly, fixes an actuator assembly. In one embodiment, such a mechanism can comprise a pin that engages a corresponding hole or slot, or such a mechanism can comprise multiple pins or toothed arrangements that engage corresponding features enabling multiple locking positions. In another embodiment, such a mechanism can comprise corresponding brake pads that enable continuous locking independent of tracker position. Off-normal loading can also be used to engage a locking mechanism in accordance with some embodiments. 
     In further embodiments, a bar-linkage lockout can be used to stow or lock an actuator assembly  101 . For example, in one embodiment, an actuator-piloted four bar linkage can be used to lock out tracker motion. In such an embodiment, an over-center four bar linkage between the top plate  330  and the bottom plate  310  can be used to fix the position of the actuator assembly  101  for the purpose of stow, and the like. Such a mechanism can be actuated by an external actuator, collective bladder pressure, off-normal loading, or the like. 
     Other embodiments can require instantaneous lockout, or lockout in any position. Mechanisms that can be used to achieve this behavior include but are not limited to: air brakes, drum brakes, lockout pins. Lockout mechanisms can be piloted by pneumatics, hydraulics, electronics, passive means, or any other method. 
     In some embodiments, damping can be desirable for an actuator assembly  101 . Damping can be incorporated into the architecture of the actuator assembly  101  directly, or through a peripheral/add-on mechanism. A damper can be configured to smooth movement of a photovoltaic cells  103  coupled to the actuator assembly by providing resistance that reduces sudden or jerky movement of the solar panel. In other words, a damper can be configured to counter dynamic loading modes (for example, wind-induced oscillatory modes) and help with smoothing oscillation of an actuator assembly. Additionally, inclusion of dampers can be beneficial because it can allow an actuator assembly  101  to operate at a lower operating pressure, which can result in reduced stress on the actuator assembly, including stress on bellows, bladders, and the like. 
     To increase energy loss due to friction and for enhancing damping, in some examples, material choice of high coefficient of friction materials can be employed. In some embodiments, including in various friction-based pivot dampers, the damping coefficient can be modulated by varying the collective force applied by the bladder(s). By increasing collective bladder pressure, the stiffness provided by the damper can be increased, ideal for high dynamic load cases. 
     In further embodiments, the damper can be configured in any suitable way. For example, the damper can be coupled to a top plate  330  and a bottom plate  310  (see  FIG.  3   ); the damper can be coupled to the bottom plate  310  and the second support; or the like. Add-on dampers can be linear or rotary in nature. 
     Add-on dampers can make use of viscous fluid dynamics, centripetal acceleration, friction losses, gas diffusion or any other applicable phenomenon. In further embodiments, a damper can be internally located or integrated directly into a compliant fluidic actuator, bellows or bladders. For example, the material of inflatable bladders can have a high damping coefficient; the inflatable bladders can be partially filled with a compliant material with a high damping coefficient; a block of porous material can be inserted into the inflatable bladders that restricts the passage of fluids in and out of said material thereby achieving damping; a block of elastomeric material that changes volume in response to external pressure with a significant damping coefficient the bladders can be wrapped in a damping elastomeric material, and so forth. 
     Add-on mechanisms that increase damping and energy loss include but are not limited to: centrifugal clutches, viscous speed governors, linear viscous dampers, dashpots, viscoelastic crush ribs, or the like. In further embodiments, bladders or bellows can be filled with a fluid such as water, or the like, to generate a suitable damping effect. The damper can take both linear and rotary forms in accordance with various embodiments. In further embodiments a damper can be integrated with a flexure, hub or pivot system or between plates. For example, a flexure can be encased in an elastomeric damping material which might further serve to maintain separation of endplates, or elastomeric damping blocks can be stacked between plates. 
     The actuator assembly  101  can be fixed to a rack, a driven post, a space frame, directly to the ground, or any other suitable substrate. For example, the actuator assembly  101  can be coupled to the ground or other structure via a post  104  as shown in  FIGS.  1   a ,  1   b    and  2 . The actuator assembly  101  can be mounted to this post using bolts, nuts and washers through the flange of the member, or through a web of a bladder unit. An actuator bottom-plate can have built-in mounting features, or separate mounting brackets can be used. 
     The actuator assembly  101  can be attached to a substrate through a mounting bracket. A mounting bracket can comprise a plurality of components. A mounting bracket can allow for positional adjustment in one or many vectors or rotational angles. The mounting bracket can be incorporated into, or act in place of an actuator plate. In some embodiments, the actuator assembly  101  can be mounted directly on the substrate, such as a driven beam. In others, the actuator assembly  101  can utilize the mounting substrate, beam or frame to add strength to the actuator assembly  101 . 
     In another embodiment, the actuator assembly  101  can include a base that comprises a plurality of legs. In a further embodiment, the solar-actuator assembly  101  can include a base architecture that holds one or more weights. In one embodiment, the weights can comprise tanks that can be filled with fluid such as water. Such an embodiment can be desirable because the actuator assembly  101  can be lightweight for transport and then secured in place by filling the weights with water or other ballast at a desired location. 
     The actuator assembly can rotate a payload in various examples, including a payload of photovoltaic cells  103  as shown in  FIGS.  1   a ,  1   b    and  2 . The payload can be attached to the actuator assembly  101  in a variety of ways. In some embodiments, a top plate can be attached to the payload, while a bottom plate remains fixed to a mount. In embodiments with different architecture, the payload can be attached to a center plate, while the frame plate can be fixed to a static mount. 
     To attach the payload to the actuator assembly  101 , the use of spreader brackets or spreader rails can be employed. A spreader bracket rigidly attaches to the rotating plate or component of the actuator assembly  101 . The bracket can extend beyond the extreme end of the plate to which it can be attached. The distance of this spread can vary depending on the structural, regulatory or commercially stipulated needs of the payload. 
     A spreader bracket can be constructed of a metal, such as but not limited to steel, aluminum, a plastic, or a composite such as carbon fiber or fiberglass. A spreader bracket can comprise roll-formed sections, extrusions, castings, composite layup or parts manufactured by any suitable method. A payload can be attached to rails that run perpendicular to and can be attached to spreader brackets. 
     Some embodiments of the actuator assembly  101  can attach a payload to the actuator via a central tube. The tube can couple the payload and the actuator assembly  101  and can transmit torsional load from the actuator to far down the axis of rotation. The torque tube can incorporate spreader brackets to spread attachment points to payload attachment points. 
     In some embodiments, one or more actuator assemblies  101  can be coupled together. For example, a pair of single-axis actuator assemblies  101  can be coupled together via one or more photovoltaic cells  103  and/or supports that extend between the actuator assemblies  101 . Similarly, another embodiment comprises a plurality of actuator assemblies  101  coupled together via one or more photovoltaic cells  103  and/or supports that extend between the actuator assemblies  101  (e.g., as shown in  FIGS.  1   a  and  1   b   ). In such embodiments, two or more actuator assemblies  101  can move in concert to move a single set of a plurality of photovoltaic cells  103  or solar panels collectively. As shown in various embodiments, such an actuator assembly  101  can be anchored in the ground via posts  104 , or the like. Supports can be linked together using bolts and nuts with a connecting bracket, or with a nesting feature between the two lengths of support that can eliminate the need for an additional part. For example, an actuator assembly  101  can be coupled to a post  104  via a bolt assembly. 
     In one application, the actuator assembly can be used to move and position a photovoltaic cells  103  that is coupled to a top-plate. For example, in a first example the actuator assembly  101  can include a post  104  that the actuator assembly rests on. The post  104  can be held by a base or disposed in the ground (e.g., via a ground post, ground screw, or the like) in accordance with some embodiments. This post  104  can be driven into the ground at a variable length depending on loading conditions at the site. The post  104  can be a steel (e.g., alloy steel) component with an I, C, hat, or other cross section. The post  104  can be treated with zinc plating, hot dip galvanizing, or some other method for corrosion resistance. 
     Although various example embodiments herein describe the use of an actuator assembly  101  with photovoltaic cells  103 , in further embodiments, an actuator assembly  101  can be used to actuate or otherwise move any other suitable object, including concentrators, reflectors, refractors, and the like. 
     An actuator assembly  101  having two bladders or bellows can be configured to move a photovoltaic cells  103  that is coupled to a top plate of the actuator assembly  101  via respective supports  102  that can be mounted perpendicularly to one another and extend along respective lengths of the photovoltaic cells  103 . As discussed herein, the bladders or bellows of a one-axis actuator assembly can be configured to inflate and/or deflate to move the solar panel. Supports  102  can be some lightweight steel channel. This channel can have a C, Z, or some other desirable cross section. This channel can be roll-formed, bent, or fabricated in some other manner. 
       FIG.  3    illustrates a side view of an actuator assembly  101  in accordance with one embodiment. As shown in the example of  FIG.  3   , the actuator assembly  101  comprises a V-shaped bottom plate  310 , a planar top-plate  330 , and a plurality of bladders  300  of a bladder assembly  301  disposed between the top and bottom plates  330 ,  310 . A hub assembly  370  rotatably couples the bottom and top plates  310 ,  330  and extends between the bottom and top plates  310 ,  330 . In various embodiments, the bottom plate can be or be referred to as being V-shaped, inverted V-shaped, A-shaped, angled, or the like. 
     The example embodiment of  FIG.  3    illustrates the actuator assembly  101  in a neutral configuration N (see  FIG.  2   ), where the top plate  330  extends along axis Y, which is perpendicular to axis Z in the neutral configuration N. However, as discussed herein, the top plate  330  can be configured to tilt to the left and right (or east and west as discussed herein) based on selective inflation and/or deflation of the bladder  300  of the bladder assembly  301 . Components of an actuator assembly  101  can comprise various suitable materials, including metal (e.g., steel, aluminum, iron, titanium, or the like), plastic, composite materials or the like. In various embodiments, metal parts can be coated for corrosion prevention (e.g., hot dip galvanized, pre galvanized, or the like). 
     A row controller  380  can be operably coupled with bladder  300  of the actuator via pneumatic lines  390 . More specifically, an east bladder  300 E can be coupled to a pneumatic circuit  382  of the row controller  380  via an east pneumatic line  390 E. A west bladder  300 W can be coupled to the pneumatic circuit  382  of the row controller  380  via a west pneumatic line  390 W. A pneumatic control unit  384  can be operably coupled to the pneumatic circuit  382 , which can control the pneumatic circuit  382  to selectively inflate and/or deflate the bladder  300  to move the top plate  330  of the actuator assembly  101  to tilt photovoltaic cells  103  coupled to the top plate  330 . 
     For example, as described herein, bladder  300  of an actuator assembly  101  can be inflated and/or deflated which can cause the bladder  300  to expand and/or contract along a width of the bladder  300  and cause rotation of the hub assembly  370  and movement of the bottom and top plates  310 ,  330  relative to each other. Such movement of the hub assembly  370  can be generated when a solar tracker  100  is moving between a neutral position N and the maximum tilt positions A, B as shown in  FIG.  2   . 
     As discussed in more detail herein, a bladder assembly  301  can comprise any suitable plurality of bladders  300 , with the bladder  300  being any suitable size and shape. Additionally, as discussed in more detail herein a bladder assembly  301  can comprise one or more bladder units (see, e.g., bladder unit  302  of  FIGS.  5   a - c   ) with each of the one or more bladder units comprising any suitable plurality of bladders, including in some embodiments, any suitable number of even numbers of bladder  300 . As discussed herein, in some embodiments, a plurality of bladder units that each have two bladders  300  can be stacked to form a bladder assembly  301 . 
     In various embodiments, the bladders  300  can be configured to expand along the width of the bladders  300  when fluid is introduced into the hollow bladders  300  or when the bladders  300  are otherwise inflated. Accordingly, the bladders  300  can be configured to contract along the width of the bladders  300  when fluid is removed from the hollow bladders  300  or when the bladders  300  are otherwise deflated. 
     Where bladders  300  are configured to expand widthwise based on increased pressure, fluid or inflation and configured to contract widthwise based on decreased pressure, fluid or deflation, movement of the photovoltaic cells  103  via one or more actuators  101  can be achieved in various ways. For example, referring to the example of  FIG.  2   , rotating the photovoltaic cells  103  west (i.e., to the right in this example) can be achieved via one or more of the following: 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Examples of Actions to Rotate Actuator Assembly 101 West 
               
            
           
           
               
               
               
            
               
                 East Bladder 300E 
                 West Bladder 300W 
                 Result 
               
               
                   
               
               
                 Increase Pressure 
                 Maintain Pressure 
                 Rotate West 
               
               
                 Increase Pressure 
                 Reduce Pressure 
                 Rotate West 
               
               
                 Maintain Pressure 
                 Reduce Pressure 
                 Rotate West 
               
               
                 Decrease Pressure 
                 Decrease Pressure More Than 
                 Rotate West 
               
               
                   
                 East Bladder 300E 
               
               
                 Increase Pressure 
                 Increase Pressure Less Than 
                 Rotate West 
               
               
                   
                 East Bladder 300E 
               
               
                   
               
            
           
         
       
     
     Referring again to the example of  FIG.  2   , rotating the photovoltaic cells  103  east (i.e., to the left in this example) can be achieved via one or more of the following: 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Examples of Actions to Rotate Actuator Assembly 101 East 
               
            
           
           
               
               
               
            
               
                 East Bladder 300E 
                 West Bladder 300W 
                 Result 
               
               
                   
               
               
                 Maintain Pressure 
                 Increase Pressure 
                 Rotate East 
               
               
                 Reduce Pressure 
                 Increase Pressure 
                 Rotate East 
               
               
                 Reduce Pressure 
                 Maintain Pressure 
                 Rotate East 
               
               
                 Decrease Pressure More Than 
                 Decrease Pressure 
                 Rotate East 
               
               
                 West Bladder 300W 
               
               
                 Increase Pressure Less Than 
                 Increase Pressure 
                 Rotate East 
               
               
                 West Bladder 300W 
               
               
                   
               
            
           
         
       
     
     Accordingly, in various embodiments, by selectively increasing and/or decreasing the amount of fluid within bladder  300 E,  300 W, the top plate  330  and photovoltaic cells  103  can be actuated to track the location or angle of the sun. 
     A tubular actuator assembly  101  can be a fluid driven, antagonistic type actuator. The Tubular actuator assembly  101  can be driven by a pressurized working fluid. The working fluid can be gas, such as air, or a liquid, such as water, oil or the like. 
     The tubular actuator assembly  101  can work on a principle of antagonistic differential forces. For example, in an antagonistic actuator, two force-generating linear sub-actuators (e.g., bladder  300 , bladder assembly  301  and/or bladder units  302 ) can be placed on either side of a pivot. The sub-actuators can generate forces of varying magnitudes. The extension length of the linear sub-actuator can be closely tied to a force it is generating. The sub-actuator can be said to have a “force to position” relationship. The magnitudes of the forces generated and thus the correlated length of the actuator assembly  101  can be dictated by a pneumatic control unit  384 . The pneumatic control unit  384  can choose the force values for both sub-actuators. When this is completed the free component or top plate  330  of the actuator assembly  101  can rotate until the torque generated by each actuator (force multiplied by the moment arm) sums to zero. If an external torque is applied to the rotating portion (e.g., top plate  330 ) of the actuator assembly  101 , the actuator assembly  101  can rotate until the sum of the torques, external and internal, is zero. 
     In some examples of a tubular actuator assembly  101 , the sub-actuators can be inflated bladders or bladder  300  as discussed herein. These bladders or bladder  300  can be positioned on opposing sides of a pivot. Depending on the pressure, the pneumatic control unit  384  can inflate to the angle of a free plate (e.g., top plate  330 ) of the actuator assembly  101 , the bladder  300  can supply a deterministic amount of force. The bladders or bladder  300  can apply this force given the specified angle, at a deterministic distance from the central hub assembly  370 . This can create a deterministic moment applied by each bladder  300  given an angle assumed by the rotating top plate  330 . All of this can result in a deterministic position given a specific control condition that can set the pressure in either bladder  300 . When the pressure in both bladders  300  has been set by the pneumatic control unit  384 , the actuator assembly  101  can rotate until the torque (force times the moment arm) generated by both bladders  300  is equal. If an external torque is applied to the top plate  330 , the actuator assembly  101  can rotate until the sum of the torques, external and internal, is zero. Given external loading conditions, the actuator assembly  101  can exhibit a deterministic “pressure to position” relationship. 
     Depending on how the bladders  300  are affixed to the top plate  330  and/or bottom plate  310  in some examples, the center of action can migrate in towards, or out away from a balance point or pivot of the hub assembly  370 . As an example, when a bladder  300  is at high pressure, and on the extended side of the hub assembly  370 , the contact patch, and thus the center of action of the force applied by the bladder  300 , can move closer towards a center pivot of the hub assembly  370 . As the top plate  330  rotates and the bladder  300  can go from an extended state to a compressed state, the contact patch can expand and the center of action can move out away from the pivot point of the hub assembly  370 . A variety of actuator configurations can be devised to take advantage of this effect. 
     In various embodiments, the hollow bladder  300  can be configured to be inflated and/or deflated with a fluid (e.g., air, a liquid, or the like), which can cause the bladder  300  to change size, shape and/or configuration. Additionally, the bladder  300  can be deformable such that the bladder  300  can change size, shape and/or configuration. 
     The bladder  300  can change between a first and second configuration in various suitable ways. For example, the bladder  300  can naturally assume the first configuration when unpressurized or at neutral pressure and then can assume the second configuration via physical compression and/or a negative pressurization of the bladder  300 . Additionally, the bladder  300  can naturally assume the second configuration when unpressurized or at neutral pressure and then can assume the first configuration via physical expansion and/or a positive pressurization of the bladder  300 . 
     Additionally, the bladder  300  can be in the second configuration at a first pressurization and expand to the first configuration by pressurization to a second pressure that is greater than the first pressure. Additionally, the bladder  300  can be in the first configuration at a first pressurization and contract to the second configuration by pressurization to a second pressure that is less than the first pressure. In other words, the bladder  300  can be expanded and/or contracted via selective pressurization and/or via physical compression or expansion. 
     In some embodiments, it can be desirable for the bladder  300  to engage the top and/or bottom plates  330 ,  310  in a contacting and/or rolling manner in various configurations. In some embodiments, a contact-region of the top and/or bottom plates  330 ,  310  can provide for a rolling contact between convolutions of a bladder  300 , which can be beneficial during movement of the bladder  300  as discussed in more detail herein. Additionally, such a contact-region can be beneficial because it can reduce strain on the bladder  300  during compression and can increase the stiffness of the bladder  300  in certain configurations. 
     Although certain example embodiments of a bladder  300  are illustrated herein (e.g.,  FIGS.  5   a - c ,  6   a - c   ,  25 ,  26   a ,  26   b ,  27   a  and  27   b ), these example embodiments should not be construed to be limiting on the wide variety of bladder shapes, sizes and geometries that are within the scope and spirit of the present disclosure. For example, in some embodiments, convolutions can have varying size and shape, including varying in a pattern, or the like. Additionally, the bladder  300  can have a curved or rounded contour or can include edges, square portions, or the like. 
     An actuator assembly  101  can move to assume a plurality of configurations based on the inflation and/or deflation of the bladder  300 . For example, the actuator assembly  101  can assume a first configuration A, where a plane TO of the top plate  330  is parallel to a plane BA of the base plate  310 . In this first example configuration A, the bladders  300  are of equal length and have a straight central axis CE that is perpendicular to top and bottom planes TO, BA. In such a configuration, the bladder  300  can be at a neutral pressure, partially inflated, or partially deflated. Accordingly, by selectively inflating and/or deflating the bladder  300  of the actuator assembly  101 , the plane TO of the top plate  330  can be moved to various desired positions. 
     In some embodiments, single degree of freedom (DOF) actuators can be stacked, to achieve 2 DOF, 3 DOF or any other numbers of DOF. 
     The architecture of the actuator assembly  101  can take a variety of forms. One example actuator assembly  101  can comprise a top plate  330  rotatably coupled to a bottom plate  310 . The bottom plate  310  is then rigidly coupled to a post  104 , frame or any other suitable substrate. Inflatable, flexible sub-actuators, bladders, or bladder  300  can be disposed on either side of the coupling. When inflated differentially, the bladder  300  can rotate the top plate  330  to a specific position. This example architecture can be modified in any suitable manner. 
     In one embodiment, a top plate  330  can be rotatably coupled to a bottom plate  310  in the shape of an inverted V. The bladder  300  can engage with the top plate  330  on the underside of its wings and with legs  311  of the V-plate bottom plate  310 . The V-plate can take any suitable angle to achieve the desired range of motion, stiffness or any other behavior or performance. In some embodiments, it can be desirable for the V plate angle to be 90 degrees. For greater range of motion, the V-Plate can have an angle less than 10 degrees. For greater stiffness, the actuator assembly  101  can have a bottom plate angle greater than 120 degrees. In some embodiments, it can be desirable to have a bottom plate angle at the extremes, 180 degrees, flat, where bladder  300  press on the wings of the plate on either side of the coupling. It can also be desirable in some examples to have a plate with an angle of 0 degrees. In some examples, the bottom plate  310  can more aptly be called a middle plate, in that the bladder  300  can act on either side of the thin plate, rather than on opposing lobes. Likewise, the top plate  330  can take a V-shape and can be configured in any suitable angle. The V-shape in either plate  310 ,  330  can also be inverted in some examples. An actuator assembly  101  can comprise any combination of top and bottom plates  310 ,  330 . 
     Another embodiment can comprise an A-frame that is rigidly affixed to a mounting substrate. A center plate can be rotatably coupled to the center of the A-frame. The bladder  300  can mount to engage with either side of the center plate. The bladder  300  can be attached to a coupling point by a web or fascia attached to the bladder  300 . The bladder  300  can also be affixed to either the frame or the center plate. 
     Turning to  FIG.  4   , in various embodiments, a plurality of solar trackers  100  can be actuated by a row controller  380  in a solar tracking system  400 . In this example, four solar trackers  100 A,  100 B,  100 C,  100 D can be controlled by a single row controller  380 , which is shown being operably coupled thereto. As described in more detail herein, in some examples, a plurality of solar trackers  100  or a subset of solar trackers  100  can be controlled in unison. However, in further embodiments, one or more solar trackers  100  of a plurality of trackers  100  can be controlled differently than one or more other trackers  100 . 
     While various examples shown and described herein illustrate a solar tracking system  400  having various pluralities of rows of solar trackers  100 , these should not be construed to be limiting on the wide variety of configurations of photovoltaic cells  103  and fluidic actuators  101  that are within the scope and spirit of the present disclosure. For example, some embodiments can include a single row or any suitable plurality of rows, including one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, fifteen, twenty, twenty-five, fifty, one hundred, and the like. 
     Additionally, a given row can include any suitable number of actuator assemblies  101  and photovoltaic cells  103 , including one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, fifteen, twenty, twenty-five, fifty, one hundred, two hundred, five hundred, and the like. Rows can be defined by a plurality of physically discrete tracker units. For example, a solar tracker  100  can comprise one or more actuator assemblies  101  coupled to one or more photovoltaic cells  103 . 
     In some preferred embodiments, the axis of a plurality of solar trackers  100  can extend in parallel in a north-south orientation, with the actuator assemblies  101  of the rows configured to rotate the photovoltaic panels about an east-west axis. However, in further embodiments, the axis of solar trackers  100  can be disposed in any suitable arrangement and in any suitable orientation. For example, in further embodiments, some or all rows may not be parallel or extend north-south. Additionally, in further embodiments, rows can be non-linear, including being disposed in an arc, circle, or the like. Accordingly, the specific examples herein (e.g., indicating “east” and “west”) should not be construed to be limiting. 
     Also, the rows of solar trackers  100  can be coupled to the ground, over water, or the like, in various suitable ways, including via a plurality of posts. Additionally, while various embodiments described herein describe a solar tracking system  400  configured to track a position of the sun or move to a position that provides maximum light exposure, further examples can be configured to reflect light to a desired location (e.g., a solar collector), and the like. 
     Turning to  FIGS.  5   a - c   , three example embodiments  302 A,  302 B,  302 C of a bladder unit  302  are illustrated. As shown in  FIGS.  5   a - c   , a bladder unit  302  can comprise a pair of bladders  300  that are coupled via a web  303 , with each of the bladder  300  defining one or more bladder cavity  305 . For example,  FIG.  5   a    illustrates a bladder unit  302 A comprising a pair of bladders  300  connected via a web  303  with the bladder  300  defining a respective and separate single bladder cavity  304 .  FIG.  5   b    illustrates a bladder unit  302 B comprising a pair of bladders  300  connected via a web  303  with the bladder  300  defining a respective and separate first and second bladder cavity  304 A,  304 B.  FIG.  5   c    illustrates a bladder unit  302 C comprising a pair of bladders  300  connected via a web  303  with the bladder  300  defining a respective first and second bladder cavity  304 A,  304 B that are connected via a port  305  that allows for fluid to pass between the bladder cavities  304 A,  304 B. 
     While three examples  302 A,  302 B,  302 C of a bladder unit  302  are illustrated, this should not be construed to be limiting on the wide variety of further embodiments of a bladder unit that are within the scope and spirit of the present disclosure. For example, further embodiments can include bladder  300  having any suitable plurality of cavities  304  (e.g., three, four, five, ten, twenty, and the like). 
     Additionally, in various embodiments, the bladder unit  302  can comprise one or more plane of symmetry. For example, as shown in examples  302 A,  302 B,  302 C of  FIGS.  5   a - c   , a bladder unit can include a first plane of symmetry that extends vertically through the web  303 ; and can include a second plane of symmetry that extends horizontally through the web  303  and the bladder  300  and can include a third plane of symmetry that extends vertically through the web  303  and the bladder  300 . In some embodiments, one or more of such planes of symmetry can be absent. 
     Also, in various embodiments, the bladder  300  can have a shape such that the bladder  300  become increasingly thicker from the web  303  outward as shown in  FIGS.  5   a - c    and then thinner toward a terminal end. However, the bladder can have various suitable shapes and sizes in further embodiments. For example, in some examples, the bellows or bladders can comprise convolutions, ribs, or the like. 
     Turning to  FIGS.  6   a - c   , one embodiment  301 A of a bladder assembly  301  is illustrated that comprises a first and second bladder unit  302 X,  302 Y. As shown in this example embodiment  301 A, the first bladder unit  302 X comprises a first and second elongated tubular bladder  300 X 1 ,  300 X 2  that are coupled via a first web  303 X and a second bladder unit  302 Y comprises a first and second bladder  300 Y 1 ,  300 Y 2  that are coupled via a second web  303 Y. 
     The first and second bladder units  302 X,  302 Y are shown stacked and coupled together via elongated top and bottom clamp-down bars  307 ,  308  disposed at and extending along a length of the webs  303  of the bladder units  302 . More specifically, the top clamp-down bar  308  is disposed abutting the first web  303 X of the first bladder unit  302 X with the bottom clamp-down bar  307  disposed abutting the second web  303 Y of the second bladder unit  302 Y. The top and bottom clamp-down bars  307 ,  308  are coupled via bolts  309  that extend through the webs  303 . 
     As shown in the example of  FIGS.  6   a - c   , the portions of the top and bottom clamp-down bars  307 ,  308  that engage the webs  303  of the bladder units  302  can have a rounded profile, which can be desirable for being less likely to damage and introduce failure points to the webs  303 ; however, in further examples, the top and bottom clamp-down bars  307 ,  308  can have any suitable profile. Also, top and bottom clamp-down bars  307 ,  308  can be coupled together in various suitable ways in addition to or as an alternative to bolts  309 . 
     The first and second bladder units  302 X,  302 Y further comprise ports  306  that communicate with cavities  304  (see, e.g.,  FIGS.  5   a - c   ) defined by the bladder  300 . For example, the first bladder unit  302 X comprises a first port  306 X 1  associated with the first bladder  300 X 1  and a second port  306 X 2  associated with the second bladder  300 X 2 . The second bladder unit  302 Y comprises a first port  306 Y 1  associated with the first bladder  300 Y 1  and a second port  306 Y 2  associated with the second bladder  300 Y 2 . All of the ports  306  are shown disposed on the same side of the bladder assembly  301 A. For example, the first bladder unit  302 X comprises a first port  306 X 1  associated with the first bladder  300 X 1  and a second port  306 X 2  associated with the second bladder  300 X 2 . The second bladder unit  302 Y comprises a first port  306 Y 1  associated with the first bladder  300 Y 1  and a second port  306 Y 2  associated with the second bladder  300 Y 2 . All of the ports  306  are shown disposed on the same side of the bladder assembly  301 A. 
     The first and second bladder units  302 X,  302 Y can be configured in various suitable ways, including configurations  302 A,  302 B,  302 C, shown in  FIGS.  5   a - c   , or any other suitable configuration. Also, while the example bladder assembly  301 A of  FIGS.  6   a - c    has two bladder, units  302 , further examples can include any suitable plurality of bladder units  302  or can have a single bladder unit  302 . 
     Although certain example embodiments of an actuator assembly  101  shown herein comprise a specific number of bladder  300  (e.g., four, two, one, zero), these examples should not be construed to be limiting on the wide variety of configurations of an actuator assembly  101  that are within the scope and spirit of the present invention. For example, various embodiments of an actuator assembly  101  can include any suitable plurality of bladders  300  (e.g., 3, 5, 6, 7, 8 or more); can include a single bladder  300 ; or bladder  300  can be absent. The orientation of the bladder  300  and the direction of the force they exert can also change. Rotational motion of an actuator assembly  101  can be accomplished with bladder  300  providing a force that is not parallel and in the same direction, but the bladder  300  can be oriented on the same side of a pivot point of the rotational actuation, so that the forces are parallel but in opposite directions, or the bladder  300  can be oriented so that they are offset 90 degrees from the pivot point, so that the forces are perpendicular, or in many other orientations where the moments created by each bladder  300  in an actuator assembly  101  are in different directions. 
     A bladder  300  (or a bladder, or the like) can be made of any suitable material, including polymers, copolymers, terpolymers, and polymer blends (both miscible and immiscible), thermoplastic elastomers, and the like. For example, a bladder  300  can comprise plastics, elastomers, thermoset polymers, thermoplastics, thermoplastic elastomers, copolymers, terpolymers, block copolymers, graft copolymers, polymer composites, polysiloxanes, and both miscible and immiscible polymer blends. Specific examples include high-density polyethylene (HDPE), cross-linked polyethylene (PEX), polypropylene (PP), low-density polyethylene (LDPE), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polystyrene (PS), polyetherimide (PEI), polyphenylene ether (PPE), thermoplastic polyurethane (TPU), thermoplastic elastomers (TPE), polycarbonate, acrylic, nylon, poly vinyl chloride (PVC), flurocarbons, epoxies, phenolics and vinyls, Silicone Rubber (SIR) and the like. 
     Some embodiments can include thermoplastic vulcanizates (TPV) that can be part of the thermoplastic elastomer (TPE) family of polymers. Some examples can have elastomeric properties similar to ethylene propylene diene monomer (EPDM) thermoset rubber, with characteristics of vulcanized rubber, and with the processing properties of thermoplastics. TPV can be a dynamically vulcanized alloy comprising or consisting essentially of fully cured EPDM rubber particles encapsulated in a polypropylene (PP) matrix. 
     In some embodiments it can be desirable for a bladder  300  to comprise one or more ultra-violet (UV) stabilizers, UV-absorber, anti-oxidant, thermal stabilizer, hydrolysis stabilizer, carbon black, glass fill, fiber reinforcement, electrostatic dissipater, lubricant concentrate, antiozonants, ozone resistant additives, or the like. Materials of the bladder  300  can be selected based on a desired manufacturing technique, bladder strength, bladder durability, range of motion, compliance, sun-resistance, temperature resistance, humidity, wear resistance, fatigue resistance and the like. In some embodiments, where the bladder  300  is employed in a location that experiences sun exposure, it can be desirable to include a protective UV coating or UV stabilizer in the bladder  300 . 
     One or more additives may be added to a material of the bladder  300  in some examples to achieve various desirable properties, such as ozone resistance, UV resistance, oxidation resistance, hydrolysis resistance, abrasion resistance, temperature resistance, resistance to environmental and/or operational conditions, and the like. The addition of additives can occur during polymer production, part production, as a coating step, or the like. In some embodiments, such one or more additives can be particles, fillers, fibers, whiskers, or the like. 
     In some embodiments, a bladder  300  can include one or more surface coatings such as inert barrier compounds (e.g., Microcrystalline, paraffin, nano silicone wax, and the like), formulated or blended waxes, synthetic waxes, silicone oil, petroleum-based oil, machine grease, and the like. In some embodiments, a bladder  300  can include one or more surface treatments (e.g., surface cross linking, optimizing surface energy, modifying surface morphology and/or properties, and the like). Such surface modifications in some examples can be applied using laser cladding, plasma treatment, protective coatings deposition, a thermal processes, and the like. 
     While some embodiments of the bladder  300  can only comprise a single layer, others can comprise a plurality of layers. For example, the thickness of a bladder  300  can comprise three layers. An inner layer can be constructed of thin impermeable layer of thermoplastic elastomer that is flexible and holds pressure when inflated. A middle layer can comprise a structural layer constructed of a biaxially stretched PET or other material capable of higher tensile loads. Such a layer can provide structural integrity or aid in the restraint of the bladders. A third, external layer can comprise a carbon black doped HDPE to protect against UV, wind-blown sand abrasion, or other environmental irritants. In this sense, the external layer can act as a shielding layer. An external layer can also act as a sacrificial layer. The outer layer can also exhibit other special properties, such as low coefficient of friction, special texture, or desirable optical or aesthetic properties that can enhance the performance or value of the product. In other embodiments, a bladder  300  can be made of two or more materials in sequence. For example, one embodiment can comprise a bladder  300  with sequentially alternating HDPE and PP convolutions, or the like. A bladder  300  can comprise any suitable constructions with the purpose of offloading particular functions or requirements of the bladder  300  to different layers while keeping aggregate costs down. A bladder  300  can include strengthening or protective shrouding in some embodiments. 
     In some embodiments, the walls of a bladder  300  can be made of a composite of materials. For example, one embodiment can include co-extruding softer materials on an outer layer of the wall and stiffer materials on the inner layer of the wall, which can cause the bladder  300  to experience less displacement driven load (and stress) when compressed while maintaining a desired stiffness to hold pressurized air when extended. The different materials in some embodiments can be different durometers of the same material family (e.g., ThermoPlastic Vulcanisate material (TPV) blends) or multiple materials which share the same base polymer, including but not limited to polymeric composites and alloys (e.g., Santoprene, polypropylene, or the like). 
     For example,  FIGS.  13   a  and  13   b    illustrate an example of a bladder  300  comprising a plurality of layers, including an external layer  1310  that defines an external face of the bladder  300 , a central layer  1320  and an internal layer  1330  that can define an internal face of a bladder cavity  304 . In some embodiments, the external and internal layers  1310 ,  1330  can be the same material, a similar material, or different materials. In some embodiments, the central layer  1320  can be same material, a similar material, or different material compared to one or both of the external and internal layers  1310 ,  1330 . Further embodiments can include any suitable plurality of layers, including 2, 3, 4, 5, 6, 7, 8, 9, 10, 25, 100 or the like. 
     In some embodiments, the bladder  300  of  FIGS.  13   a  and  13   b    can be multi-stiffness fluidic bladder  300  where the external and internal layers  1310 ,  1330  are softer materials and the central layer  1320  is a stiffer materials compared to the external and internal layers  1310 ,  1330 . In various examples, the stiff material of the central layer  1320  can be configured to prevent or substantially prevent stretch on the inside of the wall of the multi-layer bladder  300  with the softer materials of the external and internal layers  1310 ,  1330  allowing for bending of the wall multi-layer bladder  300 . In some embodiments a stiffer material or layer can have a Shore D hardness value (durometer) of 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58 or the like, or a range between such example values. In some embodiments, a softer material or layer can have a Shore D hardness value (durometer) of 37, 38, 39, 40, 41, 42, 43, 44, 45 or the like, or a range between such example values. 
     A bladder  300 , web  303 , bladder unit  302 , or the like, can have various other suitable configurations of layers. For example,  FIG.  24    illustrates an example of a multi-layer portion of a bladder  300  that includes a first outer protective layer  2410 , a second outer protective layer  2420 , a fabric layer  2430 , a first gas-barrier layer  2440  and a second gas-barrier layer  2450 . 
     In various embodiments, one or more protective coatings (e.g., protective layers  2410 ,  2420 ) can be configured to protect a bladder  300  from application use operating conditions (e.g., environmental conditions of an outdoor environment where the bladder  300  operates) to prevent or delay failure of the bladder  300  or deterioration of the bladder  300  that causes undesirable or reduced performance or failure of the bladder  300 . In various embodiments, one or more gas-barrier layers (e.g., gas barrier layers  2440 ,  2450 ) can be any suitable material that substantially or completely prevents gas seepage through the material(s). In various embodiments, one or more fabric layers (e.g., fabric layer  2430 ) can comprise a weave of various suitable synthetic and/or natural fibers. Since a fabric layer  2430  can be porous in some examples, one or both of the barrier layers  2440 ,  2450  can prevent fluid (e.g., gas) held within the bladder  300  under pressure, as discussed herein, to permeate into the fabric layer  2430  and leak out of the bladder  300 . 
     In some embodiments, the protective layers  2410 ,  2420 , the fabric layer  2430  and/or the gas-barrier layers  2440 ,  2450  can include various suitable materials including polymers, copolymers, terpolymers, and polymer blends (both miscible and immiscible), thermoplastic elastomers, and the like. For example, such layers can include plastics, elastomers, thermoset polymers, thermoplastics, thermoplastic elastomers, copolymers, terpolymers, block copolymers, graft copolymers, polymer composites, polysiloxanes, and both miscible and immiscible polymer blends. Specific examples include high-density polyethylene (HDPE), cross-linked polyethylene (PEX), polypropylene (PP), low-density polyethylene (LDPE), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polystyrene (PS), polyetherimide (PEI), polyphenylene ether (PPE), thermoplastic polyurethane (TPU), thermoplastic elastomers (TPE), polycarbonate, acrylic, nylon, poly vinyl chloride (PVC), flurocarbons, epoxies, phenolics and vinyls, Silicone Rubber (SIR) and the like. Some embodiments can include thermoplastic vulcanizates (TPV) that can be part of the thermoplastic elastomer (TPE) family of polymers. Some examples can have elastomeric properties similar to ethylene propylene diene monomer (EPDM) thermoset rubber, with characteristics of vulcanized rubber, and with the processing properties of thermoplastics. TPV can be a dynamically vulcanized alloy comprising or consisting essentially of fully cured EPDM rubber particles encapsulated in a polypropylene (PP) matrix. All different variations of such layers with such materials, including some or all layers being different materials are within the scope and spirit of the present disclosure. In various embodiments, one or more fabric layer (e.g., fabric layer  2430 ) can comprise a weave of one or more example materials discussed herein. 
     In various embodiments, layered structures can include two or more layers of elastomers including Polyurethane (PU), Polyvinyl chloride (PVC), Polychloroprene elastomer (CR), Nitrile butadiene rubber (NBR), Fluorocarbon (FKM), chlorosulfonated rubber (CSM), isobutylene isoprene rubber (IIR), ethylene propylene diene monomer (EPDM) and the like. Elastomer layer itself can be fiber/particle reinforced in some examples. The fabric layer (e.g., fabric layer  2430 ) can be woven or nonwoven with some examples being mainly polyester and polyamide. In some examples, there can be a plurality of fabric layers. Various suitable processing methods can be used to incorporate and/or attach fabric and/or elastomer layers, including calendaring/dry coating, solution coating, and the like. 
     In various embodiments, any suitable portion of a bladder unit  302  can have a multi-layer structure including a web  303  and/or one or more bladders  300 . For example, in some embodiments, such elements can have the same layers or different portions can have different layers. For example, the bladders  300  of a bladder unit  302  can have different layering than the web  303  of the bladder unit  302 . Additionally, in some embodiments, some portions can have a single layer, with other portions having a plurality of layers. 
     In various examples, a multi-layer configuration of the bladders  300  and/or web  303  can allow the bladders  300  to rotate more easily relative to a fixed web  303  but prevent the bladders  300  from translating away from a fixed position (e.g., a stiff central layer  1320  of a laminated web  303  can prevent the web  303  from stretching). 
     A bladder  300 , web  303  and/or bladder unit  302  can be made via any suitable manufacturing process, including extrusion blow-molding (EBM), injection stretch blow-molding (ISBM), multi-layer blow-molding, co-extrusion blow molding, co-injection blow molding, suction blow-molding, 3D blow-molding, sequential co-extrusion blow-molding, vacuum forming, injection molding, thermoforming, rotational molding, process cooling, three-dimensional printing, dip modeling, hydroforming, plastic welding or the like. 
     Multilayer bladder  300 , web  303  and/or bladder unit  302  can be constructed by any suitable manufacturing processes, including: co-extrusion, sequential co-extrusion, co-extrusion blow molding, glue lamination, heat lamination, fabric wrapping, filament winding and any other manner of manufacturing. In some embodiments bladders can be manufactured from sheet material. In these embodiments, fabric or plastic sheeting can be sewn, heat welded, ultrasonically welded, laser welded, glued laminated, clamped or bonded by any other suitable manufacturing processes. In some embodiments, a single or multi-layer structure can be coated to generate a multi-layer structure. 
     In some embodiments extrusion or other suitable method can be used to create a web  303  between opposing fluidic bladders  300 , where the web  303  bends easily but does not stretch. For example, various embodiments include a method of manufacturing a bladder unit  302  comprising generating (e.g., blow molding) an elongated member having a cross-section profile along its length such as shown in  FIGS.  5   a ,  5   b ,  5   c   , or the like, which includes an elongated web portion and a pair of elongated cavities on opposing sides of the web portion with each of the cavities being open on opposing ends of the elongated member. Generating an elongated member with open ends can be done in various suitable ways as discussed herein, which can include extrusion, co-extrusion, additive manufacturing (e.g., 3D printing), and the like. 
     The method can further include closing the elongated cavities by closing the openings of the cavities on the opposing ends of the elongated member to generate closed bladder cavities  304  and define the bladders  300  on opposing sides of the web  303 . In various embodiments, one or more ports  306  can be incorporated into the bladder unit  302 , which can be part of the closure of one or both ends of the open cavities or can be a separate step after one or both ends of the open cavities have been closed. Closing the ends of the open cavities to generate a seal such that the bladders  300  can hold fluid can be done in various suitable ways including via welding (e.g., impulse welding, radio frequency welding, ultrasonic welding, chemical welding, applied heat welding, and the like) and/or other suitable method such as an adhesive, fold, clip, clasp, clamp, or the like. In various embodiments, the bladders  300  and/or web  303  of the bladder unit  302  can then be coated with oil (e.g., silicone oil). 
     Some embodiments can include a method of manufacturing a fluidic actuator that comprises placing a first bladder unit  302  on a V-shaped bottom plate  310  having a ridge  312  and a first arm  311  and second arm  311  disposed at an angle of 90°-60° relative to each other, with the web  303  of the first bladder unit  302  coupled to the ridge  312  of the angled bottom plate  310 , with a first closed bladder  300  engaging the first arm  311  of the angled bottom plate  310 , and with a second closed bladder  300  engaging the second arm  311  of the angled bottom plate  311 . The assembly of the angled bottom plate  310  and the first bladder unit  302  can have a plane of symmetry coincident with the ridge  312  of the angled bottom plate  310 . 
     The method of manufacturing a fluidic actuator can further comprise placing a second bladder unit  302  over the first bladder unit  302 , the second bladder unit  302  having the same configuration as the first bladder unit  302 , the second bladder unit  302  having a second web  303  and a second first bladder  300  and a second bladder  300 , the second web  303  disposed on and coupled to the web  303  of the first bladder unit  302 , the second first bladder  300  disposed on the first bladder  300  of the first bladder unit  302 , and the second bladder  300  disposed on the second bladder  300  of the first bladder unit  302 , the assembly of the angled bottom plate  310  and the first and second bladder units  302  having a plane of symmetry coincident with the ridge  312  of the angled bottom plate  310 . 
     The method of manufacturing a fluidic actuator can further comprise coupling a planar top plate  330  to the angled bottom plate  310  via first and second hub assembly  370  extending between the angled bottom plate  310  and the planar top plate  330  on opposing front sides of the angled bottom plate  310 , the first and second hub assembly  370  comprising a respective rotatable coupling that forms a rotatable coupling between the planar top plate  330  and the angled bottom plate  310 . 
     For example,  FIGS.  14  and  15    illustrate example embodiments of bladders  300  that can be generated via such a method.  FIG.  14    illustrates an example embodiment of a bladder  300  having a cylindrical elongated body with first and second ends  1400  that have been closed (e.g., via a weld). The first end  1400 A includes a port  306  that can be formed in or inserted into the first end as part of the closure of the first end  1400  or as a separate manufacturing step.  FIG.  15    illustrates an example embodiment of a bladder  300  having an elongated body with a teardrop shape with first and second ends  1400  that have been closed (e.g., via a weld). The first end  1400 A includes a port  306  that can be formed in or inserted in the first end as part of closure of the first end  1400  or as a separate manufacturing step. 
     In some embodiments, (including where bladders  300  are separate and not connected via an integral web  303  or where bladders  300  are connected via a web  303 ), it can be desirable to retain the bladders  300 . For example,  FIGS.  16  and  17    illustrate example embodiments where bladders  300  are held by a retention system  1600 , which can comprise one or more sheets  1610  (e.g., sleeves) that encircle and retain the bladders  300 . For example, a sheet  1610  can encircle a bladder  300  and be coupled to the bottom plate  310  and/or top plate  330  to create a loop or sleeve of a fixed size in which the bladder  300  is retained. Such a configuration can retain the bladder  300  in place for engaging the bottom plate  310 , top plate  330  and/or another bladder  300 . Additionally, in various embodiments, the retention system  1600  can constrain lateral expansion of one or more bladders  300 , which can be desirable in various examples for directing force generated by inflation of the one or more bladders  300 . 
     A bladder  300  can have fabric or fiber reinforcement in some embodiments. Such incorporations can afford a bladder  300  with enhanced tensile strength or wear properties, while preserving flexibility and function. Enhanced tensile strength from fiber reinforcement can allow for greater factors of safety, increased operating pressures and associated stiffness, longer fatigue life, enhanced resistance to puncture, and generally boosted durability. 
     Fiber reinforcement can be incorporated via filament winding, sewn fabric shrouding, extrusion-coated fabric, pultrusion, transfer molding, compression molding, solution coating, powder coating, and the like. Fiber reinforcement can be directly incorporated into the bladder  300 , for example, as an additive to plastic extrusion. Fiber reinforcement can be incorporated into a bladder  300  through the welding, fusing or laminating of a fabric or fibered layer to a plastic or elastomeric bladder wall. Fiber reinforcement can also be indirectly incorporated. For example, a fabric sheet can be wrapped around a hermetic bladder and then secured to actuator plates. An architecture of this nature can, in some examples, reinforce and strengthen the bladder while simultaneously affixing it to the rigid plate components. 
     In some embodiments, a bladder  300  can be defined by a thin elastic or hyperelastic inner-portion with an inelastic and flexible weave around the thin elastic inner-portion. Some such examples can withstand high amounts of pressure while also sealing fluid in a thin-walled bladder  300  by splitting the functions of sealing and withstanding the pressure between two separate components. Fabric weaves can be made to be inextensible along the axes of the plane of the fabric while also being flexible in other directions. When paired with a soft, sealing polymer as a thin elastic inner-portion, the fabric weave can bear some or substantially all of the planar stress generated by internal pressure within the bladder  300 . By passing the load onto the weave, the inner-portion sealing polymer can be made thin in various examples, which may make the bladder  300  easy to compress. For example, in some embodiments such an inner-portion sealing polymer or other “thin” material can be less than 0.1 mm, 0.05 mm, 0.04 mm, 0.03 mm, 0.025 mm, 0.02, 0.015 mm 0.01 mm, 0.005 mm, or the like, or a range between such example values. 
     For example,  FIG.  18    illustrates an example of a bladder  300  defined by an inner-portion  1810  and an enclosure  1820  where the inner portion  1810  is configured to be disposed within a cavity  1822  defined by the enclosure  1820  by inserting the inner portion  1810  into a first end  1824  of the enclosure  1820 . The first end  1824  can then be closed (e.g., via sewing, welding, and adhesive, or the like). In various embodiments, the inner portion  1810  can comprise a thin, soft and elastic sealing polymer such as materials discussed herein. In various embodiments, the enclosure  1820  can comprise an inextensible yet flexible woven fabric such as woven nylon, polyester, acrylic, polypropylene, organic fibers (e.g., cotton), or the like such as fibers of one or more materials discussed herein. Respective second ends  1814 ,  1826  of the inner portion  1810  and enclosure  1820  can define a port  306 , which can be fitted with a fluidic (e.g., pneumatic) fitting  1830  secured with a hose clamp  1840 . 
     Various embodiments of a bladder  300 , web  303  and/or bladder unit  302  can include a rubber/fabric or TPE/fabric or polymer/textile laminate vulcanized, calendared together or solution coated. Some embodiments can include a nylon, polyester, or blended weave coated in a poly-urethane, rubber or other thermoplastic elastomer (e.g., Polyurethane (PU), Polyvinyl chloride (PVC), Polychloroprene elastomer (CR), Nitrile butadiene rubber (NBR), Fluorocarbon (FKM), chlorosulfonated rubber (CSM), isobutylene isoprene rubber (IIR), ethylene propylene diene monomer (EPDM), and the like). Various embodiments can include an elastomer/fiber laminate, which can be a combination of elastomer/woven fabric and elastomer/nonwoven or the elastomer itself can be fiber reinforced. For example, some embodiments can include a rubber/fiber laminate that splits the functions of holding pressure and maintaining a seal into two separate components, but in some examples also uses the sealing material to protect the inelastic weave (e.g., the fiber is partially or completely enclosed in the rubber). The result can be a bladder  300 , web  303  and/or bladder unit  302  which compresses easily but can withstand high internal pressure which may also have some amount of abrasion resistance and/or environmental protection. 
     Various embodiments of bladder  300 , web  303  and/or bladder unit  302  can include a warp and/or weft of laminate. For example,  FIG.  19    illustrates an example of a bladder  300  that includes cords  1900  laminated into the body of the bladder  300  in longitudinal and transverse directions. Such cords  1900  in some examples can be fabric that is co-planar with a rubber layup in at least the wall of a bladder  300 . 
     In some embodiments, generating a bladder  300  or bladder unit  302  can comprise coupling a web, tab or other structure to one or more bladders  300  such as via welding, an adhesive, clamp, bolt, or the like. Such an element can provide for retention of the one or more bladders  300  as discussed herein. For example,  FIG.  20    illustrates a cross-sectional view of an example embodiment of a bladder  300  with a tab  2010  coupled to an edge  2020  of the bladder  300 . The tab  2010  in various examples can comprise coupling holes  2012  that allows the bladder to be coupled to a bottom plate  310  as discussed herein. In further embodiments, the tab  2010  can be coupled to a second bladder  300  to generate a bladder unit  302 . 
     In various embodiments, such a retention feature (e.g., a tab  2010  or web  303 ) can be laid up along with the air-filled portion of the bladder  300 . In some examples, such a retention feature can be made of a rubber/fabric or TPE/fabric laminate vulcanized, calendared together, or solution coated, a nylon, polyester, or blended weave coated in a polyurethane, rubber or other thermoplastic elastomer, fiber laminate or other suitable material in order to maximize the component strength. Such a tab  2010  or web  303  can extend from various suitable locations of a bladder. For example, in the embodiment of  FIG.  15   , the bladder  300  is shown being teardrop shaped with the tab extending from a rounded bulbous end and coincident with a main axis of the bladder, but further embodiments can include a tab  2010  or web  303  extending from the smaller end of the bladder  300  or other suitable location. Such tabs can be attached using welding, impulse welding, radio frequency welding, ultrasonic welding, chemical welding, gluing, applied heat welding, and the like. In some embodiments, such a tab  2010  can be integrated into the inherent design of the bladder  300 . For example, the tab  2010  or web  303  can be an integral part to the body of the bladder  300 . 
     Turning to  FIGS.  21 ,  22  and  23   , in some embodiments such a tab  2010  can be generated in a bladder  300  via a method that includes rolling a sheet of material  2100  onto itself to form a cavity  2104  that is open on both ends  2106 . The method can further include generating a coupling  2108  (e.g., a welded lap seam) between adjacent portions of the sheet material  2100  with one end  2102  of the sheet material  2100  remaining extending from an exterior face to generate a tab  2010 . Such a coupling can have various suitable widths W (see e.g.,  FIG.  23   ), which can include 0.1 inch, 0.25 inch, 0.5 inch, 0.75 inch, 1 inch, or the like, or a range between such values. In some embodiments, edges of the tab  2010  can comprise a bevel or can have any other suitable configuration. 
     In some embodiments, end caps  2110  can be coupled (e.g., welded) to both ends  2106  of the rolled sheet of material  2100  to close the open ends  2106  and enclose the cavity  2104 . In some embodiments, however, the ends  2106  can be closed in various ways as discussed herein such as coupling portions of the ends  2106  together (e.g., welding the ends  2106  shut). For example, closing or coupling the ends  2016  can comprise hot-wedge welding, hot air welding, impulse welding, radio frequency welding and ultrasonic welding, or the like. A port  305  can be present in or generated in one or both of the end caps  2110 , or otherwise generated in the bellows  300  in various suitable ways. 
     In various embodiments, two or more such bladders  300  can be coupled together to generate one or more a bladder units  302 . For example, as shown in  FIG.  22   , coupling holes  2012  can be aligned to allow a pair of bladders  300  to be coupled together, coupled to a bottom plate  310 , coupled to a top plate  330 , or the like. For example, in some embodiments, two or more bladders  300  can be coupled to a ridge  312  of an angled bottom plate  310 . 
     In some embodiments, multiple bladder  300  can be formed as a single part. In some manufacturing processes multiple bladder  300  chambers can be joined by a connecting fascia. Manufacturing processes in which such a construction could be formed include, but are not limited to, extrusion blow molding, injection stretch blow molding, fabric sewing, injection molding, dip molding, blow molding, 3d printing, injection molding, extrusion, vacuum forming, casting, rotational molding, fabric sewing, or the like. 
     In one such embodiment, a two-chambered bladder  300  can be formed through extrusion blow molding, blow molding, 3d printing, injection molding, extrusion, vacuum forming, casting, rotational molding, fabric sewing, or the like. An oversized tube of molten plastic can be extruded, a two-chambered mold can be closed around it, and the chambers can be pressurized to set the part shape. The resulting part can have two independent chambers connected at the center by a solid plastic fascia. The independent chambers can each have in-molded barb tubes for pneumatic connections, or can have molded features that enable attachment of another appropriate connection type. This method of manufacture can also place features such as weld or pinch lines in ideal areas, where operation stress and strain can be minimized. The material connecting the chambers of the bladder  300  can be thicker than the chambers of the bladder and capable of taking high tensile loads. For example, the material connecting the chambers of the bladder  300  can be twice as thick as the chambers of the bladder  300 . In some actuator architectures, a connecting web  303  of a bladder unit  302  can be slung over the pivot ridge  312  on the bottom plate  310 , or any other suitable attachment point in the actuator assembly  101 . This web  303 , in some examples, can act as a constraint, affixing the bladder  300 , and obviating the need for a secondary or external method of bladder constraint. 
     A similar bladder  300  construction can be achieved by sewing fabric and/or welding (e.g., impulse welding, radio frequency welding, and ultrasonic welding, chemical welding, glue welding, applied heat welding, and the like). A fabric sheet can be folded and sewn in such a way to create independent bladder  300  chambers, as well as a connecting web  303 . 
     Parts with a plurality of bladder chambers can also be made so that the chambers are not independent of each other. In such an embodiment, two chambers can be connected to each other by a tube, channel, pillow plate bead, or any other feature that allows for unimpeded fluid flow between the chambers. Such a construction can be useful in actuator architectures that utilize stacked bladder  300 . In this architecture, a multi-chamber bladder  300  can be folded such that one bladder  300  resides on top of the other on one side of the actuator pivot ridge  312 . A similar architecture can be found on the other side of the pivot ridge  312 . A channel between the chambers of the bladder  300  that allows for fluid flow can generate equal pressurization of both chambers and can obviate the need for separate fluid connections to the chambers in some examples. 
     A bladder  300  can be any suitable thickness in various portions, including about between 0.002 inches and 0.125 inches, and about between 0.0005 inches and 0.25 inches. In various embodiments, the thickness of various portions of the bladder  300  can be selected based on a desired manufacturing technique, bladder strength, bladder durability, range of motion, compliance, sun-resistance, temperature resistance, and the like. 
     Embodiments of the actuator assembly  101  can comprise bladder  300  of various shapes and sizes. For example,  25 ,  26   a ,  26   b ,  27   a  and  27   b  illustrate various views of further embodiments  300 E,  300 F,  300 G,  300 H,  300 J of bladders  300 . While figures herein illustrate some example embodiments of a bladder  300 , these examples should not be construed to be limiting. Additionally, it should be clear that aspects of one embodiment can be present in other embodiments or vice versa, or various elements can be explicitly absent in some embodiments. 
     A bladder  300  can be designed to have one of a variety of diameters. The diameter of a bladder  300  incorporated into an actuator assembly  101  can dictate the pressure-to-position relationship achieved by the actuator assembly  101 . In some embodiments, a small diameter can be chosen to optimize for cost or packing efficiency. In other embodiments a large diameter can be chosen to optimize for strength, stiffness and dynamic performance. 
     A bladder  300  can be designed to be of any length. For a bladder  300  having shapes with an extended or extruded body section, the body section can be of any length. A bladder  300  with a short body section can approximate a sphere. A bladder  300  with a longer body section can have a pill shape or a noodle shape. A body of a bladder  300  can be extended indefinitely and take the form of a true tube or hose. 
     A bladder  300  can be designed to have one of a variety of fundamental shapes. Some embodiments can feature a bladder  300  that comprises an extruded form body. The extruded cross-section can be circular, oval, teardrop-shaped, have convoluted lobes or take on any extrudable profile. In some embodiments, a bladder  300  may not have a defined body section. In these embodiments the boundary between body and cap can be blurred. Some examples of bladder  300  in this category can be cone-shaped, tapered, spherical, kidney bean-shaped, incorporate convolutions, or have some other amorphous shape. 
     A body section of bladder  300  can be terminated at either end with caps. Caps of a bladder  300  can take on various shapes depending on the application. The terminations or end caps on the bladder  300  can take a variety of shapes, including hemispheres, truncated cones, right cones, oblique cones, convoluted bladder, ellipsoid, or the like. 
     In some embodiments, features can be formed into bladder  300  during the molding process. Such features can include, but are not limited to, locating bosses, hard stops, convolutions, tubing, pneumatic connectors, and the like. In other embodiments, features can be attached to bladder  300  in any number of suitable manners. Attachment methods can include hot plate welding, ultrasonic welding, heat sealing, gluing, press fitting, or a variety of other methods. 
     In some examples a tube/bulbous bladder  300  can be desirable over other types of inflatable fluidic actuators. The following provides some examples of potential benefits of some embodiments. 
     Stronger Pressure to Position Relationship— A large areal change can generate a stronger pressure to position relationship (&gt;&gt;Δ psi/Δ degree). In some embodiments, this not only means greater static stiffness, but can also generate better accuracy (e.g., actual angle to command angle), and/or intra-tracker precision (e.g., tracker to tracker consistency). Some examples can include hysteresis and accuracy that is less dependent on recent actuator positional history. Further examples can have better leak tolerance (e.g., positional stability given a leak rate). 
     Better Static Stiffness—Due to the large areal change from the compressed to extended positions in some examples, as well as a change in effective moment arm over the full range of motion, a tube actuator of some examples can provide 2-5× the static stiffness of other types of actuators. If static stiffness is a limiting factor in some examples (e.g., interior tracker), this can mean the actuator can be tolerant to increased load and allow more W/Actuator in some examples. 
     Reduced Compressed Air Burden—In some examples, a tubular actuator operating at the same peak pressure as an alternative fluidic actuator design may exhibit substantially reduced compressed air consumption while retaining at least the same dynamic stiffness as other types of bladder  300 . This can reduce the parasitic power loss, can decrease the needed compressor output (e.g., per 2 MW array) and can also increase the number of actuators per row controller (e.g., if stow or another fill related metric can be limiting). 
     Simpler Pivot Solution—In some examples, a bladder-based actuator can utilize a pure pivot instead of a bending wire rope flexure. In some embodiments, a simple pivot design can enable the inclusion of a viscous damper; however, in some embodiments, a viscous damper may not be included on every actuator in every tracker, but can be used in various situations (e.g., exterior trackers) to deal with excessive wind/dynamic loads, and the like. 
     Lower Payload Center of Mass—In some embodiments, a simple pivot can enable a low center-of-mass design. An actuator assembly  101  configured with a lower center-of-mass can take a greater payload while keeping performance constant, compared to other types of actuators. 
     Less Complexity—In some examples, tube actuator constraints can be less complex and embody less material than constraints in other actuator systems. Accordingly, in various embodiments, the assembly part count of bladder actuators can be greatly reduced compared to other actuator systems. 
     Efficient Plate Geometries—Actuator configurations of some embodiments of a bladder actuator can allow the top and bottom plates  310 ,  330  to take more efficient shapes compared to other actuator systems. Plates  310 ,  330  can be designed to be bent at high angles to make use of compressive and tensile elements that effectively and efficiently bear the antagonistic forces with less material. 
     Enhanced Bladder Protection—Various bladder actuator configurations can better protect pneumatic bladder from UV, blown sand and accidental puncture (e.g., during installation or maintenance) compared to other actuator systems. 
     Improved Moldability—In various examples, tube bladder can be much easier to blow mold compared to other actuator systems. For example, cylinders can be the easiest thing for some molders to process. This can mean that various examples of tube bladder can have less value-added cost and better average quality (e.g., better material distribution/low thickness variation) compared to other actuator systems. 
     Reduced Part Weight—Compared to some other actuator systems, a bladder can comprise about one-quarter to one-eighth less material. In addition to the material savings, the lower part weight can also result in reduced molding cycle times. Cycle times of bladder actuator systems can be on the order of 15-30 seconds, as opposed to 80-110 seconds for other actuator systems. This can mean less value added per part and more annual output per mold for some embodiments of bladder actuators. 
     Fiber Reinforcement—In some examples, cylindrical bladder, or the like, can be desirable for fiber incorporation. For example, filament winding, fabric wrapping, and the like can be used in one or more bladder of bladder actuators. Fiber reinforcement can allow for increased operating pressures, greater durability/resistance to puncture, a reduction in expensive engineered materials per molded part, and the like. 
     Turning to  FIGS.  7   a  and  7   b   , the bladder assembly  301  of  FIGS.  6   a - c    is shown with pneumatic lines  390  coupled to ports  306  of the bladder  300 . More specifically, a pair of pneumatic lines  390 E,  390 W are shown with each comprising lines  705  that are coupled to respective ports via crimps  710  at a first end of the lines  705 . A second end of the lines  705  are coupled to a Y-connector  715  that communicates with a coupler  720 . The east pneumatic lines  390 E are coupled to the first bladder  300 X 1 ,  300 Y 1  of the first and second bladder units  302 X,  302 Y and the west pneumatic lines  390 W are coupled to the second bladder  300 X 2 ,  300 Y 2  of the first and second bladder units  302 X,  302 Y. 
     As discussed herein, the pneumatic lines  390  can provide for fluid being introduced to and/or removed from the bladder assembly  301  to move an actuator assembly  101  as discussed herein (see, e.g.,  FIGS.  2  and  3   ). For example, the east pneumatic lines  390 E can allow the first bladder  300 X 1 ,  300 Y 1  to be inflated and/or deflated in unison. In various embodiments, the east pneumatic lines  390 E are configured to provide the same amount of fluid and the same fluid pressure to the first bladder  300 X 1 ,  300 Y 1 . Similarly, the west pneumatic lines  390 W can be configured to provide the same amount of fluid and the same fluid pressure to the second bladder  300 X 2 ,  300 Y 2 . For example, the coupler  720  of the east pneumatic lines  390 E can be fluidically coupled to a first fluid source that controls the first bladder  300 X 1 ,  300 Y 1 , and the coupler  720  of the west pneumatic lines  390 W can be fluidically coupled to a second fluid source that controls the second bladder  300 X 1 ,  300 Y 1 . 
       FIG.  8    illustrates a close-up side view of ports  306  and couplers  710  of the bladder assembly  301 A of  FIGS.  6   a ,  6   b ,  7   a  and  7   b   . Tubing  705  is shown coupled to ports  306  of bladder  300  via a barbed fitting  711  disposed within ends of the tubing  705  and ports  306  with crimps  710  locking the fittings  711  to the ports  306 .  FIGS.  7   a ,  7   b    and  8  illustrate example embodiments of how pneumatic lines  390  can be coupled to a bladder assembly  301 ; however, in further embodiments, pneumatic lines  390  can be coupled to a bladder assembly  301  in various other suitable ways. 
     Various examples can include use of interference fit barbed fittings pressed into blow-molded bladders. Various examples can include a pneumatic architecture, including: Harness tube branch-&gt;orifice connector-&gt;Y connector-&gt;2× tube to top bladder. 
     In some examples, locating the flow limiting orifice on the harness side of the Y connector results in twice the flow through the orifice relative to putting orifices on the bladder side. This can enable greater flow restriction from the same orifice geometry. 
     Flow restriction devices can include any suitable device or structure. For example, a restrictor can comprise a body that defines a fluid passage having a pair of ports that provide for entry and/or exit of fluid into the fluid passage. Another example can include a coiled fluid passage. A further example can include a serpentine fluid passage. In various embodiments, such a restrictor can be a portion of a bladder, cap, or the like. In other embodiments, a restrictor can comprise a multi-layer fluid passage, or the like. 
     Turning to  FIGS.  9   a  and  9   b   , a perspective and side view of a top plate  330  with top portions  372  of a hub assemblies  370  disposed on opposing sides of the top plate  330 . The top plate is shown comprising a planar and rectangular slab  331  with rims  333  extending perpendicularly from the slab  331  and with the rims  333  extending parallel to each other. The slab  331  and rims  333  define a tray  335  having open ends. Hub assembly top portions  372  are coupled to opposing sides of the top plate  330  on external sides of the rims  333 , with the hub assembly top portions  372  extending below a plane of the slab  331 . 
     The hub assembly top portions  372  can comprise at least a portion of a shoulder bolt  374 , which can rotatably couple with hub assembly bottom portions  376  (See, e.g.,  FIGS.  10   a ,  10   b ,  11   a ,  11   b   ) to define a hub assembly  370 . 
     Turning to  FIGS.  10   a  and  10   b   , a perspective and side view the bottom plate  310  of  FIG.  3    is illustrated which comprises a pair of arms  311  that extend from a ridge  312  where the arms  311  are coupled to hub assembly bottom portions  376 . The arms  311  define faces  313  on which bladder  300  of bladder assemblies  301  can bear against to move the actuator assembly  101  as discussed herein (see, e.g.,  FIGS.  2  and  3   ). The arms  311  can further define a slot  314  that is defined by sidewalls  316  of the arm  311 . In various embodiments, the slot  314  and sidewalls  316  can be configured to couple with various structures such as a post, or the like, which can serve as a stand or support for the actuator assembly  101  and tracker  100  (see, e.g.,  FIGS.  1  and  2   ). 
     The hub assembly bottom portions  376  can include a bolt hole  378  that can comprise or engage with a shoulder bolt  374  ( FIGS.  9   a ,  9   b   ) such that the bottom plate  310  can be rotatably coupled with the top plate  330  via the hub assembly  370  defined by the top and bottom hub assembly portion  372 ,  376 . 
     Additionally, the hub assembly bottom portions  376  can include one or more coupling holes  379 , which can provide a location for a bladder assembly  301  to couple with the base plate  310 . While a hub assembly  370  defined by top and bottom hub assembly portions  372 ,  376  and including a shoulder bolt  374  is shown in various examples, further embodiments can include various suitable structures to couple the top and bottom plates  310 ,  330  such that the top and bottom plates  310 ,  330  can move relative to each other by inflation and/or deflation of bladder  300  of a bladder assembly  301  having one or more bladder units  302 . 
     For example, in some embodiments, the hub assembly  370  can comprise a joint, a pivot, a hinge, a bending flexure, a linkage, or another suitable mechanism or form of attachment. 
     In some embodiments, a hub assembly  370  can comprise pivot or an axle seated in bearing or bushing and can be employed to connect the mount to the payload. An actuator assembly  101  can comprise a single hub assembly  370 , or a plurality of hub assemblies  370 . Hub assemblies  370  can be cantilevered, supported on both sides, or have any other suitable construction. An axle component of a hub assembly  370  can be a hardened steel shaft, a flanged clevis pin, a shoulder bolt, or any other type of axle. An axle can be threaded on one or both ends and screwed into a threaded hole, or fastened with a nut and washer assembly. The axle can be fastened with shaft clamps or any other securement method for smooth shafts. Additionally, a shaft can have any number of features formed into it to aid fastening, or location of assembly components. Some such features can include girdling grooves for circlip fasteners, transverse holes for securement by cotter pin, set screw or twisted wire, or shaft shoulders, for locating other assembly components or features. 
     A bearing component of a hub assembly  370  can include a ball bearing, a sleeve bushing or any other species of bearing. The bearing can be constructed of metal, included, but not limited to, steel, copper, brass, bronze, as well as plastics, including, but not limited to, acetal, HDPE, nylon, and Teflon. The bearing can also be some combination of materials, or made of oil impregnated or alloyed material. 
     In some embodiments, a hub assembly  370  can comprise a flexure to attach the payload to the base or to connect top and bottom plates  310 ,  330  of an actuator assembly  101 . A flexure, or flexible/bending connector, can take a variety of forms in various examples. A flexure can be constructed of metal sheets or twisted strands such as spring steel sheets flexures, wire rope, or springs, or the like. A flexure can take any suitable length. Metal flexures can also comprise assemblies of metal flexure components such as crossed or angled wire rope, spring steel crosses or the like. 
     A wire rope can be used as a flexure. The flexure can hold the actuator plates  310 ,  330  together under tensile load, while still allowing for rotation of the free plate relative to the fixed plate. The wire rope can be made of any suitable material and can have any suitable strand and bundle configuration. The flexure can be coupled via a Nicopress fitting, via swaging, via a Spelter socket, or the like. 
     In further embodiments, a flexure for a single-axis actuator assembly  101  can comprise a parallel rope flexure, a planar flexure, a load bearing pivot, a four-bar linkage, a tetrahedral linkage, or the like. Such flexures can comprise any suitable material, including a metal, plastic, fiber reinforced composite, or the like. 
     For example, an embodiment of an actuator assembly  101  can comprise a flexible planar flexure that extends between a bottom and top plate  310 ,  330 . Another embodiment of an actuator assembly  101  can comprise a flexible tetrahedral linkage defined by a rope that extends between a bottom and top plate  310 ,  330 . A further embodiment of an actuator assembly  110  can comprise a pivot that extends between a bottom and top plate  310 ,  330 . 
     An actuator assembly  101  can also comprise snap-in connections, twist-in connections, one-way push-in barb connections, toggle locks or any other suitable mechanism or connection to facilitate quick and inexpensive assembly of an actuator assembly  101 . 
     In some embodiments, a 2-degree-of-freedom actuator can be employed. The corresponding attachment method can comprise a universal joint, a spring, a spherical bearing, a wire rope or any other mechanism. 
     The faces  313  of the arms  311  of the bottom plate can have flat profile as shown in  FIGS.  10   a  and  10   b   ; however, in further embodiments, the faces  313  can have a convex or concave profile. Similarly, while the slab  331  of the top plate  330  can have a flat profile on the underside of the top plate  330  where bladder  300  of a bladder assembly  301  engage the underside of the top plate  330 , in further embodiments, the underside of the top plate  330  can have a convex or concave profile. The angle θ between the faces  313  of the arms  311  is shown as being 70° in the example of  FIGS.  10   a  and  10   b   ; however, in further examples, the angle θ can be within the range of 90°-60°, 75°-65°, 71°-69°, and the like. 
     An actuator can comprise one or a plurality of plates in various examples. An actuator assembly  101  with multiple plates can have plates that are rotatably coupled. Bladder  300  can be disposed between the plates, with the surface of the plates interfacing with the bladder  300 . An actuator assembly  300  can comprise plates in any suitable architecture, in any suitable shape. This can include strain plates, angled plates, ribbed plated, extruded section plates, multi-piece plates, or the like. 
     In some embodiments, the interfacing faces of the plates  310 ,  330  can be curved, or have some complex geometry. Modifying the topography of a plate can change the performance of an actuator assembly  101  in some examples. Actuator performance or durability can be optimized by such deviations from the baseline, flat, plate design. Geometric deviations can be of a variety of forms, including single plane curvature, compound, multi-plane curvature, the addition of bosses or holes, or the like. Top and bottom plates  310 ,  330  can be fabricated through a variety of processes, including die casting, progressive stamping, laser cut and bent, injection over-molded, or the like. 
     In various embodiments, the top and bottom plates  310 ,  330  can comprise any suitable material, including a polymer, metal, wood, composite material, a combination of materials, or the like. Additionally, although specific configurations of the top and bottom plates  310 ,  330  is shown herein, further embodiments can include plates having any suitable configuration. For example, various suitable embodiments of the top and bottom plates  310 ,  330  can be configured to interface with the bladder  300  so as to distribute a point load from a flexure, pivot, axel or hub assembly. Plates can also comprise and leverage existing structures, such as mounting piles, spanning beams or the like. 
     Top and bottom plates  310 ,  330  can be made in any suitable way. For example, in one embodiment, a cold rolling process can be used in conjunction with metal stamping to create a C-channel plate with the appropriate interfacing features for the top and bottom plates  310 ,  330  as described herein. Plates can also be formed of standard hot and cold-rolled sections. Plate features can be die cut, CNC punched, laser cut, waterjet cut, milled or any other suitable subtractive manufacturing method. A plate can also comprise multiple standard sections or custom formed parts. Plates of this nature can be bonded together with a variety of fasteners, including rivets, nuts and bolts, welds or the like. 
     In another embodiment, manufacture of the top and bottom plates  310 ,  330  can include the creation and processing of composite panels. For example, a composite top or bottom plate  310 ,  330  can comprise a multi-material sandwich plate that takes advantage of a lightweight and inexpensive core material and the stiffness and strength of thinner sheets of skin material that can adhere to either side of the core substrate. Such composite paneling can be used as high stiffness, high strength, low weight, low-cost flooring or construction material. 
     In some embodiments, a composite top or bottom plate  310 ,  330  can comprise a honeycombed polymer core that can take compressive and shear loads, sandwiched between two metal skins that can bear the high tensile stresses caused by bending. It is possible to bind the top or bottom plate  310 ,  330  with bolts, heated staked columns, ultrasonic welding, or the top or bottom plates  310 ,  330  can be assembled with an adhesive. 
     Utilizing metal stamping, top and bottom plates  310 ,  330  can be produced having multi-planar curvature stamped metal skins and an injection-molded polymer core. The structure that such geometry creates can give greater stiffness to a top and bottom plate  310 ,  330  per the volume of material used and provides an opportunity to cut down on the expensive metal skin material. Stiffening features, such as ribs, bosses, deep drawn pockets and webbing, can also be incorporated into the design of top and bottom plates  310 ,  330  in some embodiments. 
     In some embodiments, the plates need not be single planar elements. For instance, the bottom plate  310  can be two individual surfaces each parallel to the two opposing flanges of the post such that the bellow interfaces point 180 degrees away from one another rather than 0 degrees as in other example configurations. The body of each of the bladder  300  then could bend through 90 degrees to meet the top plate  330  when the actuator assembly  101  is level. In this case, the plate may not be a bending element, but instead be compressive. The plates  310 ,  330  can also take a V-shape with major angle dictated by the desired range of motion of the actuator assembly  101 . 
     For example, an actuator assembly  101 , in accordance with a further embodiment, can include a top plate having first and second portions that are rotatably coupled at a joint. Such first and second bladder  300  can be coupled to respective bottom sides of the first and second portions and to a side of a post. Inflation of the bladder  300  can make the top plate assume a flat configuration, whereas deflation of the bladder  300  can make the top plate assume a V-shape, inverted V-shape, A-shape, angled configuration, and the like. 
     Bladder  300  can be affixed to the actuator assembly  101  and top and bottom plates  310 ,  330  in various suitable ways. Bladder  300  that are not securely attached in some examples can fall out of position, causing improper actuator behavior and performance, or can cause the actuator assembly  101  to cease to work together. A feature or mechanism used to keep the bladder  300  in place can be a “constraint,” or the like. 
     In one embodiment, such a constraint can comprise a fabric sheath that wraps around the bladder  300  and connects them to an attachment point on the plates  310 ,  330  and/or hub assembly  370  of the actuator assembly  101 . The fabric wrap can encircle a single bladder  300  in some embodiments. In such an embodiment, the wrap can be terminated with a slotted rod, hooks, grommets or any other suitable feature. These features can then be used to attach the constraint-wrapped bladder  300  to the actuator assembly  101 . In another embodiment, the constraint can be designed to encircle two separate bladders and connect them by an interstitial web  303 . This web  303  can be perforated with grommets or have any other features or fasteners incorporated to it. The connected wrapped bladder  300  can then by disposed on either side of the actuator pivot point or ridge  312 , between top and bottom plates  310 ,  330 , the web  303  draped either over the pivot point or ridge  312 , the center axis of the top or bottom V-plate  310 ,  330 , or over any other suitable feature. 
     As an example, a flat sheet of polymer-coated fabric can be laid out on a table. Two bladder  300  can be disposed, parallel to each other on top of the fabric. The two edges of the fabric, parallel to the long axis of the bladder  300 , can be pulled over their respective bladder  300 . The edges can be then joined in the middle and pinned to the center of the fabric sheet. This assembly of two bladder  300  can be wrapped in fabric and connected to each other via a web  303 , which can define a bladder unit  302 , as discussed herein. The web  303  can be perforated or can have grommets installed. These holes can then be draped over interfacing bolts or pins, located on the ridge  312  of a bottom V-Plate  310 . Nuts or other suitable fasteners can be used to secure the constraint and, thus, the bladder  300  in the appropriate location. 
     In another example, the aforementioned construction, two separate bladder  300  wrapped by fabric and connected via an interstitial fascia, can be disposed on the same side of the pivot on an actuator assembly  101  to form a stacked bladder configuration. This can be mirrored onto opposing side of the actuator assembly  101 , across the pivot point for a total of four bladder  300 , two on each side in a stacked configuration. A wire rope can then be looped to girdle the interstitial webs  303  between each bladder chamber pair and constrain them to the central pivot point, hub assembly  370  or V-plate ridge  312 . 
     Constraints can be made of any suitable material, including steel, aluminum, HDPE, PVC, fiberglass, carbon fiber, fabric, polymer-coated fabric, spun polymer like Spectra or Dyneema, or the like. Constraints can be reinforced with nylon webbing, wire rope, fabric, Spectra, Dyneema, or any other suitable method. Constraints can be manufactured by sewing, heat welding, extrusion, injection molding, blow molding, roto-molding, die casting, stamping or any other suitable method. 
     In various examples, the bottom plate  310  can be configurable from an angled configuration as shown in  FIGS.  10   a  and  10   b   , to a flat configuration as shown in  FIGS.  11   a  and  11   b   , where the arms  311  can be folded from being disposed relative to each other at angle θ to being generally flat. Such a flat configuration can be desirable in some embodiments for shipping and transportation of an assembled actuator assembly  101  having the bottom plate or transportation of the bottom plate  310  as a separate unit.  FIGS.  12   a  and  12   b    illustrate an embodiment  101 A of an actuator assembly  101  having a top plate  330 , bottom plate  310  and bladder assembly  301 , with the bottom plate  310  in a flat configuration (e.g., as shown in  FIGS.  11   a  and  11   b   ). 
     While various embodiments of an actuator assembly  101  include top and bottom plates  310 ,  330  that are spaced apart via a hub assembly  370  (e.g., actuator assembly  101 A of  FIGS.  6   a - 12   b   ) in some embodiments, the top and bottom plates  310 ,  330  can be directly coupled or proximately coupled via a hub assembly  370 . 
     Also, an actuator assembly  101  can be configured in various suitable ways and the examples of  FIGS.  2 ,  3 ,  12     a ,  12   b ,  16 ,  17  and  19  should not be construed as limiting. For example,  FIGS.  28   a  and  28   b    illustrate an actuator assembly  101  in accordance with another embodiment and  FIGS.  29   a  and  29   b    illustrate an actuator assembly  101  in accordance with a further embodiment. 
     The described embodiments are susceptible to various modifications and alternative forms, and specific examples thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the described embodiments are not to be limited to the particular forms or methods disclosed, but to the contrary, the present disclosure is to cover all modifications, equivalents, and alternatives. Additionally, elements of a given embodiment should not be construed to be applicable to only that example embodiment and therefore elements of one example embodiment can be applicable to other embodiments. Additionally, elements that are specifically shown in example embodiments should be construed to cover embodiments that comprise, consist essentially of, or consist of such elements, or such elements can be explicitly absent from further embodiments. Accordingly, the recitation of an element being present in one example should be construed to support some embodiments where such an element is explicitly absent.