Supports – Mirror or picture type – Bracket
Reexamination Certificate
2001-09-04
2003-04-08
Ramirez, Ramon O. (Department: 3632)
Supports
Mirror or picture type
Bracket
C248S479000
Reexamination Certificate
active
06543740
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a mechanism for positioning objects, particularly mirrors, in up to six degrees-of-freedom, namely X-, Y- and Z-translation and rotation about X-, Y- and Z-axes.
BACKGROUND OF THE INVENTION
Known six degrees-of-freedom mechanisms are varied in structure and operation, resulting in different levels of orientational freedom (work volume), positional repeatability, stiffness and coupling. Coupling is related to the extent to which isolation of motion in one of the degrees-of-freedom is possible.
U.S. Pat. No. 5,028,180 discloses a six degrees-of-freedom motion mechanism that is similar to a Stewart Platform in operation, but is intended for machine tools. Six legs, adjustable in length, connect a platform to a base and can be adjusted to set the platform at a desired orientation.
U.S. Pat. No. 5,263,382 discloses a mechanism that provides six degrees-of-freedom with only three fixed-length legs attached to the movable platform. The legs are in two sections with a one degree-of-freedom hinge joint at their connection point. Each leg is driven by a pair of motors, by way of a differential drive system. The pitch and yaw of each leg is controlled. By controlling the two degrees-of-freedom of each of the three legs, six degrees-of-freedom motion of the moveable platform is accomplished. This mechanism is complex, particularly the differential drive system.
U.S. Pat. No. 5,301,566 discloses a hybrid manipulator. Three fixed length limbs are attached to a platform via universal joints. By changing the location of the lower end of each of the three limbs using two degrees-of-freedom parallel drivers, the platform can be positioned in six degrees-of-freedom.
U.S. Pat. No. 5,333,514 discloses a six degrees-of-freedom parallel manipulator. This manipulator is fully parallel but instead of using linear actuators for the links as in a traditional Stewart Platform, the six arms are in two sections. The first section is mounted to a rotary actuator. By rotating these six base links, the position of the platform can be controlled in six degrees-of-freedom.
U.S. Pat. No. 5,656,905 discloses a hybrid manipulator for machine tools. Two parallel mechanisms are described in which each is a three degrees-of-freedom mechanism. These two mechanisms can be combined in serial fashion to form a hybrid mechanism or they can be combined in parallel to form a cooperating mechanism. One mechanism is dedicated to translational motion while the other is dedicated to rotational motion.
U.S. Pat. No. 5,901,936 discloses a fully parallel six degrees-of-freedom motion mechanism. This mechanism is similar to a Stewart Platform. Disclosed is the use of rotary actuators in place of linear actuators for the legs of the manipulator. There are two main embodiments disclosed. In the first embodiment, there are two fixed length links joined by a hinge at their attachment point. The lower link attaches to the base and the upper link attaches to the moving platform. The hinge joint at the connection of the two links is actuated. Combining six copies of this mechanism allows motion in six degrees-of-freedom. In the second embodiment, a universal driver is used at the base. One axis of the universal joint is actuated while the other is passive. The link then attaches to the moving platform.
U.S. Pat. No. 6,047,610 discloses a hybrid six degrees-of-freedom manipulator. The disclosed device uses two five-bar linkages mounted so that the plane in which they act can rotate. These five-bars are attached to a platform. Coupling the two five-bars together provides five degrees-of-freedom motion. A final motor near the platform provides the last degree-of-freedom. The two serial five-bar linkages, together in parallel arrangement, form the hybrid manipulator.
SUMMARY OF THE INVENTION
The mechanisms in the above known devices are fundamentally different from the mechanism providing motion in six degrees-of-freedom in the apparatus of the present invention.
In one aspect, the present invention provides a positioner for transmitting movement in up to six degrees-of-freedom to an object on the positioner, the positioner comprising a base plate, a first plate mounted on the base plate by a first mechanical linkage, a first actuator arrangement for moving the first plate, a second plate mounted on the first plate by a second mechanical linkage, a second actuator arrangement for moving the second plate, and a holder attached to the second plate for mounting the object. One of the first and second plates is movable in a plane in up to three degrees-of-freedom, and the other of the first and second plates is movable in up to three degrees-of-freedom that are out of the plane.
An additional plate, including an actuator arrangement for moving the additional plate, can be mounted by a mechanical linkage between the second plate and the holder and, by this approach, the three degrees-of-freedom systems can be stacked to provide redundantly actuated mechanisms depending on the needs of a given situation. The additional plate can be movable in a plane in up to three degrees-of-freedom if it is desired to provide planar motion, decoupled from non-planar motion, directly to the object in the holder. It is also possible to provide this decoupled motion by arranging the two plates mentioned above with the second plate being movable in a plane in up to three degrees-of-freedom, and the first plate being movable in up to three degrees-of-freedom that are out of the plane in which the second plate can be moved. Such arrangements are suitable when decoupled planar motion of the object is required.
In a preferred embodiment, the first plate is movable in a plane in up to three degrees-of-freedom, and the second plate is movable in up to three degrees-of-freedom that are out of the plane in which the first plate can be moved.
Conveniently, the positioner further includes a first bias for biasing the first plate (also referred to herein as “stage one”) against the first actuator arrangement, and a second bias for biasing the second plate (also referred to herein as “stage two”) against the second actuator arrangement. Preferably, the first bias comprises a set of springs (also referred to herein as “actuator preload springs”) anchored to the base plate and to the first plate. More preferably, the first bias comprises a first set of springs anchored to the base plate and to the first plate, for biasing the first edge of the first plate against the first actuator, and a second set of springs anchored to the base plate and to the first plate, for biasing the second edge of the first plate against the second and third actuators. Preferably, the second bias comprises a third set of springs anchored to the second plate and to the first plate.
It is also possible to use magnetic-based biasing as the first and/or second bias.
The first actuator arrangement for moving the first plate is suitably a first plurality of actuators mounted on the base plate. Preferably, the first plurality of actuators comprises a first, a second and a third actuator (also referred to herein as “X-, Y
1
- and Y
2
-actuators”, respectively), the first actuator conveniently contacting a first edge of the first plate and the second and third actuators contacting a second edge of the first plate. The first and second edges of the first plate are preferably at substantially right angles to each other (orthogonal). Conveniently, the first, second and third actuators each comprise a micrometer. Motorized micrometers or piezo actuators could also be used.
The second actuator arrangement is suitably a second plurality of actuators mounted on the first plate. Preferably, the second plurality of actuators comprises a fourth, a fifth and a sixth actuator (also referred to herein as “Z
1
-, Z
2
- and Z
3
-actuators”). More preferably, the fourth, fifth and sixth actuators are spaced apart and extend substantially orthogonally from the first plate and contact a surface of the second plate. Conveniently, the fourth, fifth and sixth actuators each comprise a
Anthony Andre
Gaunt Robert
Roberts Scott
(Marks & Clerk)
National Research Council of Canada
Ramirez Ramon O.
Wujciak, III A. Joseph
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