Solar Positioning System and Method

BACKGROUND OF THE INVENTION

p-00021. Field of the Invention

p-0003The present invention is generally directed to apparatuses and methods for positioning an object and, more particularly, to apparatuses and methods for positioning a solar energy capture device using linear actuators.

p-00042. Background

p-0005For numerous reasons—including lowering the concentrations of greenhouse gases, strengthening the ozone, reducing global warming effects, and obtaining a sustainable source of energy—energy sources other than fossils fuels are becoming more popular. One common alternative energy source is solar energy.

p-0006There are two common systems for generating electricity from solar energy: a thermal system and a photovoltaic system. In a thermal system, a mirror assembly reflects sunlight onto a receiver. The receiver, in turn, may heat a fluid or gas. In some thermal systems, the receiver heats the fluid or gas to power a turbine to create electricity, for example, by turning a fluid into a gas. In other thermal systems, the receiver can simply heat the fluid or gas for process heat applications. In photovoltaic systems, a photovoltaic panel converts sunlight into electricity. In both systems, the position of the solar energy capture device—the mirror assembly in a thermal system or the photovoltaic panel in a photovoltaic system, for example—should continuously change as the position of the sun changes. For example, as the sun moves, the orientation of the mirror assembly needs to change to keep the reflected light focused on the receiver. In photovoltaic systems, the photovoltaic panel should be reoriented to ensure that the panel is orthogonal to the direction of the sunlight to achieve peak efficiency.

p-0007In many of these systems, a solar energy capture devices is coupled to a frame post by two direct-drive motors located at the top of the post. One of the motors is aligned to change the elevation angle of the solar energy capture device, and the other motor is aligned to change the azimuth angle of the solar energy capture device. The weight of the motors and their relatively high position on the post can require a frame that is large and, consequently, one that may be expensive and heavy. This requirement can make implementation and scaling of many solar energy systems unduly expensive, especially when increasing the size of solar energy capture devices and the number of devices deployed in an array.

BRIEF SUMMARY OF THE INVENTION

p-0008In one embodiment, an apparatus for receiving sunlight includes a frame, a solar energy capture device, a joint, and first and second linear actuators. The joint connects the solar energy capture device to the frame and allows the solar energy capture device to rotate relative to the frame. The first and second linear actuators are coupled to the solar energy capture device. The first and second actuators actuate in combination to rotate the solar energy capture device about a pitch axis, and the first and second actuators actuate differentially to rotate the solar energy capture device about a roll axis. The solar energy capture device may include a mirror assembly or a photovoltaic panel.

p-0009In another embodiment, an apparatus includes a frame having a lateral axis and a longitudinal axis, a solar energy capture device, a joint assembly, a first variable length actuator, and a second variable length actuator. The joint assembly connects the solar energy capture device to the frame, while allowing rotation of the solar energy capture device relative to the frame. The joint assembly includes a lower portion connected to the frame to allow rotation of the solar energy capture device about the lateral axis. The joint assembly also includes an upper portion connected to the solar energy capture device and the lower portion to allow rotation of the solar energy capture device about the longitudinal axis. The first variable length actuator has a first pivot end coupled to the solar energy capture device on a first side of the joint assembly, and the second variable length actuator has a second pivot end coupled to the solar energy capture device on a second side of the joint assembly opposite the first pivot end. The first and second actuators actuate in combination to rotate the solar energy capture device about the lateral axis and actuate differentially to rotate the solar energy capture device about the longitudinal axis.

p-0010In one embodiment, an apparatus for positioning an object at a desired pitch angle and a desired roll angle includes a frame, an object, a joint, a first linear actuator, and a second linear actuator. The joint connects to the object and the frame to allow rotation of the object relative to the frame. The first and second linear actuators each have a variable length member. The variable length members are coupled to the object and the frame. The lengths of the first and second variable length members are simultaneously and equally changed to rotate the object about a pitch axis, while the length of the first variable length member is differentially changed relative to the length of the second variable length member to rotate the object about a roll axis. The object can be a solar energy capture device.

p-0011Methods for using apparatuses according to embodiments described herein are also provided.

p-0012In one embodiment, a method for positioning a solar energy capture device comprises moving the solar energy capture device to a desired orientation by collectively actuating first and second linear actuators to rotate the solar energy capture device about a pitch axis and by differentially actuating the first and second linear actuators to rotate the solar energy capture device about a roll axis. The first and second linear actuators are coupled to the solar energy capture device and a frame.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

p-0013The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the relevant art(s) to make and use the invention.

p-0014<figref idrefs="DRAWINGS">FIG. 1</figref> depicts a block diagram of an apparatus that positions an object at a desired orientation according to an embodiment of the present invention.

p-0015<figref idrefs="DRAWINGS">FIG. 2</figref> illustrates a perspective view of an apparatus that positions a solar energy capture device at a desired orientation according to an embodiment of the present invention.

p-0016<figref idrefs="DRAWINGS">FIG. 3</figref> illustrates an enlarged perspective view of a joint as illustrated in <figref idrefs="DRAWINGS">FIG. 2</figref> according to an embodiment of the present invention.

p-0017<figref idrefs="DRAWINGS">FIG. 4</figref> illustrates a perspective view of an apparatus that positions a solar energy capture device at a desired orientation according to an embodiment of the present invention.

p-0018<figref idrefs="DRAWINGS">FIG. 5</figref> illustrates a perspective view of an apparatus that positions a solar energy capture device at a desired orientation according to an embodiment of the present invention.

p-0019<figref idrefs="DRAWINGS">FIG. 6</figref> illustrates a front perspective view of an apparatus that positions a solar energy capture device at a desired orientation according to an embodiment of the present invention.

p-0020<figref idrefs="DRAWINGS">FIG. 7</figref> illustrates a rear perspective view of an apparatus that positions a solar energy capture device at a desired orientation according to an embodiment of the present invention.

p-0021<figref idrefs="DRAWINGS">FIG. 8</figref> illustrates a process flowchart depicting a method of positioning a solar energy capture device according to an embodiment of the present invention.

p-0022<figref idrefs="DRAWINGS">FIG. 9</figref> illustrates a block diagram depicting a closed loop configuration for moving solar energy capture device <b>100</b> according an embodiment of the present invention.

p-0023The features and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements.

DETAILED DESCRIPTION OF THE INVENTION

p-0024In the detailed description that follows, references to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

p-0025<figref idrefs="DRAWINGS">FIG. 1</figref> is a block diagram of an apparatus <b>10</b> that positions an object <b>100</b> at a desired orientation according to an embodiment of the present invention. In one embodiment, apparatus <b>10</b> includes a frame <b>200</b>, a joint <b>300</b>, at least two linear actuators <b>400</b>, and a control unit <b>500</b>. Object <b>100</b> may be any object that has at least two different desired orientations. For example, object <b>100</b> may be a solar energy capturing device such as a mirror assembly used with a solar thermal system or a photovoltaic panel used with a solar photovoltaic system. Object <b>100</b> can also be other types of object having at least two different desired orientations such as a communication antenna, a weapon platform, a directed-energy appliance, and any other suitable object.

p-0026In one embodiment, frame <b>200</b> is adapted to structurally support and position object <b>100</b>. Frame <b>200</b> can be figured to directly or indirectly contact a mounting surface, for example, the ground, a roof, a wall, an overhead surface, or other suitable surface. Frame <b>200</b> elevates object <b>100</b> above the mounting surface. Frame <b>200</b> may define a lateral axis that runs from the left side of frame <b>200</b> to the right side of frame <b>200</b>, and define a longitudinal axis that runs from the front of frame <b>200</b> to the back of frame <b>200</b>. The longitudinal axis may be orthogonal to the lateral axis. Frame <b>200</b> can be made of any suitable rigid material having sufficient strength to support object <b>100</b>. For example, frame <b>200</b> can be formed from square tubing, piping, or channel made of iron, aluminum, composites (e.g., carbon fiber composites), wood, plastic, or any other suitable material.

p-0027Joint <b>300</b> rotatably couples object <b>100</b> to frame <b>200</b> such that object <b>100</b> can rotate relative to frame <b>200</b>. Joint <b>300</b> defines a pitch axis PA and a roll axis RA. In one embodiment, pitch axis PA is parallel to the lateral axis of frame <b>200</b>, and roll axis RA can project on the longitudinal axis of frame <b>200</b> and may be planar with the longitudinal axis of frame <b>200</b>. When coupled to joint <b>300</b>, object <b>100</b> can rotate about pitch axis PA and roll axis RA. Joint <b>300</b> can be a universal joint (U-joint), a ball and socket joint, or any other type of joint that has at least two degrees of freedom. In one embodiment, joint <b>300</b> can be made of one or more rotating members.

p-0028In one embodiment, apparatus <b>10</b> includes at least two linear actuators <b>400</b>. Linear actuators <b>400</b> are coupled to object <b>100</b> and are adapted to position the object relative to a source. Linear actuators <b>400</b> can include a drive component, for example, a motor or hydraulic pump and cylinder, and a variable length member that can selectively change its length. Linear actuators <b>400</b> can selectively apply a force to object <b>100</b> by changing the length of the variable length member, which rotates object <b>100</b> about pitch axis PA and roll axis RA. Particularly, as further described below, in one embodiment linear actuators <b>400</b> may collectively rotate object <b>100</b> about pitch axis PA and differentially rotate object <b>100</b> about roll axis RA. In some embodiments, apparatus <b>10</b> may include two, three, or more than three linear actuators. In one embodiment, each linear actuator <b>400</b> may comprise a cable actuation mechanism including a motor and a cable, a hydraulic piston, a scissor-jack, a linear screw drive, or any other suitable linear actuator having a variable length member. Linear actuators <b>400</b> coupled to object <b>100</b> may comprise the same type or different types of actuators. For example, in some embodiments, first and second linear actuators <b>400</b> may both comprise a cable-actuated mechanism. In other embodiments, for example, a first linear actuator <b>400</b> may comprise a cable actuator and a second linear actuator <b>400</b> may comprise a hydraulic piston actuator.

p-0029In one embodiment, apparatus <b>10</b> includes control unit <b>500</b>. Control unit <b>500</b> includes a processor and memory. Control unit <b>500</b> is operatively connected to linear actuators <b>400</b>. Control unit <b>500</b> is adapted to generate and manipulate control signals that cause the variable length member of linear actuators <b>400</b> to change lengths and, thus, change the orientation of object <b>100</b>.

p-0030Apparatus <b>10</b> may be used as an individual unit for positioning a single object <b>100</b> or as a series of units in an array for positioning a plurality of objects <b>100</b>. For example, in one embodiment, a plurality of apparatuses <b>10</b> each having a solar energy capture device <b>100</b> may be arranged in a solar field. In one embodiment such as a thermal system, the plurality of apparatuses <b>10</b> may be arranged to concentrate the reflected sunlight onto a receiver that powers a heat engine which, in turn, drives a rotary generator, for example, a turbine. In one embodiment, apparatuses <b>10</b> in an array can be arranged in one or more linear or arcuate rows.

p-0031<figref idrefs="DRAWINGS">FIG. 2</figref> illustrates a perspective view of apparatus <b>10</b> according to an embodiment of the present invention. As illustrated in <figref idrefs="DRAWINGS">FIG. 2</figref>, object <b>100</b> is a solar energy capture device, for example, a mirror assembly or a photovoltaic panel. Solar energy capture device <b>100</b> has a back surface <b>102</b> and a front surface <b>104</b>. Solar energy capture device <b>100</b> can also include a reinforcement plate <b>106</b> coupled to back surface <b>102</b>. Reinforcement plate <b>106</b> strengthens back surface <b>102</b> of solar energy capture device <b>100</b> and may be used as an interface with joint <b>300</b>. For example, reinforcement plate <b>106</b> may act as a mounting plate for joint <b>300</b>.

p-0032Apparatus <b>10</b> also includes frame <b>200</b>. As shown in <figref idrefs="DRAWINGS">FIG. 2</figref>, frame <b>200</b> includes a base portion <b>201</b>. Base portion <b>201</b> may be any suitable configuration to support frame <b>200</b> on the mounting surface, and to allow stable positioning of object <b>100</b>. In one embodiment, base portion <b>201</b> is triangular and configured to contact a mounting surface, for example, the ground. The base portion of frame <b>200</b> includes a right diagonal strut <b>202</b> and a left diagonal strut <b>204</b>. Right diagonal strut <b>202</b> and left diagonal strut <b>204</b> are angled towards each other such that they join at the front of apparatus <b>10</b>. The base portion can also include a cross strut <b>206</b> that runs between right diagonal strut <b>202</b> and left diagonal strut <b>204</b>. Cross strut <b>206</b> prevents right diagonal strut <b>202</b> and left diagonal strut <b>204</b> from moving towards or away from each other. In an embodiment, the base portion can include a surface anchor <b>208</b> that fixedly secures frame <b>200</b> to the mounting surface. For example, in one embodiment, surface anchor <b>208</b> can be a cork screw or helical ground anchor as illustrated in <figref idrefs="DRAWINGS">FIG. 2</figref>. In other embodiments, surface anchor <b>208</b> can be any other type of suitable fasteners, for example, one or more bolts or screws. In another embodiment, surface anchor <b>208</b> may include one or more posts that extend into the mounting surface.

p-0033In one embodiment, frame <b>200</b> further includes a vertically extending front strut <b>210</b>. In an embodiment, front strut <b>210</b> extends upward from the intersection of right diagonal strut <b>202</b> and left diagonal strut <b>204</b>. Frame <b>200</b> also includes right diagonal vertical strut <b>212</b> and left diagonal vertical strut <b>214</b>. Right diagonal vertical strut <b>212</b> extends from the back portion of right diagonal strut <b>202</b> to the top portion of vertical front strut <b>210</b>. Left diagonal vertical strut <b>214</b> extends from the back portion of left diagonal strut <b>204</b> to the top portion of vertical front strut <b>210</b>. Collectively, right and left vertical diagonal struts <b>212</b> and <b>214</b> help prevent vertical strut <b>210</b> from moving, particularly, from rotating front to back or left to right. An intermediate cross strut <b>216</b> extends horizontally from right diagonal vertical strut <b>212</b> to left diagonal vertical strut <b>214</b>. Intermediate cross strut <b>216</b> stabilizes right and left vertical diagonal struts <b>214</b> and <b>216</b> and may limit right vertical diagonal strut <b>214</b> and left vertical diagonal strut <b>216</b> from moving relative to each other.

p-0034Apparatus <b>10</b> includes joint <b>300</b> that rotatably couples solar energy capture device <b>100</b> to frame <b>200</b>. Joint <b>300</b> defines pitch axis PA and roll axis RA. In an embodiment, pitch axis PA and roll axis RA are parallel to a plane defined by solar energy capture device <b>100</b>, and pitch axis PA and roll axis RA are perpendicular. Joint <b>300</b> allows solar energy capture device <b>100</b> to rotate about pitch axis PA and roll axis RA relative to frame <b>200</b>.

p-0035In an embodiment as shown in <figref idrefs="DRAWINGS">FIGS. 2-3</figref>, joint <b>300</b> may comprise a U-joint that allows solar energy capture device <b>100</b> to rotate in any direction relative to frame <b>200</b>. U-joint <b>300</b> may include a lower yoke <b>302</b> and an upper yoke <b>304</b>. Lower yoke <b>302</b> couples joint <b>300</b> to frame <b>200</b>, for example, at the top portion of vertical strut <b>210</b>. Upper yoke <b>304</b> couples joint <b>300</b> to solar energy capture device <b>100</b>, for example, by interfacing with reinforcement plate <b>106</b>. In other embodiments, upper yoke <b>304</b> may connect directly to solar energy capture device <b>100</b>.

p-0036<figref idrefs="DRAWINGS">FIG. 3</figref> illustrates an enlarged perspective view of joint <b>300</b> as illustrated in <figref idrefs="DRAWINGS">FIG. 2</figref> according to an embodiment of the present invention. Lower yoke <b>302</b> can include a hub <b>330</b> that defines a hollow channel that corresponds to the shape of vertical strut <b>210</b>. The top end portion of vertical strut <b>210</b> is inserted within hub <b>330</b>. In one embodiment, lower yoke <b>302</b> can be secured to frame <b>200</b> by using a retention pin <b>348</b>. For example, retention pin <b>348</b> can pass through a pair of holes in lower hub <b>330</b> and an aligned pair of holes in vertical strut <b>210</b>, securing joint <b>300</b> to frame <b>200</b>.

p-0037Extending upward from hub <b>330</b> is a pair of opposing arms <b>332</b> and <b>334</b>. Arms <b>332</b> and <b>334</b> are spaced apart to create a gap in a substantially U-shaped configuration. Upper yoke <b>304</b> includes a base portion <b>336</b> and a pair of opposing arms <b>338</b> and <b>340</b> extending from the ends of base portion <b>336</b> in a substantially inverted U-shaped configuration. Lower yoke <b>302</b> and upper yoke <b>304</b> are rotatably coupled together by center portion <b>342</b>. Center portion <b>342</b> can be X-shaped or cross-shaped with a first pair of pins <b>306</b> extending from opposing legs of the center portion <b>342</b> and a second pair of pins <b>308</b> extending from the other pair of opposing legs. Accordingly, second pair of pins <b>306</b> are perpendicular to first pair of pins <b>306</b>. First pair of pins <b>306</b> are rotatably coupled to lower yoke <b>302</b>, for example, by coupling pins <b>306</b> with ball bearings seated in openings defined in the top portions of arms <b>332</b> and <b>334</b>. Similarly, second pair of pins <b>308</b> are rotatably coupled to upper yoke <b>304</b>, for example, by coupling pins <b>308</b> with ball bearings seated in openings defined in the lower portions of arms <b>338</b> and <b>340</b>.

p-0038Upper yoke <b>304</b> can be coupled to reinforcement plate <b>106</b> of solar energy capture device <b>100</b>. Reinforcement plate <b>106</b> can include a mounting surface <b>108</b>. Mounting surface <b>108</b> is securely coupled to back surface <b>102</b> of device <b>100</b> using any suitable adhesive or any suitable fasteners. A pair of opposing front and back walls <b>112</b> and a pair of opposing side walls <b>114</b> extend perpendicularly from mounting surface <b>108</b>. Front and back walls <b>112</b> and side walls <b>114</b> define a space that closely corresponds to the shape of base portion <b>336</b> of upper yoke <b>304</b>. Accordingly, base portion <b>336</b> can be seated in the space defined by front and back walls <b>112</b> and side walls <b>114</b>. Upper yoke <b>304</b> can be secured to reinforcement plate <b>106</b> by fasteners extending through front and back walls <b>112</b> and side walls <b>114</b> into base portion <b>336</b> of upper yoke <b>304</b> or by any other suitable means of attaching yoke <b>304</b> to reinforcement plate <b>106</b>.

p-0039In one embodiment, as shown, for example, in <figref idrefs="DRAWINGS">FIG. 3</figref>, lower yoke <b>302</b> is adapted to allow rotation of solar energy capture device <b>100</b> about pitch axis PA and upper yoke <b>304</b> is adapted to allow rotation of solar energy capture device <b>100</b> about roll axis RA. In this manner, upper yoke <b>304</b> may be positioned intermediate to device <b>100</b> and lower yoke <b>302</b>, and lower yoke <b>302</b> may be positioned intermediate to upper yoke <b>304</b> and frame <b>200</b>. The relative orientation of upper yoke <b>304</b> and lower yoke <b>302</b> permit stable rotation of device <b>100</b> relative to frame <b>200</b>.

p-0040With reference to <figref idrefs="DRAWINGS">FIG. 2</figref>, in one embodiment apparatus <b>10</b> also includes a first linear actuator <b>400</b><i>a </i>and a second linear actuator <b>400</b><i>b</i>. Each linear actuator <b>400</b><i>a </i>and <b>400</b><i>b </i>has a variable length member coupled to solar energy capture device <b>100</b>. In one embodiment, first and second linear actuators <b>400</b><i>a </i>and <b>400</b><i>b </i>each comprise a cable actuation mechanism including a motor <b>402</b> and a cable <b>404</b>. Motor <b>402</b> can be any suitable motor that can rotate a spool in one direction to spool cable <b>404</b> on the spool, which decreases the length of the variable length member, and can rotate the spool in an opposite direction to release cable <b>404</b> from the spool, which increases the length of the variable length member. For example, in one embodiment, motor <b>402</b> can be a stepper motor having a gear ratio of about 70:1 for spooling cable <b>404</b>. In other embodiments, other suitable gear ratios may be used. Cable <b>404</b> can be made of any suitable material having sufficient strength to apply the necessary forces to solar energy capture device <b>100</b>, for example, strands of fiber or metal. The distal end of left cable <b>404</b> is coupled to solar energy capture device <b>100</b> near its left edge, and the distal end of right cable <b>404</b> is coupled to solar energy capture device <b>100</b> near its right edge. The flexible nature of cables <b>404</b> allow cables <b>404</b> to rotate relative to solar energy capture device <b>100</b>, eliminating the requirement that the distal end portion of the variable length member be connected to object <b>100</b> by a U-joint or a ball-and-socket joint. For example, cables <b>404</b> can be coupled to solar energy capture device <b>100</b> using mounting brackets. Each cable <b>404</b> can be looped around a mounting pin on mounting bracket <b>406</b>.

p-0041In embodiments using linear actuators having variable length members that cannot withstand compressive forces, for example, cables <b>404</b>, apparatus <b>10</b> can also include a return mechanism that prevents unwanted rotation of object <b>100</b> about pitch axis PA toward the variable length member. The return mechanism can be any device capable of applying a force (for example, tension or torsion springs, elastic chords, or linear actuators) or a counter weight (for example, the weight of object <b>100</b> or a separate weight coupled to joint <b>300</b> below pitch axis PA). In one embodiment, the return mechanism can be the weight of solar energy capture device <b>100</b> below pitch axis PA as determined by the location at which joint <b>300</b> couples to solar energy capture device <b>100</b>. For example, as shown in <figref idrefs="DRAWINGS">FIG. 2</figref>, joint <b>300</b> is coupled to solar energy capture device above the center of mass of solar energy capture device <b>100</b>. In this manner, the weight of the portion of solar energy capture device <b>100</b> below the joint <b>300</b> and pitch axis PA biases solar energy capture device <b>100</b> against rotating about pitch axis PA towards the back of apparatus <b>10</b>. In embodiments that use a cable actuation mechanism as a linear actuator, the return mechanism can also provide cable tension or preload to prevent the cable from tangling while spooling and releasing.

p-0042In some embodiments, the majority of the weight attributed to linear actuators <b>400</b><i>a </i>and <b>400</b><i>b </i>can be located relatively low on apparatus <b>10</b>, for example, at the base portion of frame <b>200</b>. The low center of mass attributed to linear actuators <b>400</b><i>a </i>and <b>400</b><i>b </i>may allow frame <b>200</b> to be lighter, especially at the top, which may decrease the fabrication costs of frame <b>200</b> and allow for favorable scaling with increasing the size of object <b>100</b>.

p-0043Apparatus <b>10</b> may further include a control unit <b>500</b> (not shown in <figref idrefs="DRAWINGS">FIG. 2</figref>) for operating linear actuators <b>400</b><i>a </i>and <b>400</b><i>b</i>. During operation, control unit <b>500</b> is adapted to send one or more control signals to linear actuators <b>400</b><i>a </i>and <b>400</b><i>b</i>, causing motors <b>402</b> to spin in a desired direction to either spool or release cables <b>404</b>. To rotate solar energy capture device <b>100</b> about pitch axis PA, control unit <b>500</b> collectively actuates linear actuators <b>400</b><i>a </i>and <b>400</b><i>b </i>so that motors <b>402</b> spin in a direction that cause cables <b>404</b> to be simultaneously spooled (decreasing the length of the variable length members) or simultaneously released (increasing the length of the variable length members). As cables <b>404</b> are spooled, solar energy capture device <b>100</b> rotates about pitch axis PA towards the back of apparatus <b>10</b>. Conversely, as cables <b>404</b> are released, solar energy capture device <b>100</b> rotates about pitch axis PA towards the front of apparatus <b>10</b> due to the force of the return mechanism.

p-0044To rotate solar energy capture device <b>100</b> about roll axis RA, control unit <b>500</b> differentially actuates linear actuators <b>400</b><i>a </i>and <b>400</b><i>b </i>so that one motor <b>402</b> spins in a direction that causes its respective cable <b>404</b> to be spooled (decreasing the length of the variable length member), and/or so that the other motor <b>402</b> spins in a direction that causes its respective cable <b>404</b> to be released (increasing the length of the variable length member). For example, as cable <b>404</b> of linear actuator <b>400</b><i>a </i>is spooled and cable <b>404</b> of linear actuator <b>400</b><i>b </i>is released, solar energy capture device <b>100</b> rotates about roll axis RA towards the left of apparatus <b>10</b>. Conversely, as cable <b>404</b> of linear actuator <b>400</b><i>a </i>is released and cable <b>404</b> of linear actuator <b>400</b><i>b </i>is spooled, solar energy capture device <b>100</b> rotates about roll axis RA towards the right of apparatus <b>10</b>.

p-0045Accordingly, the pitch angle and the roll angle of solar energy capture device <b>100</b> can be changed by a combination of collectively and/or differentially actuating linear actuators <b>400</b><i>a </i>and <b>400</b><i>b. </i>

p-0046In some embodiments in which solar energy capture device <b>100</b> is a mirror assembly <b>100</b> for a thermal system, the mirror assembly may include a mirror structure particularly adapted for edge actuation provided by embodiments of the present invention. In one embodiment, linear actuators <b>400</b><i>a </i>and <b>400</b><i>b </i>may be coupled to the solar energy capture device <b>100</b> at points more proximate to the edge of the mirror structure than the center point of the mirror structure. This configuration may provide an increased lever arm that may increase the effective actuator force (i.e., torque) on the mirror. In such an embodiment, the mirror structure may be adapted to have additional strength and stiffness proximate to its edges to accommodate edge actuation without breaking or defocusing. In some embodiments in which the mirror assembly is mounted to universal joint <b>300</b>, the attachment may be provided such that the loading around the reinforcement plate <b>106</b> is symmetric. In this manner, joint <b>300</b> will not pivot on its own absent actuation forces from linear actuators <b>400</b><i>a </i>and <b>400</b><i>b</i>. In such an embodiment, the stiffness of the mirror structure may be less at the joint attachment location (e.g., at reinforcement plate <b>106</b>) than at the edges of the mirror structure. In contrast, a center actuated mirror must be very strong around the joint mount location to avoid stress concentration at the edge of the bracket. Accordingly, in some embodiments of the present invention, the mirror structure may be thicker at a point proximate its edge than at a point proximate the joint attachment location to provide effective edge actuation.

p-0047<figref idrefs="DRAWINGS">FIG. 4</figref> illustrates apparatus <b>10</b> according to an embodiment of the present invention. To the extent the illustrated embodiment in <figref idrefs="DRAWINGS">FIG. 4</figref> shares similar features as described above regarding <figref idrefs="DRAWINGS">FIGS. 1-3</figref>, similar reference numbers are used. In this embodiment, object <b>100</b> can be a solar energy capture device. Frame <b>200</b> includes a base portion <b>201</b> having a base cross strut <b>218</b> configured to contact the mounting surface, for example, the ground. Extending forward from the midpoint of base cross strut <b>218</b> is longitudinal strut <b>219</b>, which helps prevent frame <b>200</b> from tilting forward. Extending backward from the midpoint of base cross strut <b>218</b> is longitudinal strut <b>221</b>, which helps prevent frame <b>200</b> from tilting backward. Extending upward from one end of cross base strut <b>218</b> is a right diagonal support <b>220</b>, and extending upward from the other end of cross bass strut <b>218</b> is left diagonal support <b>222</b>. The top portion of right diagonal support <b>220</b> and the top portion of left diagonal support <b>222</b> intersect at apex <b>226</b>. A longitudinal diagonal strut <b>224</b> extends backwards and downwards from apex <b>226</b>. The bottom portion of diagonal strut <b>224</b> is configured to contact the mounting surface.

p-0048As shown in <figref idrefs="DRAWINGS">FIG. 4</figref>, joint <b>300</b> may be a U-joint similar to the joint discussed above regarding <figref idrefs="DRAWINGS">FIG. 3</figref>. Joint <b>300</b> includes a lower yoke <b>302</b> extending forward from apex <b>226</b>. Joint <b>300</b> may also include a reinforcement plate <b>314</b>. One side of reinforcement plate <b>314</b> is coupled to solar energy capture device <b>100</b> by adhesive, fasteners, or any other suitable attachment method. For example, as shown in <figref idrefs="DRAWINGS">FIG. 4</figref>, reinforcement plate <b>314</b> can be mounted to device <b>100</b> using brackets that are fastened to the back side <b>102</b> of device <b>100</b>. The back side of reinforcement plate <b>314</b> is coupled to upper yoke <b>304</b>. Upper yoke <b>304</b> is rotatably coupled to lower yoke <b>302</b>.

p-0049In another embodiment, joint <b>300</b> may be a ball and socket joint. In this embodiment, joint <b>300</b> includes an arm extending from apex <b>226</b>. The front portion of the arm defines a ball or spherical surface. Joint <b>300</b> further comprises reinforcement plate <b>314</b> having one side coupled to solar energy capture device <b>100</b>. The other side of reinforcement plate <b>314</b> defines a socket that has a shape that corresponds to the ball defined by arm <b>310</b>. The socket captures the ball of the arm, allowing plate <b>314</b> and, thus, solar energy capture device <b>100</b> to rotate relative to the arm and frame <b>200</b>. Alternatively, the arm can define a socket that captures a ball defined by reinforcement plate <b>314</b>.

p-0050As illustrated in <figref idrefs="DRAWINGS">FIG. 4</figref>, joint <b>300</b> can be coupled to solar energy capture device <b>100</b> at or below the center of mass of the solar energy capture device <b>100</b>. In this embodiment, apparatus <b>10</b> includes a return mechanism that prevents solar energy capture device <b>100</b> from completely rotating about pitch axis PA towards the back of apparatus <b>10</b>. In one embodiment, the return mechanism is an elastic member <b>408</b> that prevents solar energy capture device <b>100</b> from rotating completely about pitch axis PA. Elastic member <b>408</b> is coupled to the bottom edge of solar energy capture device <b>100</b> using a mounting bracket <b>410</b>. On the other end, elastic member <b>408</b> is coupled to a portion of frame <b>200</b>, for example, a middle portion of diagonal strut <b>224</b>. As cables <b>404</b> are spooled, elastic member <b>408</b> stretches to allow solar energy capture device <b>100</b> to rotate about pitch axis PA towards the back, but prevents complete rotation about pitch axis PA. As cables <b>404</b> are released or lengthened, elastic member <b>408</b> provides a tension force causing solar energy capture device <b>100</b> to rotate about pitch axis PA towards the front.

p-0051<figref idrefs="DRAWINGS">FIG. 5</figref> illustrates apparatus <b>10</b> according to an embodiment of the present invention. To the extent the illustrated embodiment in <figref idrefs="DRAWINGS">FIG. 5</figref> shares similar features as described above regarding <figref idrefs="DRAWINGS">FIGS. 1-4</figref>, similar reference numbers are used. As shown in <figref idrefs="DRAWINGS">FIG. 5</figref>, frame <b>200</b> includes a base portion <b>201</b> having a pair of longitudinal struts <b>230</b> that are spaced apart. Struts <b>230</b> are configured to contact the mounting surface. Joint <b>300</b> can include a horizontal rotating member <b>316</b> and a vertical rotating member <b>318</b>. Horizontal rotating member <b>316</b> defines pitch axis PA about which it can rotate. Each end of horizontal rotating member <b>316</b> is rotatably coupled to longitudinal struts <b>230</b>, for example, by using bushings or bearings. Vertical rotating member <b>318</b> defines roll axis RA about which it can rotate. Vertical rotating member <b>318</b> is rotatably coupled to horizontal rotating member <b>316</b> at joint <b>320</b>, for example, by using bushings or bearings. The upper portion <b>322</b> of vertical rotating member <b>318</b> is coupled to solar energy capture device <b>100</b> by any suitable means, for example, U-brackets, fasteners, adhesives, or any other suitable means. In one embodiment, horizontal rotating member <b>316</b> may be positioned below vertical rotating member <b>318</b>. In this manner, horizontal rotating member <b>316</b> may be a lower rotating member and vertical rotating member <b>318</b> may be an upper rotating member. In other embodiments, for example, wherein frame <b>200</b> may be attached to an overhead surface, horizontal rotating member <b>316</b> may be positioned above vertical rotating member <b>318</b>.

p-0052As shown in <figref idrefs="DRAWINGS">FIG. 5</figref>, linear actuators <b>400</b><i>a </i>and <b>400</b><i>b </i>can be hydraulic piston assemblies. Hydraulic piston assemblies <b>400</b><i>a </i>and <b>400</b><i>b </i>each include a cylinder <b>402</b> and a linearly reciprocating piston <b>404</b>. Each piston assembly can have a fixed length mounting stem <b>412</b> that rotatably couples to longitudinal strut <b>230</b>. In one embodiment, the lower portion of mounting stem <b>412</b> forms a ball and socket joint <b>414</b> with longitudinal strut <b>230</b>. In other embodiments, each piston assembly can be coupled to longitudinal strut <b>230</b> using a one-dimensional pivot, limiting rotation of the piston assembly. The upper portion of piston <b>404</b> can be rotatably coupled to an edge of solar energy capture device <b>100</b>, for example, by a ball and socket joint <b>406</b>. Ball and socket joints <b>406</b> and <b>414</b> allow piston assemblies <b>400</b><i>a </i>and <b>400</b><i>b </i>to rotate in any direction relative to solar energy capture device <b>100</b>. Accordingly, collective actuation of piston assemblies <b>400</b><i>a </i>and <b>400</b><i>b </i>causes piston <b>404</b> to simultaneously change lengths, which causes solar energy capture device <b>100</b> to rotate about pitch axis PA as horizontal rotating member <b>316</b> rotates relative to frame <b>200</b>. Differential actuation of piston assemblies <b>400</b><i>a </i>and <b>400</b><i>b </i>causes solar energy capture device to rotate about roll axis RA as vertical rotating member <b>318</b> rotates relative to horizontal rotating member <b>316</b>. In some embodiments, because pistons <b>404</b> are generally rigid, a separate return mechanism is not needed if the hydraulic pressure is maintained.

p-0053<figref idrefs="DRAWINGS">FIG. 6</figref> illustrates a front perspective view of apparatus <b>10</b> according to an embodiment. To the extent the illustrated embodiment in <figref idrefs="DRAWINGS">FIG. 6</figref> shares similar features as described above regarding <figref idrefs="DRAWINGS">FIGS. 1-5</figref>, similar reference numbers are used. Frame <b>200</b> includes a base portion <b>201</b> having a pair of longitudinal struts <b>230</b> that are spaced apart by a pair of cross struts <b>232</b> and <b>234</b>. A pair of vertical struts <b>236</b> and <b>238</b> extend upward from the right and left longitudinal struts <b>230</b>. To provide additional support the angle between the vertical struts <b>236</b> and <b>238</b> and the respective longitudinal struts <b>230</b> can be buttressed by diagonal struts <b>244</b> running there between. Between right and left vertical struts <b>236</b> and <b>238</b> is cross support <b>240</b>, for example, a plate as shown in <figref idrefs="DRAWINGS">FIG. 6</figref>. Similar to the embodiment illustrated in <figref idrefs="DRAWINGS">FIG. 5</figref>, joint <b>300</b> includes horizontal rotating member <b>316</b> and a vertical rotating member <b>318</b>. Horizontal member <b>316</b> rotatably couples with vertical struts <b>236</b> and <b>238</b> at joints <b>242</b>, for example, ball bearings or bushings.

p-0054As illustrated in <figref idrefs="DRAWINGS">FIG. 6</figref>, linear actuators <b>400</b><i>a </i>and <b>400</b><i>b </i>are cable actuation mechanisms each including motor <b>402</b> and cable <b>404</b>. In this embodiment, apparatus <b>10</b> may include a return mechanism as described above. In one embodiment, the return mechanism can be a counter weight <b>326</b>, a torsion spring <b>324</b>, or both. The weight of counter weight <b>326</b> or the applied force of torsion spring <b>324</b> applies a moment about pitch axis PA to vertical rotating member <b>318</b>, biasing it and coupled solar energy capture device <b>100</b> to rotate towards the front. Cables <b>404</b> prevent complete forward rotation about pitch PA. When the return mechanism comprises a counter weight, horizontal rotating member <b>316</b> can be elevated such that a portion of vertical rotating member <b>318</b> can extend below horizontal rotating member <b>316</b> and pitch axis PA without interfering with the mounting surface.

p-0055<figref idrefs="DRAWINGS">FIG. 7</figref> illustrates a back perspective view of apparatus <b>10</b> according to an embodiment. To the extent the illustrated embodiment in <figref idrefs="DRAWINGS">FIG. 7</figref> shares similar features as described above regarding <figref idrefs="DRAWINGS">FIGS. 1-6</figref>, similar reference numbers are used. Frame <b>200</b> includes a base portion <b>201</b> having two converging side struts <b>246</b> and <b>248</b>, forming a substantially V-shaped configuration. Base portion <b>201</b> may also include a front cross support <b>250</b> extending between struts <b>246</b> and <b>248</b> near the front of frame <b>200</b>. Base portion <b>201</b> may further include a back cross support <b>252</b> extending between struts <b>246</b> and <b>248</b> near the back or middle of frame <b>200</b>. Cross support <b>250</b> can define a recess at its center for seating horizontal rotating member <b>316</b>, which is rotatably coupled to frame <b>200</b> therein. A front strut <b>254</b> can extend upward from the front of frame <b>200</b>. In one embodiment, the return mechanism can be a tension spring <b>328</b>. One end of spring <b>328</b> is coupled to vertical front strut <b>254</b>, and the other end of spring <b>328</b> is coupled to rotating vertical member <b>318</b>. Spring <b>328</b> applies a force to create a moment about pitch axis PA to vertical member <b>318</b>, biasing vertical member <b>318</b> to rotate about pitch axis PA. As shown in <figref idrefs="DRAWINGS">FIG. 7</figref>, control unit <b>500</b> can be mounted on frame <b>200</b> and operatively connected to linear actuators <b>400</b><i>a </i>and <b>400</b><i>b. </i>

p-0056In some embodiments having a square or rectangular object <b>100</b>, object <b>100</b> can be coupled to joint <b>300</b> and frame <b>200</b> in an orthogonal configuration as shown in FIGS. <b>2</b> and <b>4</b>-<b>6</b> or a diamond configuration as shown in <figref idrefs="DRAWINGS">FIG. 7</figref>. Mounting a square or generally rectangular object in an orthogonal configuration improves field packing density, but may limit ground clearance and range of motion. Mounting a square or generally rectangular object in a diamond configuration may improve ground clearance and range of motion.

p-0057In one embodiment, apparatus <b>10</b> can include a third linear actuator. The third linear actuator can be coupled to object <b>100</b> at a point below pitch axis PA. Accordingly, the third linear actuator can function as the return mechanism.

p-0058In an embodiment having joint <b>300</b> that includes a horizontal rotating member <b>316</b> and a vertical rotating member <b>318</b>, linear actuators <b>400</b><i>a </i>and <b>400</b><i>b </i>can be replaced with a motor embedded within or operatively connected to horizontal rotating member <b>316</b>, and a motor embedded within or operatively connected to vertical rotating member <b>318</b>. Activation of the motor connected to the horizontal rotating member <b>316</b> causes object <b>100</b> to rotate about pitch axis PA, and activation of the motor connected to the vertical rotating member <b>318</b> causes object <b>100</b> to rotate about roll axis RA.

p-0059<figref idrefs="DRAWINGS">FIG. 8</figref> illustrates a block diagram depicting a method of positioning a solar energy capture device <b>100</b> according to an embodiment. In step <b>1000</b>, the current orientation of solar energy capture device <b>100</b> is determined relative to one or more of frame <b>200</b>, pitch axis PA, and/or roll axis RA. In one embodiment, the current orientation of solar energy capture device <b>100</b> may be provided relative to a default or “home” position of the device. In one embodiment, the current orientation of solar energy capture device <b>100</b> is determined by using a sensor, for example, one or more proximity sensors. In one embodiment, the proximity sensors can be located on the base portion of frame <b>200</b>. In embodiments having a horizontal rotating member and a vertical rotating member, the proximity sensor(s) can be located on the horizontal and vertical rotating members. In some embodiments, a proximity sensor may be disposed on object <b>100</b>. In one embodiment, the proximity sensor(s) may comprise an accelerometer. The proximity sensor is in communication with the control unit and is adapted to provide real time position information.

p-0060In step <b>1100</b>, the current position of the sun is determined. For example, in one embodiment, the position of the sun is determined by known orbital patterns determined by date. As will be appreciated, the current position of the sun may be determined by one or more data elements including, but not limited to, date, time, and geographic location (e.g., latitude and longitude coordinates). In another embodiment, the position of the sun is determined by using a sensor.

p-0061Using the current position of the sun determined at step <b>1100</b>, a desired orientation of the solar energy capture device is determined at step <b>1200</b>. For example, if solar energy capture device <b>100</b> is a mirror assembly for a thermal system, the desired orientation can be one that positions the mirror assembly so that the reflected light is focused on a receiver. If solar energy capture device <b>100</b> is a photovoltaic panel, the desired orientation can be, for example, a position that orients the photovoltaic panel to be perpendicular to the incident light from the sun.

p-0062At step <b>1300</b>, solar energy capture device <b>100</b> is moved to the determined desired position by collectively actuating the first and second actuators to rotate the mirror assembly about a pitch axis and by differentially actuating the first and second actuators to rotate the mirror assembly about a roll axis. Consequently, solar energy capture device <b>100</b> can be positioned at an orientation having a desired pitch angle and roll angle.

p-0063In one embodiment, control unit <b>500</b> can perform steps <b>1000</b>, <b>1100</b>, and <b>1200</b>, and control the actuation in step <b>1300</b>. In some embodiments, the method is repeated after a predetermined time interval, for example, every thirty minutes, every hour, every other hour, or any other suitable time interval. In some embodiments, positioning of solar energy capture device <b>100</b> is continuously updated in real-time.

p-0064<figref idrefs="DRAWINGS">FIG. 9</figref> illustrates a block diagram depicting a closed loop configuration for moving solar energy capture device <b>100</b> according an embodiment. As illustrated in <figref idrefs="DRAWINGS">FIG. 9</figref>, control unit <b>500</b> is operatively connected to linear actuators <b>400</b><i>a </i>and <b>400</b><i>b </i>such that control unit <b>500</b> can collectively or differentially actuate linear actuators <b>400</b><i>a </i>and <b>400</b><i>b</i>. After determining the desired position of solar energy capture device <b>100</b> (step <b>1200</b>), control unit <b>500</b> actuates linear actuator <b>400</b><i>a </i>and <b>400</b><i>b </i>collectively to rotate solar energy capture device <b>100</b> about pitch axis PA and/or differentially to rotate solar energy capture device <b>100</b> about roll axis RA. In one embodiment, a sensor <b>510</b> monitors the current position of solar energy capture device <b>100</b> (step <b>1000</b>) and communicates the position to control unit <b>500</b>. Control unit <b>500</b> compares the current position of solar energy capture device <b>100</b> as communicated by sensor <b>510</b> to the desired position of the solar energy capture device <b>100</b>. Control unit <b>500</b> continues to actuate linear actuators <b>400</b><i>a </i>and <b>400</b><i>b</i>, either collectively or differentially, until the current position equals the desired position. Once this result occurs, control unit <b>500</b> may cease actuation of linear actuators <b>400</b><i>a </i>and <b>400</b><i>b. </i>

p-0065In another embodiment, instead of determining an absolute desired orientation from the current position of the sun, for example, a desired rate and direction of orientation change of the device <b>100</b> can be determined. Accordingly, knowing the geometry of apparatus <b>10</b>, control unit <b>500</b> can be programmed to move device <b>100</b> at the desired rate and direction by controlling the length and rate of change of the variable length member of each linear actuator <b>400</b>.

p-0066The present invention has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.

p-0067The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. For example, although the figures illustrate the object <b>100</b> as a solar energy capture device, apparatus <b>10</b> can be adapted to position other objects such as communication antennas, weapon platforms, and directed-energy appliances, for example. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

p-0068It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance. The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.