CN1829948A - Lorentz motor control system for a payload - Google Patents

Abstract

Control arrangement for and method of controlling a plurality of Lorentz motors (1, 2) actuating a payload (4) where the payload has a center of gravity (12). Height signals (z1,z2) are received from sensors sensing heights of said payload. At least one angle of rotation of the center of gravity about a horizontal axis is calculated from these height signals (z1, z2) and from this at least one angle of rotation control signals (C1, C2) for the Lorentz motors (1, 2) are calculated such that a predetermined rotational stiffness for supporting the payload (4) is achieved.A typical application is a suspension for floor vibration isolation of an electron microscope or of a lithographic apparatus.

Description

The Lorentz motor control system that is used for useful load

The present invention relates to a kind of control device that is used to control a plurality of Lorentz motors (Lorenz motor), described a plurality of Lorentz motor activates the useful load with center of gravity, this control device comprises a controller, and this controller is used for from the sensor reception altitude signal of the height of the described useful load of sensing and is used for calculating the control signal that is used for described Lorentz motor according to described altitude signal.

Known usefulness a plurality of (for example three or four) vibroshock (mount) supports a useful load.Described vibroshock can respectively comprise an airmounts (airmount) and one or two Lorentz motor.Replace airmounts, can use " spring " of other type.Described useful load has a center of gravity, and this center of gravity can be above described airmounts, also can be not above described airmounts.Depend on the design of airmounts, the center of gravity critical altitude that useful load becomes unbalance may be lower or higher.Therefore, done strict regulation for the allowed upper limit of the height of C.G. above the airmounts.Those skilled in the art know that described airmounts is soft more or base is more little (being the distance between the airmounts), and then critical altitude is low more.Otherwise the true altitude of the center of gravity of useful load is high more, just must design airmounts highly more or makes the distance between the airmounts big more.

In the prior art, the another kind of mode of handling this problem is to apply some additional horizontal springs, and these springs engage the side surface of useful load and the wall relative with described side surface.These springs increase the rotational stiffness of useful load, and prevent that it from becoming unstable aspect inclination.

Yet, may there be the space that additional horizontal spring is installed in some position, therefore also just additional framework can't be installed.In addition, described scheme may be comparatively expensive.And when wishing to use softer airmounts to replace existing airmounts, described base may have been fixed.

A typical example is suspend an electron microscope or lithographic equipment (or its parts).In order to improve the isolation with floor vibration, preferably use softer airmounts.The height of C.G. of this equipment requires to locate airmounts higher or is farther.Yet the height that increases airmounts may hinder to some extent to the equipment operator, and for example since with the conflicting or consider of casing of electronic apparatus for commerce, may not allow to increase base.

Therefore, an object of the present invention is to provide improved control, so that under the situation that does not significantly increase vertical stiffness, lower useful load to the instable susceptibility of gravity to vibroshock.

For this reason, the invention provides a kind of as the described control device of opening paragraph, it is characterized in that, described controller is used for calculating center of gravity at least one anglec of rotation about a transverse axis according to described altitude signal, and calculate the described control signal that is used for described Lorentz motor according to this at least one anglec of rotation, thereby reach a predetermined rotational stiffness to support described useful load.

Therefore, use a multi-input multi-output controller, this controller calculates at least one rotational component and the control Lorentz motor of useful load center of gravity, so that additional rotational stiffness is provided under the situation that does not increase vertical stiffness.It is possible improving gravitational stability.Compared with prior art systems, useful load can have higher center of gravity, and can not make system become unstable.

In one embodiment, the present invention relates to a kind of method that is used to control a plurality of Lorentz motors, described a plurality of Lorentz motor activates the useful load with center of gravity, this method comprises from the sensor of the height of the described useful load of sensing and receives altitude signal and calculate the control signal that is used for described Lorentz motor according to described altitude signal, it is characterized in that, calculate described center of gravity at least one anglec of rotation according to these altitude signals about a transverse axis, and calculate the described control signal that is used for described Lorentz motor according to this at least one anglec of rotation, thereby reach a predetermined rotational stiffness to support described useful load.

In addition, the present invention relates to a kind of computer program that comprises the instruction and data that is loaded by computing machine, after being loaded, described instruction and data makes this computing machine carry out aforesaid method.

At last, the present invention relates to a kind of data carrier that comprises this computer program.

Explain the present invention below with reference to accompanying drawings, these accompanying drawings only are used to the present invention is described rather than limit its scope.Scope of the present invention is only limited by appended claims and technical equivalences statement thereof.

Fig. 1 illustrates the useful load that is supported by a plurality of vibroshocks;

Fig. 2 illustrates the general schematic block diagram of the multiple-input and multiple-output control device that is used for Lorentz motor.

Fig. 1 illustrates the useful load 4 that is supported by a plurality of vibroshocks.Useful load 4 has center of gravity 12.Described vibroshock comprisesairmounts 15,16 and Lorentzmotor 1,2.For simplicity's sake, Fig. 1 illustrates 15,16 and two Lorentzmotors 1,2 of two airmounts, yet, three or four airmounts in most cases will be arranged, and at least one Lorentz motor of each airmounts.Described airmounts supports useful load 4, and as the part of control concept, 1,2 of described Lorentz motors activated the power of applying so that produce vertical servo stiffness and/or servo damping.In addition,, have at least one or more extra Lorentz motors to be used for applying horizontal force, so that produce horizontal servo stiffness and/or servo damping, as known in those skilled in the art as the part of control concept.The present invention does not discuss the extra Lorentz motor that is used for applying horizontal force.

Distance between the Lorentz motor among the figure is l.

Defined x, a y, z axle system, its initial point is in the pre-position. is defined as around the rotation of x axle with rotation.Center ofgravity 12 is positioned at the height h place of Lorentzmotor 1,2 tops.

Fig. 2 illustrates the control device that is used to control twoLorentz motors 1,2.As shown in the figure, this control device comprises that two are respectively applied for level sensing z₁, z₂Sensor 6,7.These two sensors 6,7 are to controller 8 feedback altitude signal z₁, z₂This controller 8 is according to these altitude signals z₁, z₂Calculate the control signal C that is respectively applied for Lorentzmotor 1,2₁, C₂Fig. 2 is a reduced graph, and two sensors 6,7 wherein only are shown, and for 8 of controllers two input signals and two output signals is shown.As a rule, will use three z sensors to provide about the information of z, q and the rotation that centers on the y axle.

For the embodiment of two Lorentz motors shown in Fig. 1, propose to carry out following control concept by controller 8:

-from z₁, z₂Derive angle , for example according to (z₁-z₂)/l

-according to angle calculating torque T:T=-k. , wherein k is the tolerance of rotational stiffness, its unit is Nm/rad

-according to torque T calculation control signal C₁, C₂: C₁=-T/a, C₂=T/b, wherein a and b are constants, its value can freely be selected, but they have identical symbol.

In one embodiment, can use a low-pass filter.So can pass through T=-k. .H_1pCome calculating torque, wherein H_1pIt is low pass filter transfer function.

In a three-dimensional embodiment, general conception is as follows: will arrive controller 8 from the height and position signal feedback of whole employed height sensors, according to the anglec of rotation of these height and position calculated signals around x axle and y axle, according to these anglecs of rotation is whole employed Lorentz motor calculation control signals, so that be issued to a predetermined rotational stiffness in the situation that does not significantly produce additional vertical stiffness.

It is known to those skilled in the art that the vibroshock that to use other type except that the air-cushion type vibroshock, such as spring.In addition, when usingairmounts 15,16, they can be equipped with air supply line, so that provide air for it.Therefore, can come air feed with suitable pressure source, described pressure source is also by controller 8 controls.Should be appreciated that controller 8 is known as individual unit.Yet, also can implement controller 8 with a plurality of computing machines of collaborative work, described a plurality of computing machines are for example with principal and subordinate's configuration effort.Can distribute appropriate software by data carrier or other any suitable mode.In addition, be used for pneumatic controller and can be independent of the controller that is used for Lorentz motor.

Claims (5)

1, is used to control a plurality of Lorentz motors (1,2) control device, described a plurality of Lorentz motor activates the useful load (4) with center of gravity (12), this control device comprises a controller (8), and this controller is used for receiving altitude signal (z from the sensor of the height of the described useful load of sensing₁, z₂) and be used for calculating the control signal (C that is used for described Lorentz motor according to described altitude signal₁, C₂), it is characterized in that described controller (8) is used for according to described altitude signal (z₁, z₂) calculate described center of gravity at least one anglec of rotation about a transverse axis, and calculate the described control signal (C that is used for described Lorentz motor (1,2) according to this at least one anglec of rotation₁, C₂), thereby reach a predetermined rotational stiffness to support described useful load (4).

2, control device as claimed in claim 1, wherein said controller (8) are used to control three or four Lorentz motors.

3, be used to control the method for a plurality of Lorentz motors (1,2), described a plurality of Lorentz motors activate the useful load (4) with center of gravity (12), and this method comprises the sensor reception altitude signal (z from the height of the described useful load of sensing₁, z₂) and calculate the control signal (C that is used for described Lorentz motor according to described altitude signal₁, C₂), it is characterized in that, according to these altitude signals (z₁, z₂) calculate described center of gravity at least one anglec of rotation about a transverse axis, and calculate the described control signal (C that is used for described Lorentz motor (1,2) according to this at least one anglec of rotation₁, C₂), thereby reach a predetermined rotational stiffness to support described useful load (4).

4, the computer program that comprises the instruction and data that will be loaded by computing machine, after being loaded, described instruction and data makes this computing machine carry out method as claimed in claim 3.

5, the data carrier that comprises computer program as claimed in claim 4.

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