Electromechanical linear drive units for precise positioning of large reflectors or communication antennas used, for example, in radio astronomy

Abstract

The present invention relates to a linear drive unit, which comprises a first actuator element and a second actuator element, a guide unit, a first power unit and a second power unit, and a control unit, wherein the guide unit is configured to enable a linear relative motion between the two actuator elements; the first power unit and the second power unit are both attached to the first actuator element and are configured to provide a corresponding first driving force and a second driving force to the second actuator element; the control unit is used to control the two power units and is configured to control the first driving force and the second driving force so that the first driving force can be different from the second driving force. The present invention also relates to a telescope comprising a linear drive unit, and a method for aligning such a telescope.

Description

Background Art

[0001] Radio astronomy devices (like the reflectors of radio telescopes) or communication antennas must be able to be adjusted very precisely to be able to detect weak signals from distant extraterrestrial objects.

[0002] The rotation of the telescope reflector about the pitch axis is achieved by an adjustable linear drive unit, which is connected to the fixed and moving parts via corresponding suspensions. Extension and retraction of the linear drive unit causes the reflector to tilt about the pitch axis. To achieve this purpose, spindle drives are usually used in radio telescopes. However, these spindle drives have play and are subject to high friction.

[0003] The linear drive unit is controlled in sync with other drive units to achieve precise alignment of the telescope with an astronomical source and tracking of that source. While fast motion is required to quickly align the telescope with a source, or to change from one source to another, slow and high-precision tracking is also required to compensate for the rotation of the Earth during continuous measurements.

[0004] Known electromechanical linear drive units always have a certain degree of play and / or friction, thereby adversely affecting the performance of radio astronomy devices. Therefore, the object of the present invention is to provide an electromechanical linear drive unit with minimal play and friction to achieve precise positioning of radio astronomy devices. Summary of the invention

[0005] This object is achieved by combining a plurality of high-quality drive elements in a novel, high-precision linear drive unit and by preferred embodiments thereof.

[0006] According to the present invention, the linear drive unit includes a first actuator element and a second actuator element, a guide unit, a first power unit and a second power unit, and a control unit. The guide unit is configured to enable linear relative movement between the first actuator element and the second actuator element; the first power unit and the second power unit are both attached to the first actuator element and are configured to provide corresponding first driving force and second driving force to the second actuator element; the control unit is used to control the first power unit and the second power unit, and is configured to control the first driving force and the second driving force, so that the first driving force can be different from the second driving force.

[0007] By using two power units to drive the relative movement between the two actuator elements, the individual drive forces of the two power units can reinforce each other. As a result, the total drive force of the linear drive unit can reach twice the maximum drive force of a single power unit, which is advantageous for fast movements with medium precision requirements. Being able to control the individual drive forces independently of each other allows the total drive force to be adjusted very precisely.

[0008] The control unit is preferably configured to control the first driving force and the second driving force such that the first driving force and the second driving force may act in opposite directions.

[0009] By controlling the respective drive forces so that they are different from each other and act in opposite directions, a slow but precise movement can be achieved, wherein the first drive force causes the movement and the second drive force (smaller than the first drive force) acts as a brake. Since the two power units are always in mechanical engagement, whether during movement in one direction, when reversing the movement or when holding a position, play in the power units can be eliminated.

[0010] When the motion is reversed, the relationship between the drive forces is inverted so that, unlike conventional linear drive units, no backlash occurs. The equal drive forces acting in opposite directions further allow a precise and play-free position to be maintained, so that it is not affected by external loads such as wind.

[0011] In a preferred embodiment, the first power unit includes a first motor having a first drive pinion, and the second power unit includes a second motor having a second drive pinion, wherein the first drive pinion is configured to engage with the first rack of the second actuator element, and the second drive pinion is configured to engage with the first rack or the second rack of the second actuator element.

[0012] The rack and pinion drive is highly efficient, has low friction losses, saves space and is easy to implement, especially when two power units are used synchronously in the form of electric motors. In the case where both motors are engaged with the same rack, the driving forces generated are collinear, so that tilting torques that could cause inaccuracies or damage can be avoided. In contrast, a spindle drive with two power units would require the two spindles to be spaced apart, so that the occurrence of tilting torques cannot be avoided.

[0013] It is further preferred that the first rack and / or the second rack is a spur rack. Spur racks are quite cost-effective, easy to implement, and are particularly suitable for linear motion.

[0014] In a preferred embodiment, the first driving force is generated by a first driving torque generated by a first power unit, and the second driving force is generated by a second driving torque generated by a second power unit, and the control unit is configured to control the first driving torque and the second driving torque so that the first driving torque and the second driving torque act in opposite directions, and so that the first driving torque or the second driving torque reaches between 0 and 30% of the respective other driving torque, preferably, between 5% and 15%.

[0015] Experiments have shown that, in the case of a braking torque that is significantly smaller than the driving torque, the described relationship between the respective driving torques allows the desired movement to be controlled and the play to be eliminated very precisely and reliably.

[0016] The first power unit and the second power unit are preferably electric motors having a first rotation axis and a second rotation axis respectively, the electric motors are especially asynchronous electric motors, wherein the first rotation axis and the second rotation axis are preferably parallel, more preferably coincident.

[0017] Electric motors, in particular asynchronous electric motors, are particularly suitable because they can be controlled very accurately. The coincidence of the axes of rotation further helps to avoid disadvantageous tilting torques.

[0018] It is further preferred that the first power unit and / or the second power unit comprises a gearbox, which is preferably configured as a planetary gearbox.

[0019] Gearboxes adjust the relationship between torque and rotational speed of a power unit to meet the specific requirements of the respective application. In high-precision drive units, the rotational speed is often reduced, thereby increasing the torque and enabling precise movements. Planetary gearboxes are particularly suitable for such applications because they are compact and can transmit high torques.

[0020] In a preferred embodiment, the first actuator element or the second actuator element has a cavity which is configured to accommodate the other actuator element.

[0021] This telescopic design is characterized by favorable load distribution, high stability and the ability to accommodate drive components internally, which are protected from external influences (such as dust or dirt, for example), especially in the retracted state. In addition, the risk of crushing damage is reduced when the drive components are not exposed and inaccessible.

[0022] The guide unit preferably comprises at least one guide rail and at least one guide carriage, which is configured to be guided along the at least one guide rail.

[0023] Linear guides with rails and carriages provide support against tilting torques that may be generated by the weight of the linear drive unit itself or by operating conditions. Linear guides are reliable, cost-effective, easy to implement and allow precise motion, so they are particularly suitable for high-precision linear drive units.

[0024] It is further preferred that the guide rail or guide carriage is attached to the inner surface of the cavity. Placing the guide unit inside the cavity has the advantage that the guide unit is protected from external influences (such as dust or dirt, for example), especially when in the retracted state. Furthermore, the risk of crushing damage is reduced when the guide component is not exposed and inaccessible.

[0025] The first actuator element and / or the second actuator element preferably comprises a flange, wherein the first rack and / or the second rack is attached to a first side of the flange and at least one component of the guide unit is attached to a second side of the flange, which second side is preferably opposite to the first side of the flange.

[0026] Reducing the orthogonal distance between the drive element (i.e., rack) and the guide element (i.e., guide rail or guide carriage) helps to reduce the tilting torque caused by the friction of the guide unit. Attaching the drive element and the guide element to opposite sides of the same flange is an effective and efficient design of a linear drive unit (the drive element and the guide element are arranged closely).

[0027] In a preferred embodiment, the linear drive unit further comprises at least one end stop for limiting the relative movement between the first actuator element and the second actuator element, the end stop comprising a substantially elastic first element and a substantially rigid second element, the first element being such as a rubber element or a spring element, and the second element being such as a metal plate.

[0028] The end stop prevents exceeding the permissible adjustment range, thereby preventing a potential disengagement of the drive pinion from the rack. In the case of a two-stage end stop comprising a soft first end stop and a hard second end stop, when the first end stop is struck, potential damage to the linear drive unit can be prevented due to its softness.

[0029] Taking into account the potential damage of the linear drive unit, in the event that the soft end stop cannot prevent excessive movement, the second end stop can reliably prevent the linear drive unit from exceeding the permissible adjustment range to avoid more serious damage or danger caused by the drive pinion disengaging from the rack.

[0030] The first and the second actuator element are preferably connected to the respective first and second attachment flanges via first and second cardan joints (cardan bearings).

[0031] Assembly errors or operational deformations may lead to lateral offsets between the mounting points of these actuator elements and the corresponding attachment flanges. Therefore, in order to compensate for potential lateral misalignments and avoid inadmissible bearing forces, it is advantageous to use universal joint bearings instead of simple swivel bearings. This further ensures that the drive element is only subjected to axial loads and no other loads from lateral forces.

[0032] The linear drive unit may also be part of a telescope, which further comprises a support structure and a reflector, wherein one of the first attachment flange and the second attachment flange is connected to the support structure, and wherein the other attachment flange is connected to the reflector such that the reflector is rotatable around a substantially horizontal axis by the linear drive unit.

[0033] Since a telescope must be driven very precisely to detect weak signals from distant extraterrestrial objects, the linear drive unit according to the invention is very suitable for driving a telescope.

[0034] The present invention can also provide a method for aligning a telescope or an antenna, which includes the following multiple steps performed synchronously: generating a first driving torque so that the driven face of the first driving pinion contacts the driven face of the first rack to move the reflector to a defined position; generating a second driving torque so that the second driving torque acts in a direction opposite to the direction of the first driving torque, wherein the first driving torque is greater than the second driving torque, the retarding face of the second driving pinion contacts the retarded face of the first rack or the second rack, and the driven face and the retarded face face in opposite directions to eliminate the clearance between the first driving pinion and the first rack.

[0035] By simultaneously generating two separate drive torques of opposite directions and different magnitudes, with two drive pinions meshing with one or both racks from opposite sides, a backlash-free linear motion can be achieved.

[0036] The invention also relates to a method for aligning a telescope or an antenna by simultaneously generating a first drive torque and a second drive torque, wherein the first drive torque and the second drive torque act in the same direction, have the same or different magnitudes, and are combined to move towards the position of a reflector.

[0037] Since the first drive torque and the second drive torque reinforce each other, the total drive torque generated by the linear drive unit reaches twice the maximum drive torque of a single power unit, which is advantageous for fast movements with medium precision requirements. Being able to control the respective drive torques independently of each other allows a more precise adjustment of the total drive torque.

[0038] The invention also relates to a method for aligning a telescope or an antenna by simultaneously generating a first drive torque and a second drive torque, wherein the first drive torque acts in opposite directions and has equal magnitude to the second drive torque, so that the reflector is maintained in a fixed position without play.

[0039] By simultaneously generating two equal drive torques in opposite directions, two corresponding drive pinions engage one or two racks from opposite sides, and vibrations caused by, for example, wind loads can be avoided because the play between each drive pinion and the corresponding rack is eliminated. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 FIG. 4 is a side view of a linear drive unit according to the present invention in a retracted state.

[0041] Figure 2 FIG. 4 is a top view of a linear drive unit in a retracted state according to the present invention.

[0042] Figure 3 FIG. 4 is a three-dimensional exploded view of a linear drive unit according to the present invention.

[0043] Figure 4 FIG. 1 is a schematic diagram showing a linear drive unit according to the present invention installed in a telescope arrangement. DETAILED DESCRIPTION

[0044] Figure 1 and Figure 2 A linear drive unit 10 according to the invention is shown in a retracted state, the linear drive unit comprising two actuator elements 20, 30. The first actuator element 20 is hollow in shape and is connected to a first attachment flange 180 via a first universal joint 170. The second actuator element 30 is in the shape of a T-beam and is connected to a second attachment flange 200 via a second universal joint 190.

[0045] Gimbal-mounted spherical roller bearings are used as universal joints 170, 190 to avoid inadmissible bearing forces by compensating for potential lateral offsets between two mounting points due to assembly or operation, wherein the axis of rotation of the gimbal spherical roller bearings is perpendicular to the linear drive unit 10. In addition, it is ensured that the linear drive unit 10 is only subjected to axial loads and not to other loads due to lateral forces.

[0046] The second actuator element 30 is movable within the cavity of the first actuator element 20. The second actuator element 30 is barely visible because it is located inside the first cover 21 attached to the first actuator element 20 (i.e., in a retracted state) or inside the expandable second cover 31 attached to the second actuator element 30 (i.e., in an extended state).

[0047] The first actuator element 20 and the second actuator element 30 are connected via two guide units 40, thereby allowing a linear relative movement R1 between the two actuator elements 20, 30. The first power unit 50 and the second power unit 60 are attached to the first actuator element 20 from opposite sides.

[0048] Figure 3 A three-dimensional exploded view of a linear drive unit according to the present invention is shown. The guide unit 40 consists of a guide rail 41 attached to the flange surface of the generally T-shaped second actuator element 30 and a guide carriage 42 attached to the inner surface of the hollow first actuator element 20.

[0049] The first power unit 50 and the second power unit 60 attached to the first actuator element 20 have a gear box 140 and corresponding first drive pinions 80 and second drive pinions 90, which are meshed with corresponding first racks 100 and second racks 110, which have several sections and are attached to the flange surface of the second actuator element 30 opposite to the guide rail 41.

[0050] The first power unit 50 and the second power unit 60 include, for example, a pair of asynchronous servomotors (not shown in the figure), which together generate the required torque. Each power unit 50, 60 is connected to its drive pinion 80, 90 via a combination of an intermediate shaft (countershaft) and a planetary gearbox 140. By meshing with respective racks 100, 110, the torque of the motor is increased and converted into a linear drive force.

[0051] In addition to being able to accumulate the driving forces of the two power units 50, 60, the power units 50, 60 can also be controlled so that they provide opposite torques. Although there is inevitable play in the teeth of the gearbox 140 and the drive pinions 80, 90, this ensures that the tooth surface of each drive pinion 80, 90 is always in contact with the respective rack 100, 110, so that the play is eliminated. The required counter torque is preferably about 5% to 10% of the rated torque and can be adjusted by the control software for operational reasons.

[0052] The linear drive unit 10 further comprises a two-stage end stop comprising an elastic element made of plastic and serving as a soft end stop 150 and a metal end surface serving as a hard end stop 160. This prevents the linear drive unit 10 from exceeding its permissible adjustment range to avoid potential disengagement of the drive pinions 80, 90 from the racks 100, 110.

[0053] Figure 4 A schematic diagram is shown of a linear drive unit 10 according to the present invention installed in a telescope arrangement 300, the linear drive unit being located between a telescope structure 320 and a telescope reflector 310, such that extension and retraction of the linear drive unit 10 causes a rotation of the telescope reflector 310 on a horizontal axis. It should be noted that the arrangement shown is merely exemplary and that the actual position of the linear drive unit 10 may be different.

[0054] Reference Numbers List

[0055] 10 Linear drive unit

[0056] 20 First actuator element

[0057] 21 first covering member

[0058] 30 Second actuator element

[0059] 31 Second covering member

[0060] 40 Guide Unit

[0061] 41 Guide Rail

[0062] 42 Guide carriage

[0063] 50 First Power Unit

[0064] 60 Second power unit

[0065] 80 First drive pinion

[0066] 90 Second drive pinion

[0067] 100 First rack

[0068] 110 Second rack

[0069] 140 Gear Box

[0070] 150 Soft end stop

[0071] 160 Rigid end stops

[0072] 170 First universal joint

[0073] 180 First attachment flange

[0074] 190 Second universal joint

[0075] 200 Second attachment flange

[0076] R1 Relative motion

[0077] 300 Telescope Layout

[0078] 310 Telescope Reflector

[0079] 320 Telescope Structure

Claims

1. A linear drive unit (10) having minimal play and friction for precise positioning of a radio astronomy device, the linear drive unit comprising: a first actuator element (20); a second actuator element (30); at least one guiding unit (40), the at least one guiding unit being configured to enable a linear relative movement between the first actuator element (20) and the second actuator element (30); a first power unit (50) attached to the first actuator element (20) and configured to provide a first linear driving force to the second actuator element (30); a second power unit (60) attached to the first actuator element (20) and configured to provide a second linear driving force to the second actuator element (30); as well as a control unit, the control unit being used to control the first power unit (50) and the second power unit (60), the control unit being configured to control the first linear driving force and the second linear driving force so that the first linear driving force and the second linear driving force reinforce or act on each other in opposite directions, wherein the first power unit (50) comprises a first motor, the first motor having a first drive pinion (80), wherein the second power unit (60) comprises a second motor, the second motor having a second drive pinion (90), wherein the first drive pinion (80) is arranged to mesh with a first rack (100) of the second actuator element (30), wherein the second drive pinion (90) is arranged to mesh with the first rack (100) or with the second rack (110) of the second actuator element (30), wherein the first linear driving force is generated by a first driving torque generated by the first power unit (50), wherein the second linear driving force is generated by a second driving torque generated by the second power unit (60), The control unit is configured to control the first driving torque and the second driving torque so that the first driving torque and the second driving torque act in opposite directions and the first driving torque or the second driving torque reaches between 0% and 30% of the respective other driving torque.

2. The linear drive unit (10) according to claim 1, wherein: The control unit is configured to control the first linear driving force and the second linear driving force so that the first linear driving force and the second linear driving force can act in opposite directions.

3. The linear drive unit (10) according to claim 1 or 2, wherein: The first rack (100) and / or the second rack (110) are spur racks.

4. The linear drive unit (10) according to claim 1 or 2, wherein: The first power unit (50) includes an electric motor having a first rotation axis, wherein the second power unit (60) includes an electric motor having a second rotation axis.

5. The linear drive unit (10) according to claim 1 or 2, wherein: The first power unit (50) and / or the second power unit (60) comprises a gear box (140).

6. The linear drive unit (10) according to claim 1 or 2, wherein: One of the first actuator element (20) and the second actuator element (30) has a cavity configured to accommodate the other of the first actuator element (20) and the second actuator element (30).

7. The linear drive unit (10) according to claim 6, wherein: The guide unit (40) includes at least one guide rail (41) and at least one guide carriage (42), and the at least one guide carriage (42) is configured to be guided along the at least one guide rail (41).

8. The linear drive unit (10) according to claim 7, wherein: The guide rail (41) or the guide carriage (42) is attached to the inner surface of the cavity.

9. The linear drive unit (10) according to claim 1 or 2, wherein: The first actuator element (20) and / or the second actuator element (30) comprises a flange, wherein the first rack (100) and / or the second rack (110) is attached to a first side of the flange, wherein at least one component of the guide unit (40) is arranged on a second side of the flange.

10. The linear drive unit (10) according to claim 1 or 2, further comprising at least one end stop, wherein the end stop is used to limit the relative movement between the first actuator element (20) and the second actuator element (30), and the end stop comprises a first element (150) having elasticity and a second element (160) having rigidity.

11. The linear drive unit (10) according to claim 1 or 2, wherein: The first actuator element (20) is connected to a first attachment flange (180) via a first universal joint (170), wherein the second actuator element (30) is connected to a second attachment flange (200) via a second universal joint (190).

12. A telescope or an antenna, comprising a support structure, a reflector and a linear drive unit (10) according to any one of claims 1 to 11, wherein: One of the first attachment flange (180) and the second attachment flange (200) is connected to the support structure, wherein the other of the first attachment flange (180) and the second attachment flange (200) is connected to the reflector so that the reflector can be rotated around a horizontal axis by the linear drive unit (10).

13. A method of aligning a telescope or an antenna according to claim 12, the method comprising the following steps performed simultaneously: - when the driven surface of the first driving pinion (80) contacts the driven surface of the first rack (100), the first driving torque is generated to move toward the position of the reflector; and - generating the second driving torque to act in a direction opposite to the direction of the first driving torque; in, The magnitude of the first driving torque is greater than the magnitude of the second driving torque; wherein the blocking surface of the second driving pinion (90) contacts the blocking surface of the first rack (100) or the second rack (110), and Wherein, the driven surface and the blocking surface face in opposite directions.

14. A method of aligning a telescope or antenna according to claim 12, the method comprising the following steps performed simultaneously: - generating a first drive torque; and - generating a second driving torque; in, The first driving torque and the second driving torque act in the same direction; wherein the magnitude of the first driving torque is equal to or different from the magnitude of the second driving torque, and The first driving torque and the second driving torque are combined to move toward the position of the reflector.

15. A method of aligning a telescope or an antenna according to claim 12, the method comprising the following steps performed simultaneously: - generating a first drive torque; as well as - generating a second driving torque; wherein the first driving torque and the second driving torque act in opposite directions; and wherein the magnitude of the first driving torque is equal to the magnitude of the second driving torque, This keeps the reflector in a fixed position without play.

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