ELECTRO-MECHANICAL LINEAR DRIVE UNIT FOR PRECISE POSITIONING E.G. OF A LARGE REFLECTOR USED IN RADIO ASTRONOMY OR OF A COMMUNICATION ANTENNA

Abstract

The invention relates to a linear drive unit comprising a first and second actuator element, a guiding unit configured to enable a linear relative movement between both actuator elements, a first and second power unit, each attached to the first actuator element and configured to provide the second actuator element with a respective first and second driving force, and a control unit for controlling both power units and configured to control the first and second driving force such that the first driving force can be different from the second driving force. The invention further relates to a telescope comprising a linear drive unit as well as to a method of aligning such telescope.

Claims

1. A linear drive unit (10), e.g. for a telescope, an antenna or the like, the linear drive unit (10) comprising: a first actuator element (20); a second actuator element (30); at least a guiding unit (40) configured to enable 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 the second actuator element (30) with a first driving force; a second power unit (60) attached to the first actuator element (20) and configured to provide the second actuator element (30) with a second driving force; and a control unit for controlling the first power unit (50) and the second power unit (60), the control unit being configured to control the first driving force and the second driving force such that the first driving force can be different from the second driving force.

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

3. The linear drive unit (10) of claim 1 or claim 2, wherein the first power unit (50) comprises a first motor having a first drive pinion (80), and wherein the second power unit (60) comprises a second motor having a second drive pinion (90), wherein the first drive pinion (80) is provided so as to mesh with a first toothed rack (100) of the second actuator element (30), and wherein the second drive pinion (90) is provided so as to mesh with the first toothed rack (100) or with a second toothed rack (110) of the second actuator element (30).

4. The linear drive unit (10) of claim 3, wherein the first toothed rack (100) and/or the second toothed rack (110) are straight toothed racks.

5. The linear drive unit of claim 3 or claim 4, wherein the first driving force is caused by a first driving torque generated by the first power unit (50), and wherein the second driving force is caused by a second driving torque generated by the second power unit (60), wherein the control unit is configured to control the first and second driving torques such that the first driving torque and the second driving torque act in opposite directions, and such that the first driving torque or the second driving torque amounts to between 0% and 30%, preferably between 5% and 15% of the respective other driving torque.

6. The linear drive unit (10) of any one of the preceding claims, wherein the first power unit (50) comprises an electric motor, preferably an asynchronous motor, having a first axis of rotation, and wherein the second power unit (60) comprises an electric motor, preferably an asynchronous motor, having a second axis of rotation, wherein the first axis of rotation and the second axis of rotation are preferably parallel, and more preferably, coincident.

7. The linear drive unit (10) of any one of claims 3 to 6, wherein the first power unit (50) and/or the second power unit (60) comprises a gearbox (140), preferably configured as a planetary gearbox.

8. The linear drive unit (10) of any one of the preceding claims, wherein one of the first actuator element (20) and the second actuator element (30) has a cavity configured to accommodate the other one of the first actuator element (20) and the second actuator element (30).

9. The linear drive unit (10) of any one of the preceding claims, wherein the guiding unit (40) comprises at least one guide rail (41) and at least one guide carriage (42) configured to be guided along the at least one guide rail (41).

10. The linear drive unit (10) of claim 9 and claim 8, wherein the guide rail (41) or the guide carriage (42) is attached to an interior surface of the cavity

11. The linear drive unit (10) of any one of claims 3 to 10, wherein the first actuator element (20) and/or the second actuator element (30) comprises a flange, wherein the first toothed rack (100) and/or the second toothed rack (110) is attached to a first side of the flange and wherein at least one component of the guiding unit (40) is provided on a second side of the flange, the second side preferably being an opposite side of the first side.

12. The linear drive unit (10) of any one of the preceding claims, further comprising at least one end stop for limiting a relative movement between the first actuator element (20) and the second actuator element (30), the end stop comprising a substantially elastic first element (150) such as a rubber element or a spring element, and a substantially stiff second element (160) such as a metal plate.

13. The linear drive unit (10) of any one of the preceding claims, wherein the first actuator element (20) is connected to a first attachment flange (180) via a first cardan-joint (170), and wherein the second actuator element (30) is connected to a second attachment flange (200) via a second cardan-joint (190).

14. A telescope or an antenna comprising a support structure, a reflector, and the linear drive unit (10) of any one of the preceding claims, wherein one of the first attachment flange (180) and the second attachment flange (200) is connected to the support structure, and wherein the other one of the first attachment flange (180) and the second attachment flange (200) is connected to the reflector, such that the reflector is rotatable around a substantially horizontal axis by means of the linear drive unit (10).

15. A method of aligning the telescope or the antenna of claim 14, comprising the simultaneous steps of: moving to a position of the reflector by generating the first driving torque while a driven face of the first drive pinion (80) contacts a driven face of the first toothed rack (100); and generating the second driving torque so as to act in a direction opposite to a direction of the first driving torque, wherein an amount of the first driving torque is larger than an amount of the second driving torque, wherein a retarding face of the second drive pinion (90) contacts a retarded face of the first toothed rack (100) or the second toothed rack (110), and wherein the driven face and the retarded face are facing in opposite directions.

16. A method of aligning the telescope or the antenna of claim 14, comprising the simultaneous steps of: generating a first driving torque and generating a second driving torque, wherein the first driving torque and the second driving torque act in the same direction, wherein the amount of the first driving torque equals or differs from the amount of the second driving torque, and wherein the first driving torque and the second driving torque are combined to move to a position of the reflector.

17. A method of aligning the telescope or the antenna of claim 14, comprising the simultaneous steps of: generating a first driving torque and generating a second driving torque, wherein the first driving torque and the second driving torque act in opposite direction, and wherein the amount of the first driving torque equals the amount of the second driving torque, such that the reflector is held in a fixed position free of play.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1 is a side view of a linear drive unit according to the invention in a retracted state.

[0042] FIG. 2 is a top view of a linear drive unit according to the invention in a retracted state.

[0043] FIG. 3 is a 3-dimensional exploded view of a linear drive unit according to the invention.

[0044] FIG. 4 is a schematic view of a linear drive unit according to the invention being installed in a telescope arrangement.

DETAILED DESCRIPTION OF THE DRAWINGS

[0045] FIG. 1 and FIG. 2 show a linear drive unit 10 according to the invention comprising two actuator elements 20,30 in a retracted state. The first actuator element 20 has a hollow shape and is connected via a first cardan joint 170 with a first attachment flange 180. The second actuator element 30 has the shape of a T-beam and is connected via a second cardan joint 190 with a second attachment flange 200.

[0046] Gimbal-mounted spherical roller bearings with a swivel axis perpendicular to the linear drive unit 10 are used as cardan joints 170,190 to avoid inadmissible bearing forces by compensating a potential lateral offset between both mounting points due to assembly or operational reasons. Furthermore, it ensures that the linear drive unit 10 is only exposed to axial loads and not to other loads due to transverse forces.

[0047] The second actuator element 30 is movable inside the cavity of the first actuator element 20. It is barely visible since it is either located inside a first cover 21 attached to the first actuator element 20, i.e. in the retracted state, or inside an expandable second cover 31 attached to the second actuator element 30, i.e. in the extended state.

[0048] The first and second actuator elements 20,30 are connected via two guiding units 40, allowing a linear relative movement R1 between both actuator elements 20,30. A first and a second power unit 50,60 are attached to the first actuator element 20 from opposite sides.

[0049] FIG. 3 shows a 3-dimensional exploded view of a linear drive unit according to the invention. The guiding units 40 consist of guide rails 41, which are attached to a flange surface of the essentially T-shaped second actuator element 30, and guide carriages 42, which are attached to an inside surface of the hollow first actuator element 20.

[0050] The first and second power units 50,60, which are attached to the first actuator element 20, have gearboxes 140 and respective first and second drive pinions 80,90 that engage in respective first and second toothed racks 100,110 having several sections and being attached to flange surfaces of the second actuator element 30 opposite the guide rails 41.

[0051] The first and second power units 50,60 comprise for example a pair of asynchronous servo motors that generate the required torque together and are not shown in the drawings. Each power unit 50,60 is connected with its drive pinion 80,90 via a combination of a countershaft and a planetary gearbox 140. By engaging in the respective toothed racks 100,110, the torque of the motors is increased and translated into a linear driving force.

[0052] Besides the ability to cumulate the driving forces of both power units 50,60, they can be controlled such that they provide opposing torques. Despite the unavoidable play in the gearboxes 140 and in the teeth of the drive pinions 80,90, this ensures that a tooth flank of each drive pinion 80,90 is always in contact with the respective toothed rack 100,110 so that the play is eliminated. The required counter-torque is preferably about 5-10% of the nominal torque and can be adjusted by the control software for operational reasons.

[0053] The linear drive unit 10 further comprises a two-stage end stop, comprising an elastic element made of plastic serving as a soft end stop 150 and a metallic end surface serving as a hard end stop 160. This prevents the linear drive unit 10 from exceeding its permissible adjustment range in order to avoid a potential disengagement of the drive pinions 80,90 from the toothed racks 100,110.

[0054] FIG. 4 shows a schematic view of a linear drive unit 10 according to the invention being installed in a telescope arrangement 300 between the telescope structure 320 and the telescope reflector 310 such that extending and retracting of the linear drive unit 10 causes a rotation of the telescope reflector 310 in the horizontal axis. It should be noted that the displayed arrangement is only exemplary and that the actual position of the linear drive unit 10 can differ.

REFERENCE LIST

[0055] 10 linear drive unit [0056] 20 first actuator element [0057] 21 first cover [0058] 30 second actuator element [0059] 31 second cover [0060] 40 guiding 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 toothed rack [0068] 110 second toothed rack [0069] 140 gearbox [0070] 150 soft end stop [0071] 160 hard end stop [0072] 170 first cardan-joint [0073] 180 first attachment flange [0074] 190 second cardan-joint [0075] 200 second attachment flange [0076] R1 relative movement [0077] 300 telescope arrangement [0078] 310 telescope reflector [0079] 320 telescope structure