US 6,175,169 B1 · Closed-loop planar linear motor with integral monolithic three-degree-of-freedom AC-magnetic position/orientation sensor

Abstract

The invention discloses a closed loop planar linear motor which includes a stationary stator (or platen) of arbitrary extent, and a moving forcer which is a single rigid body that can move over the planar stator surface on an air bearing with high speed and high precision in two orthogonal translational directions and a small rotation (or combinations thereof). An important distinguishing feature is a monolithic position and orientation sensor based on alternating current (AC) magnetic techniques which is an integral part of the forcer and occupies otherwise unused space in the forcer body. Also incorporated within the forcer is a special electronic processing element which converts weak AC signals from the sensor into usable high precision position and orientation information relative to the stator surface. A unique controller which is part of the closed-loop linear motor acts to combine information from the AC magnetic sensor with input from a user to provide precise, high-performance closed-loop control of the forcer, thereby enabling the forcer to be positioned with sub-micrometer precision and oriented with sub-millidegree precision on the stator surface. Additionally, owing to its closed-loop nature, the forcer can maintain its position and orientation even in the presence of disturbance forces and torques, and can emulate the operation of a mechanical spring and damper.

Claims11

Dependent claims

A precision closed-loop planar motor comprising:

(a) stator means established by a platen comprising a plurality of ferromagnetic teeth spaced regularly in an orthogonal grid surrounded by nonmagnetic material and having a flat surface;
(b) forcer means establishing a movable rigid body comprising a plurality of linear motor segment means in operative juxtaposition with said ferromagnetic teeth and within a housing having a flat surface supporting air bearing means in juxtaposition with the said flat surface of said stator means and incorporating translational and rotational alternating current magnetic sensor means for detecting the presence of said ferromagnetic teeth and providing signals indicative of their mutual planar geometric relationships;
(c) electronic processing means operatively interposed between said translational and rotational alternating current magnetic sensor means and a controller means (d), whereby position and orientation information of said forcer means with respect to said orthogonal grid is obtained and conveyed by wires to said controller means;
(d) controller means operatively connecting said linear motor segment means with position and orientation information from said electronic processing means so as to provide motive power to said linear motor segment means in response to programmed commands from a user of said closed-loop planar motor, thereby establishing feedback control means which is closed-loop;
whereby precise translational motion and precise limited rotational motion in the plane is affected.

2 more elements

A precision closed-loop planar motor comprising:

(a) stator means forming a stationary planar part incorporating a plurality of ferromagnetic teeth providing passive magnetic reaction forces and providing a passive orthogonal array of precision position reference features;
(b) forcer means establishing a movable rigid body comprising a plurality of linear motor segment means providing active electromagnetic forces in orthogonal directions and active electromagnetic torque with respect to said stator means, air bearing means providing frictionless support with respect to said stator means, and translational and rotational alternating current magnetic sensor means providing signals descriptive of the position and orientation of said rigid body with respect to said stator means;
(c) electronic processing means serving to convert said alternating current magnetic sensor means said signals to position and orientation information of said forcer means with respect to said orthogonal grid;
(d) controller means combining position and orientation information from said electronic processing means with programmed commands from a user of said closed-loop planar motor, energizing said linear motor segment means thereby producing controlled forces and torques between said forcer and said stator;
whereby precise translational motion and precise limited rotational motion in the plane is affected.

2 more elements

Dependencies are inferred from the claim text.

Closed-loop planar linear motor with integral monolithic three-degree-of-freedom AC-magnetic position/orientation sensor

Life of this patent

Closed-loop planar linear motor with integral monolithic three-degree-of-freedom AC-magnetic position/orientation sensor

Life of this patent

Abstract

Claims11