STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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REFERENCE TO A SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISK APPENDIX

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a redundant parallel positioning table device. More specifically, the present invention relates to a redundant parallel positioning table device for a precise positioning of heavy load samples, instrument and/or apparatus, e.g., in the fields and use of diffractometer machines for synchrotron facilities.

2. Description of the Related Art

Positioning systems and devices for the positioning of samples for different purposes have long been known in the prior art.

Some research on new or existent materials are involving synchrotron X-ray tool and Diffractometers (Dm) machines to investigate the physical and/or chemical properties. To discover the intrinsic molecular and/or atomic structures and its behavior under different environmental conditions, the measurements in these large (microscopes) machines are based on diffraction technique. In order to simulate the real or virtual conditions (e.g., pressure, temperature, etc.) for a sample, the additional instruments and/or apparatus are sometimes necessary. These could weigh several tens or hundreds of kilograms and appreciable size, and the aggregates (sample & instruments/apparatus) must be manipulated in the right position towards the incoming X-ray beam. A standard experimental process includes several operations (and/or phases)—fast set ups, alignments, calibrations, go to exactly required position, keeping the pose for relative long time (e.g., hours or days) then, to restart the whole cycle for another investigation. Following these, a required positioning device should be able to perform both, simple and complex motions with enough precision and speed owing at the same time the power for carrying the relative high load and to maintain it for relative long time. Especially, it must be able to do spherical motions around a fixed arbitrary chosen point, called rotation center C (or pivot point P) regarding the sample center, located at a distance (dC) from the instrument base.

Parallel kinematic (PK) principle has been recently more and more investigated as positioning concept based on some advantages against the standard serial (stacked) principle. The most common 6dof topology called hexapod is derived from GOUGH [V.E.Gough, Contribution to discussion of papers on research in automobile stability, control and tyre performance Proc. Auto Div. Inst. Mech. Eng, 1956-1957] and STEWART [D. Stewart, A platform with six degrees of freedom, Proc. Institution of Mechanical Eng.(UK), 1965-1966] works. The GOUGH-STEWART platform mechanism was applied for the first time as motion simulator [C. L. Klaus, Motion manipulator, U.S. Pat. No. 3,295,224, Jan. 3, 1967] and then latter as tool positioning in machine tools industry [P. C. Sheldon, Six-axis machine tool, U.S. Pat. No. 4,988,244, Jan. 29, 1991]. Actual hexapod structures for positioning (e.g., 6-SPS) are fully parallel kinematic mechanisms (PKM) composed from symmetric structures with six variable lengths actuators called struts arranged between two approximate hexagonal (or, disc) shapes—base and moving platform parts, respectively. The position (and, orientation) of the platform is resulting as a combination of strong coupled motions of linear actuated telescopic bars. The benefits are related with the increased payload, precision and dynamics, due to their intrinsic stiffer pyramidal structure. The distinctive class designed for precision positioning is called precision hexapods.

There are several proposed solutions; some of them as available products. However, when intended to be used inside of diffractometers (e.g. Dm5021/I07/DLS, HUBER GmbH Co&KG, DLS-Diamond Light Source, I07-Beam line) they are exhibiting some drawbacks in relation with the required manipulation (e.g. load: >50 kg, dc=170 mm, repeatability: ±2 μm, speed: 3 mm/s) and the available Dm working space (DxA=400×420 mm, D-diameter, A-height) parameters: a) the maximum manipulated load not enough (for those fulfilling DxA, or dc), b) the rotation center point distance (dc) not inside of DxA (for all caring bigger load) and c) the workspace relative small (for both, above cases). Shortly, the hexapods volume, especially the heights are too big (or, too small) compared with the performances they offer for the allocated Dm space. In addition, the mounting surface of the platform for large instruments not always well prepared (e.g., large aperture, for cable management).

This is because the designers face with: a) the necessity to pack “inside” of the actuation struts (telescopic bars) an appreciable number of components (e.g., motor, gearhead/harmonic drive, guides, sensors, etc.); b) the shape of the workspace is resulting complex, because of the intersected number and size of the actuators; c) the undesired dynamic effects for moving motorized legs, sometimes appreciable, affecting the maximum speed. And the singularities (and, collisions) occurred must be detected and avoided for precision tasks; however, difficult to be done, as is direct related with the numbers of joints and components. Finally, the simple motions: translation-X,Y,Z (and/or rotations-Rx,Ry,Rz) are difficult to be predicted by non-parallel kinematic expert staff, when simple and fast alignment operations are to be done in the experimental rooms.

Other architectures have been investigated during the time for precision 6dof positioning tasks.

The U.S. Pat. No. 5,301,566 relates to a six degree-of-freedom parallel-(mini)manipulator having three inextensible limbs for manipulating a platform attached via three non-collinear universal joints and two-degree-of-freedom parallel drivers. By using the minimum number of actuated and supporting points, and bidirectional planar motors an increased workspace, stiffness and accuracy compared with Stewart/Gough mechanism have been claimed, beside of other advantages e.g. (direct kinematics, few components, etc.). However, the static and dynamic characteristics are very much depending on the number of components (three) being one axis symmetric arranged, only.

There are also several proposals for PK mechanisms working as positioning table devices. PCT publication No. WO2007/055339A1 describes a three-dimensional positioning table (rectangular shape) which has the ability to perform high-precision motions, as a result of combined actions of mainly two separated positioning devices. An elevating (Z) and a table plate (XYRz/PKM) devices are both connected through a planar bearing support plate and three vertical linear guides. The elevation device is including a stage system of two guided wedges which in their relative motions against a fixed support produced the lifting/down of the platform. However, these combined hybrid parallel-serial structures cannot provide whole motion capabilities spectrum (6dof). The Japanese patent publication No. JP2012-51054A describes a positioning table which is using three mobile supports, each of them providing a lifting/down motion through a combination of three linear guided parts on which on one, the motor is attached; and, on the second a spherical bearing. A load in space (3dof) is positioned with this tripod architecture through several moving parts and guiding means supposing to affect the general stiffness.

Redundancy is a relative new concept applied to parallel kinematic mechanisms. It increases the mechanisms capabilities of stiffness, working space, accuracy and speed for both, spatial and planar structures. Two concepts have been studied until now—the kinematic redundancy (adding a chain/leg) and the actuation redundancy (adding an active joint), respectively. The redundancy has also the advantage of avoiding singularities and to work in difficult conditions when one or more actuators are falling. However, few manipulation and/or positioning products have been released until now.

The Japanese patent publication No. JP2010-264526A relates to a redundant spatial parallel mechanism using four pairs of two actuators having one dof each. The architecture is similar with hexapod ones based on strut actuators but with special designed interconnected joints at the top end. In order to perform the required motion task, the control function must take into account only six suitable selected active struts. The resulting height (high) of the device related upon the actuators lengths is similar as in the hexapods case one.

The French patent application No. FR2965207A1 describes a redundant parallel robot having six degrees of freedom. The mechanism can be seen as comprising four articulated kinematic closed chains each with two dof actuation from the base. A main serial chain is supported from other through a rotational joint and then it is connected to the platform through separated rotational joints including a pivotal one. The pairs of actuators are located alongside of a quadrilateral shape moving the platform and acting around the corners. The parallel type singularities are avoided. And, by using rotational motors and arms (bars) high workspaces and dexterity manipulation tasks could be delivered, but not together with precision because the stiffness is not at its best. Improved values perhaps are obtained in the embodiment using vertical linear actuators (FR2964337A1), but the platform size is still supposed to be much smaller than the base is.

The Chinese patent No. CN1730235A relates to a redundant parallel mechanism with six degrees of freedom used as a structure for machine tool in order to increase its axial rigidity and workspace, by using four telescopic legs, each of them moving around a ring base through revolving pairs as part of their sliding blocks. The circular guides realize a large range of rotational movement and increase the attitude space, but the active joints are interposed between passive ones diminishing the maximum stiffness.

All these devices described above have the capability to partially (less than 6 degrees of freedom) or fully (6 degrees of freedom) pose a body in space using either non-redundant (e.g., parallel or hybrid) or redundant (e.g., parallel) structures. However, none of the above devices is perfectly suitable for specific synchrotron related diffractometer applications.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a 6 or fewer degrees of freedom positioning device with superior performance and capabilities by being more adapted to the scope compared with devices of the current art.

An object of the present invention is to provide a positioning table with an increased size (including the aperture) and adequate shape (flat) supporting and fixing surface for carry the specific diffractometers loads. Another object is to provide a table which can accommodate the most demanding tight space requirements by being more compact (e.g., having a lower profile). Another object is to provide a positioning table with increased precision, including stability. Another object is to provide a device with increased speed. Another object is to provide a method to intuitively perform simple Cartesian motions (e.g., translations and/or rotations) automatically or manually.

