Patent application title: ROBOTIC HELIOSTAT SYSTEM AND METHOD OF OPERATION
Salomon Trujillo (Redwood City, CA, US)
Daniel Fukuba (Palo Alto, CA, US)
Thomas Currier (Rochester, MN, US)
Wasiq Bokhari (Half Moon Bay, CA, US)
IPC8 Class: AF24J240FI
Class name: Solar heat collector with means to reposition solar collector for optimum radiation exposure computer
Publication date: 2012-01-19
Patent application number: 20120012101
A system and method for operating a robotic controller to automatically
position multiple solar surfaces in order to increase solar energy
generation from the solar surfaces. In an embodiment the robotic
controller travels in a sealed track and adjusts the solar surfaces using
1. A robotic controller for controlling a position of multiple solar
surfaces in response to movement of multiple solar surface adjustment
wheels, each solar surface having a corresponding solar surface
adjustment wheel, the robotic controller positioned on a track, the
robotic controller including: a processing unit, a location determining
unit, communicatively coupled to said processing unit, for determining a
position of the robotic controller; a drive system, for moving said
robotic controller along the track in response to instructions from the
processing unit; an adjustment determining system for determining first
adjustment parameters for a first solar surface adjustment wheel of said
multiple solar surface adjustment wheels; and an engagement system for
adjusting the first solar surface adjustment wheel based upon said first
2. The robotic controller of claim 1, wherein said location determining unit identifies a first location of the robotic controller on the track that is adjacent to the solar surface adjustment wheel; and wherein said drive system positions said robotic controller at said first location.
3. The robotic controller of claim 2, wherein said robotic controller includes: a Hall effect sensors; and said location determining unit utilizes magnetic communication between said Hall effect sensor and one of the solar surface adjustment wheels to identify said robotic controller location as being adjacent to said one of the solar surface adjustment wheels.
4. The robotic controller of claim 3, wherein said communication between said Hall effect sensors and one of said solar surface adjustment wheels identifies said one of the solar surface adjustment wheel as said first solar surface adjustment wheel and said location as said first location.
5. The robotic controller of claim 2, wherein robotic controller includes: a Hall effect sensor; and said engagement system utilizes magnetic coupling between said Hall effect sensor and said first solar surface adjustment wheel to rotate said first solar surface adjustment wheel based upon said first adjustment parameters.
6. The robotic controller of claim 1, wherein said engagement system includes a rack and pinion mechanism, said rack and pinion mechanism automatically adjustable based upon said first adjustment parameters, said engagement system adjusts the first solar adjustment wheel while the robotic controller is moving.
7. The robotic controller of claim 1, wherein the track in which the robotic controller traverses is sealed to prevent any significant ingress of dust or water.
8. The robotic controller of claim 1, further comprising drive wheels to propel the robotic controller along the track.
9. The robotic controller of claim 1, further comprising: a power storage system for storing power to said robotic controller.
10. The robotic controller of claim 9, wherein said power storage system is an electric energy storage device.
11. The robotic controller of claim 9, wherein said power storage system recharges wirelessly.
12. The robotic controller of claim 1, further comprising an energy receiving device for receiving power from the track
13. The robotic controller of claim 12, wherein said energy receiving device receives power either inductively from the track or using a direct connection to the track.
14. The robotic controller of claim 1, wherein said location determining unit utilizes a triangulation methodology to identify the location of the robotic controller, the triangulation methodology receives signals from at least three devices external to the robotic controller positioned in the local vicinity.
15. The robotic controller of claim 1, wherein said location determining unit includes a global positioning satellite receiver to identify the location of the robotic controller.
16. The robotic controller of claim 1, further comprising: a climate control system disposed to receive signals from said processor for moderating the environmental conditions in which the robotic controller operates.
17. The robotic controller of claim 1, further comprising: a communication system, to communicate wirelessly with at least one of a central server, a second robotic controller, and/or a central controller.
18. The robotic controller of claim 1, further comprising: a camera, for detecting at least one of the orientation of one or more of the solar surfaces and/or abnormalities in the track.
19. A method for a robotic controller to control a position of multiple solar surfaces in response to movement of multiple solar surface adjustment wheels, each solar surface having a corresponding solar surface adjustment wheel, the robotic controller positioned on a track, the method comprising the steps of: determining a position of the robotic controller; moving said robotic controller along the track to a position adjacent to a first of said multiple solar surface adjustment wheels; determining first adjustment parameters for said first solar surface adjustment wheel; and adjusting the first solar surface adjustment wheel based upon said first adjustment parameters.
20. The method of claim 19, further comprising the steps of: wirelessly communicating with at least one of a central server, a second robotic controller, and/or a central controller.
 This application claims priority from U.S. provisional application No. 61/364,729 filed on Jul. 15, 2010, and U.S. provisional application No. 61/419,685 filed on Dec. 3, 2010 which are all incorporated by reference herein in their entirety. This application is related to U.S. application Ser. No. 13/118,274 which is incorporated by reference herein in its entirety.
FIELD OF THE INVENTION
 The present invention relates to solar tracking and calibration devices, and in particular tracking systems for photovoltaic, concentrated photovoltaic, and concentrated solar thermal systems that require constant repositioning to maintain alignment with the sun.
BACKGROUND OF THE INVENTION
 In an attempt to reduce the price of solar energy, many developments have been made with respect to lowering the cost of precisely repositioning and calibrating a surface with two degrees of freedom. In concentrated solar thermal systems, heliostat arrays utilize dual axis repositioning mechanisms to redirect sunlight to a central tower by making the normal vector of the heliostat mirror bisect the angle between the current sun position and the target. Heat generated from the central tower can then be used to create steam for industrial applications or electricity for the utility grid.
 Concentrated photovoltaic (CPV) systems take advantage of dual axis mechanisms in order to achieve a position where the vector normal to the CPV surface is coincident with the solar position vector. When the CPV surface is aligned to the sun, internal optics are able to concentrate sunlight to a small, high efficiency photovoltaic cell.
 Dual axis positioning systems also enable flat plate photovoltaic (PV) systems to produce more power through solar tracking Compared to fixed tilt systems, dual axis PV systems produce 35-40% more energy on an annualized basis. While this increase in energy production may seem attractive, current technology marginalizes the value of biaxial solar tracking by increasing total system capital and maintenance costs by 40-50%.
 Traditional solutions to the problem of controlling and calibrating an individual surface fall into one of three main categories: active individual actuation, module or mirror ganging, and passive control. In the active individual actuation model, each dual axis system requires two motors, a microprocessor, a backup power supply, field wiring, and an electronic system to control and calibrate each surface. Moreover, all components must carry a 20+ year lifetime and the system needs to be sealed from the harsh installation environment. In an attempt to spread out the fixed cost of controlling an individual surface, conventional engineers' thinking within the individual actuation paradigm are building 150 square meter (m 2) heliostats and 225 square meter PV/CPV trackers. While control costs are reduced at this size, large trackers suffer from increased steel, foundational, and installation requirements.
 Another approach attempts to solve the fixed controls cost problem by ganging together multiple surfaces with a cable or mechanical linkage. While this effectively spreads out motor actuation costs, it places strict requirements on land grading, greatly complicates the installation process, and incurs a larger steel cost due to the necessary stiffness of the mechanical linkages. Due to constant ground settling and imperfections in manufacturing and installation, heliostat and CPV systems require individual adjustments that increase system complexity and maintenance cost.
 Passive systems utilizing hydraulic fluids, bimetallic strips, or bio-inspired materials to track the sun are limited to flat plate photovoltaic applications and underperform when compared to individually actuated or ganged systems. Moreover, these systems are unable to execute backtracking algorithms that optimize solar fields for energy yield and ground coverage ratio.
 A robotic controller for controlling a position of multiple solar surfaces in response to movement of multiple solar surface adjustment wheels, each solar surface having a corresponding solar surface adjustment wheel, the robotic controller positioned on a track, the robotic controller including a processing unit, a location determining unit, communicatively coupled to the processing unit, for determining a position of the robotic controller, a drive system, for moving the robotic controller along the track in response to instructions from the processing unit, an adjustment determining system for determining first adjustment parameters for a first solar surface adjustment wheel of the multiple solar surface adjustment wheels; and an engagement system for adjusting the first solar surface adjustment wheel based upon the first adjustment parameters.
 Particular embodiments and applications of the present invention are illustrated and described herein, it is to be understood that the invention is not limited to the precise construction and components disclosed herein and that various modifications, changes, and variations may be made in the arrangement, operation, and details of the methods and apparatuses of the present invention without departing from the spirit and scope of the invention which is set forth in the claims.
 In an embodiment the invention can be used in conjunction with a heliostat or solar tracker that has its microprocessor, azimuth drive, elevation drive, central control system, and wiring removed. The elimination of these components allows for extreme cost reduction over conventional systems, and creates a fourth actuation paradigm: passive with active robotic control. In this model, a single robotic controller assumes the functional duties of calibrating and adjusting two or more solar surfaces in 3D space.
 In a second embodiment of the present invention a robotic controller can move between passive solar surfaces and accurately control the rotation of one or more adjustment wheels near aforementioned surface. These adjustment wheels may be connected to a rigid or flexible shaft that could be routed to a gear train, lead screw assembly, or directly to the solar surface. The gear train, lead screw assembly, or direct drive system transforms rotational input motion into movement of the solar surface. If the gear train, lead screw assembly, or direct drive system is back drivable, additional adjustment wheels may be used to actuate braking mechanisms. The robotic controller is able to reposition a solar surface in one or two axes through control of one or more adjustment wheels and therefore replaces 100+ sets of wiring, motors, central controllers, and calibration sensors. It also eliminates the core engineering assumption--a high, relatively fixed control cost per surface--that drives the development of large heliostats and solar trackers.
 As an individual robot must endure 5 to 8 million adjustment cycles per year, the ideal adjustment interface will not use contact to control the position of the adjustment wheel. In a third embodiment, the invention can utilize a magnetic or electromagnetic interface to control the rotation of the adjustment wheels. If an axial flux motor mechanism is utilized, the robotic controller's adjustment wheel interface may contain no moving parts.
 In a fourth embodiment the robotic controller can sense the position of an adjustment wheel before, during, and after adjustment. This may be achieved through the use of Hall effect sensors on the robotic controller and a distinct magnet or piece of metal on the adjustment wheel. Methods of metal detection include, but are not limited to: Very Low Frequency (VLF), Pulse Induction (PI), and Beat-Frequency Oscillation (BFO). The robot may also use optical, electromagnetic, or physical marking systems and sensing methods to determine the instantaneous position of an adjustment wheel. This interface may also be used to detect an individual solar surface station in order to reduce the complexity of an individual robot's station sensing mechanism.
 In a fifth embodiment, the robotic controller is optimized for rapid adjustment of solar surfaces. The robotic adjustor can quickly analyze: 1) the robotic controller's location in 3D space, 2) Its relation to a solar surface in 3D space, 3) The current sun position based on time of day and location, and 4) the desired pointing position. Once these four variables are known, the robotic controller may calculate the necessary amount of adjustment for an individual solar surface. For PV and CPV applications, the solar surface may be pointed directly toward the sun or at an optimal angle as defined by backtracking control algorithms. In addition, for PV applications, the robot may utilize existing methods that rely on the location, date and time information to determine the position of the sun and point the PV panel in an open loop fashion. Heliostat power tower systems will require the solar surface to bisect an angle between the sun and a central target. As the solar surfaces will not be constantly updated, the optimal position in some applications will place the surface such that it will be in its best orientation midway between adjustments. For example, if 26 degrees is the optimal elevation angle at the time of the adjustment, and 27 degrees will be the new maximum at the time of the subsequent adjustment, a robotic controller may place the surface at 26.5 degrees tilt.
 Once calculated, the robotic controller may use an onboard adjustment interface to control the position of a solar surface. The final step in the robotic controller's process is to analyze the distance to an adjacent adjustment station, and utilize an onboard or external drive mechanism to reposition itself for a subsequent adjustment.
 In a sixth embodiment two, three, or more grades of robotic controllers can be used to cost effectively reposition a field of solar surfaces. The top and most expensive grade robotic controller may include all mechanisms necessary to precisely calibrate and adjust a field of solar surfaces. The mid grade robotic controller may contain all mechanisms needed to reposition a solar surface and would be built to withstand ten or more years of field operation. The low-grade robotic controller may have the minimum number of functional components to adjust a solar surface quickly, and may be engineered for low cost over longevity.
 The ideal passively actuated field may utilize one top grade robotic controller for initial calibration and re-calibration purposes. Mid grade robotic controllers may be used for normal operation and would adjust the solar surfaces based on inputs from the top grade robotic controller. Low-grade robotic controllers may be used in emergency situations and would enable rapid and low cost emergency defocus and/or wind stow.
 In a seventh embodiment a field of robotic controllers to communicate with each other and/or a central controller system via a wireless network, direct link system, external switch, or by storing data near individual solar surfaces or groups of solar surfaces.
 In an eighth embodiment, the robotic controller includes multiple adjustment wheel interfaces so that a multiplicity of solar surfaces can be adjusted simultaneously.
 In a ninth embodiment the robotic controller can control the position of an individual adjustment wheel or wheels without stopping. This may be achieved using a gear rack and pinion system that uses contact, magnetism, and/or electromagnetism to rotate an adjustment wheel.
 In a tenth embodiment the robotic controller can move between stations through a hermetically sealed tube to prevent large object, water, and dust ingress. It also may be desirable for the robotic controller to be hermetically sealed in order to add another layer of ingress redundancy.
 In an eleventh embodiment the robot transport tube can be routed such that the robotic controllers can be easily returned to a central location.
 In a twelfth embodiment two or more robotic controllers can adjust one group of solar surfaces. This enables the solar surface repositioning system to be redundant in the case of a single robotic failure.
 In a thirteenth embodiment the robotic controller can include an onboard climate control system that utilizes heat sinks, active cooling/heating systems, and moisture control mechanisms to maintain a constant temperature and environment for internal components. This system is particularly useful in extending the effective life of various onboard energy storage mechanisms.
 In a fourteenth embodiment the robotic controller can be charged wirelessly. If electromagnetic coils are used to control the rotation of the adjustment wheels, this interface could be reused to charge an onboard energy storage system inductively.
 In a fifteenth embodiment a robotic controller can include a diagnostic system that is able to relay the health of onboard components to other robotic controllers and/or a central control system. This diagnostic system may communicate a regular and periodic message back to the remote operator or be accessed as needed. This system may also be used for in-field quality assurance of passive trackers or heliostats as the robot may actively measure the amount of torque or energy needed to control the position of a solar surface's adjustment wheel. This system may also be used for defect detection in the case that a solar surface's adjustment wheel cannot be rotated. The robotic controller may also utilize onboard sensors to determine if the robot transport tube has any faults.
 In a sixteenth embodiment faulty solar surfaces for PV and CPV applications can be detected. In this model, the robotic controller may communicate with a central power collection system to determine the immediate output from a field of solar surfaces. If a single solar surface is rotated away from the sun, and the central power collection system detects no change in power output, the robotic controller may deem the solar surface to be defective. It may also place the solar surface in a special orientation to alert field maintenance workers that a piece of a PV or CPV system is malfunctioning.
 In a seventeenth embodiment various pre-programmed control protocols and algorithms can be incorporated into the robotic controller for dealing with various field level scenarios. These robotic control algorithms may also be updated by a field or remote operator.
 In an eighteenth embodiment various security features in the robot can be incorporated to deter from reverse engineering and theft. The robot may also include a tracking feature to enable recovery of lost or stolen robots.
 The features and advantages described in the specification are not all inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings and specification. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
 FIG. 1 is an illustration a passive solar surface that can be precisely repositioned without an individual microprocessor, azimuth drive motor, elevation drive motor, central control system, backup power supply, or calibration sensor in accordance with an embodiment of the present invention.
 FIG. 2 is an illustration of a passive solar tracker or heliostat that does not require a gear reduction to transform rotational input motion from an adjustment wheel or wheels into single or dual axis control of a solar surface in accordance with an embodiment of the present invention.
 FIG. 3 is an illustration of a robotic controller in accordance with an embodiment of the present invention.
 FIG. 4 is an illustration of an embodiment of a non-contact interface between a robotic controller and an adjustment wheel.
 FIG. 5 is an illustration of various components of the robotic controller in accordance with an embodiment of the present invention.
 FIG. 6 is a flowchart of the operation of the robotic controller in accordance with an embodiment of the present invention.
 FIG. 7 is a flowchart of the operation of a mid-grade robotic controller in accordance with an embodiment of the present invention.
 FIG. 8 is a flowchart of the operation of a lower-grade robotic controller in accordance with an embodiment of the present invention.
 FIG. 9 is an illustration of some communication techniques that may be used by the robotic controllers in accordance with an embodiment of the present invention.
 FIG. 10 is an illustration of a robotic controller with multiple adjustment wheel interfaces in accordance with an embodiment of the present invention.
 FIG. 11 is an illustration of a robotic controller that is able to control adjustment wheels without stopping at an adjustment station in accordance with an embodiment of the present invention.
 FIG. 12 is an illustration showing the manner in which a robot transport tube may be routed in a system with many solar surfaces in accordance with an embodiment of the present invention.
 FIG. 13 is an illustration of a climate control system for the robotic controller in accordance with an embodiment of the present invention.
 FIG. 14 is an illustration of a robotic controller that utilizes a wireless power transfer interface to charge an energy storage mechanism in accordance with an embodiment of the present invention.
 FIG. 15 is a flowchart of an operational process of a robotic controller's onboard diagnostic and quality assurance system in accordance with an embodiment of the present invention.
 The figures depict various embodiments of the present invention for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein.
DETAILED DESCRIPTION OF THE INVENTION
 A preferred embodiment of the present invention is now described with reference to the figures where like reference numbers indicate identical or functionally similar elements. Also in the figures, the left most digits of each reference number corresponds to the figure in which the reference number is first used.
 Reference in the specification to "one embodiment," "a first embodiment," "a second embodiment or to "an embodiment" (for example) means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment," "a first embodiment," "a second embodiment" or "an embodiment" (for example) in various places in the specification are not necessarily all referring to the same embodiment.
 Some portions of the detailed description that follows are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps (instructions) leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical, magnetic or optical signals capable of being stored, transferred, combined, compared and otherwise manipulated. It is convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like. Furthermore, it is also convenient at times, to refer to certain arrangements of steps requiring physical manipulations or transformation of physical quantities or representations of physical quantities as modules or code devices, without loss of generality.
 However, all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as "processing" or "computing" or "calculating" or "determining" or "displaying" or "determining" or the like, refer to the action and processes of a computer system, or similar electronic computing device (such as a specific computing machine), that manipulates and transforms data represented as physical (electronic) quantities within the computer system memories or registers or other such information storage, transmission or display devices.
 Certain aspects of the present invention include process steps and instructions described herein in the form of an algorithm. It should be noted that the process steps and instructions of the present invention could be embodied in software, firmware or hardware, and when embodied in software, could be downloaded to reside on and be operated from different platforms used by a variety of operating systems. The invention can also be in a computer program product which can be executed on a computing system.
 The present invention also relates to an apparatus for performing the operations herein. This apparatus may be specially constructed for the purposes, e.g., a specific computer, or it may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium, such as, but is not limited to, any type of disk including floppy disks, optical disks, CD-ROMs, magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, application specific integrated circuits (ASICs), or any type of media suitable for storing electronic instructions, and each coupled to a computer system bus. Memory can include any of the above and/or other devices that can store information/data/programs. Furthermore, the computers referred to in the specification may include a single processor or may be architectures employing multiple processor designs for increased computing capability.
 The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may also be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the method steps. The structure for a variety of these systems will appear from the description below. In addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the present invention as described herein, and any references below to specific languages are provided for disclosure of enablement and best mode of the present invention.
 In addition, the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. Accordingly, the disclosure of the present invention is intended to be illustrative, but not limiting, of the scope of the invention.
 Referring now to the drawings, FIG. 1 depicts a passive surface (101) that can be precisely repositioned without an individual microprocessor, azimuth drive motor, elevation drive motor, central control system, backup power supply, or calibration sensor. Two adjustment wheels (102) controlled by a single robotic controller may actuate this system through a flexible or rigid drive shaft (103). The depicted system uses a flexible cable to transmit rotational motion from a fixed adjustment wheel to the azimuth gear train (104) and the elevation lead screw assembly (105). Fixed adjustment wheels are desirable as they enable a relatively simple robotic controller that can move along a track or tube (106). However, this design constraint is not necessary as the robotic controller does not need to be confined to a set path, and can move freely throughout a field of solar surfaces.
 The robot transport track may include a hollow square or circular tube made out of aluminum, steel, non-ferrous metals, ferrous metals, plastic, or composite materials. The passive solar surface may be supported by a number of foundation types including but not limited to: driven pier (107), ground screw, ballasted, or simply bolted to a rigid surface. The robot transport tube may also be used as a foundational support for individual passive solar surfaces.
 FIG. 2 demonstrates an embodiment of a passive solar tracker or heliostat that does not require a gear reduction to transform rotational input motion from an adjustment wheel (102) or wheels into single or dual axis control of a solar surface. The system may be actuated in a tip-tilt fashion directly by a flexible drive shaft (103). In one embodiment, the flexible drive shaft connects directly to a pin joint (201) that is rigidly fixed to one rotational axis. Rotation of the adjustment wheel therefore alters the rotation of the solar surface in a 1:1 manner on one axis. This system may utilize friction to lock the position of a solar surface or other active braking mechanisms described in patent application Ser. No. 13/118,274, referenced above.
 FIG. 3 demonstrates the present invention's core actuation paradigm of passive systems with active robotic control. A robotic controller (301) is able to propel itself along a track (106), stop near a solar surface (101), and precisely control the rotation of one or more adjustment wheels (102) linked to aforementioned solar surface using an onboard adjustment wheel interface (302). Each adjustment wheel is connected to a rigid or flexible shaft that can be routed to accommodate many passive tracker designs. The present invention focuses on features of the robotic controller to ensure that the adjustment wheels are reliably and precisely repositioned.
 It is desirable to provide a large amount of input torque to the adjustment wheels as to decrease the gear reduction needed to reposition a solar surface. Contact based adjustment methods may be used, but are prone to poor station alignment, mechanical fatigue, and are difficult to seal from the installation environment. If necessary, the robotic controller may use positive mechanical engagement, friction, or suction based systems, for example, to mechanically control the rotation of an adjustment wheel.
 FIG. 4 shows one embodiment of a non-contact interface between a robotic controller and an adjustment wheel (102). This system uses individually controlled electromagnets (401) to rotate a metallic adjustment wheel. The adjustment wheel may have a distinct metallic form (402) that enables certain electromagnetic coil firing patterns to alter its degree of rotation. Other systems/embodiments may utilize permanent magnets on the adjustment wheel and/or permanent magnets on the robotic controller (301). Systems that utilize a permanent magnet or contact based adjustment interface may be connected to a rotational drive system in order to rotate the adjustment wheel. Systems that utilize electromagnets on the robotic controller side may be solid state. In many embodiments adjustment interfaces using electricity to control the rotation of an adjustment wheel use electromagnets, and it is most effective from an energy usage and system lifetime perspective to reduce the adjustment interface to a simple axial flux or induction motor wherein the expensive components are contained on the robotic controller.
 FIG. 4 also shows that a robotic controller may contain a system to detect the orientation of an adjustment wheel before, after, and during adjustment. These systems may utilize one or more sensors (403) to detect the position of a distinct marking (404) on the adjustment wheel. Types of markings include, but are not limited to magnetic or metallic materials, physical indents, or markings that can be recognized by an optical, electromagnetic, or electrostatic sensing mechanism. This system is useful because it allows the robotic controller to verify that a solar surface has been correctly repositioned by a distinct number of input rotations. It also allows the robot to verify that the wheel has not rotated between adjustments.
 FIG. 5 depicts an overview of a robotic controller's components in accordance with an embodiment of the present invention. From this view it can be seen that the robot has idler (501) and drive wheels (502) that keep it aligned and propel it along an enclosed track. These idler wheels may be spring-loaded to index the robotic controller to one or two sides of the track. The robotic controller may also include a calibration camera (503) and a structured light emission mechanism to discover the orientation of a solar surface in 3D space. For systems/embodiments that utilize an enclosed track, a window(s) or other opening transparent to a particular frequency can be positioned in the track near a solar surface. This window(s) allows a calibration camera to view the underside of the solar surface. Puncturing a hole in the robot transport tube may create this window. To enable the track to remain sealed, a piece of glass, plastic, or other transparent material may cover the hole.
 To reposition a solar surface, the robotic controller must be able to control the position of one or more adjustment wheels. This may be accomplished through the use of an adjustment interface that can include solid-state electromagnetic coils (401) that may be activated/deactivated individually. Adjustment wheel rotation sensors (403) may enable the robotic controller to determine the instantaneous position of the adjustment wheel. Other components of the robotic controller not depicted may include but are not limited to an individual station detection unit, global or relative location discovery unit, internal wiring, central processing unit, motor driver controller, drive motor encoder, onboard climate control system, battery management system, contact based charging system, inductive charging system, distance proximity sensor, data storage system, capacitor storage system for regenerative braking purposes, and wireless data transmitter/receiver. The precise placement of these components varies depending on the embodiment as they can be housed in many configurations within the confines of a robotic controller.
 FIG. 6 shows the operational process of the robotic controller in accordance with an embodiment of the present invention. This operational process demonstrates how a single robotic controller (301) may reposition a multiplicity of solar surfaces (101). The functional duty of this robotic controller is to work in conjunction with one or more adjustment wheels (102) near a solar surface to properly maintain the orientation of an individual solar surface.
 When a robotic controller is first deployed, its initial goal is to understand its environment and the passive trackers/heliostats it will be controlling. This begins with the robotic controller moving towards an adjustment wheel (601) and continually searching for a braking point (602) placed near a solar surface. This point could be an actual marking on the beam, a magnet, or a piece of metal, for example. If there is an actual marking on the beam, the robotic controller may be outfitted with a camera to detect this point. If the braking point is magnetic or metallic, the robotic controller may be outfitted with Hall effect sensors or metal detection system to discover the braking point. In one embodiment, the adjustment wheel or markers on the adjustment wheel used for rotational sensing may be used as the braking point. After the braking point has been detected, the robotic controller may activate its braking mechanism (603). Methods of braking may include but are not limited to: deactivation of the drive motor, application of a wheel brake, application of a motor brake, regenerative braking, or a hybrid of these braking mechanisms. While the device is slowing down, the robotic controller searches for the final adjustment point (604). Once this point has been found, it applies a full brake and brings itself to a complete stop (605).
 After properly aligning itself to one or more adjustment wheels, the robotic controller discovers its relative orientation to the solar surface. If it is the first time that a robotic controller has visited a particular solar surface adjustment station, it may "zero" the solar surface by adjusting it to zero degrees tilt and zero degrees of azimuthal rotation or another defined setting. To achieve this goal, the robotic controller may engage an adjustment wheel (606), and begin rotating it (607). While rotating, it may use onboard adjustment wheel sensors (403) to verify that the wheel is spinning properly (608). The solar surface may have hard calibration stops that prevent it from being rotated past the zero point. In these systems, the robotic controller may stop trying to adjust the system once the wheel can no longer be rotated (609). To prevent damage to a passive surface or a gear train attached to a passive surface, a robotic controller's adjustment wheel interface may include a mechanism that prevents the system from delivering a damaging amount of torque.
 For applications that do not require much precision, the robotic controller may use these stops and record the number of adjustment wheel revolutions from an initial calibration point during daily operation to estimate the current orientation of the surface. For more precise applications, the robot may also use a structured or natural light camera to analyze the underside of a solar surface to determine its relative orientation in 3d space. Once this information has been obtained, it is relayed to a central processor for analysis.
 Depending on the solar application, it may also be necessary to find the absolute or relative location of the solar surface in X, Y, and Z coordinates. This may be accomplished with an onboard GPS unit with a triangulation system that utilizes three locations in the field of solar surfaces. In this second method, the robotic controller may emit a signal and measure the time delay from each defined point in the field. Using this information, it may determine its relative location to other components in the field of solar surfaces.
 The central processing may now analyze inputs from the calibration camera, location discovery unit, internal clock, and combine this with the known gear reduction of the passive solar tracker/heliostat, and known field geometry (610). Inputs from the robot's internal clock and discovered or known global location can be used to calculate the current solar vector (611). Inputs from the robot's calibration camera, location discovery unit, adjustment wheel sensing mechanism, and/or historic adjustment information from past adjustments can be used to approximate the orientation of a solar surface in 3D space. In one embodiment, the passive solar tracker or heliostat driven by the adjustment wheels has anti-back drive properties. These systems only require a one-time calibration as wind and other forces are unable to move the solar surface between adjustments.
 PV and CPV applications may use up to five pieces of information for proper repositioning. The orientation of the solar surface, the position of the sun, the orientation of adjacent trackers, the distance between trackers, and the pre-defined tracker area and dimensions of the solar surface. Standard solar tracking algorithms may only require the first two pieces of information, but the robot uses the other three to properly execute backtracking control algorithms. These algorithms optimize a solar field for minimal inter-tracker shading, and therefore understand the shadows that are currently being generated by adjacent trackers, and the shadow that an individual solar tracker will cast on its neighbors. More details regarding backtracking are found at Mack, Solar Engineering: http:/www.rw-energy.com/pdf/yield-of-s_wheel-Almansa-graphics.pdf which is incorporated by reference herein in its entirety.
 Heliostat applications require the robot to discover the vector from a solar surface to a solar target. This may be achieved by finding the location of both the solar target and the solar surface in a global or relative coordinate plane. Once the desired change in solar surface orientation has been calculated, the central processor analyzes a passive system's known gear reduction to determine how many degrees it should rotate an adjustment wheel linked mechanically or magnetically to the solar surface (612).
 For passive trackers or heliostats that do not have inherent friction braking or anti-back drive properties, an active solar surface braking mechanism may be necessary. For these systems, the robotic controller deactivates the brake prior to rotating the adjustment wheel or wheels. This brake may be actuated with another adjustment wheel. The robotic controller may then use its adjustment wheel interface to rotate one or more adjustment wheels. In one embodiment, the robotic controller has a multiplicity of electromagnetic coils that can be activated individually or in groups. This system is able to control the rotation of a metal or magnetic adjustment wheel by firing the coils as an axial flux or induction style motor (613). The coils may be fired blindly or may obtain feedback from an adjustment wheel sensing mechanism that determines the instantaneous degree of rotation of an adjustment wheel (614).
 Once adjustment is complete, the central processor may send a signal to actuate the braking mechanism if necessary. This re-engages the gear braking mechanism and prevents outside forces from altering a solar surface's orientation until its next adjustment from the robotic controller. As a final step of this process, the robotic controller may use onboard proximity sensors or past operational history to determine if it is currently at the end of a row of solar surfaces (615). If yes, it may move backward until it reaches the first solar surface adjustment point (616). If no, the controller may repeat this adjustment cycle (617). Also note that it is possible to connect the ends of a robot transport tube such that it forms a continuous loop. In this embodiment, robotic controller would continue circulating the robot transport tube until nighttime or stopping for maintenance.
 The processor that determines the behavior of the robotic controller and its sub components could be located on the robotic controller directly, at a central processing station, or on another robotic controller in the field of solar surfaces. If the processor is not onboard, the robotic controller may require a wireless or direct data link to receive operational instructions.
 After a day of adjusting solar surfaces, the robotic controller may need to recharge its onboard energy storage mechanism. It may also recharge this system two or more times throughout the day.
 It may be desirable for a field of solar surfaces to be adjusted by three or more grades of robotic controllers. FIG. 6 demonstrates the operational process of a top grade robotic controller. This robot may work in conjunction with less sophisticated robotic controllers. A purpose of the top grade robotic controller is to permit the removal of the location discovery unit and calibration camera from both the mid and low grade robotic controllers. In an embodiment, a field of solar surfaces may only use one top grade robotic controller (if any) and could therefore greatly reduce total system and robotic controller replacement costs by removing expensive components from the unit.
 FIG. 7 shows the operational process of a less sophisticated, mid grade robotic controller in accordance with an embodiment of the present invention. The main difference between this unit and the top grade robotic controller described in FIG. 6 is that this adjustor does not have a calibration camera or a location discovery unit. The functional duties of the calibration camera and the location discovery unit are assumed by a data discovery unit that communicates with other robots or a central control station, and a data storage unit that stores the last known orientation of individual solar surfaces. When a mid grade robotic controller first interacts with a passive solar surface and has no prior data points, it may assume that the top grade robotic controller has properly "zeroed" the solar surface.
 Unlike a top grade robot, a mid-grade robotic controller pulls its input for the adjustment point's location from a data storage unit instead of a location discovery unit (701). It also determines the relative orientation of a solar surface from an onboard data storage unit and Hall effect sensors instead of a precise calibration camera. The data storage unit stores the number of adjustment wheel rotations from the zero point, and the adjustment wheel sensing mechanism is used to determine the exact degree of wheel rotation (702). Combined with known gear reduction information, this data may be sufficient for the mid grade robotic controller to approximate the orientation of a solar surface in 3D space. As the mid grade robotic controller does not have a method of determining the exact orientation of a solar surface directly, it may save the degree of adjustment wheel rotation performed to one or more adjustment wheels so that it may properly reorient a solar surface in future adjustments.
 After a day of adjusting solar surfaces, the robotic controller may need to recharge its onboard energy storage mechanism. It may also recharge this system two or more times throughout the day.
 FIG. 8 shows the operational process of a less sophisticated, low-grade robotic controller in accordance with an embodiment of the present invention. The purpose of a low-grade robotic controller is similar to a spare tire for a car--it is to be used only in emergency situations. This third class of robotic controllers enables a low cost, and rapid wind stow procedure. It also enables a high-speed emergency defocus procedure for heliostat applications. This robotic controller may have a similar operational process as the mid grade robotic controller described in FIG. 7, but it may only require one adjustment interface to move a passive solar tracker or heliostat to its wind stow position, and would not need to be built for long lifetime.
 During emergency procedures, the low-grade robotic controller would not need to know the current position of a solar surface, only that the solar surface must be either a) moved 2-5 degrees away from its current position or b) moved into a horizontal wind stow position. It may have an onboard anemometer to determine current wind speed or may be connected to a central network that sends the low-grade robotic controller a signal to initiate an emergency wind stow procedure (801). This procedure begins with the robotic controller moving itself near an individual solar surface, stopping near a solar surface's adjustment wheel (605), and rotating the adjustment wheel a pre-defined number of revolutions (802). It may also use an adjustment wheel sensing mechanism (403) to determine if the adjustment wheel has stopped rotating (614). If it has, this may indicate that the low-grade robotic controller has driven the passive solar tracker or heliostat into its wind stow hard stop.
 The process for emergency defocus may be even simpler than for emergency wind stow. As the purpose of this procedure is to move a heliostat's image away from a solar target, the low-grade robotic controller only needs to be able to quickly alter the position of many solar surfaces.
 FIG. 9 demonstrates some of the methods that could be used by a field of robotic controllers to communicate with each other and/or with a centralized network. These methods include, but are not limited to: wireless data communication (901), direct data link (902), external switches, or by storing information near individual passive solar surfaces or groups of passive solar surfaces (903). For wireless data communication, each robotic controller may be equipped with an electromagnetic frequency transmitter and/or receiver (904) that is able to communicate with other robots (301) or a centralized network (905).
 For direct data transfer, each robotic controller may be equipped with contacts that can interact with contacts on other robots or a centralized data unit. When these systems make physical contact, data may be transferred from one device to another.
 A human or robotic field operator may activate certain features on a top, mid, or low-grade robot that correspond to certain pre-programmed actions. Actuating an external, magnetic, or electromagnetic switch may initiate these actions. For example, if a low-grade robot has a pre-programmed emergency defocus feature, a mid-grade robot may be able to activate it simply by running into it and depressing a push button switch.
 It is also useful to be able to store relevant data near individual solar surfaces or groups of solar surfaces. In one embodiment, an RFID chip (903) placed near a solar surface may be used to store the information about each solar surface's absolute or relative location in the field and how this corresponds to the initial position of each adjustment wheel. These systems would require individual robotic controllers to have an RFID writer and/or RFID reader. Other methods of storing data locally include but are not limited to using semiconductor, magnetic, and/or optical based data storage technologies.
 FIG. 10 shows a robotic controller (301) with multiple adjustment wheel interfaces (302). The purpose of adding more adjustment interfaces is to distribute the cost of the most expensive onboard components and to allow for more precise control of a solar surface (101) by permitting more frequent adjustments over the same period of time. The depicted embodiment is able to adjust two solar surfaces at one time; enabling this design to cut the number of start-stop cycles for a given field of solar surfaces in half.
 FIG. 11 shows a robotic controller (301) that is able to control adjustment wheels without stopping at an adjustment station. This system may utilize a contact, magnetic, or electromagnetic based gear rack and pinion system to control the adjustment wheel. The robotic interface conceptually serves as the gear rack (1101) and the adjustment wheel (102) as the pinion (1102). As the robot drives past an adjustment wheel, it may actuate its conceptual gear rack interface so that it couples--physically, magnetically, or electromagnetically--with one edge of an adjustment wheel. Once coupled, the linear motion of the robotic controller may be turned directly into rotation of the adjustment wheel. The robotic controller may actuate its interface (1101) a second time to decouple itself from the adjustment wheel pinion (1102). The robotic controller can precisely control the rotation of an adjustment wheel by carefully monitoring its speed and time that its adjustment interface is coupled with an adjustment wheel. For example, if a robotic controller is moving at 1 meter per second and engages the edge of a 3.18 cm diameter adjustment wheel (10 cm circumference) for 1 second, it will rotate it approximately 10 times.
 The robotic controller can utilize a long strip of sensors (403) that measure the instantaneous degree of wheel rotation to confirm that the adjustment wheel (102) has been engaged and is spinning properly. A robotic controller that does not stop or make physical contact with individual solar surfaces may accurately reposition up to 1.2 MW of photovoltaic modules if moving at a constant rate of 5 MPH.
 The robotic controller depicted in FIG. 11 uses a long line of individually actuated electromagnets (401) to control the orientation of an adjustment wheel. When these electromagnets are turned on in a (N-S-N-S-N-S) arrangement, they are able to rotate 4-pole magnetic adjustment wheel (N-S-N-S) simply by driving past the adjustment station. This magnetic gear rack system turns linear motion of the robot into rotational motion of the adjustment wheel.
 FIG. 12 shows how the robot transport tube (106) may be routed in a field with a large number of solar surfaces (101). The robot transport tube may be hermetically sealed to prevent large object, water, and dust ingress into the robotic controller. In the depicted embodiment, each passive solar tracker or heliostat has an individual foundation and the robot transport tube only has to support the weight of a robotic controller or controllers.
 This figure demonstrates that while an individual robotic controller may normally adjust a particular row of solar surfaces, it can utilize an onboard drive motor to return itself to a central station for maintenance (1201). This style of track routing also enables a field operator easily deploy a field of robotic controllers by inserting two or more of them into a central station. This central station may also be used for charging or maintenance purposes.
 FIG. 12 also demonstrates that excess robotic controllers (301) can be used redundantly. In one embodiment, one or more backup robotic controllers are placed at the central station. In the case of a robotic failure, a backup robotic controller can drive itself into the proper section of track, push the failed robot to the end of the tube and resume adjustment solar surfaces assigned to the failed robot. If the failed robot was not constantly relaying the position of its assigned solar surfaces to a central data system, it may be necessary for the backup robot to run an initial re-calibration process as outlined in FIG. 6. If this information was accurately relayed to a central data system, the backup robot may resume operation wherein the failed robot stopped adjusting.
 In the case that a field of solar surfaces does not have a central robot collection system, two or more robots may be placed into one section of track. These two or more robots may establish a constant data transfer link. One robot may assume daily operation (1202) while the other serves as a redundant robot (1203) to prevent power loss due to failed controllers not being able to properly reposition a solar surface's adjustment wheels.
 FIG. 13 shows one embodiment of a climate control system for the robotic controller (301). This system may comprise, but is not limited to including the following components: fan (1301), heat sink (1302), active heat pump, Peltier device, electric heater, ventilation system, refrigerator, humidity control system, moisture sensors, temperature sensors, and air filter. These climate control components may also be offloaded onto a sealed robot transport tube so that the system may maintain a consistent environment that prolongs the life of the robotic controller's key failure components.
 It may be useful to use batteries, capacitors, super capacitors, or other forms of energy storage to reduce installation complexity and overall system cost as a single battery can replace one mile of electrified track. FIG. 14 shows one embodiment of the present invention that utilizes a wireless power transfer interface to charge an energy storage mechanism onboard the robotic controller. Wireless charging mechanisms may be desirable, as they do not require exposed contacts to transmit power to a robotic controller. It is not necessary, however, for the robotic controller to have an onboard source of stored energy, and it could be powered by an electrified rail system, or inductively by the track.
 An inductive charging station (1401) placed at any location on the robot transport tube is able to transfer energy to the robotic controller by generating an oscillating electromagnetic field. An inductive coil loop (1402) placed on the robotic controller (301) is able to capture this energy and store it within an onboard energy storage mechanism. Other forms of power transfer that could be utilized by the robotic controller include, but are not limited to: electrostatic induction, electromagnetic radiation, and electrical conduction.
 FIG. 15 shows the operational process of a robotic controller's onboard diagnostic and quality assurance system. A robotic controller may continuously perform aspects of this process to enable a field or remote operator to determine a field's instantaneous health. This process in its entirety or certain aspects of this process may also be initiated daily, weekly, monthly, or as needed to enable field operators to perform preventive maintenance of the system. In particular, a robotic controller's diagnostic system may determine: a) the overall health of an individual robotic controller as defined by the status of key components (1501), b) the health of a robot transport tube (1502), c) the health of a passive solar tracker or heliostat (1503), and d) the health of an individual PV or CPV surface (1504).
 This process may begin with the robotic controller relaying all saved operational data to a central processing system or network (1505). This data may include, but is not limited to: historical temperature and moisture readings on internal and external sensors, historic meteorological data from an on or offsite monitoring system, historic current and voltage readings from all onboard components, and SOC/SOS readings from an onboard energy storage mechanism. The diagnostic system may then compare this information to past operational data (1506) and to pre-defined safe ranges of operation (1507). Analysis of irregularities may be used to determine the current health of individual components and/or to perform preventative maintenance of a robotic controller (1508).
 To determine the health of a robotic transport tube (1502), the robotic controller may access data from onboard cameras or proximity sensors that are able to inspect the physical features of the track (1509). If any abnormalities are discovered, such as an object protruding into the track, a large build up of dirt in one section of track, a hive of insects, or a puncturing in the track that allows foreign object ingress, the robotic controller may send a signal to a field or remote operator (1510). A field or remote operator may access a live video feed from the robotic controller's camera in order to better assess a maintenance situation.
 To determine the health of a passive solar tracker or heliostat, a robotic controller may access the data log generated from adjusting an individual tracker (1511). It may then access the data log measuring the amount of input torque/current needed to rotate an adjustment wheel (1512) and understand how this metric changes over time. If the robot uses an electromagnetic interface, this torque metric can be determined by recording the average current delivered to the interface over the course of an adjustment. In one example, if the diagnostic system recognizes that a passive solar tracker that usually requires 95 +/-5 amps suddenly begins requiring 320 +/-20 amps to adjust during normal operating conditions, it may deem this individual passive tracker to be dysfunctional and send an alert a field maintenance worker (1513). The robotic controller may also use vision-based systems to inspect and analyze the health of an individual solar tracker or heliostat. This video input may be relayed directly to a field operator to assess the health of the tracking system. If a passive tracker's torque/current readings are within an acceptable range, this portion of the process (1503) may be repeated for every passive surface (101) under a robot's control domain.
 To autonomously determine the health of an individual PV or CPV surface (1504), the robotic controller may first move an individual tracker into its optimal orientation (1515). It may then communicate with a device that is able to monitor the power output of a central inverter, combiner box, or individual string of solar modules (1516). As it is possible that in the robotically controlled system that only one module in a group of modules may be actuated at a single moment in time, the power output reading should remain relatively constant. Once a data link has been established, the robot may execute a search algorithm (1517) where it moves the passive surface in a spiral while monitoring system output. It may then record the maximum power point (1518) and adjust the tracker so that it is no longer facing the sun (1519). The diagnostic system may measure the change in central inverter, combiner box, or string level output (1520). This information can be used to determine the degradation percentage of an individual module by measuring the exact difference in central inverter, combiner box, or string level output and comparing this to a module's rated output (1521) to calculate degradation percentage (1522). If no change is detected, this may indicate that an individual solar surface (101) is not contributing to the PV or CPV system's total output. This module may be classified as defective and the robotic controller may use its adjustment interface to place this surface in a special configuration as to alert field maintenance workers of the potential problem (1523). If the degradation percentage is within an acceptable range, sub process 1504 may be repeated for all surfaces under a robot's control domain (1524).
 The robotic controller may also include pre-programmed algorithms and security features to protect itself from theft and/or reverse engineering. Onboard controllers and data storage units may be encrypted to prevent access to control protocols and data stored on the robot. In addition, there may be sensors that detect unauthorized access to the robot, including attempts to open a robotic controller. The controller may respond to such actions by notifying a remote operator and/or erasing the control algorithms and operational data. At the time of deployment, each robot may be initialized with its deployment location and unique identification number. If the robot, field operator, or remote operator detects that the robot is no longer in the assigned location, then an appropriate action may be taken to retrieve the lost or stolen robotic controller.
 While particular embodiments and applications of the present invention have been illustrated and described herein, it is to be understood that the invention is not limited to the precise construction and components disclosed herein and that various modifications, changes, and variations may be made in the arrangement, operation, and details of the methods and apparatuses of the present invention without departing from the spirit and scope of the invention.
Patent applications by Daniel Fukuba, Palo Alto, CA US
Patent applications by Thomas Currier, Rochester, MN US
Patent applications in class Computer
Patent applications in all subclasses Computer