Reaction compensated tilt platform

A reaction compensated tilt platform assembly comprises a support base, and a reaction mass, pivotally coupled to the support base. A tilt platform which can function as or support a mirror is pivotally coupled to the support base. At least two linear actuator coil assemblies are carried by the reaction mass. At least two linear actuator magnet assemblies are carried by the tilt platform and are disposable within the at least two linear actuator coil assemblies. The linear actuator magnet assemblies taper from a larger diameter toward a center of the magnet assembly to a smaller diameter toward an end of the magnet assemblies. Actuation of the linear actuator magnets results in pivotal movement of the tilt platform relative to the reaction mass.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to the field of optical communication systems. More particularly, the present invention relates to reaction compensated steering mirrors for use in free-space optical communication systems.

Related Art

Various conventional beam steering mirrors and fast steering mirrors have been developed over the years to address perceived needs in optical communication systems. While some of these attempts utilize reaction torque-compensated steering mirrors, these prior art devices generally provide very limited angular travel. Also, such prior art devices are usually limited by their support flexures and linear actuators.

While some two-axis scanning or steering mirrors have been developed that provide larger angular travel, these prior art solutions provide lower precision, lower servo bandwidth, higher jitter/noise, and often do not provide reaction torque compensation.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, a reaction compensated tilt platform assembly is provided, including: a support base, and a reaction mass, pivotally coupled to the support base. A tilt platform which can function as or support a mirror can be pivotally coupled to the support base. At least two linear actuator coil assemblies can be carried by one of the reaction mass or the tilt platform. At least two linear actuator magnet assemblies can be carried by another of the tilt platform or the reaction mass and can be disposable within the at least two linear actuator coil assemblies, the linear actuator magnet assemblies tapering from a larger diameter toward a center of the magnet assembly to a smaller diameter toward an end of the magnet assemblies. Actuation of the linear actuator magnets results in pivotal movement of the tilt platform relative to the reaction mass.

In accordance with another aspect of the invention, a reaction compensated tilt platform assembly is provided, including a support base and a reaction mass, pivotally coupled to the support base. A tilt platform can be pivotally coupled to the reaction mass. At least one electronic flexure ribbon can be coupled to the support base and the reaction mass, the at least one electronic flexure ribbon extending through the reaction mass and being oriented in a first configuration when entering the reaction mass and being oriented in a second configuration when exiting the reaction mass, the second configuration being orthogonal to the first configuration.

In accordance with another aspect of the invention, a reaction compensated tilt platform assembly is provided, including a support base and a reaction mass, pivotally coupled to the support base. A tilt platform can be pivotally coupled to the support base. A locking pin can be engageable with at least the tilt platform and/or the reaction mass. Activation of the locking pin in a single degree of movement can limit movement of the tilt platform relative to the base in two degrees of freedom and limit movement of the reaction mass relative to the base in two degrees of freedom.

DETAILED DESCRIPTION

DEFINITIONS

As used herein, the singular forms “a” and “the” can include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a voice coil actuator” can include one or more of such actuators.

As used herein, the terms “attached,” “coupled,” fixed, ” etc., can be used to describe a condition in which two or more components are coupled to one another in such a manner that they function as intended: that is, the force required to uncouple the components is sufficiently large such that the components will remain attached to one another during the service for which they were designed. In some embodiments of the invention, various components can be “permanently” coupled to one another: in such a case, the components are coupled to one another such that some deformation of one or both of the components, or the fasteners used to couple the components, will occur if the components are uncoupled from one another. One example of such a coupling can occur when two or more components are bonded or otherwise adhered to one another.

In other aspects, various components can be removably coupled to one another such that they can be separated without causing permanent deformation of the components, or the fasteners used to couple the components. One example of such a coupling can occur when two or more components are bolted to one another (in which case, removal of nuts coupled to bolts can result in uncoupling of the components without damaging the nuts or the bolts).

As used herein, the term “ribbon” is to be understood to refer to a geometry of an electronic flexure, or connector, that includes a width that is significantly larger than is its thickness. In one embodiment, the electronic flexure ribbons are at least about 5 times as wide as they are thick.

Directional terms, such as “vertical,” “horizontal,” “upper,” “lower,” etc., are used herein to describe relative positions of various components. It is to be understood that such usage is an effort to most clearly describe, and, where applicable, claim, the features of the invention and is not be to limiting unless the context clearly indicates otherwise. Such directional terms are used in a manner that will be readily understood by one of ordinary skill in the art having possession of this disclosure.

As used herein, the term “substantially” refers to the complete or nearly complete extent or degree of an action, characteristic, property, state, structure, item, or result. As an arbitrary example, an object that is “substantially” enclosed would mean that the object is either completely enclosed or nearly completely enclosed. The exact allowable degree of deviation from absolute completeness may in some cases depend on the specific context. However, generally speaking the nearness of completion will be so as to have the same overall result as if absolute and total completion were obtained. The use of “substantially” is equally applicable when used in a negative connotation to refer to the complete or near complete lack of an action, characteristic, property, state, structure, item, or result. As another arbitrary example, a composition that is “substantially free of” an ingredient or element may still actually contain such item as long as there is no measurable effect thereof.

INVENTION

The present technology can utilize a novel arrangement of cross-blade flexures, voice coil actuators, differential gap sensors, a locking pin, and flex-circuit to simultaneously provide numerous advantages in a pointing assembly. One exemplary use of the system is in a fast moving steering mirror (“FSM”).

The technology can utilize two-axis pivot flexure assemblies that can be configured to allow a locking pin to engage and lock both the tilt platform and reaction mass, while allowing the required angular travel when the lock is disengaged. Voice coil actuators can be configured to allow large angular movement as well as linear stroke between the coil and magnet assemblies. The pole pieces of the actuators can be tapered to increase the angular travel while preserving performance. Their location with respect to the pivot flexure assemblies can be optimized to maximize travel and simultaneously balance the tilt platform and reaction mass. Because the actuator coils can be mounted on a moving reaction mass, current can be delivered to them in a low-hysteresis, high-reliability method, which can be accomplished with a custom flex-circuit integrated into the pivot flexure assembly for the reaction mass in a manner that doesn't interfere with the locking pin.

Turning now to the figures, specific exemplary features of a reaction compensated steering mirror assembly10are shown. The assembly can generally include a support base12and a reaction mass14(shown more clearly inFIG. 3). The reaction mass can be pivotally coupled to the support base by way of pivot couplers16(FIG. 3). A tilt platform18can be pivotally coupled to the support base by way of, for example, a pivot coupling assembly20. At least two linear actuator coil assemblies22can be carried by the reaction mass. At least two linear actuator magnet assemblies24can be carried by the tilt platform. The magnet assemblies can be disposable within the at least two linear actuator coil assemblies. In operation, actuation of the linear actuator magnets results in pivotal movement of the tilt platform relative to the reaction mass. Thus, while the tilt platform is pivotally coupled to the support base, actuation of the magnet assemblies within the actuator coil assemblies causes the tilt platform to move relative to the reaction mass (e.g., to “push” against the reaction mass).

The present invention can thus provide a mechanism for providing precision pointing capability with high servo bandwidth, high precision, and reduced reaction forces and torques. The present technology can provide an angular travel of several degrees in two axes and extremely low jitter, and can include an integral single degree-of-freedom tilt lock. The technology has been found particularly effective as a platform to support a mirror for line-of-sight scanning and stabilization or other precision pointing uses. All of these features are presented in a compact, highly efficient mechanism.

As shown most clearly inFIG. 2, in one aspect of the invention, the linear actuator magnet assemblies24can taper from a larger diameter toward a center or midsection “C” of the magnet assembly to a smaller diameter toward an end “E” of the magnet assemblies. Thus, while the magnet portion of the magnet assemblies can include a generally continuous, cylindrical cross section, the end portions can taper to a smaller diameter. While the manner in which the taper can be provided to the magnets can vary, in one aspect the actuator magnet assemblies24can include tapered end caps28to provide the taper to the magnet portion.

In this manner, the magnet assemblies24can be capable of greater linear travel within the coil assemblies22. In one embodiment of the invention, the tilt platform18can be tilted relative to the support base12(not shown inFIG. 3) from an angle of about 0 degrees to an angle of at least about 6 degrees.

In the example shown in the figures, the linear actuator magnet assemblies24are coupled directly to the tilt platform18. In this manner, the WFE (wave front error) induced in a mirror coupled to the tilt platform (or formed integrally with or as the tilt platform) can be greatly minimized.

While not so required, in one embodiment of the invention, one or more electronic flexure ribbons (or flex ribbons)30a,30bcan be used to provide electronic signals to the various components of the assembly10. In one aspect, the flex ribbons30a,30bcan be coupled to the support base12and also to one of the reaction mass14or the tilt platform18. The electronic flexure ribbon can extend through the reaction mass14and can be oriented in a first configuration when entering the reaction mass and can be oriented in a second configuration when exiting the reaction mass. The second configuration can be orthogonal to the first configuration.

This aspect of the invention is best illustrated inFIG. 4, where flex ribbon30ais shown, in this example, configured to be coupled to the support base12(not shown inFIG. 4), at the bottom-right portion ofFIG. 4. The flex ribbon then extends outwardly from the support base, and upwardly around and into the reaction mass. As shown at reference40, the flex ribbon can include a 90 degree bend formed therein that allows the flex ribbon to be turned orthogonally as it approaches the coupling location to the reaction mass14. Thus, the ribbon can be clamped or otherwise coupled to the support base at reference42in a first configuration, and can be clamped or otherwise coupled to the reaction mass in a second configuration43that is orthogonal to the first configuration.

In this manner, the flex ribbons can be subject to bending loads that are much less damaging to the flex ribbons. For example, the turns44a,44bshown inFIG. 5can be subject to bending about parallel axes46a,46bthat correspond to natural loading stresses for the configuration shown. Axis48, on the other hand, is orthogonal to axes46a,46b, and bending of the ribbon about axis48near bends44a,44bwould cause premature failure of the flex ribbon. However, because the flex ribbon is “turned” 90 degrees within the assembly (at reference40), the bending forces near turns44a,44bare primarily about axes46a,46b, while the bending forces near turn50are primarily about axis48. In this manner, out of plane stresses on the flex ribbon are greatly minimized, resulting in better performance by and greater longevity of the ribbon.

In the case that a plurality of flex ribbons30a,30bare utilized, they can be coupled to the reaction mass symmetrically about a center of the reaction mass. This can further increase the life of the flex ribbons, and can aid in providing balanced motion about the center of the overall assembly.

In addition to the illustrated example in which the flex ribbons are coupled to the reaction mass, the flex ribbons can alternately be coupled to the tilt platform. In this case, the tilt platform can be energized in addition to, or as well as, the reaction mass. In this embodiment, the flex ribbons can be coupled to the tilt platform symmetrically about a center of the tilt platform.

FIGS. 5 and 6illustrate another aspect of the invention in which a locking pin60can be engageable with at least the support base12and one or both of the reaction mass14or the tilt platform18. In this example, activation of the locking pin in a single degree of movement (e.g., along direction62inFIGS. 5 and 6) can limit movement of the tilt platform relative to the reaction mass or the base in two degrees of freedom. In the example shown inFIG. 6, the locking pin60is engageable with each of the tilt platform, the reaction mass and the base. In this case, activation of the locking pin in a single degree of movement limits movement of each of the tilt platform and the reaction mass relative to the base in two degrees of freedom.

InFIG. 5, the pin60is shown in an engaged, or locked, position by the dashed line, and in a disengaged, or unlocked position in the solid line. While not so required, the locking pin can be positioned through a geometric center of the overall assembly, to better balance the loads required to lock or fix the components relative to one another when the locking pin is engaged.

FIG. 6illustrates operation of the locking pin with much of the surrounding structure removed for clarity. The locking pin can include various engagement sections64,66,68,70that can engage various components of the overall assembly to fix or lock the components relative to one another. When the pin is in the unlocked position (e.g., the position shown by the solid line inFIG. 5), the engagement portions do not engage components of the assembly. However, when moved into the locked position (e.g., the position shown by the dashed line inFIG. 5), sections64and66engage surrounding portions of the tilt platform18; section68engages surrounding portions of reaction mass14; and section70engages surrounding portions of base12(note that the surrounding engagement structure is omitted from this view for clarity).

It is to be understood that the above-referenced arrangements are illustrative of the application for the principles of the present invention. Numerous modifications and alternative arrangements can be devised without departing from the spirit and scope of the present invention while the present invention has been shown in the drawings and described above in connection with the exemplary embodiments(s) of the invention. It will be apparent to those of ordinary skill in the art that numerous modifications can be made without departing from the principles and concepts of the invention as set forth in the examples.