US20150233607A1

US20150233607A1 - Positioning system and method for positioning an article

Info

Publication number: US20150233607A1
Application number: US14/424,775
Authority: US
Inventors: Markus Behn
Original assignee: SKF AB
Current assignee: SKF AB
Priority date: 2012-08-30
Filing date: 2013-08-30
Publication date: 2015-08-20
Also published as: WO2014033249A1; EP2890939A1; DE102012215358A1; CN104620061A

Abstract

A positioning system for an object, such as a solar panel, to be moved in a controlled manner from an initial position in a direction of movement along a movement path including an azimuthal component into a final position includes a preloading device connected to the object and configured to exert a permanently acting force on the object in the direction of movement, the force having a component acting in an azimuthal direction, and a brake apparatus configured to fix the object in a predetermined position along the movement path.

Description

Exemplary embodiments of the present invention are concerned with a positioning system and with a method for positioning an object.
Positioning systems, using which an object can be guided from an initial position into a final position in a controlled manner, are known in a variety of embodiments. For example, in a variety of solar applications, panels including photovoltaic cells or including mirrors/lenses for concentration of light at a common focal point (such as, for example, with CPV, heliostat, Stirling dish, solar trough, or linear Fresnel systems), which are all summarized in the following under the term “solar panels,” must be oriented in a defined manner with respect to the sun, wherein high-precision systems are required in order to be able to follow the daily course of the sun. In particular in systems wherein the incident light energy is to be concentrated at a point or a designated surface, the positioning, i.e. the orientation of these objects positioned using the positioning system must occur with the highest possible precision. Therefore a play in the mechanics of the system (backlash) is necessarily to be avoided.
Conventional positioning systems, which use linear actuators or worm drives, have such a play as caused by the system. For example, in some systems worm drives operate on gears in order to effect a rotation of the panels. A play results, for example, since during the driving the gears or worm gears are in contact with one another via a flank, while after the driving or after the switching-off of the propulsion a change of abutment of the flanks can occur, for example due to a dynamic load acting on the panel. Here in the case of solar applications, for example, even an imprecision from 0.105° to 0.135° can lead to a significant drop in efficiency and to an inefficiency of the entire system. Furthermore, in such conventional systems the energy required for operation of the positioning system is relatively high since the drive motors must be energized during the positioning, i.e. in the case of solar systems during the entire time of the insolation, which leads to significant power losses.
Although in the just-now mentioned tracking systems or positioning systems predominantly an orientation of the objects moved using the positioning system is changed, equivalent considerations also apply for positioning systems wherein the object changes its position while it we transferred in a controlled manner along a movement path from an initial position into a final position. In these systems the object thus changes its position, which is controlled by the positioning system, along a 3-dimensional locus in space. Here the same problems result independent of whether the positioning system has one or more degrees of freedom, i.e. whether the system can control one, two, or three axes or one, two, or three spatial coordinates.
In view of the prior art known up to now, the need exists to provide positioning systems which can be driven more energy-efficiently and more flexibly than up to now.
According to some exemplary embodiments of the present invention this is achieved by a positioning system for an object including a preload apparatus connected to the object, which preload apparatus exerts a force permanently acting on the object in the direction of the movement path, which force has a component acting in the azimuthal direction; the object is to be transferred from an initial position into a final position in a controlled manner along a movement path comprising an azimuthal rotation. In order to be able to fix the object at a predetermined position or in a predetermined orientation along the movement path, the positioning system additionally has a brake apparatus which is configured to fix the object at the predetermined position, i.e. therefore to act against the permanently acting force such that the object is fixed in the predetermined position at which the brake apparatus is activated.
That is, the object is not actively accelerated or moved along the movement path using a motor, but rather impinged on with a force acting permanently in the direction of the movement path, wherein the force at that position or orientation at which the object is to be carried or in which the object is to be fixed is compensated by the brake apparatus which fixes the object in its current orientation or position. Compared to conventional systems this leads to a significant energy savings in the positioning, since electric motors possibly used in the system need not permanently be subjected to voltage in order to suitably position the object.
Moreover, the fixing of the position of the object along the movement path increases the achievable positioning precision, since an inherent intrinsic motor-driving play cannot affect the positioning precision.
According to some exemplary embodiments the force acting in the direction of the movement path is effected by a spring that can be preloaded against the movement path so that the restoring force of the elastic spring can be used to exert the permanently acting force on the object. Here the spring force can be used, of course, for a movement in one, two, or three axes or spatial coordinates. This can be determined by appropriate selection of the geometric boundary conditions. Generally speaking, in some exemplary embodiments of the invention the force is effected by an element that can store potential or mechanical energy, which can thus change its state such that in an initial state the element has a greater potential energy than in a final state.
According to some other exemplary embodiments the permanently acting force is generated by a weight that is carried against the force of gravity into a starting position before the start of the positioning or of the moving of the object along the movement path. The weight is coupled or connected to the object such that the weight force acting on the weight causes the force in the direction of the movement path. This approach can lead to a significant energy savings since the mechanical device which causes the force permanently acting on the object need only be preloaded into the initial position at the start of a moving or of a departing of a movement path. That is, an internal-combustion- or electric-motor that is used to carry the preload apparatus into the initial position need only be supplied or driven by electricity for a short time.
Such a retracting apparatus, which transfers the object against the permanently acting force from the final position into the initial position and simultaneously carries the preload apparatus into the initial position, can be, for example, an electric motor, an internal combustion motor, a mechanism or motor driven by alternative energies such as water power, solar power, wind power, or the like.
According to some exemplary embodiments a positioning system having one or two axes is used to adjust a solar panel to the daily course of the position of the sun. This can significantly improve the overall energy balance or the overall efficiency level of the system due to the energy savings achievable with the positioning.
According to some exemplary embodiments the positioning system of the solar panel is uniaxial. That is, a solar panel rotatably supported about an axis of rotation extending in the horizontal direction is adjusted to the position of the sun using the positioning system. Here according to one embodiment a frame for the solar panel to be mounted on the frame is designed such that its center of gravity, in particular if the solar panel has already been installed on the frame, falls outside the axis of rotation of the solar panel so that the permanent weight force acting in the direction of the movement path is generated by the geometry of the solar panel itself. The functionality of a preload apparatus can thus be provided by the geometry of the frame or of the solar panel itself.
In some exemplary embodiments the size of the force can be varied such that the solar panel or its frame additionally includes a boom extending perpendicular to the axis, on which a weight is attached at a predetermined distance to the axis of rotation, whereby the level of the permanently acting force can be adapted to the conditions. In some exemplary embodiments the size of the force can also be adapted to the size of the panel used by varying the position of the additional weight on the boom, in particular the distance to the axis of rotation.
In some exemplary embodiments the position of the solar panel is adjusted not only in one axis, i.e., for example, the elevation (height over the horizon), but also in a second axis, for example the azimuth. In these exemplary embodiments the force permanently acting in the movement direction thus also has a component acting in the azimuthal direction. This component or the force can be generated by a spring, for example, which is located between two arms that are disposed on the one hand on a base and on the other hand on a movable part of the positioning system. In alternative exemplary embodiments a torsion spring can also be used between the two components rotating relative to each other.
In both uni- and bi-axial positioning systems for solar panels or for other objects whose orientation is to be changed in two axes, the brake apparatus is configured to fix the position of the object with respect to each of the axes of rotation, i.e. with respect to the axial or the horizontal axis of rotation. That is, the rotating of the object to be positioned is prevented with respect to one or both axes and the object is thus fixed with respect to these axes. Because of the separation of the drive and the fixing of the object to be positioned, the mechanical play inherent to the drive can be avoided due to the fixing relative to the axes using the additional brake apparatus.

Some preferred exemplary embodiments of the present invention are explained in more detail in the following with reference to the accompanying Figures:

FIG. 1 shows a positioning system for a solar panel having a movable axis; and

FIG. 2 shows a positioning system for a solar panel having a second movable axis.

FIG. 1 shows an exemplary embodiment of the present invention wherein a solar panel 2, for example, a photovoltaic module or even a minor, can be oriented using a positioning system such that this follows the changing position of the sun in the course of the day.
The solar panel 2 is mounted on a frame 4 which is rotatably supported, using an axis of rotation 8 extending in the horizontal direction 6, with respect to a mast 14; the mast 14 is stationary and extending in a vertical direction 10 to a base 12.
Furthermore a weight 18 is attached to a boom 16 extending away from the axis of rotation 8, which weight 18 is movable from the initial position shown in FIG. 1 of the weight 18 to a final position wherein the weight 18 is located in the lowermost possible position determined by the geometry. Due to the weight, a force serving for positioning of the solar panel 2, i.e. acting in the direction of the movement path of the solar panel 2, is permanently exerted on the solar panel 2 or the frame 4 between these two positions. In the exemplary embodiment shown in FIG. 1, the “movement path” in the sense to be understood herein is thus understood to be that change of the orientation or of the elevation angle 20 between the surface normal of the solar panel 2 and of the horizontal direction 6 that the solar panel 2 experiences with a complete tilting about the axis 8. Generally speaking, the “movement path” should be understood to be any change of a quantity that describes an orientation or a location of an object and that varies or is to be varied from the same with an adjusting or controlled moving of an object.
Even at the start of the movement, i.e. in the initial position shown in FIG. 1 of the solar panel 2, the weight force of the weight 18 acts in the direction of the movement path so that without a brake apparatus the solar panel 2 would perform an unstopped movement from the initial position into the final position. In order to prevent this, the exemplary embodiment in FIG. 1 includes a brake apparatus 22 in the form of a brake, which makes it possible to prevent the rotation of the panel 2 or of the frame 4 with respect to the axis 8, which can thus fix the position of the frame 4 or of the panel 2 with respect to the horizontal axis of rotation 8.
As retracting apparatus 24 the exemplary embodiment of FIG. 1 includes an electric motor 26 which can exert a retracting force, on an end of the boom facing away from the weight 18 via a diverted cable pull, against the permanently acting force in order to be able to carry the preload apparatus, which in this case is comprised of the weight 18 on the boom 16, back into the initial position shown in FIG. 1.
Although in the exemplary embodiment shown in FIG. 1 an additional weight 18 serving for the generation of the permanently acting force is provided, it is self-evident that in other embodiments the preload apparatus, which exerts the permanently acting force in the direction of the movement path on the solar panel 2, can also be implemented in any other manner. For example, this can be formed by the geometry of the frame 4 or of the solar panel or the attaching of the solar panel 2 to the axis 8 itself. If the geometry is designed, for example, such that the center of gravity of the panel falls outside the axis 8, the required force permanently acting in the direction of the movement path is already exerted solely due to the geometric arrangement. Of course the permanently acting force can also be exerted or effected in any manner, for example using one or more springs, for example torsion springs on the axis 8 or using weights formed in a different manner, for example by a fluid-filled reservoir or the like.
Due to the brake apparatus 22 on the axis 8 it is ensured that the positioning precision is very high since the drive and the brake are embodied separate from each other and thus plays embodied in the drive do not negatively influence the positioning precision. In other words the solar panel 2 or the frame 4 itself is part of the positioning system. In other words in the exemplary embodiment shown in FIG. 1 the solar panel or the solar mirror is equipped with a weight 18. Before the sun rises the weight 18 is lifted by the electric motor 26 into the initial position shown in FIG. 1. The system is thus “relaxed” overnight. The axis adjusting the elevation 20 is thereby preloaded, i.e. due to the weight 18 a force permanently acts thereon in the direction of the movement path of the solar panel. In the course of the day the weight 18 is continuously tilted downward in a manner controlled by the brake apparatus 22 whereby the elevation angle 20 of the solar panel 20 changes so that this always has an optimal orientation with respect to the current position of the sun. This can be determined, for example, using the spatial coordinates of the positioning system, which in turn can be determined via a GPS system, astronomical calendars, Hall sensors which indicate the current position of the axis, and a built-in reference point, so that the adjustment can optimally succeed at any point in time. Using modern energy storage and intelligent software control it is ensured that at any time the emergency positioning (panel horizontal) can be moved to. The controlling recognizes whether the weight must be lifted up or merely lowered.
In the evening the weight 18 has arrived in its final position at the lower end of the mast 14. If in the daytime storms or other weather conditions affecting the device occur, the solar panel 2 can of course be artificially moved, even before the end of the day, into an emergency position wherein the panel is situated horizontally. Before sunrise the weight is pulled back into the initial position shown in FIG. 1, for which purpose the retracting apparatus 24 is used. According to some exemplary embodiments the current generated by the solar panel itself, for example, can be used for this purpose without impairing the efficiency of the solar panel during the day such that current must be applied permanently to the positioning motors. For this reason in some exemplary embodiments a self-locking brake is also used as brake apparatus 22, i.e. a brake wherein a control current is only need for releasing the brake, so that most of the time no power loss occurs in the assembly. In other words, some exemplary embodiments are based on the fact that the center of gravity of the frame or the common center of gravity of the solar panel and of the frame deliberately lies outside the axis so that the moment thereby effected can be used for driving.
FIG. 2 shows a further exemplary embodiment of the invention, based on FIG. 1, wherein an adjusting of the solar panel 2 (tracking) also occurs in an azimuthal direction, i.e. the movement path also has a component that corresponds to an azimuthal rotation, i.e. a change of an azimuthal angle 28.
In order to make this possible, in the exemplary embodiment shown in FIG. 2 the mast 14 is rotatably supported with respect to the base 12, wherein the preload apparatus additionally includes a first arm 30 which is rigidly connected to the mast 14 and thus also to the frame 4 or the panel 2 with respect to the azimuthal direction. The positioning system further includes a second arm 32 which is rigidly connected in a stationary manner, i.e., for example, to the base 12. Using a bending spring 34 a permanently acting force is generated in the azimuthal direction 28 between the first arm 30 and the second arm 32, i.e. a force that permanently acts along the azimuthal components of the movement path of the solar panel. In order to make possible the controlled movement, the assembly of FIG. 2 furthermore includes a further brake apparatus, which acts between the mast 14 and the base 12, so that using the further brake apparatus the position of the frame can be fixed with respect to the vertical axis of rotation. It is self-evident that any other device can also be used for second, and controllably movable, axis shown in FIG. 2, in order to achieve the continuously acting force in the direction of the movement path. This can be, for example, any other form of spring, for example a torsion spring, between the mast 14 and the base 12.
Although in the previous exemplary embodiment for a uniaxial adjusting only the adjusting of the elevation has been shown, according to further uniaxial exemplary embodiments only the azimuth can be adjusted using a preload apparatus.
Although in the previous two exemplary embodiments the inventive concept for has mainly been illustrated using a tracking system for a solar panel 2, it is self-evident that in further exemplary embodiments other positioning systems can also make use of the inventive teachings. Among these of course also those wherein not only the orientation of an object is changed, but also its geometric location, wherein, i.e., it moves in a controlled manner along a predetermined trajectory in space using the positioning system for a moving object.

REFERENCE NUMBER LIST

2 Solar panel
4 Frame
6 Horizontal direction
8 Axis of rotation
10 Vertical direction
12 Base
14 Mast
16 Boom
18 Weight
20 Elevation angle
22 Brake apparatus
24 Retracting apparatus
26 Electric motor
28 Azimuth angle
30 First arm
32 Second arm
34 Bending spring

Claims

1. A positioning system for an object to be moved in a controlled manner from an initial position in a direction of movement along a movement path including an azimuthal component into a final position, comprising:

a preloading device connected to the object and configured to exert a permanently acting force on the object in the direction of movement, wherein the force has a component acting in an azimuthal direction; and

a brake apparatus configured to fix the object in a predetermined position along the movement path.

2. The positioning system according to claim 1, wherein the preloading device comprises an element that can store potential energy such that the force is generated by the stored potential energy.

3. The positioning system according to claim 2, wherein the preloading device comprises a spring tensionable against the movement path and/or a weight, movable against the force of gravity, the weight being coupled to the object such that a weight force acting on the weight causes the force acting in the direction of the movement path.

4. The positioning system according to claim 1, further comprising a retracting apparatus, which is configured to move the object against the permanently acting force from the final position into the initial position.

5. The positioning system according to claim 1, wherein the object is a solar panel that is rotatably supported about a horizontal axis of rotation.

6. The positioning system according to claim 5, further comprising a frame mounted to the solar panel such that the center of gravity of a unit comprising the frame and the solar panel falls outside the axis of rotation.

7. The positioning system according to claim 6, wherein the frame includes a boom extending perpendicular to the axis of rotation and including a weight attached to the boom at a predetermined distance from the axis of rotation.

8. The positioning system according to claim 6, wherein the brake apparatus is configured to fix the position of the frame or of the solar panel with respect to the axis of rotation.

9. The positioning system according to claim 6, wherein the frame is furthermore rotatably supported with respect to a vertical axis of rotation perpendicular to the horizontal direction, wherein the preloading device includes a first fixed arm extending perpendicular from the vertical axis and rotationally fixed with respect to the frame and a second stationary arm, wherein the first and the second arm are connected to each other via a spring.

10. The positioning system according to claim 9, wherein the brake apparatus is further configured to fix the position of the frame or the position of the solar panel with respect to the vertical axis of rotation.

11. A method for controlled movement of an object from an initial position to a final position via a plurality of intermediate positions disposed along a movement path, the movement path including an azimuthal component, the method comprising:

exerting a permanently acting force on the object in the direction of the movement path, wherein the force includes a component acting in an azimuthal direction; and

fixing the object at an intermediate position along the movement path using a brake apparatus.

12. The positioning system according to claim 1,

wherein the object includes a solar panel mounted on a frame for rotation about a horizontal axis of rotation and the preloading device comprises a boom extending from the frame and supporting a weight such that a center of gravity of the system comprising the solar panel, the frame, the weight and the boom does not lie on the axis of rotation, a position of the weight on the boom being adjustable, and

the system further including at least one motor for shifting the solar panel from the final position to the initial position against the permanently acting force.

13. The positioning system according to claim 12, wherein the frame is mounted for rotation about a vertical axis of rotation, and

wherein the preloading device further comprises a spring rotationally biasing the frame in a first rotational direction, and wherein the at least one motor is configured to rotate the frame in a second rotational direction opposite the first rotational direction.

14. The positioning system according to claim 1,

wherein the object includes a solar panel mounted on a frame for rotation about a horizontal axis of rotation,

wherein the frame is mounted for rotation about a vertical axis of rotation,

wherein the preloading device comprises a spring rotationally biasing the frame in the direction of movement, and

the system further includes a motor for shifting the solar panel from the final position to the initial position against the permanently acting force.

15. The positioning system according to claim 14, wherein the preloading device includes a first arm extending perpendicular from a vertical portion of the frame and configured to rotate with the vertical portion of the frame and a second arm rotationally fixed relative to the vertical portion of the frame and a spring connecting the first arm to the second arm.

16. A positioning system for moving, in a controlled manner, a solar panel mounted on a frame from a beginning of a movement path to an end of the movement path, the movement path having an azimuthal component, the positioning system including:

a spring configured to rotate a vertical portion of the frame in a first rotational direction; and

a brake configured to selectively block the rotation of the frame in the first rotational direction.

17. The positioning system according to claim 16, including a first arm extending from a vertical portion of the frame and configured to rotate with the vertical portion of the frame and a second arm rotationally fixed relative to the vertical portion of the frame, the spring connecting the first arm to the second arm.

18. The positioning system according to claim 16, further including at least one motor for rotating the vertical portion of the frame in a second direction opposite the first direction.

19. The positioning system according to claim 16, wherein the frame is mounted for ration about a horizontal axis of rotation and further comprising a boom extending from the frame and supporting a weight such that a center of gravity of a system comprising the solar panel, the frame, the weight and the boom does not lie on the horizontal axis of rotation, a position of the weight on the boom being adjustable, and

the system further including at least one motor for shifting the solar panel from the end of the movement path to the beginning of the movement path and for rotating the vertical portion of the frame in a second direction opposite the first direction.