U.S. patent application number 10/566765 was filed with the patent office on 2006-09-28 for lorentz motor control system for a payload.
This patent application is currently assigned to Koninklijke Philips Electronics N.V.. Invention is credited to Marcel Francois Heertjes, Michael Johannes Vervoordeldonk.
Application Number | 20060213362 10/566765 |
Document ID | / |
Family ID | 34112488 |
Filed Date | 2006-09-28 |
United States Patent
Application |
20060213362 |
Kind Code |
A1 |
Heertjes; Marcel Francois ;
et al. |
September 28, 2006 |
Lorentz motor control system for a payload
Abstract
Control arrangement for and method of controlling a plurality of
Lorenz motors (1, 2) actuating a payload (4) where the payload has
a center of gravity (12). Height signals (z.sub.1, z.sub.2) are
received from sensors sensing heights of said payload. At least one
rotation angle of the center of gravity about a horizontal axis is
calculated from these height signals (z.sub.1, z.sub.2) and from
this at least one rotation angle control signals (C.sub.1, C.sub.2)
for the Lorenz motors (1, 2) are calculated such that a
predetermined rotational stiffness for supporting the payload (4)
is achieved.
Inventors: |
Heertjes; Marcel Francois;
(Eindhoven, NL) ; Vervoordeldonk; Michael Johannes;
(Eindhoven, NL) |
Correspondence
Address: |
PHILIPS INTELLECTUAL PROPERTY & STANDARDS
P.O. BOX 3001
BRIARCLIFF MANOR
NY
10510
US
|
Assignee: |
Koninklijke Philips Electronics
N.V.
Eindhoven
NL
5621
|
Family ID: |
34112488 |
Appl. No.: |
10/566765 |
Filed: |
July 28, 2004 |
PCT Filed: |
July 28, 2004 |
PCT NO: |
PCT/IB04/51316 |
371 Date: |
January 31, 2006 |
Current U.S.
Class: |
91/6 |
Current CPC
Class: |
G03F 7/709 20130101;
F16F 7/1011 20130101; F16F 15/03 20130101; G03F 7/70816 20130101;
F16F 15/005 20130101; G03F 7/70758 20130101 |
Class at
Publication: |
091/006 |
International
Class: |
F01B 25/02 20060101
F01B025/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 4, 2003 |
EP |
03102413.6 |
Claims
1. Control arrangement for controlling a plurality of Lorenz motors
(1, 2) actuating a payload (4), the payload having a center of
gravity (12), the control arrangement comprising a controller (8)
for receiving height signals (z.sub.1, z.sub.2) from sensors
sensing heights of said payload and for calculating control signals
(C.sub.1, C.sub.2) for said Lorenz motors from said height signals,
characterized in that said controller (8) is arranged to calculate
from these height signals (z.sub.1, z.sub.2) at least one rotation
angle of the center of gravity about a horizontal axis and
calculate from this at least one rotation angle said control
signals (C.sub.1, C.sub.2) for said Lorenz motors (1, 2) such that
a predetermined rotational stiffness for supporting said payload
(4) is achieved.
2. Control arrangement according to claim 1, wherein said
controller (8) is arranged to control three or four Lorenz
motors.
3. Method of controlling a plurality of Lorenz motors (1, 2)
actuating a payload (4), the payload having a center of gravity
(12), comprising receiving height signals (z.sub.1, z.sub.2) from
sensors sensing heights of said payload and calculating control
signals (C.sub.1, C.sub.2) for said Lorenz motors from said height
signals, characterized by calculating from these height signals
(z.sub.1, z.sub.2) at least one rotation angle of the center of
gravity about a horizontal axis and calculating from this at least
one rotation angle said control signals (C.sub.1, C.sub.2) for said
Lorenz motors (1, 2) such that a predetermined rotational stiffness
for supporting said payload (4) is achieved.
4. Computer program product comprising instructions and data to be
loaded by a computer, and after being loaded allowing the computer
to perform the method according to claim 3.
5. Data carrier comprising a computer program product according to
claim 4.
Description
[0001] The invention relates to a control arrangement for
controlling a plurality of Lorenz motors actuating a payload, the
payload having a center of gravity, the control arrangement
comprising a controller for receiving height signals from sensors
sensing heights of said payload and for calculating control signals
for said Lorenz motors from said height signals.
[0002] It is known to support a payload with a plurality of, e.g.
three or four, mounts. The mounts may each comprise an airmount and
one or two Lorenz motors. Instead of airmounts, other type of
"springs" may be used The payload has a center of gravity that may
or may not be above the airmounts. In dependence on the design of
the airmounts, the critical height of the center of gravity of the
payload where the payload gets unbalanced may be lower or higher.
Therefore, strict rules apply with respect to allowable upper limit
of the height of the center of gravity above the airmounts. As is
known to persons skilled in the art, the softer the airmounts or
the smaller the base, i.e., distance between the airmounts, the
lower the critical height. And, the higher the actual height of the
center of gravity of the payload, the higher the airmounts or the
greater the distance between the airmounts must be designed.
[0003] Another way to cope with this problem, as is also known from
the prior art, is to apply some additional horizontal springs
engaging side surfaces of the payload and walls opposite to the
side surfaces. These springs increase rotational Oddness of the
payload and keep it from instability with respect to tilt
[0004] However, there may be locations where there is little room
building in additional horizontal springs and an additional frame
therefore. Moreover, this maybe an expensive solution. When one
wishes to replace existing airmounts by softer airmounts the base
may already be fixed, etc.
[0005] A typical example is a suspension of an electron microscope
or (parts) of a lithographic apparatus. For improved floor
vibration isolation, softer airmounts are preferred. The height of
the center of gravity of such an apparatus requires airmounts to be
located higher or to be located further apart from one another.
However, increasing the heights of the airmounts may form obstacles
to an operator of the apparatus, and increasing the base may not be
allowable, e.g., due to a conflict with an electronics cabinet or
to commercial reasons.
[0006] Therefore, it is an object of the invention to provide an
improved control of the mounts such that the sensitivity of a
payload to gravitational instability is reduced without
substantially increasing vertical stiffness.
[0007] To that end, the invention provides a control arrangement as
defined at the outset, characterized in that said controller is
arranged to calculate from these height signals at least one
rotation angle of the center of gravity about a horizontal axis and
calculate from this at least one rotation angle said control
signals for said Lorenz motors such that a predetermined rotational
stiffness for supporting said payload is achieved.
[0008] Thus a multiple-input-multiple-output controller is applied
that calculates at least one rotation component of the center of
gravity of the payload and controls the Lorenz motors to provide
additional rotational stiffness without increase of vertical
stress. It is possible to improve the gravitational stability. The
payload may have a higher center of gravity than in prior art
systems, without the system becoming unstable.
[0009] In an embodiment, the invention relates to a method of
controlling a plurality of Lorenz motors actuating a payload, the
payload having a center of gravity, comprising receiving height
signals from sensors sensing heights of said payload and
calculating control signals for said Lorenz motors from said height
signals, characterized by calculating from these height signals at
least one rotation angle of the center of gravity about a
horizontal axis and calculating from this at least one rotation
angle said control signals for said Lorenz motors such that a
predetermined rotational stiffness for supporting said payload is
achieved.
[0010] Moreover, the invention relates to a computer program
product comprising instructions and data to be loaded by a
computer, and after being loaded allowing the computer to perform
the method as defined above.
[0011] Finally, the invention relates to a data carrier comprising
such a computer program product.
[0012] The invention will be explained with reference to some
drawings that are only intended to illustrate the invention and not
to limit its scope. The scope is defined by the annexed claims and
their technical equivalents only.
[0013] FIG. 1 shows a payload supported by a plurality of
mounts;
[0014] FIG. 2 shows a general, schematic block diagram of a
multiple-input-multiple output control arrangement for the Lorenz
motors.
[0015] FIG. 1 shows a payload 4 supported by a plurality of mounts.
The payload 4 has a center of gravity 12. The mounts comprise
airmounts 15, 16, and Lorenz motors 1, 2. For sake of simplicity,
FIG. 1 shows two airmounts 15, 16 and two Lorenz motors 1, 2,
however, there will mostly be three or four airmounts and at least
one Lorenz motor per airmount The airmounts support the payload 4
whereas the Lorenz motors 1, 2 are actuated to apply forces as part
of a control concept to create vertical servo stiffness and/or
servo damping. Additionally, there may be one or more extra Lorenz
motors arranged to apply horizontal forces as part of a control
concept to create horizontal servo stiffness and/or servo damping,
as is evident to persons skilled in the art. These latter Lorenz
motors are not of interest to the present invention.
[0016] The distance between the Lorenz motors is l.
[0017] An x, y, z-axes system is defined having an origin at a
predetermined location. A rotation .phi. is defined as a rotation
about the x-axis. The center of gravity 12 is at height h above the
Lorenz motors 1, 2.
[0018] FIG. 2 shows a control arrangement for control of the two
Lorenz motors 1, 2. The control arrangement shown comprises two
sensors 6, 7 for sensing heights z.sub.1, z.sub.2, respectively.
The sensors 6, 7 feed back height signals z.sub.1, z.sub.2 to a
controller 8. The controller 8 calculates control signals C.sub.1,
C.sub.2 from these height signals z.sub.1, z.sub.2 for the Lorenz
motors 1, 2, respectively. FIG. 2 is simplified in the sense that
it shows only two sensors 6, 7, and two input signals and two
output signals for the controller 8. In most cases, three z-sensors
will be used that provide information as to z, q and a rotation
around the y-axis.
[0019] For the two Lorenz motors embodiment shown in FIG. 1, the
following control concept performed by controller 8 is
proposed.
[0020] derive angle .phi. from z.sub.1, and z.sub.2, e.g., from
(z.sub.1-z.sub.2)/l
[0021] calculate a torque T from angle .phi.: T=-k.phi., where k is
a measure of rotational stiffness in Nm/rad
[0022] calculate control signals C.sub.1, C.sub.2 from torque T:
C.sub.1=-T/a, and C.sub.2=T/b, where a and b are constants the
values of which can be chosen freely but have equal sign.
[0023] In an embodiment, a low pass filter may be applied. Then,
the torque T is calculated from T=-k..phi..H.sub.1p, where H.sub.1p
is the low pass filter transfer function.
[0024] In a 3 dimensional environment, the general idea is as
follows: feed back the height position signals from all height
sensors used to the controller 8, calculate rotation angles about
the x-axis and the y-axis from these height position signals,
calculate control signals for all Lorenz motors used from these
rotation angles such that a predetermined rotational stiffness is
achieved, without substantially creating additional vertical
stiffness.
[0025] As is evident to persons skilled in the art, there may be
applied other types of mounts than airmounts, e.g., springs.
Moreover, When the airmounts 15, 16 are applied, they will be
provided with supply lines to supply air to them. Then, air is
supplied by suitable pressure sources also controlled by the
controller 8. It is to be understood that the controller 8 is shown
as one single unit. However, the controller 8 may be implemented by
multiple computers acting together, e.g., in a master slave
configuration. The suitable software may distributed via data
carriers or any other suitable way. Moreover, the controller for
the pneumatics part may be independent from the controller for the
Lorenz motors.
* * * * *